K-rod Posterior Dynamic Stabilization Could Reduce Adjacent Segment Degeneration: A Mi nimum 5-Year Follow-up

K-rod Posterior Dynamic Stabilization Could Reduce Adjacent Segment Degeneration: A Mi nimum 5-Year Follow-up | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article K-rod Posterior Dynamic Stabilization Could Reduce Adjacent Segment Degeneration: A Mi nimum 5-Year Follow-up Jiezhong Deng, Yu Xiang, Ruonan Bai, Shuang Liu, Zuoqiang Yan, and 6 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6946140/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 7 You are reading this latest preprint version Abstract Objective To evaluate the efficacy of posterior dynamic stabilization (PDS) in treating single-level lumbar degenerative disease and to examine its effect on first cephalad adjacent segment (FCAS) degeneration. Methods This retrospective study included 97 patients who underwent single-level lumbar fusion or PDS between April 2010 and April 2012. Clinical outcomes were assessed using the Visual Analog Scale (VAS) and Oswestry Disability Index (ODI) preoperatively and postoperatively. Radiographic analysis quantified the range of motion (ROM) at the surgical segment, FCAS, and entire lumbar spine. Magnetic resonance imaging (MRI) was used to evaluate degenerative changes in the FCAS. Results Eighty-six patients completed a minimum 5-year follow-up and were categorized into two groups: the PDS group (n = 42) and the fusion group (n = 44). Baseline demographic and clinical characteristics were comparable between groups (all P > 0.05). Both groups showed significant postoperative improvements in VAS and ODI scores (P < 0.05), with no significant intergroup differences at any time point. The PDS group had significantly shorter operative times and less intraoperative blood loss than the fusion group (P < 0.05). Radiographic evaluation demonstrated that the K-rod dynamic system partially preserved ROM at the surgical level over 5 years and limited the increase in FCAS ROM compared to the fusion group (P < 0.05). Postoperative lumbosacral alignment parameters were similar between groups. During follow-up, one case of radiographic adjacent segment degeneration (ASDeg) occurred in the PDS group, while the fusion group showed five cases of ASDeg and one case of symptomatic adjacent segment degeneration (ASDis) requiring revision surgery. Conclusion PDS effectively preserves motion at the surgical segment and has a smaller impact on FCAS mobility. Over long-term follow-up, the incidence of ASDeg and ASDis was lower in the PDS group compared to fusion surgery. Single level Posterior Dynamic Stabilization Fusion Adjacent Segment Degeneration Long Follow-up Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 INTRODUCTION Posterior dynamic stabilization (PDS) has been used clinically for decades as a non-fusion stabilization technique. Compared with fusion surgery, PDS preserves partial range of motion (ROM) at the instrumented segment, helping to maintain lumbar function and reduce fusion-related complications, particularly adjacent segment degeneration (ASD) [ 1 – 3 ]. Over the past fifteen years, numerous studies have compared PDS and fusion surgery in the treatment of lumbar degenerative conditions, including lumbar stenosis[ 4 – 6 ], disc herniation[ 4 , 5 , 7 ], degenerative spondylolisthesis[ 8 – 10 ], and degenerative scoliosis[ 11 , 12 ]. Most of these studies reported favorable short-term clinical and radiological outcomes. However, long-term results remain controversial[ 10 , 13 – 17 ]. For instance, St-Pierre et al.[ 17 ] followed 52 patients who underwent PDS for at least five years and found that 15 developed ASD, with 9 requiring revision fusion surgery. Based on these findings, they concluded that the Dynesys system may not effectively prevent ASD. In contrast, Zhang et al. [ 15 ] reported satisfactory outcomes with Dynesys in both single-level and multi-level fixation cases, with an average follow-up of 53 months, showing a lower incidence of ASD compared to the fusion group. ASD is a major complication of lumbar fusion, often leading to new clinical symptoms and, in some cases, the need for revision surgery. Long-term follow-up studies have shown that the incidence of radiographic ASD (ASDeg) and symptomatic ASD (ASDis) following lumbar fusion is approximately 26.6% and 8.5%, respectively[ 2 ]. Although the exact etiology remains unclear, many studies suggest that the loss of motion at the fused segment results in compensatory hypermobility at adjacent levels, leading to increased intradiscal pressure and facet joint stress, which may accelerate degeneration[ 18 ]. This compensatory motion is most pronounced at the first cephalad adjacent segment (FCAS), making it particularly vulnerable to degeneration[ 19 , 20 ]. By preserving partial ROM at the operated level, PDS may reduce biomechanical stress on adjacent segments and potentially lower the risk of ASD. However, postoperative adjacent segment degeneration is influenced by multiple factors, including patient age, body mass index (BMI), lumbosacral alignment, and the number of fused levels[ 21 ]. Most existing clinical studies on PDS include both single- and multi-level cases, with limited data specifically examining ASD after single-level PDS versus fusion, especially over the long term. Therefore, the aim of this study is to minimize confounding factors and evaluate the long-term clinical and radiographic outcomes of single-level laminotomy decompression combined with K-rod dynamic stabilization, with a particular focus on the relationship between PDS and FCAS degeneration. MATERIALS AND METHODS Patients This study was approved by the Ethics Committee of Southwest Hospital. A total of 97 patients with single-level lumbar degenerative disease who underwent surgery between April 2010 and April 2012 were included. Patients were divided into two groups: the K-rod posterior dynamic stabilization (PDS) group and the single-level transforaminal lumbar interbody fusion (TLIF) group, which served as the control. The K-Rod Posterior Dynamic Stabilization System (Paonan Biotech Co., Ltd., Taiwan) is a pedicle screw-based device designed for dynamic spinal stabilization. Its flexibility is provided by a composite rod composed of titanium alloy cable cords encased in polyetheretherketone (PEEK) shells. The inclusion criteria were as follows: age between 18 and 60 years; clinical symptoms consistent with lumbar degenerative disease (e.g., radicular back or lower extremity pain, muscle weakness, or sensory disturbances); radiographic evidence of single-level disc degeneration (including lumbar stenosis, disc herniation, or spondylolisthesis); a history of single-level decompression and fusion or K-rod stabilization; absence of symptoms at non-surgical levels; and a minimum follow-up duration of five years. Exclusion criteria were: cauda equina syndrome; a dual-energy X-ray absorptiometry (DEXA) T-score < − 3.0; lumbar spondylolisthesis greater than Grade I; spinal deformities; spinal tuberculosis; infections; tumors; or congenital anomalies. For patients meeting these criteria, the surgical approach was determined collaboratively by the patient and the operating surgeon. Surgical Approach All procedures were performed by the corresponding author’s surgical team. In the PDS group, a midline skin incision combined with the Wiltse approach was used according to the manufacturer's guidelines. Following pedicle screw placement and rod installation, unilateral laminotomy decompression was performed at the symptomatic level identified by preoperative imaging. In the fusion group, all patients underwent single-level TLIF using the same surgical approach. Both groups received identical perioperative management. Patients in the PDS group were required to wear a lumbar brace for 1 month postoperatively, while those in the fusion group wore the brace for 3 months. Clinical and Radiological Data Visual Analog Scale (VAS) and Oswestry Disability Index (ODI) scores were collected preoperatively, at 2 years postoperatively, and at the final follow-up. Standard radiographic assessments—including X-rays and magnetic resonance imaging (MRI)—were conducted at the same intervals. In the fusion group, computed tomography (CT) scans were routinely performed at 6 months postoperatively, with additional scans at 12 months if bony fusion was not confirmed. All radiographic measurements were performed using the Picture Archiving and Communication System (PACS). The evaluation methods for radiographic parameters and the diagnostic criteria for ASD were based on our previously established protocol[ 3 ]. The following parameters were measured preoperatively, at 2 years postoperatively, and at the final follow-up: lumbar ROM, surgical segment ROM, FCAS ROM, FCAS disc height, lumbar lordosis (LL), pelvic incidence (PI), and sacral slope (SS). Definitions were as follows: Lumbar ROM: Calculated as the difference between flexion and extension angles measured between the superior endplates of L1 and S1 on lateral radiographs. Surgical Segment ROM: Defined as the difference between flexion and extension angles measured between the superior and inferior endplates of the operated segment. FCAS ROM: Defined as the difference between flexion and extension angles measured between the superior and inferior endplates of the FCAS. FCAS Disc Height: Calculated as the average of the anterior and posterior disc heights of the FCAS. LL: The angle between the superior endplates of L1 and S1 on neutral lateral radiographs. PI: The angle formed between a line connecting the center of the femoral head to the midpoint of the sacral endplate and a line perpendicular to the sacral endplate. SS: The angle between the sacral endplate and a horizontal reference line. ASD Diagnosis ASDeg was defined by the presence of any of the following criteria: (1) a reduction in FCAS disc height exceeding 3 mm on lateral radiographs compared to preoperative measurements; (2) FCAS vertebral slip greater than 3 mm on lateral radiographs and/or FCAS ROM exceeding 15°; (3) MRI evidence of FCAS degeneration progression, such as an increase in Pfirrmann grade, new disc herniation, or spinal stenosis (see Fig. 1 for Pfirrmann grade illustrations). ASDis was diagnosed if ASDeg was accompanied by new clinical symptoms, such as low back pain or radicular lower extremity pain, attributable to the FCAS level[ 2 ]. Statistical Analysis: All statistical analyses were conducted using SPSS 27.0 (IBM-SPSS, Chicago, IL, USA). Continuous variables are reported as mean ± standard deviation. Independent samples t-tests compared age, BMI, follow-up duration, operative time, intraoperative blood loss, VAS and ODI scores, and radiographic parameters between groups. Categorical variables (e.g., sex and surgical segment) were analyzed using the Chi-square or Fisher’s exact test as appropriate. Repeated measures ANOVA assessed within-group changes over time for VAS, ODI, lumbar ROM, surgical segment ROM, FCAS ROM, FCAS disc height, LL, PI, and SS. Statistical significance was set at p < 0.05. RESULTS A total of 97 consecutive patients were initially enrolled. After excluding 11 patients lost to follow-up, 86 were included in the final analysis, with 42 in the PDS group and 44 in the fusion group. Baseline demographic and clinical characteristics, including age, sex distribution, BMI, follow-up duration, surgical level, preoperative VAS and ODI scores, and radiographic parameters, were comparable between groups (all P > 0.05). All patients were younger than 60 years (Tables 1 – 4 ). Table 1 Demographic and clinical data Variable PDS group (N = 42) Fusion group (N = 44) P-value Age (years) 46.50 ± 9.35 49.34 ± 8.18 0.137 Males/Females 24/18 24/20 0.808 Follow-up(months) 66.31 ± 3.54 67.59 ± 3.57 0.105 BMI (kg/m2) 23.57 ± 2.99 23.31 ± 2.98 0.693 Operation Level 0.521 L4-5 22 20 L5-S1 20 24 Operation Duration (min) 144.12 ± 21.66 166.91 ± 29.63 < 0.001 Blood Loss (ml) 180.33 ± 34.76 227.93 ± 40.43 < 0.001 Values are presented as number (%) or mean ± standard deviation. BMI, Body Mass Index. Both groups demonstrated significant improvement in VAS and ODI scores at the 2-year follow-up compared to baseline (P < 0.05). These improvements remained stable at the final follow-up, with no significant within-group differences between the 2-year and final evaluations. Additionally, there were no significant between-group differences in VAS or ODI scores at any time point (all P > 0.05) (Table 2 , Figs. 2 – 3 ). Table 2 Clinical Outcomes Variable PDS group (N = 42) Fusion group (N = 44) P-value Back pain VAS Preoperative 4.67 ± 1.56 5.11 ± 1.20 0.139 2 years follow-up 1.90 ± 1.49 2.18 ± 1.67 0.421 Last follow-up 1.90 ± 0.73 2.16 ± 1.06 0.199 Leg pain VAS Preoperative 6.38 ± 1.41 6.59 ± 1.32 0.478 2 years follow-up 1.52 ± 0.92 1.70 ± 0.85 0.346 Last follow-up 1.14 ± 0.65 1.34 ± 0.75 0.193 ODI Preoperative 53.71 ± 8.10 54.55 ± 5.71 0.583 2 years follow-up 20.00 ± 3.51 20.91 ± 3.87 0.257 Last follow-up 19.29 ± 4.46 21.14 ± 4.32 0.054 Values are presented as mean ± standard deviation. VAS, visual analogue scale; ODI, Oswestry Disability Index. Radiographic analysis revealed a significant reduction in lumbar ROM from baseline to final follow-up in both groups (P < 0.05), though all values remained within normal physiological ranges. At 2 years, the PDS group preserved 59% of surgical segment ROM, with similar values maintained through final follow-up. In contrast, complete fusion without residual motion was confirmed in all fusion group cases (Table 3 , Figs. 4 – 5 ). Regarding FCAS kinematics, both groups showed increased ROM. The fusion group demonstrated a significant increase from baseline (P 0.05 vs. preoperative) and between the 2-year and final follow-ups (P > 0.05). However, a significant increase in FCAS ROM was observed in the PDS group at the final follow-up compared to baseline (P < 0.05). Notably, FCAS ROM in the fusion group was significantly higher than in the PDS group at both 2-year and final follow-ups (P 0.05) (Tables 3 – 4 , Figs. 4 – 7 ). MRI follow-up identified 1 case of ASDeg in the PDS group and 5 cases of ASDeg plus 1 case of ASDis in the fusion group. The ASDis patient experienced recurrent lower extremity pain at the 5-year mark, with MRI-confirmed degeneration at both cephalad and caudal adjacent segments, ultimately requiring revision surgery after failed conservative treatment (Table 5 , Fig. 8 ). No neurovascular injuries, spinal cord damage, nerve root impairment, or implant-related complications were observed in either group. Table 3 Lumbar X-ray Outcomes Variable PDS group (N = 42) Fusion group (N = 44) P-value Lumbar ROM Preoperative 36.93 ± 5.92 37.05 ± 4.29 0.916 2 years follow-up 36.60 ± 2.64 35.64 ± 2.56 0.942 Last follow-up 33.69 ± 3.33 34.86 ± 3.55 0.118 Surgical segment ROM Preoperative 7.64 ± 1.46 7.16 ± 1.60 0.147 2 years follow-up 4.50 ± 0.92 0 Last follow-up 4.24 ± 0.79 0 FCAS ROM Preoperative 7.05 ± 2.38 6.61 ± 2.37 0.400 2 years follow-up 7.93 ± 1.47 10.73 ± 3.05 < 0.001 Last follow-up 8.88 ± 1.63 12.50 ± 2.60 < 0.001 FCAS disc height Preoperative 8.88 ± 1.40 8.91 ± 1.44 0.927 2 years follow-up 8.76 ± 1.48 8.64 ± 1.43 0.690 Last follow-up 8.64 ± 1.65 8.45 ± 1.47 0.577 Values are presented as mean ± standard deviation. ROM, range of motion; FCAS, first cephalad adjacent segment. Table 4 Lumbosacral X-ray Parameters Variable PDS group (N = 42) Fusion group (N = 44) P-value PI Preoperative 44.10 ± 7.56 44.41 ± 7.56 0.848 2 years follow-up 43.86 ± 7.69 43.84 ± 7.46 0.992 Last follow-up 43.05 ± 6.58 43.77 ± 6.97 0.622 SS Preoperative 35.05 ± 5.07 36.16 ± 6.05 0.360 2 years follow-up 35.40 ± 5.32 36.39 ± 4.83 0.373 Last follow-up 34.86 ± 5.68 35.95 ± 5.39 0.361 LL Preoperative 41.00 ± 6.21 41.82 ± 7.05 0.570 2 years follow-up 42.36 ± 7.23 43.41 ± 6.89 0.491 Last follow-up 44.17 ± 6.59 44.75 ± 6.36 0.677 Values are presented as mean ± standard deviation. PI, pelvic incident angle; SS, sacral tilt angle; LL, lumbar lordosis. Table 5 FCAS MRI Pfirrmann Classification PDS group (N = 42) Fusion group (N = 44) Preoperative Grade 1 23 23 Grade 2 14 17 Grade 3 5 4 Grade 4 0 0 Grade 5 0 0 Last follow-up Grade 1 23 21 Grade 2 13 16 Grade 3 6 4 Grade 4 0 2 Grade 5 0 1 DISCUSSION As an alternative to rigid fusion, PDS systems use pedicle screw instrumentation to create a semi-mobile construct. This approach aims to alleviate pain caused by pathological motion while preserving residual mobility in unaffected segments[ 1 , 3 ]. However, the long-term efficacy of PDS remains controversial, especially regarding its ability to prevent or reduce ASD compared to fusion[ 2 , 18 ]. Although the exact pathogenesis of ASD is unclear[ 21 ], in vitro studies suggest that loss of ROM at the operated level may alter the biomechanics of adjacent segments, accelerating their degeneration[ 22 , 23 ]. Notably, increased motion tends to occur at the cranial adjacent segment, which may explain its higher susceptibility to ASD[ 19 , 20 ]. Therefore, this study focused on the relationship between cranial adjacent segment ROM and ASD occurrence. Our results showed no significant differences in BMI or lumbosacral sagittal parameters between groups. All patients were under 60 years old, below the World Health Organization’s elderly threshold. In the PDS group, approximately 59% of surgical segment ROM was preserved at two years postoperatively and maintained through a minimum five-year follow-up. In contrast, surgical segment ROM was nearly abolished in the fusion group. Both groups exhibited increased cranial adjacent segment ROM; however, the increase was significantly greater in the fusion group. Correspondingly, the fusion group had a higher incidence of both ASDeg and ASDis, suggesting a protective effect of PDS consistent with previous studies. One patient in the fusion group initially presented with severe low back pain and bilateral lower limb pain. Preoperative imaging showed L4/5 spinal stenosis and instability of the L4 vertebra, with an FCAS disc height of 8.21 mm and a ROM of 3.8°. After three months of unsuccessful conservative treatment, the patient underwent L4/5 TLIF, resulting in significant symptom relief. However, during routine follow-up, the patient experienced recurrent lower limb pain. Imaging revealed degeneration of both cranial and caudal adjacent segments, with the L3/4 FCAS disc height decreasing to 6.75 mm (a 1.46 mm reduction) and ROM increasing to 7.6°, twice the preoperative value. The Pfirrmann grade of the cranial adjacent segment progressed from 3 to 5. These findings suggest that compensatory increased mobility—particularly at the cranial L3/4 segment following fusion—accelerated adjacent segment degeneration and led to nerve compression symptoms. After failed conservative management, revision surgery significantly alleviated symptoms (see Fig. 8 ). Beyond this revision, no mechanical complications—such as screw breakage, rod fracture, or screw loosening—were observed in either group. Compared to rigid fixation, the PDS system offers greater biomechanical flexibility, reducing the risk of screw breakage. However, retained mobility may increase the risk of screw loosening[ 24 , 25 ]. The absence of such complications in our study may be attributed to (1) limited destabilization from fenestration decompression, (2) exclusion of patients with severe osteoporosis, and (3) a relatively short follow-up period. Although radiographic screw loosening can be concerning, prior studies indicate it does not significantly affect clinical outcomes (e.g., VAS, ODI, JOA scores)[ 10 , 24 , 25 ], possibly due to unintended facet joint fusion following PDS—reported in over 50% of patients in some series. The likelihood of unintended fusion and subsequent motion loss increases with age, particularly in patients over 60[ 26 , 27 ]. Therefore, we believe the cost-effectiveness of PDS is lower in elderly individuals. Accordingly, patients over 60 were excluded from this study for two reasons: (1) reduced physical activity in older adults diminishes the clinical relevance of motion preservation, and (2) more advanced adjacent segment degeneration in this population may lead to suboptimal outcomes with PDS compared to fusion. A recent biomechanical study investigated the effects of dynamic stabilization systems on spinal kinematics using rods of five different stiffness levels to stabilize the L4–5 segment. The results showed that increasing construct stiffness progressively reduced ROM and intradiscal pressure at the stabilized level, while simultaneously increasing both parameters at the cranial adjacent level (L3–4). The authors concluded that greater stiffness at the index segment limits its mobility and induces compensatory hypermobility in adjacent segments[ 28 ]. These in vitro findings align with finite element analyses, which suggest that dynamic stabilization preserves segmental motion, enabling more balanced load distribution and reducing excessive adjacent segment motion[ 29 , 30 ]. Jahng et al.[ 31 ] performed a finite element analysis comparing various fixation techniques in terms of six degrees of freedom and the center of rotation (COR) in the lumbar spine. The K-rod system preserved greater flexion-extension and lateral bending ROM than traditional titanium rods. Notably, although a posterior shift in COR was commonly observed postoperatively, the K-rod group maintained a COR position closer to physiological norms. The authors emphasized that altered COR may elevate mechanical stress on adjacent segments and implants, increasing the risk of degeneration and mechanical failure. In a long-term follow-up study, Hoppe et al.[ 16 ] treated L5–S1 degenerative spondylolisthesis with PDS and reported a 28% ASD incidence after an average of 7 years. In 74% of cases, the index-level flexion-extension ROM was less than 4°, which the authors interpreted as a functional fusion state and a potential ASD risk factor. In our study, the PDS group preserved approximately 55% of index-level ROM at final follow-up (mean 4.24°), with only one case of ASDeg (2.38%), which required no intervention. In a representative case, surgical segment ROM decreased from 9.13° preoperatively to 5.11° postoperatively, while FCAS ROM slightly increased from 6.89° to 7.36°. This patient retained ~ 60% of preoperative ROM and showed favorable clinical outcomes without ASDeg (Fig. 9 ). Lumbosacral sagittal alignment also plays a key role in ASD development. Although no significant differences in sagittal parameters were found between groups in our study, previous research highlights the importance of restoring lumbar lordosis to maintain biomechanical balance and reduce adjacent segment stress[ 32 ]. Restoration of lordosis is associated with a lower ASD risk. Some studies suggest that PDS systems support more natural lordosis restoration by preserving segmental motion and promoting physiological alignment. In contrast, rigid fusion—despite offering strong stabilization—may restrict lordosis correction and lead to less optimal biomechanical results. Furthermore, successful lordosis restoration in fusion relies heavily on surgical technique, particularly rod contouring and cage insertion depth, both of which critically influence sagittal reconstruction. Although both the PDS and fusion groups showed significant improvements in VAS and ODI scores, no statistically significant differences were observed between groups at any follow-up point. However, the PDS group demonstrated distinct advantages, including shorter operative time and reduced intraoperative blood loss, thereby minimizing perioperative trauma—findings consistent with previous reports[ 3 , 15 , 18 ]. These differences likely reflect the inherent procedural characteristics. Fusion surgery involves a more extensive workflow, including removal of the cartilaginous endplate, exposure of the bony endplate, bone grafting, and cage implantation. In contrast, PDS eliminates the need for grafting and fusion, often requiring only excision of herniated nucleus pulposus tissue. In some cases, the intervertebral disc remains largely intact, preserving disc height and segmental stability. Moreover, fusion surgery typically results in greater blood loss due to longer operative time and increased bleeding from endplate preparation. The comparable clinical outcomes between the two approaches are likely attributable to adequate neural decompression, rather than interbody fusion per se. That said, the relatively short follow-up period in this study may not be sufficient to fully evaluate the potential long-term benefits of non-fusion techniques. Additionally, by avoiding bone grafting, PDS eliminates complications related to autograft harvesting (e.g., donor site pain, hematoma, fracture) and the rare risk of disease transmission from allografts[ 7 – 10 ]. As ASD most commonly affects the cranial adjacent segment, this study primarily focused on changes at that level and did not systematically assess the surgical disc itself—an acknowledged limitation. Nonetheless, prior studies have explored the potential regenerative effects of PDS on the operated disc[ 33 , 34 ]. Because the nucleus pulposus is avascular, nutrient exchange relies on pressure gradients generated by spinal motion. This "pumping effect," driven by cyclic loading, promotes fluid circulation, maintains hydration, and facilitates nutrient transport[ 35 ]. Disc cell viability and extracellular matrix metabolism depend on moderate, periodic mechanical stimulation; decreased mobility can result in disc dehydration, cell apoptosis, and matrix degradation[ 33 , 36 ]. A retrospective study reported increased T2-weighted MRI signal intensity in the nucleus pulposus following dynamic stabilization, suggesting disc rehydration after an average follow-up of 46.7 months[ 34 ]. Current evidence suggests that ASD is a multifactorial process influenced by age, BMI, lumbosacral sagittal alignment, ROM at the index level, and the number of fused segments. Among these, surgical segment ROM appears to be a key determinant[ 21 , 28 – 31 ]. Both biomechanical and finite element studies have demonstrated a strong association between reduced segmental motion and adjacent segment degeneration. While the K-rod dynamic stabilization system provides clinical outcomes comparable to fusion, it also offers advantages such as shorter operative time, less blood loss, and potentially lower ASD incidence. Nevertheless, the system has limitations. Although it offers posterior column support, it provides limited stabilization to the anterior and middle columns—especially after partial discectomy, which may further compromise anterior stability. However, in our study, this did not significantly affect lumbar lordosis. Additionally, the system permits motion not only in flexion-extension but also in lateral bending, complicating assessment of how preserved mobility impacts adjacent segment biomechanics. Finally, the long-term clinical significance of ASD remains uncertain. In many cases, its impact on overall outcomes appears minimal, potentially diminishing the theoretical advantage of PDS in preventing ASD[ 37 ]. This study has several limitations. First, as a single-center retrospective study, it is subject to inherent selection and assessment biases. Second, given the biomechanical variability among different pedicle-based dynamic stabilization systems, our results may not be generalizable to other devices. Third, the relatively short follow-up period and limited sample size may restrict the strength and external validity of our conclusions. Lastly, ASD may partly reflect natural spinal aging and cannot be entirely attributed to surgical intervention[ 38 ]. Future research should include a non-instrumented control group to better delineate the treatment-specific effects. CONCLUSION The PDS system achieved clinical outcomes comparable to spinal fusion in treating single-level lumbar degenerative disease, while providing additional benefits such as shorter operative time, reduced intraoperative blood loss, preservation of segmental motion, and potentially less impact on adjacent segments. Long-term follow-up revealed a lower incidence of FCAS ASDeg and ASDis in the PDS group compared to fusion. These results suggest that, for appropriately selected patients, the PDS system represents a viable and advantageous alternative to conventional fusion surgery. Declarations Ethics approval and consent to participate The project protocols were reviewed and approved by the ethnic committee of Southwest Hospital, Army Medical University ((B) KY2025100). Consent to Participate Statement This study utilizes retrospectively collected clinical data obtained during routine diagnosis and treatment. The research involves no commercial interests and does not involve direct human intervention, interaction for biological sample collection, or additional data acquisition. The study does not affect participants' diagnosis or treatment and poses no physiological risks. A waiver of informed consent was approved by the Ethics Committee of Southwest Hospital, Army Medical University. Consent for publication Not applicable. Availability of data and materials The dataset analyzed for this study is available from the corresponding author upon reasonable request. Competing interests The authors declare that they have no competing interests. Clinical trial number: not applicable. Funding The research has been funded by Chongqing Science and Health Joint Medical Research (2025ZDXM002) and Chongqing Talent Plan (CQYC202105037). Authors' contributions Conceptualization: FD, FL, JZX, JYH, ZHZ; Formal Analysis: JZD, YX, RNB, SL, ZQY, CMZ; Data curation: JZD, YX, RNB, SL, ZQY, CMZ; Methodology: JZD, YX, JYH, ZHZ; Project administration: FL, JZX, JYH, ZHZ; Writing – Original Draft: JZD, YX; Writing – Review & Editing: JYH, ZHZ; Funding acquisition: ZHZ; All authors read and approved the final manuscript. Acknowledgements Not applicable References Prud'homme M, Barrios C, Rouch P, Charles YP, Steib JP, Skalli W. 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J Neurosurg Spine. 2022;37(6):836–42. Zhang Y, Zhang ZC, Li F, Sun TS, Shan JL, Guan K, Zhao GM, Zhang LZ. Long-Term Outcome of Dynesys Dynamic Stabilization for Lumbar Spinal Stenosis. Chin Med J (Engl). 2018;131(21):2537–43. Helgeson MD, Bevevino AJ, Hilibrand AS. Update on the evidence for adjacent segment degeneration and disease. Spine J. 2013;13(3):342–51. Cunningham BW, Dawson JM, Hu N, Kim SW, McAfee PC, Griffith SL. Preclinical evaluation of the Dynesys posterior spinal stabilization system: a nonhuman primate model. Spine J. 2010;10(9):775–83. Strube P, Tohtz S, Hoff E, Gross C, Perka C, Putzier M. Dynamic stabilization adjacent to single-level fusion: part I. Biomechanical effects on lumbar spinal motion. Eur Spine J. 2010;19(12):2171–80. Ko CC, Tsai HW, Huang WC, Wu JC, Chen YC, Shih YH, Chen HC, Wu CL, Cheng H. Screw loosening in the Dynesys stabilization system: radiographic evidence and effect on outcomes. Neurosurg Focus. 2010;28(6):E10. Wu JC, Huang WC, Tsai HW, Ko CC, Wu CL, Tu TH, Cheng H. Pedicle screw loosening in dynamic stabilization: incidence, risk, and outcome in 126 patients. Neurosurg Focus. 2011;31(4):E9. Fay LY, Chang PY, Wu JC, Huang WC, Wang CH, Tsai TY, Tu TH, Chang HK, Wu CL, Cheng H. Dynesys dynamic stabilization-related facet arthrodesis. Neurosurg Focus. 2016;40(1):E4. Fay LY, Huang WC, Chang CC, Chang HK, Tsai TY, Tu TH, Wu CL, Cheng H, Wu JC. Unintended facet fusions after Dynesys dynamic stabilization in patients with spondylolisthesis. J Neurosurg Spine. 2019;30(3):353–61. Chun K, Yang I, Kim N, Cho D. Effect of Device Rigidity and Physiological Loading on Spinal Kinematics after Dynamic Stabilization: An In-Vitro Biomechanical Study. J Korean Neurosurg Soc. 2015;58(5):412–8. Chien CY, Kuo YJ, Lin SC, Chuang WH, Luh YP. Kinematic and mechanical comparisons of lumbar hybrid fixation using Dynesys and Cosmic systems. Spine (Phila Pa 1976). 2014;39(15):E878–84. Shih SL, Chen CS, Lin HM, Huang LY, Liu CL, Huang CH, Cheng CK. Effect of spacer diameter of the Dynesys dynamic stabilization system on the biomechanics of the lumbar spine: a finite element analysis. J Spinal Disord Tech. 2012;25(5):E140–9. Jahng TA, Kim YE, Moon KY. Comparison of the biomechanical effect of pedicle-based dynamic stabilization: a study using finite element analysis. Spine J. 2013;13(1):85–94. Guan J, Liu T, Chen H, Yang K, Liang H. Correlation of the single-segment dynamic stabilization with different segmental mobility and zygapophysial (facet) joint degeneration: a retrospective study in northern China. BMC Musculoskelet Disord. 2024;25(1):756. Guehring T, Omlor GW, Lorenz H, Engelleiter K, Richter W, Carstens C, Kroeber M. Disc distraction shows evidence of regenerative potential in degenerated intervertebral discs as evaluated by protein expression, magnetic resonance imaging, and messenger ribonucleic acid expression analysis. Spine (Phila Pa 1976). 2006;31(15):1658–65. Fay LY, Wu JC, Tsai TY, Tu TH, Wu CL, Huang WC, Cheng H. Intervertebral disc rehydration after lumbar dynamic stabilization: magnetic resonance image evaluation with a mean followup of four years. Adv Orthop. 2013;2013:437570. Bowles RD, Setton LA. Biomaterials for intervertebral disc regeneration and repair. Biomaterials. 2017;129:54–67. Guan J, Liu T, Yu X, Li W, Feng N, Jiang G, Zhao H, Yang Y. Biomechanical and clinical research of Isobar semi-rigid stabilization devices for lumbar degenerative diseases: a systematic review. Biomed Eng Online. 2023;22(1):95. Mannion AF, Leivseth G, Brox JI, Fritzell P, Hägg O, Fairbank JC. ISSLS Prize winner: Long-term follow-up suggests spinal fusion is associated with increased adjacent segment disc degeneration but without influence on clinical outcome: results of a combined follow-up from 4 randomized controlled trials. Spine (Phila Pa 1976). 2014;39(17):1373–83. Kumar MN, Baklanov A, Chopin D. Correlation between sagittal plane changes and adjacent segment degeneration following lumbar spine fusion. Eur Spine J. 2001;10(4):314–9. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Reviews received at journal 03 Aug, 2025 Reviewers agreed at journal 28 Jul, 2025 Reviewers invited by journal 21 Jul, 2025 Editor invited by journal 30 Jun, 2025 Editor assigned by journal 27 Jun, 2025 Submission checks completed at journal 27 Jun, 2025 First submitted to journal 21 Jun, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6946140","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":488285648,"identity":"a43640c8-2f74-44c2-9f91-d5adfd3cdc20","order_by":0,"name":"Jiezhong Deng","email":"","orcid":"","institution":"Army Medical University","correspondingAuthor":false,"prefix":"","firstName":"Jiezhong","middleName":"","lastName":"Deng","suffix":""},{"id":488285649,"identity":"49202279-3151-4bc7-a28e-d78d0cf704b7","order_by":1,"name":"Yu Xiang","email":"","orcid":"","institution":"Army Medical University","correspondingAuthor":false,"prefix":"","firstName":"Yu","middleName":"","lastName":"Xiang","suffix":""},{"id":488285650,"identity":"3d4fedd6-cbea-436b-aad7-0d88bbd12ad3","order_by":2,"name":"Ruonan Bai","email":"","orcid":"","institution":"Army Medical University","correspondingAuthor":false,"prefix":"","firstName":"Ruonan","middleName":"","lastName":"Bai","suffix":""},{"id":488285653,"identity":"365fcb5b-4040-4301-b506-933b997f4cc7","order_by":3,"name":"Shuang Liu","email":"","orcid":"","institution":"Army Medical University","correspondingAuthor":false,"prefix":"","firstName":"Shuang","middleName":"","lastName":"Liu","suffix":""},{"id":488285656,"identity":"8edf375e-9c61-43f0-9daf-3791f3619d7e","order_by":4,"name":"Zuoqiang Yan","email":"","orcid":"","institution":"Army Medical 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Zhang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA8klEQVRIiWNgGAWjYDACCQiVAOXa8PDzNxCthRlEp8lIzjhAmpbDNgYNCbhVg4D87OZnD7/8sckzOH7+6Kabbed5DBgOMH74mINbC+OcY+bGMjxpxQZnktlu57bd5jFnbmCWnLkNtxZmiQQzaQmJw4kbDkC1WDYcYGPmxaOFTSL9m7SEwf/EDecfg7Sc4zE4kIBfC49Ejpnkh4QDiRtugG05QFiLhEROmTTDgeTEmTcem93OOZfMIznjYDNev8jPSN8m+eOPXWLf+cRnt3PK7Oz5+ZsPfviIRws4CHhQ+YwN+NWDlPwgqGQUjIJRMApGNAAAqDFVB/JdDfoAAAAASUVORK5CYII=","orcid":"","institution":"Army Medical University","correspondingAuthor":true,"prefix":"","firstName":"Zehua","middleName":"","lastName":"Zhang","suffix":""}],"badges":[],"createdAt":"2025-06-21 16:38:13","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6946140/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6946140/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":87439959,"identity":"fbda12c5-033d-43a7-9005-9b8e10889e8d","added_by":"auto","created_at":"2025-07-23 19:32:57","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":64110,"visible":true,"origin":"","legend":"\u003cp\u003ePfirrmann grading system.\u003c/p\u003e","description":"","filename":"image1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6946140/v1/3f93903c8ccd86178efc3b4f.jpeg"},{"id":87439609,"identity":"ec111442-19e3-4211-a11f-27170b6ca4f3","added_by":"auto","created_at":"2025-07-23 19:24:57","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":33093,"visible":true,"origin":"","legend":"\u003cp\u003eIntragroup Comparison of Clinical Outcomes in the PDS Group. visual analogue scale (VAS), Oswestry Disability Index (ODI), preop, preoperative; postop, postoperative. *p \u0026lt; 0.05\u003c/p\u003e","description":"","filename":"image2.png","url":"https://assets-eu.researchsquare.com/files/rs-6946140/v1/d2208f9bebfcb0df6bcd4a60.png"},{"id":87439611,"identity":"97f3631c-3424-4961-8450-23acc207df24","added_by":"auto","created_at":"2025-07-23 19:24:57","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":32399,"visible":true,"origin":"","legend":"\u003cp\u003eIntragroup Comparison of Clinical Outcomes in the Fusion Group. visual analogue scale (VAS), Oswestry Disability Index (ODI), preop, preoperative; postop, postoperative. *p \u0026lt; 0.05.\u003c/p\u003e","description":"","filename":"image3.png","url":"https://assets-eu.researchsquare.com/files/rs-6946140/v1/04ffafc277ea6015d3fa00a7.png"},{"id":87439960,"identity":"cf0d1ba0-04d3-43cb-ab75-cd671c6e33d4","added_by":"auto","created_at":"2025-07-23 19:32:57","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":63194,"visible":true,"origin":"","legend":"\u003cp\u003eIntragroup Comparison of Lumbar X-ray Outcomes in the PDS Group. range of motion (ROM), first cephalad adjacent segment (FACS), preop, preoperative; postop, postoperative. *p \u0026lt; 0.05.\u003c/p\u003e","description":"","filename":"image4.png","url":"https://assets-eu.researchsquare.com/files/rs-6946140/v1/1f3af3258daf3eb9abc5447c.png"},{"id":87467182,"identity":"597ae8ef-a973-4268-91ec-e45e0adf060b","added_by":"auto","created_at":"2025-07-24 08:02:15","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":33185,"visible":true,"origin":"","legend":"\u003cp\u003eIntragroup Comparison of Lumbar X-ray Outcomes in the Fusion Group. range of motion (ROM), first cephalad adjacent segment (FACS), preop, preoperative; postop, postoperative. *p \u0026lt; 0.05.\u003c/p\u003e","description":"","filename":"image5.png","url":"https://assets-eu.researchsquare.com/files/rs-6946140/v1/2cc1c8c1dc80256a8f158ea1.png"},{"id":87439613,"identity":"24ed461b-8c42-4dfb-8fef-5f9d647151b3","added_by":"auto","created_at":"2025-07-23 19:24:57","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":29634,"visible":true,"origin":"","legend":"\u003cp\u003eIntragroup Comparison of Lumbosacral Parameters in the PDS Group. pelvic incident angle (PI), sacral tilt angle (SS), lumbar lordosis (LL), preop, preoperative; postop, postoperative.\u003c/p\u003e","description":"","filename":"image6.png","url":"https://assets-eu.researchsquare.com/files/rs-6946140/v1/6a517f63fe0889c76f1373a1.png"},{"id":87440752,"identity":"dd6a5dcb-5774-48e3-aba3-ec86b3c087ea","added_by":"auto","created_at":"2025-07-23 19:56:57","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":29633,"visible":true,"origin":"","legend":"\u003cp\u003eIntragroup Comparison of Lumbosacral Parameters in the Fusion Group. pelvic incident angle (PI), sacral tilt angle (SS), lumbar lordosis (LL), preop, preoperative; postop, postoperative.\u003c/p\u003e","description":"","filename":"image7.png","url":"https://assets-eu.researchsquare.com/files/rs-6946140/v1/aba05b29078fb13c593ae1ff.png"},{"id":87439637,"identity":"7bc8f2e3-1b7e-42c7-bb9d-4f0f95b8a0cc","added_by":"auto","created_at":"2025-07-23 19:24:57","extension":"jpeg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":365458,"visible":true,"origin":"","legend":"\u003cp\u003eA representative case from the fusion group. (A, B) Preoperative radiographs. (C, D) Preoperative MRI images. Based on clinical symptoms and imaging findings, the symptomatic level was confirmed as L4/5, and a single-level TLIF procedure was performed. (E) Immediate postoperative radiograph. (F, G) Follow-up radiographs at 5 years postoperatively. (H, I) Follow-up MRI at 5 years, demonstrating degenerative changes at both the cranial and caudal adjacent segments. The patient experienced recurrent lower limb pain that was refractory to conservative treatment, ultimately necessitating revision surgery. (J) Radiographic image from the revision surgery.\u003c/p\u003e","description":"","filename":"image8.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6946140/v1/366b8cbcd22f7f9af12bdea1.jpeg"},{"id":87440506,"identity":"f675f845-df71-4bbe-9bbe-ca1085a85888","added_by":"auto","created_at":"2025-07-23 19:48:57","extension":"jpeg","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":324030,"visible":true,"origin":"","legend":"\u003cp\u003eA representative case from the PDS group. (A–C) Preoperative radiographs, including flexion-extension lateral views (B, C). (D, E) Preoperative MRI images. Based on clinical symptoms and imaging findings, the symptomatic level was identified as L5/S1, and a single-level PDS procedure was performed. (F) Immediate postoperative radiograph. (G, H) Follow-up flexion-extension radiographs at final follow-up. (I, J) Follow-up MRI images at final follow-up. Comparative analysis of preoperative and final follow-up imaging demonstrated that the PDS procedure achieved satisfactory decompression while maintaining the following advantages: no significant loss of disc height or degenerative changes at the cranial adjacent segment, and excellent preservation of both segmental and overall lumbar range of motion.\u003c/p\u003e","description":"","filename":"image9.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6946140/v1/fa0a9cacff09019eb4d8f30d.jpeg"},{"id":87472907,"identity":"b2eaf8ea-9ad2-4ee4-9a75-25ba85d04b66","added_by":"auto","created_at":"2025-07-24 08:37:03","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1753837,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6946140/v1/6be730cb-ed28-46dc-9a8e-2dd717ec7205.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"K-rod Posterior Dynamic Stabilization Could Reduce Adjacent Segment Degeneration: A Mi nimum 5-Year Follow-up","fulltext":[{"header":"INTRODUCTION","content":"\u003cp\u003ePosterior dynamic stabilization (PDS) has been used clinically for decades as a non-fusion stabilization technique. Compared with fusion surgery, PDS preserves partial range of motion (ROM) at the instrumented segment, helping to maintain lumbar function and reduce fusion-related complications, particularly adjacent segment degeneration (ASD) [\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eOver the past fifteen years, numerous studies have compared PDS and fusion surgery in the treatment of lumbar degenerative conditions, including lumbar stenosis[\u003cspan additionalcitationids=\"CR5\" citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e], disc herniation[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e], degenerative spondylolisthesis[\u003cspan additionalcitationids=\"CR9\" citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e], and degenerative scoliosis[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Most of these studies reported favorable short-term clinical and radiological outcomes. However, long-term results remain controversial[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan additionalcitationids=\"CR14 CR15 CR16\" citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. For instance, St-Pierre et al.[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e] followed 52 patients who underwent PDS for at least five years and found that 15 developed ASD, with 9 requiring revision fusion surgery. Based on these findings, they concluded that the Dynesys system may not effectively prevent ASD. In contrast, Zhang et al. [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e] reported satisfactory outcomes with Dynesys in both single-level and multi-level fixation cases, with an average follow-up of 53 months, showing a lower incidence of ASD compared to the fusion group.\u003c/p\u003e\u003cp\u003eASD is a major complication of lumbar fusion, often leading to new clinical symptoms and, in some cases, the need for revision surgery. Long-term follow-up studies have shown that the incidence of radiographic ASD (ASDeg) and symptomatic ASD (ASDis) following lumbar fusion is approximately 26.6% and 8.5%, respectively[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Although the exact etiology remains unclear, many studies suggest that the loss of motion at the fused segment results in compensatory hypermobility at adjacent levels, leading to increased intradiscal pressure and facet joint stress, which may accelerate degeneration[\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. This compensatory motion is most pronounced at the first cephalad adjacent segment (FCAS), making it particularly vulnerable to degeneration[\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. By preserving partial ROM at the operated level, PDS may reduce biomechanical stress on adjacent segments and potentially lower the risk of ASD. However, postoperative adjacent segment degeneration is influenced by multiple factors, including patient age, body mass index (BMI), lumbosacral alignment, and the number of fused levels[\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eMost existing clinical studies on PDS include both single- and multi-level cases, with limited data specifically examining ASD after single-level PDS versus fusion, especially over the long term. Therefore, the aim of this study is to minimize confounding factors and evaluate the long-term clinical and radiographic outcomes of single-level laminotomy decompression combined with K-rod dynamic stabilization, with a particular focus on the relationship between PDS and FCAS degeneration.\u003c/p\u003e"},{"header":"MATERIALS AND METHODS","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003ePatients\u003c/h2\u003e\u003cp\u003e This study was approved by the Ethics Committee of Southwest Hospital. A total of 97 patients with single-level lumbar degenerative disease who underwent surgery between April 2010 and April 2012 were included. Patients were divided into two groups: the K-rod posterior dynamic stabilization (PDS) group and the single-level transforaminal lumbar interbody fusion (TLIF) group, which served as the control. The K-Rod Posterior Dynamic Stabilization System (Paonan Biotech Co., Ltd., Taiwan) is a pedicle screw-based device designed for dynamic spinal stabilization. Its flexibility is provided by a composite rod composed of titanium alloy cable cords encased in polyetheretherketone (PEEK) shells.\u003c/p\u003e\u003cp\u003eThe inclusion criteria were as follows: age between 18 and 60 years; clinical symptoms consistent with lumbar degenerative disease (e.g., radicular back or lower extremity pain, muscle weakness, or sensory disturbances); radiographic evidence of single-level disc degeneration (including lumbar stenosis, disc herniation, or spondylolisthesis); a history of single-level decompression and fusion or K-rod stabilization; absence of symptoms at non-surgical levels; and a minimum follow-up duration of five years. Exclusion criteria were: cauda equina syndrome; a dual-energy X-ray absorptiometry (DEXA) T-score \u0026lt; \u0026minus;\u0026thinsp;3.0; lumbar spondylolisthesis greater than Grade I; spinal deformities; spinal tuberculosis; infections; tumors; or congenital anomalies. For patients meeting these criteria, the surgical approach was determined collaboratively by the patient and the operating surgeon.\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eSurgical Approach\u003c/h3\u003e\n\u003cp\u003eAll procedures were performed by the corresponding author\u0026rsquo;s surgical team. In the PDS group, a midline skin incision combined with the Wiltse approach was used according to the manufacturer's guidelines. Following pedicle screw placement and rod installation, unilateral laminotomy decompression was performed at the symptomatic level identified by preoperative imaging. In the fusion group, all patients underwent single-level TLIF using the same surgical approach. Both groups received identical perioperative management. Patients in the PDS group were required to wear a lumbar brace for 1 month postoperatively, while those in the fusion group wore the brace for 3 months.\u003c/p\u003e\n\u003ch3\u003eClinical and Radiological Data\u003c/h3\u003e\n\u003cp\u003eVisual Analog Scale (VAS) and Oswestry Disability Index (ODI) scores were collected preoperatively, at 2 years postoperatively, and at the final follow-up. Standard radiographic assessments\u0026mdash;including X-rays and magnetic resonance imaging (MRI)\u0026mdash;were conducted at the same intervals. In the fusion group, computed tomography (CT) scans were routinely performed at 6 months postoperatively, with additional scans at 12 months if bony fusion was not confirmed. All radiographic measurements were performed using the Picture Archiving and Communication System (PACS). The evaluation methods for radiographic parameters and the diagnostic criteria for ASD were based on our previously established protocol[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe following parameters were measured preoperatively, at 2 years postoperatively, and at the final follow-up: lumbar ROM, surgical segment ROM, FCAS ROM, FCAS disc height, lumbar lordosis (LL), pelvic incidence (PI), and sacral slope (SS).\u003c/p\u003e\u003cp\u003eDefinitions were as follows: Lumbar ROM: Calculated as the difference between flexion and extension angles measured between the superior endplates of L1 and S1 on lateral radiographs. Surgical Segment ROM: Defined as the difference between flexion and extension angles measured between the superior and inferior endplates of the operated segment. FCAS ROM: Defined as the difference between flexion and extension angles measured between the superior and inferior endplates of the FCAS. FCAS Disc Height: Calculated as the average of the anterior and posterior disc heights of the FCAS. LL: The angle between the superior endplates of L1 and S1 on neutral lateral radiographs. PI: The angle formed between a line connecting the center of the femoral head to the midpoint of the sacral endplate and a line perpendicular to the sacral endplate. SS: The angle between the sacral endplate and a horizontal reference line.\u003c/p\u003e\n\u003ch3\u003eASD Diagnosis\u003c/h3\u003e\n\u003cp\u003eASDeg was defined by the presence of any of the following criteria: (1) a reduction in FCAS disc height exceeding 3 mm on lateral radiographs compared to preoperative measurements; (2) FCAS vertebral slip greater than 3 mm on lateral radiographs and/or FCAS ROM exceeding 15\u0026deg;; (3) MRI evidence of FCAS degeneration progression, such as an increase in Pfirrmann grade, new disc herniation, or spinal stenosis (see Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e for Pfirrmann grade illustrations). ASDis was diagnosed if ASDeg was accompanied by new clinical symptoms, such as low back pain or radicular lower extremity pain, attributable to the FCAS level[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\u003ch2\u003eStatistical Analysis:\u003c/h2\u003e\u003cp\u003eAll statistical analyses were conducted using SPSS 27.0 (IBM-SPSS, Chicago, IL, USA). Continuous variables are reported as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation. Independent samples t-tests compared age, BMI, follow-up duration, operative time, intraoperative blood loss, VAS and ODI scores, and radiographic parameters between groups. Categorical variables (e.g., sex and surgical segment) were analyzed using the Chi-square or Fisher\u0026rsquo;s exact test as appropriate. Repeated measures ANOVA assessed within-group changes over time for VAS, ODI, lumbar ROM, surgical segment ROM, FCAS ROM, FCAS disc height, LL, PI, and SS. Statistical significance was set at p\u0026thinsp;\u0026lt;\u0026thinsp;0.05.\u003c/p\u003e\u003c/div\u003e"},{"header":"RESULTS","content":"\u003cp\u003eA total of 97 consecutive patients were initially enrolled. After excluding 11 patients lost to follow-up, 86 were included in the final analysis, with 42 in the PDS group and 44 in the fusion group. Baseline demographic and clinical characteristics, including age, sex distribution, BMI, follow-up duration, surgical level, preoperative VAS and ODI scores, and radiographic parameters, were comparable between groups (all P\u0026thinsp;\u0026gt;\u0026thinsp;0.05). All patients were younger than 60 years (Tables\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eDemographic and clinical data\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eVariable\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePDS group\u003c/p\u003e\u003cp\u003e(N\u0026thinsp;=\u0026thinsp;42)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eFusion group\u003c/p\u003e\u003cp\u003e(N\u0026thinsp;=\u0026thinsp;44)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP-value\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAge (years)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e46.50\u0026thinsp;\u0026plusmn;\u0026thinsp;9.35\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e49.34\u0026thinsp;\u0026plusmn;\u0026thinsp;8.18\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.137\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMales/Females\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e24/18\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e24/20\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.808\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFollow-up(months)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e66.31\u0026thinsp;\u0026plusmn;\u0026thinsp;3.54\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e67.59\u0026thinsp;\u0026plusmn;\u0026thinsp;3.57\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.105\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBMI (kg/m2)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e23.57\u0026thinsp;\u0026plusmn;\u0026thinsp;2.99\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e23.31\u0026thinsp;\u0026plusmn;\u0026thinsp;2.98\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.693\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eOperation Level\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.521\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eL4-5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e22\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e20\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eL5-S1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e20\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e24\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eOperation Duration (min)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e144.12\u0026thinsp;\u0026plusmn;\u0026thinsp;21.66\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e166.91\u0026thinsp;\u0026plusmn;\u0026thinsp;29.63\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBlood Loss (ml)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e180.33\u0026thinsp;\u0026plusmn;\u0026thinsp;34.76\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e227.93\u0026thinsp;\u0026plusmn;\u0026thinsp;40.43\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"4\"\u003eValues are presented as number (%) or mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation.\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd colspan=\"4\"\u003eBMI, Body Mass Index.\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eBoth groups demonstrated significant improvement in VAS and ODI scores at the 2-year follow-up compared to baseline (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05). These improvements remained stable at the final follow-up, with no significant within-group differences between the 2-year and final evaluations. Additionally, there were no significant between-group differences in VAS or ODI scores at any time point (all P\u0026thinsp;\u0026gt;\u0026thinsp;0.05) (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e2\u003c/span\u003e, Figs.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e\u0026ndash;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eClinical Outcomes\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eVariable\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePDS group\u003c/p\u003e\u003cp\u003e(N\u0026thinsp;=\u0026thinsp;42)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eFusion group\u003c/p\u003e\u003cp\u003e(N\u0026thinsp;=\u0026thinsp;44)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP-value\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"4\" nameend=\"c4\" namest=\"c1\"\u003e\u003cp\u003eBack pain VAS\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePreoperative\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e4.67\u0026thinsp;\u0026plusmn;\u0026thinsp;1.56\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e5.11\u0026thinsp;\u0026plusmn;\u0026thinsp;1.20\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.139\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2 years follow-up\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1.90\u0026thinsp;\u0026plusmn;\u0026thinsp;1.49\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2.18\u0026thinsp;\u0026plusmn;\u0026thinsp;1.67\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.421\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLast follow-up\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1.90\u0026thinsp;\u0026plusmn;\u0026thinsp;0.73\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2.16\u0026thinsp;\u0026plusmn;\u0026thinsp;1.06\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.199\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"4\" nameend=\"c4\" namest=\"c1\"\u003e\u003cp\u003eLeg pain VAS\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePreoperative\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e6.38\u0026thinsp;\u0026plusmn;\u0026thinsp;1.41\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e6.59\u0026thinsp;\u0026plusmn;\u0026thinsp;1.32\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.478\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2 years follow-up\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1.52\u0026thinsp;\u0026plusmn;\u0026thinsp;0.92\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1.70\u0026thinsp;\u0026plusmn;\u0026thinsp;0.85\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.346\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLast follow-up\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1.14\u0026thinsp;\u0026plusmn;\u0026thinsp;0.65\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1.34\u0026thinsp;\u0026plusmn;\u0026thinsp;0.75\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.193\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"4\" nameend=\"c4\" namest=\"c1\"\u003e\u003cp\u003eODI\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePreoperative\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e53.71\u0026thinsp;\u0026plusmn;\u0026thinsp;8.10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e54.55\u0026thinsp;\u0026plusmn;\u0026thinsp;5.71\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.583\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2 years follow-up\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e20.00\u0026thinsp;\u0026plusmn;\u0026thinsp;3.51\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e20.91\u0026thinsp;\u0026plusmn;\u0026thinsp;3.87\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.257\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLast follow-up\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e19.29\u0026thinsp;\u0026plusmn;\u0026thinsp;4.46\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e21.14\u0026thinsp;\u0026plusmn;\u0026thinsp;4.32\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.054\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"4\"\u003eValues are presented as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation.\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd colspan=\"4\"\u003eVAS, visual analogue scale; ODI, Oswestry Disability Index.\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eRadiographic analysis revealed a significant reduction in lumbar ROM from baseline to final follow-up in both groups (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05), though all values remained within normal physiological ranges. At 2 years, the PDS group preserved 59% of surgical segment ROM, with similar values maintained through final follow-up. In contrast, complete fusion without residual motion was confirmed in all fusion group cases (Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e3\u003c/span\u003e, Figs.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). Regarding FCAS kinematics, both groups showed increased ROM. The fusion group demonstrated a significant increase from baseline (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05), while the PDS group maintained stable FCAS ROM at 2 years (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05 vs. preoperative) and between the 2-year and final follow-ups (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05). However, a significant increase in FCAS ROM was observed in the PDS group at the final follow-up compared to baseline (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05). Notably, FCAS ROM in the fusion group was significantly higher than in the PDS group at both 2-year and final follow-ups (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05) (Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e3\u003c/span\u003e, Figs.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). Postoperative imaging showed preserved FCAS disc height and stable lumbosacral alignment in both groups (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05) (Tables\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e3\u003c/span\u003e\u0026ndash;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e4\u003c/span\u003e, Figs.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e). MRI follow-up identified 1 case of ASDeg in the PDS group and 5 cases of ASDeg plus 1 case of ASDis in the fusion group. The ASDis patient experienced recurrent lower extremity pain at the 5-year mark, with MRI-confirmed degeneration at both cephalad and caudal adjacent segments, ultimately requiring revision surgery after failed conservative treatment (Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e). No neurovascular injuries, spinal cord damage, nerve root impairment, or implant-related complications were observed in either group.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eLumbar X-ray Outcomes\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eVariable\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePDS group\u003c/p\u003e\u003cp\u003e(N\u0026thinsp;=\u0026thinsp;42)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eFusion group\u003c/p\u003e\u003cp\u003e(N\u0026thinsp;=\u0026thinsp;44)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP-value\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"4\" nameend=\"c4\" namest=\"c1\"\u003e\u003cp\u003eLumbar ROM\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePreoperative\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e36.93\u0026thinsp;\u0026plusmn;\u0026thinsp;5.92\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e37.05\u0026thinsp;\u0026plusmn;\u0026thinsp;4.29\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.916\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2 years follow-up\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e36.60\u0026thinsp;\u0026plusmn;\u0026thinsp;2.64\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e35.64\u0026thinsp;\u0026plusmn;\u0026thinsp;2.56\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.942\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLast follow-up\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e33.69\u0026thinsp;\u0026plusmn;\u0026thinsp;3.33\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e34.86\u0026thinsp;\u0026plusmn;\u0026thinsp;3.55\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.118\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"4\" nameend=\"c4\" namest=\"c1\"\u003e\u003cp\u003eSurgical segment ROM\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePreoperative\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e7.64\u0026thinsp;\u0026plusmn;\u0026thinsp;1.46\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e7.16\u0026thinsp;\u0026plusmn;\u0026thinsp;1.60\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.147\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2 years follow-up\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e4.50\u0026thinsp;\u0026plusmn;\u0026thinsp;0.92\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLast follow-up\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e4.24\u0026thinsp;\u0026plusmn;\u0026thinsp;0.79\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"4\" nameend=\"c4\" namest=\"c1\"\u003e\u003cp\u003eFCAS ROM\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePreoperative\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e7.05\u0026thinsp;\u0026plusmn;\u0026thinsp;2.38\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e6.61\u0026thinsp;\u0026plusmn;\u0026thinsp;2.37\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.400\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2 years follow-up\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e7.93\u0026thinsp;\u0026plusmn;\u0026thinsp;1.47\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e10.73\u0026thinsp;\u0026plusmn;\u0026thinsp;3.05\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLast follow-up\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e8.88\u0026thinsp;\u0026plusmn;\u0026thinsp;1.63\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e12.50\u0026thinsp;\u0026plusmn;\u0026thinsp;2.60\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"4\" nameend=\"c4\" namest=\"c1\"\u003e\u003cp\u003eFCAS disc height\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePreoperative\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e8.88\u0026thinsp;\u0026plusmn;\u0026thinsp;1.40\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e8.91\u0026thinsp;\u0026plusmn;\u0026thinsp;1.44\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.927\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2 years follow-up\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e8.76\u0026thinsp;\u0026plusmn;\u0026thinsp;1.48\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e8.64\u0026thinsp;\u0026plusmn;\u0026thinsp;1.43\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.690\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLast follow-up\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e8.64\u0026thinsp;\u0026plusmn;\u0026thinsp;1.65\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e8.45\u0026thinsp;\u0026plusmn;\u0026thinsp;1.47\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.577\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"4\"\u003eValues are presented as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation.\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd colspan=\"4\"\u003eROM, range of motion; FCAS, first cephalad adjacent segment.\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eLumbosacral X-ray Parameters\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eVariable\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePDS group\u003c/p\u003e\u003cp\u003e(N\u0026thinsp;=\u0026thinsp;42)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eFusion group\u003c/p\u003e\u003cp\u003e(N\u0026thinsp;=\u0026thinsp;44)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP-value\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"4\" nameend=\"c4\" namest=\"c1\"\u003e\u003cp\u003ePI\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePreoperative\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e44.10\u0026thinsp;\u0026plusmn;\u0026thinsp;7.56\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e44.41\u0026thinsp;\u0026plusmn;\u0026thinsp;7.56\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.848\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2 years follow-up\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e43.86\u0026thinsp;\u0026plusmn;\u0026thinsp;7.69\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e43.84\u0026thinsp;\u0026plusmn;\u0026thinsp;7.46\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.992\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLast follow-up\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e43.05\u0026thinsp;\u0026plusmn;\u0026thinsp;6.58\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e43.77\u0026thinsp;\u0026plusmn;\u0026thinsp;6.97\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.622\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"4\" nameend=\"c4\" namest=\"c1\"\u003e\u003cp\u003eSS\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePreoperative\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e35.05\u0026thinsp;\u0026plusmn;\u0026thinsp;5.07\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e36.16\u0026thinsp;\u0026plusmn;\u0026thinsp;6.05\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.360\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2 years follow-up\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e35.40\u0026thinsp;\u0026plusmn;\u0026thinsp;5.32\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e36.39\u0026thinsp;\u0026plusmn;\u0026thinsp;4.83\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.373\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLast follow-up\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e34.86\u0026thinsp;\u0026plusmn;\u0026thinsp;5.68\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e35.95\u0026thinsp;\u0026plusmn;\u0026thinsp;5.39\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.361\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"4\" nameend=\"c4\" namest=\"c1\"\u003e\u003cp\u003eLL\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePreoperative\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e41.00\u0026thinsp;\u0026plusmn;\u0026thinsp;6.21\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e41.82\u0026thinsp;\u0026plusmn;\u0026thinsp;7.05\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.570\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2 years follow-up\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e42.36\u0026thinsp;\u0026plusmn;\u0026thinsp;7.23\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e43.41\u0026thinsp;\u0026plusmn;\u0026thinsp;6.89\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.491\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLast follow-up\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e44.17\u0026thinsp;\u0026plusmn;\u0026thinsp;6.59\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e44.75\u0026thinsp;\u0026plusmn;\u0026thinsp;6.36\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.677\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"4\"\u003eValues are presented as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation.\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd colspan=\"4\"\u003ePI, pelvic incident angle; SS, sacral tilt angle; LL, lumbar lordosis.\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eFCAS MRI Pfirrmann Classification\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePDS group\u003c/p\u003e\u003cp\u003e(N\u0026thinsp;=\u0026thinsp;42)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003eFusion group\u003c/p\u003e\u003cp\u003e(N\u0026thinsp;=\u0026thinsp;44)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e\u003cp\u003ePreoperative\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"1\" nameend=\"c4\" namest=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eGrade 1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e23\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003e23\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eGrade 2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e14\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003e17\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eGrade 3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003e4\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eGrade 4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eGrade 5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e\u003cp\u003eLast follow-up\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"1\" nameend=\"c4\" namest=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eGrade 1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e23\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003e21\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eGrade 2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e13\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003e16\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eGrade 3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003e4\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eGrade 4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eGrade 5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e"},{"header":"DISCUSSION","content":"\u003cp\u003eAs an alternative to rigid fusion, PDS systems use pedicle screw instrumentation to create a semi-mobile construct. This approach aims to alleviate pain caused by pathological motion while preserving residual mobility in unaffected segments[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. However, the long-term efficacy of PDS remains controversial, especially regarding its ability to prevent or reduce ASD compared to fusion[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. Although the exact pathogenesis of ASD is unclear[\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e], in vitro studies suggest that loss of ROM at the operated level may alter the biomechanics of adjacent segments, accelerating their degeneration[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. Notably, increased motion tends to occur at the cranial adjacent segment, which may explain its higher susceptibility to ASD[\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. Therefore, this study focused on the relationship between cranial adjacent segment ROM and ASD occurrence.\u003c/p\u003e\u003cp\u003eOur results showed no significant differences in BMI or lumbosacral sagittal parameters between groups. All patients were under 60 years old, below the World Health Organization\u0026rsquo;s elderly threshold. In the PDS group, approximately 59% of surgical segment ROM was preserved at two years postoperatively and maintained through a minimum five-year follow-up. In contrast, surgical segment ROM was nearly abolished in the fusion group. Both groups exhibited increased cranial adjacent segment ROM; however, the increase was significantly greater in the fusion group. Correspondingly, the fusion group had a higher incidence of both ASDeg and ASDis, suggesting a protective effect of PDS consistent with previous studies. One patient in the fusion group initially presented with severe low back pain and bilateral lower limb pain. Preoperative imaging showed L4/5 spinal stenosis and instability of the L4 vertebra, with an FCAS disc height of 8.21 mm and a ROM of 3.8\u0026deg;. After three months of unsuccessful conservative treatment, the patient underwent L4/5 TLIF, resulting in significant symptom relief. However, during routine follow-up, the patient experienced recurrent lower limb pain. Imaging revealed degeneration of both cranial and caudal adjacent segments, with the L3/4 FCAS disc height decreasing to 6.75 mm (a 1.46 mm reduction) and ROM increasing to 7.6\u0026deg;, twice the preoperative value. The Pfirrmann grade of the cranial adjacent segment progressed from 3 to 5. These findings suggest that compensatory increased mobility\u0026mdash;particularly at the cranial L3/4 segment following fusion\u0026mdash;accelerated adjacent segment degeneration and led to nerve compression symptoms. After failed conservative management, revision surgery significantly alleviated symptoms (see Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e). Beyond this revision, no mechanical complications\u0026mdash;such as screw breakage, rod fracture, or screw loosening\u0026mdash;were observed in either group. Compared to rigid fixation, the PDS system offers greater biomechanical flexibility, reducing the risk of screw breakage. However, retained mobility may increase the risk of screw loosening[\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. The absence of such complications in our study may be attributed to (1) limited destabilization from fenestration decompression, (2) exclusion of patients with severe osteoporosis, and (3) a relatively short follow-up period. Although radiographic screw loosening can be concerning, prior studies indicate it does not significantly affect clinical outcomes (e.g., VAS, ODI, JOA scores)[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e], possibly due to unintended facet joint fusion following PDS\u0026mdash;reported in over 50% of patients in some series. The likelihood of unintended fusion and subsequent motion loss increases with age, particularly in patients over 60[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. Therefore, we believe the cost-effectiveness of PDS is lower in elderly individuals. Accordingly, patients over 60 were excluded from this study for two reasons: (1) reduced physical activity in older adults diminishes the clinical relevance of motion preservation, and (2) more advanced adjacent segment degeneration in this population may lead to suboptimal outcomes with PDS compared to fusion.\u003c/p\u003e\u003cp\u003eA recent biomechanical study investigated the effects of dynamic stabilization systems on spinal kinematics using rods of five different stiffness levels to stabilize the L4\u0026ndash;5 segment. The results showed that increasing construct stiffness progressively reduced ROM and intradiscal pressure at the stabilized level, while simultaneously increasing both parameters at the cranial adjacent level (L3\u0026ndash;4). The authors concluded that greater stiffness at the index segment limits its mobility and induces compensatory hypermobility in adjacent segments[\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. These in vitro findings align with finite element analyses, which suggest that dynamic stabilization preserves segmental motion, enabling more balanced load distribution and reducing excessive adjacent segment motion[\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. Jahng et al.[\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e] performed a finite element analysis comparing various fixation techniques in terms of six degrees of freedom and the center of rotation (COR) in the lumbar spine. The K-rod system preserved greater flexion-extension and lateral bending ROM than traditional titanium rods. Notably, although a posterior shift in COR was commonly observed postoperatively, the K-rod group maintained a COR position closer to physiological norms. The authors emphasized that altered COR may elevate mechanical stress on adjacent segments and implants, increasing the risk of degeneration and mechanical failure. In a long-term follow-up study, Hoppe et al.[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e] treated L5\u0026ndash;S1 degenerative spondylolisthesis with PDS and reported a 28% ASD incidence after an average of 7 years. In 74% of cases, the index-level flexion-extension ROM was less than 4\u0026deg;, which the authors interpreted as a functional fusion state and a potential ASD risk factor. In our study, the PDS group preserved approximately 55% of index-level ROM at final follow-up (mean 4.24\u0026deg;), with only one case of ASDeg (2.38%), which required no intervention. In a representative case, surgical segment ROM decreased from 9.13\u0026deg; preoperatively to 5.11\u0026deg; postoperatively, while FCAS ROM slightly increased from 6.89\u0026deg; to 7.36\u0026deg;. This patient retained\u0026thinsp;~\u0026thinsp;60% of preoperative ROM and showed favorable clinical outcomes without ASDeg (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eLumbosacral sagittal alignment also plays a key role in ASD development. Although no significant differences in sagittal parameters were found between groups in our study, previous research highlights the importance of restoring lumbar lordosis to maintain biomechanical balance and reduce adjacent segment stress[\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. Restoration of lordosis is associated with a lower ASD risk. Some studies suggest that PDS systems support more natural lordosis restoration by preserving segmental motion and promoting physiological alignment. In contrast, rigid fusion\u0026mdash;despite offering strong stabilization\u0026mdash;may restrict lordosis correction and lead to less optimal biomechanical results. Furthermore, successful lordosis restoration in fusion relies heavily on surgical technique, particularly rod contouring and cage insertion depth, both of which critically influence sagittal reconstruction.\u003c/p\u003e\u003cp\u003eAlthough both the PDS and fusion groups showed significant improvements in VAS and ODI scores, no statistically significant differences were observed between groups at any follow-up point. However, the PDS group demonstrated distinct advantages, including shorter operative time and reduced intraoperative blood loss, thereby minimizing perioperative trauma\u0026mdash;findings consistent with previous reports[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. These differences likely reflect the inherent procedural characteristics. Fusion surgery involves a more extensive workflow, including removal of the cartilaginous endplate, exposure of the bony endplate, bone grafting, and cage implantation. In contrast, PDS eliminates the need for grafting and fusion, often requiring only excision of herniated nucleus pulposus tissue. In some cases, the intervertebral disc remains largely intact, preserving disc height and segmental stability. Moreover, fusion surgery typically results in greater blood loss due to longer operative time and increased bleeding from endplate preparation. The comparable clinical outcomes between the two approaches are likely attributable to adequate neural decompression, rather than interbody fusion per se. That said, the relatively short follow-up period in this study may not be sufficient to fully evaluate the potential long-term benefits of non-fusion techniques. Additionally, by avoiding bone grafting, PDS eliminates complications related to autograft harvesting (e.g., donor site pain, hematoma, fracture) and the rare risk of disease transmission from allografts[\u003cspan additionalcitationids=\"CR8 CR9\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eAs ASD most commonly affects the cranial adjacent segment, this study primarily focused on changes at that level and did not systematically assess the surgical disc itself\u0026mdash;an acknowledged limitation. Nonetheless, prior studies have explored the potential regenerative effects of PDS on the operated disc[\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. Because the nucleus pulposus is avascular, nutrient exchange relies on pressure gradients generated by spinal motion. This \"pumping effect,\" driven by cyclic loading, promotes fluid circulation, maintains hydration, and facilitates nutrient transport[\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. Disc cell viability and extracellular matrix metabolism depend on moderate, periodic mechanical stimulation; decreased mobility can result in disc dehydration, cell apoptosis, and matrix degradation[\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]. A retrospective study reported increased T2-weighted MRI signal intensity in the nucleus pulposus following dynamic stabilization, suggesting disc rehydration after an average follow-up of 46.7 months[\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eCurrent evidence suggests that ASD is a multifactorial process influenced by age, BMI, lumbosacral sagittal alignment, ROM at the index level, and the number of fused segments. Among these, surgical segment ROM appears to be a key determinant[\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan additionalcitationids=\"CR29 CR30\" citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. Both biomechanical and finite element studies have demonstrated a strong association between reduced segmental motion and adjacent segment degeneration. While the K-rod dynamic stabilization system provides clinical outcomes comparable to fusion, it also offers advantages such as shorter operative time, less blood loss, and potentially lower ASD incidence. Nevertheless, the system has limitations. Although it offers posterior column support, it provides limited stabilization to the anterior and middle columns\u0026mdash;especially after partial discectomy, which may further compromise anterior stability. However, in our study, this did not significantly affect lumbar lordosis. Additionally, the system permits motion not only in flexion-extension but also in lateral bending, complicating assessment of how preserved mobility impacts adjacent segment biomechanics. Finally, the long-term clinical significance of ASD remains uncertain. In many cases, its impact on overall outcomes appears minimal, potentially diminishing the theoretical advantage of PDS in preventing ASD[\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThis study has several limitations. First, as a single-center retrospective study, it is subject to inherent selection and assessment biases. Second, given the biomechanical variability among different pedicle-based dynamic stabilization systems, our results may not be generalizable to other devices. Third, the relatively short follow-up period and limited sample size may restrict the strength and external validity of our conclusions. Lastly, ASD may partly reflect natural spinal aging and cannot be entirely attributed to surgical intervention[\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]. Future research should include a non-instrumented control group to better delineate the treatment-specific effects.\u003c/p\u003e"},{"header":"CONCLUSION","content":"\u003cp\u003eThe PDS system achieved clinical outcomes comparable to spinal fusion in treating single-level lumbar degenerative disease, while providing additional benefits such as shorter operative time, reduced intraoperative blood loss, preservation of segmental motion, and potentially less impact on adjacent segments. Long-term follow-up revealed a lower incidence of FCAS ASDeg and ASDis in the PDS group compared to fusion. These results suggest that, for appropriately selected patients, the PDS system represents a viable and advantageous alternative to conventional fusion surgery.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe project protocols were reviewed and approved by the ethnic committee of Southwest Hospital, Army Medical University ((B) KY2025100).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to Participate Statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study utilizes retrospectively collected clinical data obtained during routine diagnosis and treatment. The research involves no commercial interests and does not involve direct human intervention, interaction for biological sample collection, or additional data acquisition. The study does not affect participants\u0026apos; diagnosis or treatment and poses no physiological risks. A waiver of informed consent was approved by the Ethics Committee of Southwest Hospital, Army Medical University.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe dataset analyzed for this study is available from the corresponding author upon reasonable request.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical trial number: \u003c/strong\u003enot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe research has been funded by Chongqing Science and Health Joint Medical Research (2025ZDXM002) and Chongqing Talent Plan (CQYC202105037).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026apos; contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eConceptualization: FD, FL, JZX, JYH, ZHZ; Formal Analysis: JZD, YX, RNB, SL, ZQY, CMZ; Data curation: JZD, YX, RNB, SL, ZQY, CMZ; Methodology: JZD, YX, JYH, ZHZ; Project administration: FL, JZX, JYH, ZHZ; Writing \u0026ndash; Original Draft: JZD, YX; Writing \u0026ndash; Review \u0026amp; Editing: JYH, ZHZ; Funding acquisition: ZHZ; All authors read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements \u0026nbsp;\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003ePrud'homme M, Barrios C, Rouch P, Charles YP, Steib JP, Skalli W. 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Intervertebral disc rehydration after lumbar dynamic stabilization: magnetic resonance image evaluation with a mean followup of four years. Adv Orthop. 2013;2013:437570.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBowles RD, Setton LA. Biomaterials for intervertebral disc regeneration and repair. Biomaterials. 2017;129:54\u0026ndash;67.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eGuan J, Liu T, Yu X, Li W, Feng N, Jiang G, Zhao H, Yang Y. Biomechanical and clinical research of Isobar semi-rigid stabilization devices for lumbar degenerative diseases: a systematic review. Biomed Eng Online. 2023;22(1):95.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMannion AF, Leivseth G, Brox JI, Fritzell P, H\u0026auml;gg O, Fairbank JC. ISSLS Prize winner: Long-term follow-up suggests spinal fusion is associated with increased adjacent segment disc degeneration but without influence on clinical outcome: results of a combined follow-up from 4 randomized controlled trials. Spine (Phila Pa 1976). 2014;39(17):1373\u0026ndash;83.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eKumar MN, Baklanov A, Chopin D. Correlation between sagittal plane changes and adjacent segment degeneration following lumbar spine fusion. Eur Spine J. 2001;10(4):314\u0026ndash;9.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-musculoskeletal-disorders","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bmsd","sideBox":"Learn more about [BMC Musculoskeletal Disorders](http://bmcmusculoskeletdisord.biomedcentral.com/)","snPcode":"","submissionUrl":"https://author-welcome.nature.com/12891","title":"BMC Musculoskeletal Disorders","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Single level, Posterior Dynamic Stabilization, Fusion, Adjacent Segment Degeneration, Long Follow-up","lastPublishedDoi":"10.21203/rs.3.rs-6946140/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6946140/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eObjective\u003c/h2\u003e\u003cp\u003eTo evaluate the efficacy of posterior dynamic stabilization (PDS) in treating single-level lumbar degenerative disease and to examine its effect on first cephalad adjacent segment (FCAS) degeneration.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e\u003cp\u003eThis retrospective study included 97 patients who underwent single-level lumbar fusion or PDS between April 2010 and April 2012. Clinical outcomes were assessed using the Visual Analog Scale (VAS) and Oswestry Disability Index (ODI) preoperatively and postoperatively. Radiographic analysis quantified the range of motion (ROM) at the surgical segment, FCAS, and entire lumbar spine. Magnetic resonance imaging (MRI) was used to evaluate degenerative changes in the FCAS.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e\u003cp\u003eEighty-six patients completed a minimum 5-year follow-up and were categorized into two groups: the PDS group (n\u0026thinsp;=\u0026thinsp;42) and the fusion group (n\u0026thinsp;=\u0026thinsp;44). Baseline demographic and clinical characteristics were comparable between groups (all P\u0026thinsp;\u0026gt;\u0026thinsp;0.05). Both groups showed significant postoperative improvements in VAS and ODI scores (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05), with no significant intergroup differences at any time point. The PDS group had significantly shorter operative times and less intraoperative blood loss than the fusion group (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05). Radiographic evaluation demonstrated that the K-rod dynamic system partially preserved ROM at the surgical level over 5 years and limited the increase in FCAS ROM compared to the fusion group (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05). Postoperative lumbosacral alignment parameters were similar between groups. During follow-up, one case of radiographic adjacent segment degeneration (ASDeg) occurred in the PDS group, while the fusion group showed five cases of ASDeg and one case of symptomatic adjacent segment degeneration (ASDis) requiring revision surgery.\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e\u003cp\u003ePDS effectively preserves motion at the surgical segment and has a smaller impact on FCAS mobility. Over long-term follow-up, the incidence of ASDeg and ASDis was lower in the PDS group compared to fusion surgery.\u003c/p\u003e","manuscriptTitle":"K-rod Posterior Dynamic Stabilization Could Reduce Adjacent Segment Degeneration: A Mi nimum 5-Year Follow-up","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-07-23 19:24:52","doi":"10.21203/rs.3.rs-6946140/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"editorInvitedReview","content":"","date":"2025-08-04T02:21:42+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"221122236046328226284235446296404261724","date":"2025-07-28T07:40:27+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-07-21T05:27:48+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-06-30T10:56:11+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-06-27T07:50:07+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-06-27T07:49:50+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Musculoskeletal Disorders","date":"2025-06-21T16:29:37+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-musculoskeletal-disorders","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bmsd","sideBox":"Learn more about [BMC Musculoskeletal Disorders](http://bmcmusculoskeletdisord.biomedcentral.com/)","snPcode":"","submissionUrl":"https://author-welcome.nature.com/12891","title":"BMC Musculoskeletal Disorders","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"dc821194-5d09-45f5-b0a9-904d00da850f","owner":[],"postedDate":"July 23rd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2025-07-23T19:24:52+00:00","versionOfRecord":[],"versionCreatedAt":"2025-07-23 19:24:52","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6946140","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6946140","identity":"rs-6946140","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}