Reoperation Risk by Subtype in Proximal Junctional Kyphosis and the Impact of Osteoporosis Treatment in Adult Spinal Deformity Surgery

Reoperation Risk by Subtype in Proximal Junctional Kyphosis and the Impact of Osteoporosis Treatment in Adult Spinal Deformity Surgery | 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 Reoperation Risk by Subtype in Proximal Junctional Kyphosis and the Impact of Osteoporosis Treatment in Adult Spinal Deformity Surgery Tetsuro Ohba, Tanaka Nobuki, Kotaro Oda, Hayato Takei, Kai Mizukami, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6487108/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Purpose Proximal junctional kyphosis (PJK) is a common mechanical complication following adult spinal deformity (ASD) surgery. Although various preventive strategies exist, the clinical relevance of PJK subtypes and the impact of osteoporosis medications remain unclear. This study examined which PJK subtypes and grades are most associated with reoperation and evaluates whether osteoporosis treatment, particularly teriparatide, affects PJK incidence or severity. Methods This retrospective study included 189 patients who underwent long spinal fusion for ASD. PJK was classified by type (0–3) and grade (0–C). Osteoporosis medication use and bone mineral density (BMD) were recorded. Reoperation rates were compared across subtypes and treatment groups using the chi-square test and analysis of variance. Results Type 2 (vertebral fracture) and Type 3 (implant failure) PJK were significantly associated with higher reoperation rates (p < 0.0001). Patients with lower BMD exhibited a significantly higher prevalence of Type 2 PJK (p = 0.0082), whereas teriparatide users showed a significantly lower incidence of Type 2 PJK (p = 0.0141 vs. Type 0) as well as a trend toward fewer reoperations. Preoperative teriparatide administration was linked to the lowest revision rate among treatment groups. Conclusion PJK subtype and BMD strongly predicted reoperation after ASD surgery. Teriparatide may reduce structural PJK risk, especially when used preoperatively. Prevention strategies should be tailored to PJK subtype and bone quality. Proximal junctional kyphosis Adult spinal deformity Reoperation Teriparatide Osteoporosis treatment Figures Figure 1 Figure 2 Figure 3 Introduction Adult spinal deformity (ASD) surgery has advanced markedly over recent years; however, mechanical complications remain a major concern, with proximal junctional kyphosis (PJK) among the most prevalent and impactful. PJK occurs in up to 20–40% of cases following long spinal fusion, with ~ 20% of these patients ultimately requiring revision surgery due to progressive kyphosis, implant failure, or intractable pain [1–3]. PJK has been linked to decreased health-related quality-of-life, sagittal imbalance, and limited walking ability [4–7]. Although numerous risk factors have been proposed, including excessive postoperative correction, upper thoracic fusion, older age, and paraspinal muscle loss, no definitive preventive strategy has been established [8–10]. Surgical techniques, such as transition rods, prophylactic hooks, and ligament augmentation, have been explored, but none have shown consistent efficacy across patient populations [11, 12]. These challenges underscore the complexity of PJK pathogenesis and the need to identify modifiable risk factors. Emerging evidence suggests that bone quality is critical to postoperative outcomes in ASD surgery. Osteoporotic bone is associated with higher risks of proximal junctional failure, pedicle screw loosening, rod fracture, and pseudarthrosis. Consequently, bone-modifying agents have garnered attention as a means of improving surgical outcomes. For example, teriparatide, a recombinant parathyroid hormone analog, has been shown to promote spinal fusion and reduce complications (e.g., implant loosening and PJK) in preclinical and clinical studies [13]. The roles of denosumab and romosozumab, which act via different mechanisms on bone metabolism, have also been reported [14]. Nevertheless, it remains unclear whether the type or timing of osteoporosis treatment affects PJK risk or the need for revision surgery in clinical practice. Although often treated as a single complication, PJK is radiologically and clinically heterogeneous. Classification systems categorize PJK by failure mechanism, including ligamentous failure, vertebral fracture, and implant-related causes. A grading system based on angular progression severity has also been associated with clinical outcomes [3]. However, few studies have examined how PJK subtypes or grades relate to the likelihood of revision surgery. To improve perioperative management and personalize treatment strategies, it is essential to acknowledge that not all PJKs have equal clinical impact. This study had two objectives. First, we aimed to determine whether specific PJK subtypes or grades are associated with a higher likelihood of reoperation following ASD surgery. Second, we evaluated whether osteoporosis medications, particularly the type and timing of administration, affect the incidence and severity of PJK or the need for revision surgery. Materials and Methods Study Design and Patient Selection This retrospective cohort study included patients aged > 60 years old, diagnosed with ASD characterized by sagittal or coronal imbalance, who underwent corrective spinal fusion at a single center between April 2016 and March 2023. The study was approved by the Institutional Review Board (No. 1183), and informed consent was obtained from all participants. Surgical indications included structural ASD unresponsive to prolonged conservative management. Inclusion criteria were as follows: age > 60 years and radiographic confirmation of ASD, defined by at least one of the following: coronal Cobb angle > 30°, C7 sagittal vertical axis (SVA) > 5 cm, or pelvic tilt (PT) > 30°. Only patients with de novo degenerative deformities were included; secondary scoliosis from adolescent idiopathic scoliosis (AIS) was excluded. Additional exclusion criteria included ankylosing spondylitis, Parkinson’s disease-associated deformity, prior AIS, procedures without iliac screw fixation, or follow-up < 2 years. All surgeries were performed by two experienced spinal surgeons, with iliac screw fixation employed in every case. Demographic and surgical characteristics, including age, bone mineral density (BMD), fusion level, and surgical approach, were recorded (Table 1). Surgical Procedures Surgical correction involved a lateral interbody fusion at L1–L5 via an anterior approach, followed by posterior lumbar interbody fusion at L5–S1 after repositioning the patient into the prone position. Sagittal realignment was achieved using a cantilever technique with bilateral S1 screws and supplemental iliac fixation. Osteotomies were performed as needed for limited spinal flexibility, categorized by the Scoliosis Research Society-Schwab osteotomy classification (grades 1–6). Fusion material included autologous and allograft bone; bone morphogenetic proteins were not used. Radiographic Evaluation Full-spine lateral radiographs were obtained preoperatively, at 4–6 weeks postoperatively, and at the 2-year follow-up, with patients in a freestanding posture and their hands placed on the clavicles. Parameters measured included thoracic kyphosis (T5–T12), thoracolumbar kyphosis (T10–L2), lumbar lordosis (T12–S1), pelvic incidence, PT, sacral slope, SVA, T1 pelvic angle, and global tilt. The lordosis distribution index was derived from the L1–S1 and L4–S1 angles. PJK was defined as a postoperative increase in the proximal junctional angle (PJA) of ≥ 10° and at least 10° greater than the preoperative measurement, following the criteria proposed by Yagi et al. [3]. PJK was also classified by failure mechanism into three types: Type 1: soft tissue and ligamentous failure; Type 2: vertebral fracture; Type 3: implant or bone–implant interface failure. Severity was graded based on angular progression: Grade A: PJA increase of 10°–14°; Grade B: PJA increase of 15°–19°; Grade C: PJA increase ≥ 20°. Radiographs were independently evaluated by two board-certified spine surgeons (blinded to clinical data), with their average used for analysis. Inter-rater reliability was confirmed by an intraclass correlation coefficient of 0.882. Statistical Analysis Continuous variables were presented as means ± standard deviations (SD), whereas categorical variables were shown as counts and percentages. The Shapiro–Wilk test was used to assess data normality. For comparisons between two groups, the Student’s t -test was applied to normally distributed data, whereas the Mann–Whitney U test was used for nonparametric data. For comparisons among more than two groups, one-way analysis of variance (ANOVA) was employed, followed by Tukey’s test applied post-hoc. The chi-square test or Fisher’s exact test was used to compare categorical variables as appropriate. The relationship between BMD and complication types was assessed via one-way ANOVA and Tukey’s post-hoc test. All statistical analyses were performed using GraphPad Prism version 8.0 (GraphPad Software, Boston, MA, USA). A two-sided p-value < 0.05 was considered statistically significant, and the Bonferroni correction was applied for multiple comparisons when appropriate. Results Patient Characteristics In total, 189 patients who underwent surgery for ASD were included. The mean age was 72.1 ± 7.4 years, and 88.9% of patients were female (n = 168). The average body mass index was 24.1 ± 2.8 kg/m², and the average BMD, expressed as a percentage of the young adult mean (%YAM), was 74.5% ± 15.6%. The upper instrumented vertebra was at T9–T11 in 145 cases (76.7%) and at T8 or above in 44 cases (23.3%). Osteoporosis Medication Use For osteoporosis management, 44.4% of patients were not receiving bone-modifying agents at the time of surgery. Among those being treated, 19.6% received bisphosphonates, 13.8% received teriparatide, 10.1% received denosumab, and 3.2% received romosozumab. Selective estrogen receptor modulators were used in 4.8% of cases. Among 65 patients receiving preoperative teriparatide, the mean preoperative treatment duration was 4.1 ± 3.1 months. Additionally, 32 patients received teriparatide only postoperatively. Incidence of PJK and Reoperation Rates PJK occurred in 95 of 189 patients (50.3%). Distribution by PJK type was Type 0, 1, 2, and 3 in 94 (49.7%), 33 (17.5%), 42 (22.2%), and 13 (6.9%) cases, respectively. Reoperation rates varied significantly by PJK type (p < 0.0001). Type 3 had the highest reoperation rate (69.2%), followed by Type 2 (38.1%), Type 1 (6.1%), and Type 0 (2.1%) (Figure 2). A similar trend was observed when stratified by PJK grade (p < 0.0001). Reoperation occurred in 2.2%, 25.0%, 32.1%, and 55.6% of Grade 0, A, B, and C cases, respectively (data not shown). BMD: Association with PJK and Reoperation Although patients who underwent reoperation had a lower mean BMD compared with those who did not (70.2 ± 13.2 vs. 75.5 ± 13.5 %YAM), the difference was not statistically significant ( p = 0.1940). Similarly, a nonsignificant trend toward lower BMD was observed in patients with PJK compared to those without (73.0 ± 13.8 vs. 78.4 ± 14.0 %YAM, p = 0.0543) (Table 3). Stratified by PJK type, a significant difference in BMD was found ( p = 0.0082, one-way ANOVA). Post-hoc analysis revealed that patients with Type 2 PJK had significantly lower BMD compared to those with Type 0 ( p = 0.0141), whereas no significant differences were observed between Type 2 and the other types (Table 4). Among 42 patients with Type 2 PJK, the reoperation rate of 38.1% was the second highest among all types. Additionally, Type 2 cases in the lowest BMD tertile had numerically higher but nonsignificant reoperation rates. Effect of Teriparatide on PJK Type and Grade A subgroup analysis comparing patients treated with teriparatide with those who received no osteoporosis medication revealed significant differences in PJK type distribution ( p = 0.0002; Figure 2). The teriparatide-treated group had a higher proportion of Type 0 (59 cases) and Type 1 (21 cases), with fewer Type 2 (11 cases) and Type 3 (6 cases), compared to the group receiving no osteoporosis medication (Type 2: 23 cases; Type 3: 6 cases). Similarly, PJK grade distribution differed significantly between the groups ( p = 0.0153; Figure 2). The teriparatide-treated group had more Grade 0 and fewer Grades B and C cases, suggesting a potential benefit of the drug in reducing PJK severity. Reoperation Rate Based on Teriparatide Administration The reoperation rate was 20.7% and 15.5% in the groups receiving no osteoporosis medication and teriparatide, respectively (Figure 2), with no significant difference detected ( p = 0.5410). Among patients with Type 2 PJK, the reoperation rate was higher in the teriparatide group (63.6%, 7 of 11 cases) than in the group receiving no osteoporosis medication (34.8%, 8 of 23 cases; Figure 2), although the difference was nonsignificant ( p = 0.1512, Fisher’s exact test). Impact of Teriparatide Timing on Reoperation Patients were also grouped by the timing of teriparatide administration: preoperatively only, postoperatively only, and no administration. The reoperation rate was lowest in the preoperatively only group (13.8%), followed by the postoperatively only (18.8%), and the no administration (20.7%) groups, although no statistically significant difference was observed. Discussion In this retrospective cohort study of patients undergoing long spinal fusion for ASD, we identified several key findings regarding the relationship between PJK subtype, BMD, and osteoporosis treatment. First, we found that patients with Type 2 and Type 3 PJK were associated with significantly higher reoperation rates compared to those with Types 0 and 1, underscoring the prognostic value of subclassifying PJK beyond its presence or absence. Second, lower BMD was associated with more severe PJK subtypes, particularly Type 2, with a nonsignificant trend toward increased revision also observed. Although prior studies have suggested a link between bone quality and mechanical failure, our findings emphasize the importance of routine preoperative BMD screening and risk stratification in ASD surgery planning. Third, although teriparatide use did not significantly reduce the overall reoperation rate, patients receiving it preoperatively had numerically fewer revisions than those treated postoperatively or not at all. These findings suggest that both the use and timing of bone-modifying agents may influence surgical outcomes, warranting further prospective investigation. Our results align with prior studies highlighting worse outcomes in structural PJK types, such as vertebral fractures (Type 2) and implant-related failures (Type 3). These forms have been linked to poorer clinical outcomes and higher revision rates compared with ligamentous failure or angular deformities without collapse. Similarly, hardware failure at the proximal junction has consistently predicted reoperation [15, 16]. Although some studies have emphasized angular progression (i.e., PJA) in assessing PJK, morphological classification may better reflect the mechanical instability and clinical implication of each subtype. Our findings support an integrated approach using both angular and structural criteria in postoperative surveillance and risk prediction. The beneficial effects of anabolic agents, such as teriparatide, on spinal fusion and implant integrity have been well-documented in short-segment fusion [17][18]. Thus, there is a growing consensus that anabolic therapy enhances early postoperative spinal stability in patients with osteoporosis. However, the role of such agents in long-segment fusion for ASD remains unclear. Surgical correction for ASD often involves extensive fixation and alignment changes, with outcomes dependent on multiple interrelated factors, including sagittal balance restoration, fusion range, and baseline bone quality. Although numerous studies have addressed the elevated risk of PJK and failure in osteoporotic patients undergoing ASD surgery, standardized pharmacologic prevention strategies have yet to be established. Prospective studies have begun to fill this gap. Perioperative administration of teriparatide has been shown to reduce PJF incidence more effectively relative to antiresorptive agents, such as denosumab, although its efficacy in preventing overall PJK remains uncertain. Notably, preoperative use of teriparatide has been associated with improvements in trabecular bone microarchitecture and a reduction in vertebral fracture-type PJK [13, 14, 19-22]. These data suggest that anabolic agents may play a valuable role in mitigating structural complications, particularly those related to bone fragility. Our findings align with previous studies: patients who received teriparatide exhibited a significantly lower incidence of Type 2 PJK and a numerically but nonsignificantly reduced reoperation rate. However, no significant differences were observed among other PJK types. These results indicate that the benefit of osteoporosis therapy in ASD may depend not only on the presence of treatment but also on its timing and the biomechanical characteristics of the complication. Prospective studies stratified by complication subtype and treatment timing are warranted to validate these trends. A key strength of this study lies in its detailed characterization of PJK subtypes and their differential impact on reoperation risk. By subclassifying PJK by morphologic type and angular grade, we showed that not all PJKs have equivalent clinical implications, particularly highlighting the structural vulnerability and clinical severity of Type 2 lesions. Moreover, this study is among the few to integrate radiographic and pharmacologic variables, including BMD and osteoporosis medication timing, into the evaluation of postoperative mechanical complications following long-segment ASD surgery. Despite these strengths, several limitations must be acknowledged. First, the retrospective design and single center setting may limit the generalizability of our findings. Second, although we stratified patients by medication type and timing, the exact duration and adherence to preoperative therapy, especially with agents such as teriparatide, could not be consistently verified. Given emerging evidence that treatment efficacy may be dose- and time-dependent, this represents a critical area for further prospective investigation. Third, we did not assess patient-reported outcomes, such as pain or health-related quality-of-life, limiting our ability to correlate radiographic findings with functional endpoints. Future studies should aim to validate these findings in larger, multicenter cohorts and incorporate stratified analyses based on PJK subtype, baseline bone density, and treatment duration. Establishing the optimal preoperative preparation duration of anabolic therapy may help inform standardized osteoporosis management protocols tailored to patients with ASD at high risk of mechanical failure. Declarations Author Contribution Authors’ contribution statementsConceptualization, T.O. and H.H.; Methodology, N.T, T.H and G.G. Validation, K.O, T.N and T.O.; Formal Analysis, T.O and K.M; Investigation, H.H.; Writing – Original Draft Preparation, T.O.; Writing – Review & Editing, N.T and T.O. Acknowledgement None References Lau D, Clark AJ, Scheer JK, Daubs MD, Coe JD, Paonessa KJ, LaGrone MO, Kasten MD, Amaral RA, Trobisch PD, Lee JH, Fabris-Monterumici D, Anand N, Cree AK, Hart RA, Hey LA, Ames CP, Committee SRSASD (2014) Proximal junctional kyphosis and failure after spinal deformity surgery: a systematic review of the literature as a background to classification development. Spine (Phila Pa 1976) 39:2093-2102. doi: 10.1097/BRS.0000000000000627 Aoun M, Daher M, Daniels AH, Kreichati G, Kharrat K, Sebaaly A (2024) The predictive power of the Roussouly classification on mechanical complications after surgery for adult spinal deformity: systematic review and meta-analysis. Eur Spine J. doi: 10.1007/s00586-024-08596-w Yagi M, King AB, Boachie-Adjei O (2012) Incidence, risk factors, and natural course of proximal junctional kyphosis: surgical outcomes review of adult idiopathic scoliosis. Minimum 5 years of follow-up. Spine (Phila Pa 1976) 37:1479-1489. doi: 10.1097/BRS.0b013e31824e4888 Glattes RC, Bridwell KH, Lenke LG, Kim YJ, Rinella A, Edwards C, 2nd (2005) Proximal junctional kyphosis in adult spinal deformity following long instrumented posterior spinal fusion: incidence, outcomes, and risk factor analysis. Spine (Phila Pa 1976) 30:1643-1649 Kim YJ, Lenke LG, Bridwell KH, Kim J, Cho SK, Cheh G, Yoon J (2007) Proximal junctional kyphosis in adolescent idiopathic scoliosis after 3 different types of posterior segmental spinal instrumentation and fusions: incidence and risk factor analysis of 410 cases. Spine (Phila Pa 1976) 32:2731-2738. doi: 10.1097/BRS.0b013e31815a7ead Kim HJ, Bridwell KH, Lenke LG, Park MS, Ahmad A, Song KS, Piyaskulkaew C, Hershman S, Fogelson J, Mesfin A (2013) Proximal junctional kyphosis results in inferior SRS pain subscores in adult deformity patients. Spine (Phila Pa 1976) 38:896-901. doi: 10.1097/BRS.0b013e3182815b42 Yagi M, Rahm M, Gaines R, Maziad A, Ross T, Kim HJ, Kebaish K, Boachie-Adjei O, Complex Spine Study G (2014) Characterization and surgical outcomes of proximal junctional failure in surgically treated patients with adult spinal deformity. Spine (Phila Pa 1976) 39:E607-614. doi: 10.1097/BRS.0000000000000266 Ohba T, Ebata S, Oba H, Koyama K, Haro H (2018) Correlation Between Postoperative Distribution of Lordosis and Reciprocal Progression of Thoracic Kyphosis and Occurrence of Proximal Junctional Kyphosis Following Surgery for Adult Spinal Deformity. Clin Spine Surg. doi: 10.1097/bsd.0000000000000702 Protopsaltis TS, Diebo BG, Lafage R, Henry JK, Smith JS, Scheer JK, Sciubba DM, Passias PG, Kim HJ, Hamilton DK, Soroceanu A, Klineberg EO, Ames CP, Shaffrey CI, Bess S, Hart RA, Schwab FJ, Lafage V (2018) Identifying Thoracic Compensation and Predicting Reciprocal Thoracic Kyphosis and PJK in Adult Spinal Deformity Surgery. Spine (Phila Pa 1976). doi: 10.1097/brs.0000000000002843 Ohba T, Koji F, Koyama K, Oba H, Oda K, Tanaka N, Haro H (2021) Preoperative Radiographic Evaluation of Thoracic Flexibility and Compensation for Adult Spinal Deformity Surgery. How to Select Optimal Upper Instrumented Vertebra to Prevent Proximal Junctional Kyphosis. Spine (Phila Pa 1976). doi: 10.1097/brs.0000000000004126 Park HY, Ha KY, Kim YH, Chang DG, Kim SI, Lee JW, Ahn JH, Kim JB (2017) Minimally Invasive Lateral Lumbar Interbody Fusion for Adult Spinal Deformity: Clinical and Radiological Efficacy with Minimum Two Years Follow-up. Spine (Phila Pa 1976). doi: 10.1097/BRS.0000000000002507 Bourghli A, Boissiere L, Larrieu D, Pizones J, Alanay A, Pellisé F, Kleinstück F, Obeid I (2024) Proximal junctional kyphosis after adult spinal deformity operated patients with long fusion to the pelvis. Does the type of proximal anchor matter? Eur Spine J 33:2832-2839. doi: 10.1007/s00586-024-08332-4 Yagi M, Ohne H, Konomi T, Fujiyoshi K, Kaneko S, Komiyama T, Takemitsu M, Yato Y, Machida M, Asazuma T (2016) Teriparatide improves volumetric bone mineral density and fine bone structure in the UIV+1 vertebra, and reduces bone failure type PJK after surgery for adult spinal deformity. Osteoporos Int 27:3495-3502. doi: 10.1007/s00198-016-3676-6 Sawada Y, Takahashi S, Yasuda H, Terakawa M, Konishi S, Kato M, Toyoda H, Suzuki A, Tamai K, Iwamae M, Okamura Y, Kobayashi Y, Nakamura H, Terai H (2024) Effect of romosozumab administration on proximal junctional kyphosis in corrective spinal fusion surgery. The spine journal : official journal of the North American Spine Society. doi: 10.1016/j.spinee.2024.12.021 Reames DL, Kasliwal MK, Smith JS, Hamilton DK, Arlet V, Shaffrey CI (2015) Time to development, clinical and radiographic characteristics, and management of proximal junctional kyphosis following adult thoracolumbar instrumented fusion for spinal deformity. Journal of spinal disorders & techniques 28:E106-114. doi: 10.1097/BSD.0000000000000158 Nicholls FH, Bae J, Theologis AA, Eksi MS, Ames CP, Berven SH, Burch S, Tay BK, Deviren V (2017) Factors Associated With the Development of and Revision for Proximal Junctional Kyphosis in 440 Consecutive Adult Spinal Deformity Patients. Spine (Phila Pa 1976) 42:1693-1698. doi: 10.1097/BRS.0000000000002209 Ebata S, Takahashi J, Hasegawa T, Mukaiyama K, Isogai Y, Ohba T, Shibata Y, Ojima T, Yamagata Z, Matsuyama Y, Haro H (2017) Role of Weekly Teriparatide Administration in Osseous Union Enhancement within Six Months After Posterior or Transforaminal Lumbar Interbody Fusion for Osteoporosis-Associated Lumbar Degenerative Disorders: A Multicenter, Prospective Randomized Study. J Bone Joint Surg Am 99:365-372. doi: 10.2106/JBJS.16.00230 Oba H, Takahashi J, Yokomichi H, Hasegawa T, Ebata S, Mukaiyama K, Ohba T, Ushirozako H, Kuraishi S, Ikegami S, Uehara M, Takizawa T, Munakata R, Hatakenaka T, Matsuyama Y, Haro H (2020) Weekly Teriparatide Versus Bisphosphonate for Bone Union During 6 Months After Multi-Level Lumbar Interbody Fusion for Osteoporotic Patients: A Multicenter, Prospective, Randomized Study. Spine (Phila Pa 1976) 45:863-871. doi: 10.1097/brs.0000000000003426 Sawakami K, Watanabe K, Hasegawa K, Yamamoto N, Shimakura T, Ohashi M, Shoji H, Mizouchi T, Tanaka Y, Segawa H, Ishikawa S, Hirano T, Kawashima H, Endo N, Takahashi HE (2022) Neoadjuvant teriparatide therapy targeting the osteoporotic spine: influence of administration period from the perspective of bone histomorphometry. Journal of neurosurgery Spine 36:429-439. doi: 10.3171/2021.5.Spine202003 Baroudi M, Daher M, Maheshwari K, Singh M, Nassar JE, McDonald CL, Diebo BG, Daniels AH (2024) Surgical Management of Adult Spinal Deformity Patients with Osteoporosis. Journal of clinical medicine 13. doi: 10.3390/jcm13237173 Shen T, Shahzad H, Sierra F, Wick JB, Pina D, Van BW, Vander Voort WD, Kong S, Javidan Y, Roberto RF, Klineberg EO, Le HV (2024) Osteoporosis Treatment and Outcomes in Patients Undergoing Adult Spinal Deformity Surgery. World Neurosurg 190:e1018-e1024. doi: 10.1016/j.wneu.2024.08.053 Park JH, Kwon O, Choi JH, Yeom JS, Park SM, Kim CH, Kim HJ (2025) Perioperative teriparatide for preventing proximal junctional kyphosis and failure in patients with osteoporosis after adult thoracolumbar spinal deformity surgery: a prospective randomized controlled trial. Osteoporos Int. doi: 10.1007/s00198-025-07449-6 Tables Table 1. Baseline characteristics of patients with ASD. Variable ASD (N = 189) Age (years) 72.1 ± 7.4 Female/male (n) 168/21 BMI (kg/m 2 ) 24.1 ± 2.8 BMD (%YAM) 74.5 ± 15.6 Location of UIV(n) Th9-11 145 Th8~ 44 Abbreviations: ASD, adult spinal deformity; BMI, body mass index; BMD, bone mineral density; YAM, young adult mean; UIV, upper instrumented vertebra. Table 2. Osteoporosis medication use in patients with ASD. Medication Number of patients Percentage (%) Teriparatide 97 53.3 None 58 31.9 Deno 8 4.4 Rom 8 4.4 SERM 6 3.3 Bis 5 2.7 Abbreviations: ASD, adult spinal deformity, Bis, bisphosphonate; Deno, denosumab; Rom, romosozumab; SERM, selective estrogen receptor modulator. Table 3. Comparison of bone mineral density based on reoperation and PJK status. Comparison BMD (YAM) BMD (YAM) p-value Reoperation: yes vs. no 69.1 ± 12.8 75.6 ± 14.3 0.0445 PJK: present vs. absent 70.3 ± 13.4 78.1 ± 14.1 0.0008 Abbreviations: PJK, proximal junctional kyphosis; BMD, bone mineral density; YAM, young adult mean. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted 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. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-6487108","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":451072712,"identity":"47b0aced-1da6-4540-af3c-dd4c8d1d2c25","order_by":0,"name":"Tetsuro Ohba","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA6ElEQVRIiWNgGAWjYHACNgaGCiiTsUECTBvgU88D1nKGZC2MbXAtRLjKnr352IOf8w7L67afPfjx5w4LBv72AwzFBfhs4TmWbti77bDhtjN5ydK8ZyQYJM4kMBjPwKdFIsdMgnfbYcZtB3IMpBnbgH65wcBgzENAi+TfOYftt51/Y/zzJ1CLPDFapHkbDiduuwGyDqjFgKCWM8fSjWWOpSdvu/HGzBqohcfwTGIDXr+wtzcfe/imxtp22/kc45s/2+rk5I4fPmaML8SgoBlhLTB22owJ62CoQ+ExPyZCyygYBaNgFIwcAADqokn2cqktfQAAAABJRU5ErkJggg==","orcid":"","institution":"University of Yamanashi","correspondingAuthor":true,"prefix":"","firstName":"Tetsuro","middleName":"","lastName":"Ohba","suffix":""},{"id":451072713,"identity":"f8e39721-b309-4948-9a85-8a1659d7440c","order_by":1,"name":"Tanaka Nobuki","email":"","orcid":"","institution":"University of Yamanashi","correspondingAuthor":false,"prefix":"","firstName":"Tanaka","middleName":"","lastName":"Nobuki","suffix":""},{"id":451072714,"identity":"3b5ee3e8-8c23-4f99-815c-714bf8ea1ad6","order_by":2,"name":"Kotaro Oda","email":"","orcid":"","institution":"University of Yamanashi","correspondingAuthor":false,"prefix":"","firstName":"Kotaro","middleName":"","lastName":"Oda","suffix":""},{"id":451072716,"identity":"57655580-6f05-48be-98a7-27592c4ba0d2","order_by":3,"name":"Hayato Takei","email":"","orcid":"","institution":"University of Yamanashi","correspondingAuthor":false,"prefix":"","firstName":"Hayato","middleName":"","lastName":"Takei","suffix":""},{"id":451072717,"identity":"dcf008a6-e80a-4889-a6bc-72c1b0eaf283","order_by":4,"name":"Kai Mizukami","email":"","orcid":"","institution":"University of Yamanashi","correspondingAuthor":false,"prefix":"","firstName":"Kai","middleName":"","lastName":"Mizukami","suffix":""},{"id":451072718,"identity":"a1c60fc8-d8d4-460a-af1e-62b558c34dc5","order_by":5,"name":"Go Goto","email":"","orcid":"","institution":"University of Yamanashi","correspondingAuthor":false,"prefix":"","firstName":"Go","middleName":"","lastName":"Goto","suffix":""},{"id":451072720,"identity":"727e3909-0075-44cb-9ee5-bbcfcb4b95e6","order_by":6,"name":"Hirotaka Haro","email":"","orcid":"","institution":"University of Yamanashi","correspondingAuthor":false,"prefix":"","firstName":"Hirotaka","middleName":"","lastName":"Haro","suffix":""}],"badges":[],"createdAt":"2025-04-20 02:53:06","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6487108/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6487108/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":82711013,"identity":"7123ad5c-c885-4553-9787-9ae7d8eb0683","added_by":"auto","created_at":"2025-05-14 11:31:27","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":77344,"visible":true,"origin":"","legend":"\u003cp\u003eDistribution of PJK types (0–3) and grades (0–C) among patients who underwent ASD surgery (n = 189). Bar height reflects case frequency; redsegments represent cases requiring revision surgery. Reoperation rates were significantly higher in Types 2 and 3 compared with Types 0 and 1 (\u003cem\u003ep\u003c/em\u003e \u0026lt; 0.0001)\u003c/p\u003e","description":"","filename":"Fig1.png","url":"https://assets-eu.researchsquare.com/files/rs-6487108/v1/5281307ae0725c1d16d875eb.png"},{"id":82712407,"identity":"40e3d2f8-2d10-46d1-aa10-b721af3c9478","added_by":"auto","created_at":"2025-05-14 11:39:27","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":183188,"visible":true,"origin":"","legend":"\u003cp\u003eReoperation rates according to PJK grade. Compared with Grade 0, Grades B and C showed significantly higher revision rates (\u003cem\u003ep\u003c/em\u003e \u0026lt; 0.0001). PJK type distribution differed significantly between the teriparatide-treated and untreated groups, with a lower incidence of Type 2 PJK in the former (\u003cem\u003ep\u003c/em\u003e = 0.0002)\u003c/p\u003e","description":"","filename":"Fig2.png","url":"https://assets-eu.researchsquare.com/files/rs-6487108/v1/261eb41e389cd22627436f18.png"},{"id":82712408,"identity":"93d9de45-4afa-4b88-95b6-6a5a76feffda","added_by":"auto","created_at":"2025-05-14 11:39:27","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":5713,"visible":true,"origin":"","legend":"\u003cp\u003eReoperation rate by osteoporosis treatment group. The revision rate did not differ significantly between the teriparatide-treated and untreated groups (\u003cem\u003ep\u003c/em\u003e = 0.5410). Among patients with Type 2 PJK, the teriparatide group had a nonsignificantly higher revision rate (Fisher’s exact test: \u003cem\u003ep\u003c/em\u003e = 0.1512)\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-6487108/v1/0617610d3f60ca29396f5e9b.png"},{"id":86809340,"identity":"0d30b0ad-d557-4b2b-8489-92b6be4ffd5d","added_by":"auto","created_at":"2025-07-15 19:46:23","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":844403,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6487108/v1/ffd36e48-0197-41fa-9d42-1c7c4b9c339d.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Reoperation Risk by Subtype in Proximal Junctional Kyphosis and the Impact of Osteoporosis Treatment in Adult Spinal Deformity Surgery","fulltext":[{"header":"Introduction","content":"\u003cp\u003eAdult spinal deformity (ASD) surgery has advanced markedly over recent years; however, mechanical complications remain a major concern, with proximal junctional kyphosis (PJK) among the most prevalent and impactful. PJK occurs in up to 20\u0026ndash;40% of cases following long spinal fusion, with ~\u0026thinsp;20% of these patients ultimately requiring revision surgery due to progressive kyphosis, implant failure, or intractable pain [1\u0026ndash;3]. PJK has been linked to decreased health-related quality-of-life, sagittal imbalance, and limited walking ability [4\u0026ndash;7]. Although numerous risk factors have been proposed, including excessive postoperative correction, upper thoracic fusion, older age, and paraspinal muscle loss, no definitive preventive strategy has been established [8\u0026ndash;10]. Surgical techniques, such as transition rods, prophylactic hooks, and ligament augmentation, have been explored, but none have shown consistent efficacy across patient populations [11, 12]. These challenges underscore the complexity of PJK pathogenesis and the need to identify modifiable risk factors.\u003c/p\u003e \u003cp\u003eEmerging evidence suggests that bone quality is critical to postoperative outcomes in ASD surgery. Osteoporotic bone is associated with higher risks of proximal junctional failure, pedicle screw loosening, rod fracture, and pseudarthrosis. Consequently, bone-modifying agents have garnered attention as a means of improving surgical outcomes. For example, teriparatide, a recombinant parathyroid hormone analog, has been shown to promote spinal fusion and reduce complications (e.g., implant loosening and PJK) in preclinical and clinical studies [13]. The roles of denosumab and romosozumab, which act via different mechanisms on bone metabolism, have also been reported [14]. Nevertheless, it remains unclear whether the type or timing of osteoporosis treatment affects PJK risk or the need for revision surgery in clinical practice.\u003c/p\u003e \u003cp\u003eAlthough often treated as a single complication, PJK is radiologically and clinically heterogeneous. Classification systems categorize PJK by failure mechanism, including ligamentous failure, vertebral fracture, and implant-related causes. A grading system based on angular progression severity has also been associated with clinical outcomes [3]. However, few studies have examined how PJK subtypes or grades relate to the likelihood of revision surgery. To improve perioperative management and personalize treatment strategies, it is essential to acknowledge that not all PJKs have equal clinical impact.\u003c/p\u003e \u003cp\u003eThis study had two objectives. First, we aimed to determine whether specific PJK subtypes or grades are associated with a higher likelihood of reoperation following ASD surgery. Second, we evaluated whether osteoporosis medications, particularly the type and timing of administration, affect the incidence and severity of PJK or the need for revision surgery.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStudy Design and Patient Selection\u003c/h2\u003e \u003cp\u003eThis retrospective cohort study included patients aged\u0026thinsp;\u0026gt;\u0026thinsp;60 years old, diagnosed with ASD characterized by sagittal or coronal imbalance, who underwent corrective spinal fusion at a single center between April 2016 and March 2023. The study was approved by the Institutional Review Board (No. 1183), and informed consent was obtained from all participants. Surgical indications included structural ASD unresponsive to prolonged conservative management.\u003c/p\u003e \u003cp\u003eInclusion criteria were as follows: age\u0026thinsp;\u0026gt;\u0026thinsp;60 years and radiographic confirmation of ASD, defined by at least one of the following: coronal Cobb angle\u0026thinsp;\u0026gt;\u0026thinsp;30\u0026deg;, C7 sagittal vertical axis (SVA)\u0026thinsp;\u0026gt;\u0026thinsp;5 cm, or pelvic tilt (PT)\u0026thinsp;\u0026gt;\u0026thinsp;30\u0026deg;. Only patients with \u003cem\u003ede novo\u003c/em\u003e degenerative deformities were included; secondary scoliosis from adolescent idiopathic scoliosis (AIS) was excluded. Additional exclusion criteria included ankylosing spondylitis, Parkinson\u0026rsquo;s disease-associated deformity, prior AIS, procedures without iliac screw fixation, or follow-up \u0026lt;\u0026thinsp;2 years. All surgeries were performed by two experienced spinal surgeons, with iliac screw fixation employed in every case. Demographic and surgical characteristics, including age, bone mineral density (BMD), fusion level, and surgical approach, were recorded (Table\u0026nbsp;1).\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eSurgical Procedures\u003c/h3\u003e\n\u003cp\u003eSurgical correction involved a lateral interbody fusion at L1\u0026ndash;L5 via an anterior approach, followed by posterior lumbar interbody fusion at L5\u0026ndash;S1 after repositioning the patient into the prone position. Sagittal realignment was achieved using a cantilever technique with bilateral S1 screws and supplemental iliac fixation.\u003c/p\u003e \u003cp\u003eOsteotomies were performed as needed for limited spinal flexibility, categorized by the Scoliosis Research Society-Schwab osteotomy classification (grades 1\u0026ndash;6). Fusion material included autologous and allograft bone; bone morphogenetic proteins were not used.\u003c/p\u003e\n\u003ch3\u003eRadiographic Evaluation\u003c/h3\u003e\n\u003cp\u003eFull-spine lateral radiographs were obtained preoperatively, at 4\u0026ndash;6 weeks postoperatively, and at the 2-year follow-up, with patients in a freestanding posture and their hands placed on the clavicles. Parameters measured included thoracic kyphosis (T5\u0026ndash;T12), thoracolumbar kyphosis (T10\u0026ndash;L2), lumbar lordosis (T12\u0026ndash;S1), pelvic incidence, PT, sacral slope, SVA, T1 pelvic angle, and global tilt. The lordosis distribution index was derived from the L1\u0026ndash;S1 and L4\u0026ndash;S1 angles.\u003c/p\u003e \u003cp\u003ePJK was defined as a postoperative increase in the proximal junctional angle (PJA) of \u0026ge;\u0026thinsp;10\u0026deg; and at least 10\u0026deg; greater than the preoperative measurement, following the criteria proposed by Yagi et al. [3]. PJK was also classified by failure mechanism into three types: Type 1: soft tissue and ligamentous failure; Type 2: vertebral fracture; Type 3: implant or bone\u0026ndash;implant interface failure. Severity was graded based on angular progression: Grade A: PJA increase of 10\u0026deg;\u0026ndash;14\u0026deg;; Grade B: PJA increase of 15\u0026deg;\u0026ndash;19\u0026deg;; Grade C: PJA increase\u0026thinsp;\u0026ge;\u0026thinsp;20\u0026deg;.\u003c/p\u003e \u003cp\u003eRadiographs were independently evaluated by two board-certified spine surgeons (blinded to clinical data), with their average used for analysis. Inter-rater reliability was confirmed by an intraclass correlation coefficient of 0.882.\u003c/p\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eStatistical Analysis\u003c/h2\u003e \u003cp\u003eContinuous variables were presented as means\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviations (SD), whereas categorical variables were shown as counts and percentages. The Shapiro\u0026ndash;Wilk test was used to assess data normality. For comparisons between two groups, the Student\u0026rsquo;s \u003cem\u003et\u003c/em\u003e-test was applied to normally distributed data, whereas the Mann\u0026ndash;Whitney U test was used for nonparametric data. For comparisons among more than two groups, one-way analysis of variance (ANOVA) was employed, followed by Tukey\u0026rsquo;s test applied post-hoc. The chi-square test or Fisher\u0026rsquo;s exact test was used to compare categorical variables as appropriate. The relationship between BMD and complication types was assessed via one-way ANOVA and Tukey\u0026rsquo;s post-hoc test.\u003c/p\u003e \u003cp\u003eAll statistical analyses were performed using GraphPad Prism version 8.0 (GraphPad Software, Boston, MA, USA). A two-sided p-value\u0026thinsp;\u0026lt;\u0026thinsp;0.05 was considered statistically significant, and the Bonferroni correction was applied for multiple comparisons when appropriate.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003e\u003cem\u003ePatient Characteristics\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eIn total, 189 patients who underwent surgery for ASD were included. The mean age was 72.1 ± 7.4 years, and 88.9% of patients were female (n = 168). The average body mass index was 24.1 ± 2.8 kg/m², and the average BMD, expressed as a percentage of the young adult mean (%YAM), was 74.5% ± 15.6%. The upper instrumented vertebra was at T9–T11 in 145 cases (76.7%) and at T8 or above in 44 cases (23.3%).\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eOsteoporosis Medication\u0026nbsp;\u003c/em\u003e\u003cem\u003eUse\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eFor osteoporosis management, 44.4% of patients were not receiving bone-modifying agents at the time of surgery. Among those being treated, 19.6% received bisphosphonates, 13.8% received teriparatide, 10.1% received denosumab, and 3.2% received romosozumab. Selective estrogen receptor modulators were used in 4.8% of cases. Among 65 patients receiving preoperative teriparatide, the mean preoperative treatment duration was 4.1 ± 3.1 months. Additionally, 32 patients received teriparatide only postoperatively.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eIncidence of PJK and Reoperation Rates\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003ePJK occurred in 95 of 189 patients (50.3%). Distribution by PJK type was Type 0, 1, 2, and 3 in 94 (49.7%), 33 (17.5%), 42 (22.2%), and 13 (6.9%) cases, respectively. Reoperation rates varied significantly by PJK type (p \u0026lt; 0.0001). Type 3 had the highest reoperation rate (69.2%), followed by Type 2 (38.1%), Type 1 (6.1%), and Type 0 (2.1%) (Figure 2). A similar trend was observed when stratified by PJK grade (p \u0026lt; 0.0001). Reoperation occurred in 2.2%, 25.0%, 32.1%, and 55.6% of Grade 0, A, B, and C cases, respectively (data not shown).\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eBMD:\u003c/em\u003e\u003cem\u003e\u0026nbsp;Association with PJK and Reoperation\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eAlthough patients who underwent reoperation had a lower mean BMD compared with those who did not (70.2 ± 13.2 vs. 75.5 ± 13.5 %YAM), the difference was not statistically significant (\u003cem\u003ep\u003c/em\u003e = 0.1940). Similarly, a nonsignificant trend toward lower BMD was observed in patients with PJK compared to those without (73.0 ± 13.8 vs. 78.4 ± 14.0 %YAM, \u003cem\u003ep\u003c/em\u003e = 0.0543) (Table 3).\u003c/p\u003e\n\u003cp\u003eStratified by PJK type, a significant difference in BMD was found (\u003cem\u003ep\u003c/em\u003e = 0.0082, one-way ANOVA). Post-hoc analysis revealed that patients with Type 2 PJK had significantly lower BMD compared to those with Type 0 (\u003cem\u003ep\u003c/em\u003e = 0.0141), whereas no significant differences were observed between Type 2 and the other types (Table 4).\u003c/p\u003e\n\u003cp\u003eAmong 42 patients with Type 2 PJK, the reoperation rate of 38.1% was the second highest among all types. Additionally, Type 2 cases in the lowest BMD tertile had numerically higher but nonsignificant reoperation rates.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eEffect of Teriparatide on PJK Type and Grade\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eA subgroup analysis comparing patients treated with teriparatide with those who received no osteoporosis medication revealed significant differences in PJK type distribution (\u003cem\u003ep\u003c/em\u003e = 0.0002; Figure 2). The teriparatide-treated group had a higher proportion of Type 0 (59 cases) and Type 1 (21 cases), with fewer Type 2 (11 cases) and Type 3 (6 cases), compared to the group receiving no osteoporosis medication (Type 2: 23 cases; Type 3: 6 cases).\u003c/p\u003e\n\u003cp\u003eSimilarly, PJK grade distribution differed significantly between the groups (\u003cem\u003ep\u003c/em\u003e = 0.0153; Figure 2). The teriparatide-treated group had more Grade 0 and fewer Grades B and C cases, suggesting a potential benefit of the drug in reducing PJK severity.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eReoperation Rate\u0026nbsp;\u003c/em\u003e\u003cem\u003eBased on Teriparatide Administration\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe reoperation rate was 20.7% and 15.5% in the groups receiving no osteoporosis medication and teriparatide, respectively (Figure 2), with no significant difference detected (\u003cem\u003ep\u003c/em\u003e = 0.5410). Among patients with Type 2 PJK, the reoperation rate was higher in the teriparatide group (63.6%, 7 of 11 cases) than in the group receiving no osteoporosis medication (34.8%, 8 of 23 cases; Figure 2), although the difference was nonsignificant (\u003cem\u003ep\u003c/em\u003e = 0.1512, Fisher’s exact test).\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eImpact of Teriparatide Timing on Reoperation\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003ePatients were also grouped by the timing of teriparatide administration: preoperatively only, postoperatively only, and no administration. The reoperation rate was lowest in the preoperatively only group (13.8%), followed by the postoperatively only (18.8%), and the no administration (20.7%) groups, although no statistically significant difference was observed.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eIn this retrospective cohort study of patients undergoing long spinal fusion for ASD, we identified several key findings regarding the relationship between PJK subtype, BMD, and osteoporosis treatment. First, we found that patients with Type 2 and Type 3 PJK were associated with significantly higher reoperation rates compared to those with Types 0 and 1, underscoring the prognostic value of subclassifying PJK beyond its presence or absence. Second, lower BMD was associated with more severe PJK subtypes, particularly Type 2, with a nonsignificant trend toward increased revision also observed. Although prior studies have suggested a link between bone quality and mechanical failure, our findings emphasize the importance of routine preoperative BMD screening and risk stratification in ASD surgery planning. Third, although teriparatide use did not significantly reduce the overall reoperation rate, patients receiving it preoperatively had numerically fewer revisions than those treated postoperatively or not at all. These findings suggest that both the use and timing of bone-modifying agents may influence surgical outcomes, warranting further prospective investigation.\u003c/p\u003e\n\u003cp\u003eOur results align with prior studies highlighting worse outcomes in structural PJK types, such as vertebral fractures (Type 2) and implant-related failures (Type 3). These forms have been linked to poorer clinical outcomes and higher revision rates compared with ligamentous failure or angular deformities without collapse. Similarly, hardware failure at the proximal junction has consistently predicted reoperation [15, 16].\u003c/p\u003e\n\u003cp\u003eAlthough some studies have emphasized angular progression (i.e., PJA) in assessing PJK, morphological classification may better reflect the mechanical instability and clinical implication of each subtype. Our findings support an integrated approach using both angular and structural criteria in postoperative surveillance and risk prediction.\u003c/p\u003e\n\u003cp\u003eThe beneficial effects of anabolic agents, such as teriparatide, on spinal fusion and implant integrity have been well-documented in short-segment fusion [17][18]. Thus, there is a growing consensus that anabolic therapy enhances early postoperative spinal stability in patients with osteoporosis. However, the role of such agents in long-segment fusion for ASD remains unclear. Surgical correction for ASD often involves extensive fixation and alignment changes, with outcomes dependent on multiple interrelated factors, including sagittal balance restoration, fusion range, and baseline bone quality. Although numerous studies have addressed the elevated risk of PJK and failure in osteoporotic patients undergoing ASD surgery, standardized pharmacologic prevention strategies have yet to be established. Prospective studies have begun to fill this gap. Perioperative administration of teriparatide has been shown to reduce PJF incidence more effectively relative to antiresorptive agents, such as denosumab, although its efficacy in preventing overall PJK remains uncertain. Notably, preoperative use of teriparatide has been associated with improvements in trabecular bone microarchitecture and a reduction in vertebral fracture-type PJK\u0026nbsp;[13, 14, 19-22]. These data suggest\u0026nbsp;that\u0026nbsp;anabolic agents\u0026nbsp;may play a valuable role\u0026nbsp;in\u0026nbsp;mitigating\u0026nbsp;structural complications, particularly\u0026nbsp;those\u0026nbsp;related\u0026nbsp;to bone fragility.\u003c/p\u003e\n\u003cp\u003eOur findings align with previous studies: patients who received teriparatide exhibited a significantly lower incidence of Type 2 PJK and a numerically but nonsignificantly reduced reoperation rate. However, no significant differences were observed among other PJK types. These results indicate that the benefit of osteoporosis therapy in ASD may depend not only on the presence of treatment but also on its timing and the biomechanical characteristics of the complication. Prospective studies stratified by complication subtype and treatment timing are warranted to validate these trends.\u003c/p\u003e\n\u003cp\u003eA key strength of this study lies in its detailed characterization of PJK subtypes and their differential impact on reoperation risk. By subclassifying PJK by morphologic type and angular grade, we showed that not all PJKs have equivalent clinical implications, particularly highlighting the structural vulnerability and clinical severity of Type 2 lesions. Moreover, this study is among the few to integrate radiographic and pharmacologic variables, including BMD and osteoporosis medication timing, into the evaluation of postoperative mechanical complications following long-segment ASD surgery.\u003c/p\u003e\n\u003cp\u003eDespite these strengths, several limitations must be acknowledged. First, the retrospective design and single center setting may limit the generalizability of our findings. Second, although we stratified patients by medication type and timing, the exact duration and adherence to preoperative therapy, especially with agents such as teriparatide, could not be consistently verified. Given emerging evidence that treatment efficacy may be dose- and time-dependent, this represents a critical area for further prospective investigation. Third, we did not assess patient-reported outcomes, such as pain or health-related quality-of-life, limiting our ability to correlate radiographic findings with functional endpoints.\u003c/p\u003e\n\u003cp\u003eFuture studies should aim to validate these findings in larger, multicenter cohorts and incorporate stratified analyses based on PJK subtype, baseline bone density, and treatment duration. Establishing the optimal preoperative preparation duration of anabolic therapy may help inform standardized osteoporosis management protocols tailored to patients with ASD at high risk of mechanical failure.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eAuthors\u0026rsquo; contribution statementsConceptualization, T.O. and H.H.; Methodology, N.T, T.H and G.G. Validation, K.O, T.N and T.O.; Formal Analysis, T.O and K.M; Investigation, H.H.; Writing \u0026ndash; Original Draft Preparation, T.O.; Writing \u0026ndash; Review \u0026amp; Editing, N.T and T.O.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eNone\u003c/p\u003e"},{"header":" References","content":"\u003col\u003e\n \u003cli\u003eLau D, Clark AJ, Scheer JK, Daubs MD, Coe JD, Paonessa KJ, LaGrone MO, Kasten MD, Amaral RA, Trobisch PD, Lee JH, Fabris-Monterumici D, Anand N, Cree AK, Hart RA, Hey LA, Ames CP, Committee SRSASD (2014) Proximal junctional kyphosis and failure after spinal deformity surgery: a systematic review of the literature as a background to classification development. Spine (Phila Pa 1976) 39:2093-2102. doi: 10.1097/BRS.0000000000000627\u003c/li\u003e\n \u003cli\u003eAoun M, Daher M, Daniels AH, Kreichati G, Kharrat K, Sebaaly A (2024) The predictive power of the Roussouly classification on mechanical complications after surgery for adult spinal deformity: systematic review and meta-analysis. Eur Spine J. doi: 10.1007/s00586-024-08596-w\u003c/li\u003e\n \u003cli\u003eYagi M, King AB, Boachie-Adjei O (2012) Incidence, risk factors, and natural course of proximal junctional kyphosis: surgical outcomes review of adult idiopathic scoliosis. Minimum 5 years of follow-up. Spine (Phila Pa 1976) 37:1479-1489. doi: 10.1097/BRS.0b013e31824e4888\u003c/li\u003e\n \u003cli\u003eGlattes RC, Bridwell KH, Lenke LG, Kim YJ, Rinella A, Edwards C, 2nd (2005) Proximal junctional kyphosis in adult spinal deformity following long instrumented posterior spinal fusion: incidence, outcomes, and risk factor analysis. Spine (Phila Pa 1976) 30:1643-1649\u003c/li\u003e\n \u003cli\u003eKim YJ, Lenke LG, Bridwell KH, Kim J, Cho SK, Cheh G, Yoon J (2007) Proximal junctional kyphosis in adolescent idiopathic scoliosis after 3 different types of posterior segmental spinal instrumentation and fusions: incidence and risk factor analysis of 410 cases. Spine (Phila Pa 1976) 32:2731-2738. doi: 10.1097/BRS.0b013e31815a7ead\u003c/li\u003e\n \u003cli\u003eKim HJ, Bridwell KH, Lenke LG, Park MS, Ahmad A, Song KS, Piyaskulkaew C, Hershman S, Fogelson J, Mesfin A (2013) Proximal junctional kyphosis results in inferior SRS pain subscores in adult deformity patients. Spine (Phila Pa 1976) 38:896-901. doi: 10.1097/BRS.0b013e3182815b42\u003c/li\u003e\n \u003cli\u003eYagi M, Rahm M, Gaines R, Maziad A, Ross T, Kim HJ, Kebaish K, Boachie-Adjei O, Complex Spine Study G (2014) Characterization and surgical outcomes of proximal junctional failure in surgically treated patients with adult spinal deformity. Spine (Phila Pa 1976) 39:E607-614. doi: 10.1097/BRS.0000000000000266\u003c/li\u003e\n \u003cli\u003eOhba T, Ebata S, Oba H, Koyama K, Haro H (2018) Correlation Between Postoperative Distribution of Lordosis and Reciprocal Progression of Thoracic Kyphosis and Occurrence of Proximal Junctional Kyphosis Following Surgery for Adult Spinal Deformity. Clin Spine Surg. doi: 10.1097/bsd.0000000000000702\u003c/li\u003e\n \u003cli\u003eProtopsaltis TS, Diebo BG, Lafage R, Henry JK, Smith JS, Scheer JK, Sciubba DM, Passias PG, Kim HJ, Hamilton DK, Soroceanu A, Klineberg EO, Ames CP, Shaffrey CI, Bess S, Hart RA, Schwab FJ, Lafage V (2018) Identifying Thoracic Compensation and Predicting Reciprocal Thoracic Kyphosis and PJK in Adult Spinal Deformity Surgery. Spine (Phila Pa 1976). doi: 10.1097/brs.0000000000002843\u003c/li\u003e\n \u003cli\u003eOhba T, Koji F, Koyama K, Oba H, Oda K, Tanaka N, Haro H (2021) Preoperative Radiographic Evaluation of Thoracic Flexibility and Compensation for Adult Spinal Deformity Surgery. How to Select Optimal Upper Instrumented Vertebra to Prevent Proximal Junctional Kyphosis. Spine (Phila Pa 1976). doi: 10.1097/brs.0000000000004126\u003c/li\u003e\n \u003cli\u003ePark HY, Ha KY, Kim YH, Chang DG, Kim SI, Lee JW, Ahn JH, Kim JB (2017) Minimally Invasive Lateral Lumbar Interbody Fusion for Adult Spinal Deformity: Clinical and Radiological Efficacy with Minimum Two Years Follow-up. Spine (Phila Pa 1976). doi: 10.1097/BRS.0000000000002507\u003c/li\u003e\n \u003cli\u003eBourghli A, Boissiere L, Larrieu D, Pizones J, Alanay A, Pellis\u0026eacute; F, Kleinst\u0026uuml;ck F, Obeid I (2024) Proximal junctional kyphosis after adult spinal deformity operated patients with long fusion to the pelvis. Does the type of proximal anchor matter? Eur Spine J 33:2832-2839. doi: 10.1007/s00586-024-08332-4\u003c/li\u003e\n \u003cli\u003eYagi M, Ohne H, Konomi T, Fujiyoshi K, Kaneko S, Komiyama T, Takemitsu M, Yato Y, Machida M, Asazuma T (2016) Teriparatide improves volumetric bone mineral density and fine bone structure in the UIV+1 vertebra, and reduces bone failure type PJK after surgery for adult spinal deformity. Osteoporos Int 27:3495-3502. doi: 10.1007/s00198-016-3676-6\u003c/li\u003e\n \u003cli\u003eSawada Y, Takahashi S, Yasuda H, Terakawa M, Konishi S, Kato M, Toyoda H, Suzuki A, Tamai K, Iwamae M, Okamura Y, Kobayashi Y, Nakamura H, Terai H (2024) Effect of romosozumab administration on proximal junctional kyphosis in corrective spinal fusion surgery. The spine journal : official journal of the North American Spine Society. doi: 10.1016/j.spinee.2024.12.021\u003c/li\u003e\n \u003cli\u003eReames DL, Kasliwal MK, Smith JS, Hamilton DK, Arlet V, Shaffrey CI (2015) Time to development, clinical and radiographic characteristics, and management of proximal junctional kyphosis following adult thoracolumbar instrumented fusion for spinal deformity. Journal of spinal disorders \u0026amp; techniques 28:E106-114. doi: 10.1097/BSD.0000000000000158\u003c/li\u003e\n \u003cli\u003eNicholls FH, Bae J, Theologis AA, Eksi MS, Ames CP, Berven SH, Burch S, Tay BK, Deviren V (2017) Factors Associated With the Development of and Revision for Proximal Junctional Kyphosis in 440 Consecutive Adult Spinal Deformity Patients. Spine (Phila Pa 1976) 42:1693-1698. doi: 10.1097/BRS.0000000000002209\u003c/li\u003e\n \u003cli\u003eEbata S, Takahashi J, Hasegawa T, Mukaiyama K, Isogai Y, Ohba T, Shibata Y, Ojima T, Yamagata Z, Matsuyama Y, Haro H (2017) Role of Weekly Teriparatide Administration in Osseous Union Enhancement within Six Months After Posterior or Transforaminal Lumbar Interbody Fusion for Osteoporosis-Associated Lumbar Degenerative Disorders: A Multicenter, Prospective Randomized Study. J Bone Joint Surg Am 99:365-372. doi: 10.2106/JBJS.16.00230\u003c/li\u003e\n \u003cli\u003eOba H, Takahashi J, Yokomichi H, Hasegawa T, Ebata S, Mukaiyama K, Ohba T, Ushirozako H, Kuraishi S, Ikegami S, Uehara M, Takizawa T, Munakata R, Hatakenaka T, Matsuyama Y, Haro H (2020) Weekly Teriparatide Versus Bisphosphonate for Bone Union During 6 Months After Multi-Level Lumbar Interbody Fusion for Osteoporotic Patients: A Multicenter, Prospective, Randomized Study. Spine (Phila Pa 1976) 45:863-871. doi: 10.1097/brs.0000000000003426\u003c/li\u003e\n \u003cli\u003eSawakami K, Watanabe K, Hasegawa K, Yamamoto N, Shimakura T, Ohashi M, Shoji H, Mizouchi T, Tanaka Y, Segawa H, Ishikawa S, Hirano T, Kawashima H, Endo N, Takahashi HE (2022) Neoadjuvant teriparatide therapy targeting the osteoporotic spine: influence of administration period from the perspective of bone histomorphometry. Journal of neurosurgery Spine 36:429-439. doi: 10.3171/2021.5.Spine202003\u003c/li\u003e\n \u003cli\u003eBaroudi M, Daher M, Maheshwari K, Singh M, Nassar JE, McDonald CL, Diebo BG, Daniels AH (2024) Surgical Management of Adult Spinal Deformity Patients with Osteoporosis. Journal of clinical medicine 13. doi: 10.3390/jcm13237173\u003c/li\u003e\n \u003cli\u003eShen T, Shahzad H, Sierra F, Wick JB, Pina D, Van BW, Vander Voort WD, Kong S, Javidan Y, Roberto RF, Klineberg EO, Le HV (2024) Osteoporosis Treatment and Outcomes in Patients Undergoing Adult Spinal Deformity Surgery. World Neurosurg 190:e1018-e1024. doi: 10.1016/j.wneu.2024.08.053\u003c/li\u003e\n \u003cli\u003ePark JH, Kwon O, Choi JH, Yeom JS, Park SM, Kim CH, Kim HJ (2025) Perioperative teriparatide for preventing proximal junctional kyphosis and failure in patients with osteoporosis after adult thoracolumbar spinal deformity surgery: a prospective randomized controlled trial. Osteoporos Int. doi: 10.1007/s00198-025-07449-6\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003e\u003cstrong\u003eTable 1. Baseline characteristics of patients with ASD.\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"481\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 305px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eVariable\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 176px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eASD (N = 189)\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 305px;\"\u003e\n \u003cp\u003eAge (years)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 176px;\"\u003e\n \u003cp\u003e72.1 \u0026plusmn; 7.4\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 305px;\"\u003e\n \u003cp\u003eFemale/male (n)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 176px;\"\u003e\n \u003cp\u003e168/21\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 305px;\"\u003e\n \u003cp\u003eBMI (kg/m\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 176px;\"\u003e\n \u003cp\u003e24.1 \u0026plusmn; 2.8\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 305px;\"\u003e\n \u003cp\u003eBMD (%YAM)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 176px;\"\u003e\n \u003cp\u003e74.5 \u0026plusmn; 15.6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 305px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eLocation of UIV(n)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 176px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 305px;\"\u003e\n \u003cp\u003eTh9-11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 176px;\"\u003e\n \u003cp\u003e145\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 305px;\"\u003e\n \u003cp\u003eTh8~\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 176px;\"\u003e\n \u003cp\u003e44\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eAbbreviations: ASD, adult spinal deformity; BMI, body mass index; BMD, bone mineral density; YAM, young adult mean; UIV, upper instrumented vertebra.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 2. Osteoporosis medication use in patients with ASD.\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMedication\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eNumber of patients\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003e\u003cstrong\u003ePercentage (%)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003eTeriparatide\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003e97\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003e53.3\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003eNone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003e58\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003e31.9\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003eDeno\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003e4.4\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003eRom\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003e4.4\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003eSERM\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003e3.3\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003eBis\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 170px;\"\u003e\n \u003cp\u003e2.7\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eAbbreviations: ASD, adult spinal deformity, Bis, bisphosphonate; Deno, denosumab; Rom, romosozumab; SERM, selective estrogen receptor modulator.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 3. Comparison of bone mineral density based on reoperation and PJK status.\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" class=\"fr-table-selection-hover\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 141px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eComparison\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 123px;\"\u003e\n \u003cp\u003eBMD (YAM)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003eBMD (YAM)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003e\u003cstrong\u003ep-value\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 141px;\"\u003e\n \u003cp\u003eReoperation:\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eyes vs. no\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 123px;\"\u003e\n \u003cp\u003e69.1 \u0026plusmn; 12.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e75.6 \u0026plusmn; 14.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003e0.0445\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 141px;\"\u003e\n \u003cp\u003ePJK:\u0026nbsp;\u003c/p\u003e\n \u003cp\u003epresent vs. absent\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 123px;\"\u003e\n \u003cp\u003e70.3 \u0026plusmn; 13.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e78.1 \u0026plusmn; 14.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003e0.0008\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eAbbreviations: PJK, proximal junctional kyphosis; BMD, bone mineral density; YAM, young adult mean.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"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":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Proximal junctional kyphosis, Adult spinal deformity, Reoperation, Teriparatide, Osteoporosis treatment","lastPublishedDoi":"10.21203/rs.3.rs-6487108/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6487108/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cb\u003ePurpose\u003c/b\u003e\u003c/p\u003e \u003cp\u003eProximal junctional kyphosis (PJK) is a common mechanical complication following adult spinal deformity (ASD) surgery. Although various preventive strategies exist, the clinical relevance of PJK subtypes and the impact of osteoporosis medications remain unclear. This study examined which PJK subtypes and grades are most associated with reoperation and evaluates whether osteoporosis treatment, particularly teriparatide, affects PJK incidence or severity.\u003c/p\u003e\u003cp\u003e\u003cb\u003eMethods\u003c/b\u003e\u003c/p\u003e \u003cp\u003eThis retrospective study included 189 patients who underwent long spinal fusion for ASD. PJK was classified by type (0\u0026ndash;3) and grade (0\u0026ndash;C). Osteoporosis medication use and bone mineral density (BMD) were recorded. Reoperation rates were compared across subtypes and treatment groups using the chi-square test and analysis of variance.\u003c/p\u003e\u003cp\u003e\u003cb\u003eResults\u003c/b\u003e\u003c/p\u003e \u003cp\u003eType 2 (vertebral fracture) and Type 3 (implant failure) PJK were significantly associated with higher reoperation rates (p\u0026thinsp;\u0026lt;\u0026thinsp;0.0001). Patients with lower BMD exhibited a significantly higher prevalence of Type 2 PJK (p\u0026thinsp;=\u0026thinsp;0.0082), whereas teriparatide users showed a significantly lower incidence of Type 2 PJK (p\u0026thinsp;=\u0026thinsp;0.0141 vs. Type 0) as well as a trend toward fewer reoperations. Preoperative teriparatide administration was linked to the lowest revision rate among treatment groups.\u003c/p\u003e\u003cp\u003e\u003cb\u003eConclusion\u003c/b\u003e\u003c/p\u003e \u003cp\u003ePJK subtype and BMD strongly predicted reoperation after ASD surgery. Teriparatide may reduce structural PJK risk, especially when used preoperatively. Prevention strategies should be tailored to PJK subtype and bone quality.\u003c/p\u003e","manuscriptTitle":"Reoperation Risk by Subtype in Proximal Junctional Kyphosis and the Impact of Osteoporosis Treatment in Adult Spinal Deformity Surgery","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-05-14 11:31:22","doi":"10.21203/rs.3.rs-6487108/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"501b741c-1293-4f58-9276-6870be9ee6da","owner":[],"postedDate":"May 14th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-07-15T19:38:11+00:00","versionOfRecord":[],"versionCreatedAt":"2025-05-14 11:31:22","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6487108","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6487108","identity":"rs-6487108","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}