Differential Impact of Body Mass Index on Postoperative Complications in Orthognathic Surgery: A retrospective study of 1,309 patients

Differential Impact of Body Mass Index on Postoperative Complications in Orthognathic Surgery: A retrospective study of 1,309 patients | 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 Differential Impact of Body Mass Index on Postoperative Complications in Orthognathic Surgery: A retrospective study of 1,309 patients Junghwan Bae, Chiho Moon, Ungang Kim, Chung-woo Lee, Borim Choi, and 5 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8704505/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 13 You are reading this latest preprint version Abstract Background : Body Mass Index (BMI) is a well-established predictor of postoperative complications in various surgical fields; however, its specific role in orthognathic surgery has not been sufficiently investigated. This study aimed to comprehensively analyze the association between BMI and postoperative complications in orthognathic surgery to enhance surgical safety and establish practical clinical guidelines. Methods : A retrospective study was conducted on 1,309 patients who underwent orthognathic surgery performed by a single surgeon from 2012 to 2024. BMI was classified according to the World Health Organization Asia-Pacific criteria: underweight (<18.5 kg/m²), normal (18.5–23.0 kg/m²), overweight (23.0–25.0 kg/m²), and obese (≥25.0 kg/m²). Complications were categorized into intraoperative events, such as bad split and excessive bleeding, and postoperative issues, including hardware failure, infection, and relapse. Statistical analyses were performed using Chi-square or Fisher’s exact tests for categorical variables and One-way ANOVA or Kruskal-Wallis tests for continuous variables. Results : Statistically significant differences were observed in complication patterns across BMI categories. Among major complications, the transfusion rate was significantly highest in the underweight group (3.6%, p=0.0181). Conversely, fixation hardware failure (8.0%, p<0.001) and skeletal relapse (3.3%, p=0.0051) were significantly more prevalent in the obese group. While initial surgical overjet change increased with higher BMI (p=0.0011), postoperative overjet changes showed no significant differences among groups. No significant association was observed between BMI and infection rates. Conclusions : This study suggests that distinct pathophysiological and biomechanical risk factors are involved according to BMI categories in orthognathic surgery. Underweight patients show an increased risk of transfusion due to reduced physiological reserve, while obese patients face elevated risks of hardware failure and relapse due to biomechanical instability. Personalized clinical management strategies based on BMI are necessary, including enhanced fixation methods and long-term follow-up for obese patients. Trial registration: Clinical Research Information Service KCT0011570, February 3, 2026. Retrospectively registered. Orthognathic surgery complication Body mass index Recurrence Transfusion Obesity Underweight Figures Figure 1 Figure 2 Figure 3 Figure 4 Background Orthognathic surgery is a surgical treatment designed to correct structural disharmonies of the maxillofacial skeleton to enhance both function and esthetics.[1, 2] Despite recent advancements in three-dimensional computed tomography imaging, virtual surgical planning, and patient-specific implants, complications remain a significant concern, ranging from early events such as hemorrhage, infection, bad splits, and hardware issues to long-term sequelae including skeletal relapse, malocclusion, and temporomandibular joint disorder.[3–5] Body Mass Index (BMI) is recognized as a crucial independent predictor of perioperative complications across various surgical specialties. With the recent global increase in obesity prevalence, the influence of elevated BMI on surgical outcomes has become a major clinical concern.[6] According to previous studies, a high BMI increases the risk of postoperative complications across diverse surgical fields, where obese patients face a higher risk of thrombosis, infection, and readmission compared to normal weight individuals.[7, 8] This phenomenon is largely attributed to the synergistic effects of chronic inflammation associated with obesity, compromised blood flow, and reduced healing capacity in adipose tissue.[9, 10] Conversely, underweight patients carry a distinct risk profile, with an increased need for blood transfusion due to reduced preoperative blood volume. Both extremes of the BMI spectrum significantly influence clinical prognosis.[11] Despite the established role of BMI in general surgery, its specific impact on orthognathic surgery remains inadequately characterized. Unlike general surgical procedures, orthognathic surgery involves unique biomechanical demands including precise bone repositioning, rigid fixation under masticatory forces, and complex soft tissue dynamics. Therefore, a comprehensive analysis of BMI-associated complications specific to orthognathic surgery is needed. This study retrospectively analyzes 1,309 cases performed by a single surgeon over 13 years to evaluate the incidence, types, and, most importantly, the association between BMI and the risk of postoperative complications. By meticulously examining these complication patterns, this analysis aims to enhance surgical safety and establish practical clinical guidelines for prevention and management. Patients and methods 1) Study Design and Patient Selection This retrospective chart review study analyzed patients who underwent orthognathic surgery performed by a single surgeon over a 13-year period from January 2012 to December 2024. Patients were required to have a minimum postoperative follow-up period of 6 months. This study was approved by the IRB (Number: 2025-02-002), and a waiver of informed consent was granted due to the retrospective nature of the study. 2) Inclusion and Exclusion Criteria Inclusion Criteria: - Patients who underwent orthognathic surgery for skeletal malocclusion and facial asymmetry. Exclusion Criteria: Patients with congenital facial deformities. Patients who underwent maxillofacial reconstructive surgery due to trauma history. Patients with insufficient perioperative or follow-up periods below the required criteria. 3) BMI Measurement and Classification Preoperative BMI was calculated using the formula: Weight (kg) / Height (m) 2 . Patients were categorized into four groups based on the World Health Organization (WHO) Asia-Pacific Classification system, which is suitable for the study population:[12] Underweight: BMI < 18.5 Normal Weight: 18.5 ≤ BMI < 23.0 Overweight: 23.0 ≤ BMI < 25.0 Obese: 25.0 ≤ BMI 4) Surgical procedure - Bimaxillary surgery: The bimaxillary procedure, comprising a Le Fort I osteotomy followed by a Bilateral Sagittal Split Ramus Osteotomy (BSSRO), was performed sequentially. Initially, the Le Fort I osteotomy was executed; after the down fracture, bony interference was removed, and the maxilla was positioned using an intermediate wafer and secured with L-shape plates. Subsequently, the BSSRO was carried out using the Obwegeser-Dal Pont technique. The distal mandibular segment was repositioned according to the final wafer to correct the deformity, after which interference between the proximal and distal segments was removed and the condyle was seated in a stable position. The mandibular segments were then fixed using sliding plates in a semi-rigid fixation method; if this was inadequate, alternative rigid (screw) or non-rigid fixation methods were considered. Finally, Maxillomandibular Fixation (MMF) was applied on the second postoperative day and maintained for seven days. - Mandibular only surgery: This procedure involved a BSSRO and was performed identically to the mandibular component of the bimaxillary surgery. MMF was applied immediately post- urgery and maintained for five days. 5) Definition and Classification of Complications Postoperative complications included all adverse outcomes occurring from immediately after surgery to the final follow-up. Based on detailed medical records, the following items were analyzed as dependent variables for association with BMI: Bad split [Figure 1 ]: Unfavorable fracture deviating from the osteotomy line during BSSRO Excessive bleeding: Hemorrhage requiring either blood transfusion or surgical intervention 1) Transfusion: Administration of packed red blood cells necessitated by postoperative hemoglobin levels ≤ 7.0 coupled with clinical signs of acute anemia 2) Surgical intervention: Procedures performed under local or general anesthesia for evacuation of hematoma and subsequent bleeding control - Infection: A bacterial infection manifesting at the surgical site with clinical signs of inflammation, requiring admission for intravenous antibiotic therapy and surgical drainage - Re-fixation: A subsequent corrective procedure performed under general anesthesia to address malunion or significant malocclusion arising from the primary surgery - Malnutrition: A state of postoperative nutritional deficiency shown by re-admission after discharge due to systemic weakness, lethargy, or other signs resulting from restrictive diet - Fixation hardware failure [Figure 2 ]: 1) Plate fracture: Mechanical failure and breakage of fixation hardware 2) Plate dislocation: Displacement of fixation plates from original position 3) Plate removal: Unplanned surgical removal of hardware - Relapse [Figure 3 ]: Return of skeletal segments toward preoperative position after initial surgical correction 1) Anterior crossbite: Recurrence of Class III relationship after initial surgical correction 2) Anterior open bite: Recurrence of a vertical gap between the opposing anterior teeth 3) Asymmetry: Recurrence of facial skeletal asymmetry after initial surgical correction 6) Limitation Due to insufficient objective and consistent documentation of nerve injury and temporomandibular disorder symptoms during the retrospective chart review process, these complications were excluded from the analysis. Therefore, the complication rates presented in this study are limited to the items defined above. 7) Statistical Analysis Univariate analysis was performed to determine the association between BMI categories and the occurrence of selected complications. The Chi-square test was used for this analysis, and Fisher's exact test was applied to calculate the accurate p-value when the assumption of the Chi-square test was violated. Furthermore, to compare the difference in continuous variables across three or more independent groups, One-way ANOVA test was used when the data satisfied the assumption of normal distribution, and the Kruskal-Wallis test was utilized to compare medians when the assumption of normal distribution was not met. To ensure adequate statistical power, only complications with at least 10 events were included in the analysis. The level of statistical significance for all analyses was set at p < 0.05. Statistical analyses were performed using SPSS version 23.0 (IBM Co., Armonk, NY, USA). Results In Table 1 , the analysis of the 1,309 orthognathic surgery patients showed statistically significant differences in age, sex distribution and type of surgery across the four BMI categories. Mean age increased significantly with BMI, ranging from 22.0 ± 4.3 years in the underweight group to 23.7 ± 5.2 years in the obese group (p = 0.0186). Sex distribution showed a highly significant association with BMI (p < 0.0001), with females constituting the majority of the underweight group (69.6%), while males were predominant in the obese (69.2%) groups. Furthermore, the type of surgery differed significantly by BMI (p = 0.0002). Bimaxillary surgery was most frequent in the underweight group (74.6%) but saw a steady decline, becoming the least frequent procedure in the obese group (55.0%). Conversely, mandibular only surgery increased consistently with BMI, peaking at 45.0% in the obese patient cohort. The mean operative time showed no statistically significant differences across BMI categories for either bimaxillary surgery (p = 0.2060) or mandibular only surgery (p = 0.3256). Table 1 Baseline characteristics of 1309 patients undergoing orthognathic surgery stratified by Body Mass Index categories. Characteristic Underweight (< 18.5) Normal (18.5–23.0) Overweight (23–25.0) Obese (≥ 25.0) p-value N 138 748 212 211 - Age (years) 22.0 ± 4.3 22.7 ± 5.0 23.0 ± 5.2 23.7 ± 5.2 0.017* Sex Male, n (%) 42 (30.4%) 325 (43.4%) 146 (68.9%) 146 (69.2%) 0.000* Female, n (%) 96 (69.6%) 423 (56.6%) 66 (31.1%) 65 (30.8%) Surgery type Bimaxillary 103 (74.6%) 516 (69.0%) 135 (63.7%) 116 (55.0%) 0.000* Mandibular only 34 (24.6%) 222 (29.7%) 76 (35.8%) 95 (45.0%) Operative time (minutes) Bimaxillary 196.4 ± 40.7 191.3 ± 38.9 195.3 ± 38.7 186.7 ± 38.2 0.206 Mandibular only 107.4 ± 29.1 111.6 ± 35.4 105.8 ± 29.9 104.8 ± 36.6 0.325 Table 1 Legend. Data are presented as mean ± SD or n (%). One-way ANOVA for continuous variables; Chi-square test for categorical variables. *p < 0.05. In Table 2 , among the 1,309 patients, 192 major postoperative complications were documented. Bad split was the most frequent complication (82 cases, 6.3%), followed by fixation hardware failure (34 cases, 2.59%). Infection occurred in 22 cases, with mandibular infections significantly outweighing maxillary infections (17 vs. 5 cases). Bleeding complications occurred in 19 cases (14 requiring transfusion, 5 requiring surgical intervention). Relapse was reported in 15 cases, presenting mainly as anterior crossbite (8 cases). Additional complications included re-fixation (15 cases) and malnutrition (5 cases). Table 2 Incidence and classification of postoperative complications Classification N Total (Incidence rate) Bad split Right mandible Left mandible 39 43 82 (6.3%) Fixation hardware failure Plate fracture Plate dislocation Plate removal 15 10 9 34 (2.6%) Infection Maxilla Mandible 5 17 22 (1.7%) Bleeding Transfusion Surgical intervention 14 5 19 (1.5%) Re-fixation Maxilla Mandible 3 12 15 (1.2%) Relapse Anterior crossbite Anterior open bite Asymmetry 8 6 1 15 (1.2%) Malnutrition 5 5 (0.4%) Table 2 Legend. Complications were documented from immediately after surgery to the final follow-up period. In Table 3 , among major complications, only transfusion and relapse showed significant associations with BMI category (p < 0.05).[Figure 4 ] Transfusion risk was highest in the underweight group (3.6%, p = 0.0181), significantly exceeding the rates in the normal (0.9%), overweight (0.5%), and obese (0.5%) groups. Conversely, relapse and fixation hardware failure showed significant association with high BMI (p < 0.05), occurring at a rate of 3.3% in the obese group compared to 0.8% in the normal group and 0.0% in the underweight group. Bad split, infection, and re-fixation showed no significant association with BMI (p = 0.1913). Table 3 Association between BMI and the Incidence of postoperative complications Variable Underweight (< 18.5) Normal (18.5–23.0) Overweight (23–25.0) Obese (≥ 25.0) p-value Intraoperative Bad split 14 (10.1%) 43 (5.7%) 12 (5.7%) 13 (6.2%) 0.260 Transfusion 5 (3.6%) 7 (0.9%) 1 (0.5%) 1 (0.5%) 0.018* Postoperative Infection Fixation hardware failure 3 (2.2%) 1 (0.7%) 9 (1.2%) 13 (1.7%) 3 (1.4%) 3 (1.4%) 7 (3.3%) 17 (8.0%) 0.191 0.000* Re-fixation 1 (0.7%) 8 (1.1%) 1 (0.5%) 5 (2.4%) 0.273 Long-term Relapse 0 (0.0%) 6 (0.8%) 1 (0.5%) 7 (3.3%) 0.005* Table 3 Legend. Data are presented as n (%). p-values from Fisher's exact test. *p < 0.05. In Table 4 , analysis of overjet changes demonstrated a mixed pattern concerning BMI categories. The initial surgical correction (T1-T0) showed a statistically significant difference among groups (p = 0.001), with the magnitude of correction increasing as BMI increased, ranging from 10.1 ± 5.5 mm (underweight) to 12.4 ± 5.5 mm (obese). However, the post-surgical changes observed in the subsequent intervals (T2-T1, T3-T1 and T4-T1) were not statistically significant across the BMI categories (p = 0.313, 0.759, 0.948, respectively). Table 4 Correlation between BMI and overjet changes Overjet changes Underweight (< 18.5) Normal (18.5–23.0) Overweight (23–25.0) Obese (≥ 25.0) p-value T1-T0 10.1 ± 5.5 11.2 ± 5.5 11.9 ± 5.4 12.4 ± 5.5 0.001* T2-T1 -1.04 ± 1.88 -1.21 ± 1.95 -1.41 ± 2.07 -1.41 ± 2.17 0.313 T3-T1 -1.45 ± 1.95 -1.33 ± 2.10 -1.44 ± 2.16 -1.52 ± 2.22 0.759 T4-T1 -1.68 ± 2.39 -1.58 ± 2.36 -1.48 ± 2.26 -1.52 ± 2.38 0.948 Table 4 Legend. Data are presented as Mean ± SD. T0: 2 weeks preoperatively T1: immediately after surgery, T2: 2 months postoperatively, T3: 5 months postoperatively, T4: 12 months postoperatively. p-values from Kruskal-Wallis test. Discussion BMI is widely recognized as a major risk factor for postoperative complications. In general surgery, high BMI increases the risk of prolonged operative time, extended hospital stays, readmission, reoperation, infection, and severe systemic complications such as renal failure, pulmonary embolism, and deep vein thrombosis.[7] Orthopedic surgery, which similarly involves open reduction and internal fixation to withstand mechanical load, has reported higher rates of malunion and hardware removal in obese patients.[13] In orthognathic surgery, previous study found that high BMI was associated with prolonged operative time and antibiotic use but showed no significant effect on overall outcomes.[9] However, these studies did not analyze specific complications such as bleeding, bad split, relapse or fixation hardware failure. Therefore, comprehensive studies on BMI and complications specific to orthognathic surgery remain lacking. This study investigated the association between BMI and postoperative complications in orthognathic surgery. Our analysis demonstrates that BMI influences postoperative complications in orthognathic surgery through two distinct mechanisms: physiological reserve in underweight patients and biomechanical stability in obese patients. A comparison of patient baseline characteristics across BMI categories revealed statistically significant differences in the distribution of age, sex, and surgical type. Age tended to increase slightly with BMI, and men exhibited a higher average BMI than women, consistent with general population statistics. [12] Notably, the incidence of mandibular only surgery significantly increased in the obese group. This reflects a conservative surgical choice driven by the clinical limitation that increased soft tissue thickness associated with high BMI compromises the accuracy of predicting postoperative soft tissue changes, making the esthetic impact of skeletal changes less noticeable to both the patient and the surgeon. The BMI category did not have a statistically significant effect on the operative time for either bimaxillary or mandibular only orthognathic procedures (p > 0.05). This suggests that anatomical factors such as increased soft tissue in obese patients did not meaningfully prolong the operative time. The overall complication rate for bad split defined as an unfavorable fracture of the mandible during BSSRO was within the conventional range.[14] However, the institution's educational environment, where residents and fellows performed osteotomies during BSSRO, likely contributed to this rate. The analysis of physiological vulnerability showed that the underweight group exhibited a higher incidence of bad split (10%) compared to other groups, though this difference did not reach statistical significance (p = 0.2600). This trend may be linked to the thinner cortical bone thickness observed in low BMI patients, a known risk factor for bad split.[15–17] Furthermore, the necessity for blood transfusion during surgery was significantly higher in the underweight group (p < 0.05). Low BMI patients, who tend to possess lower absolute circulating blood volume and hemoglobin levels, quickly reach the transfusion threshold due to hemodynamic instability even with minor blood loss, suggesting their limited physiological reserve.[11, 18] This vulnerability is supported by the observation that three out of five patients readmitted due to malnutrition, belonged to the underweight group, potentially indicating their extreme sensitivity to poor nutritional intake during the MMF period. Interestingly, contrary to many previous studies identifying BMI as a risk factor for infection, this study found no statistically significant association between BMI and postoperative infection.[6, 19] This may suggest that localized contamination factors specific to orthognathic surgery, such as oral hygiene challenges and food impaction due to orthodontic hardware and surgical wafer, may exert a greater influence on infection risk than systemic factors like poor blood supply in adipose tissue.[20] A key finding on fixation hardware failure is the biomechanical instability observed in the obese group. The institution primarily utilizes semi-rigid fixation with a sliding plate during BSSRO to guide the condyle toward its physiological position and reduce excessive torque on the condyle.[21] The obese group exhibited significantly higher rates for fixation hardware failure, indicating that the forces acting on the fixation hardware exceeded the physiological tolerance of the plate. The forces exerted by the proximal and distal segments lead to a rapid shortening of the plate's fatigue life. Obese patient are known to possess developed masticatory muscles; during the recovery phase, the forceful action of these muscles imposes persistent biomechanical overload on the plate.[22] The consequence of this hardware failure appears to be reflected in long term outcome, where the incidence of relapse was statistically and significantly highest in the obese group (p < 0.05). The heightened risk of relapse in obese group is attributed to the combined effect of their masticatory muscles exerting a greater propensity for regression than those in normal weight group, and the excessive mass of soft tissue around the face contributing to instability through gravitational forces. Despite this finding of significantly higher relapse, the study's specific analysis of overjet regression revealed a complex pattern. This study, which excluded patients who underwent mandibular advance BSSRO, showed a difference in overjet quantity between pre-operative and immediate post-operative periods of approximately 11 mm. While previous studies reported overjet relapse following setback surgery to be up to 20%, the obese group in the current study demonstrated a regression of approximately 15%.[23] Critically, statistical analysis showed no significant difference in the amount of regression across the various BMI categories. This result suggests that the degree of overjet regression is independent of the patient's BMI category. Therefore, to prevent relapse in obese patients, surgical strategies should consider enhanced fixation methods such as additional fixation points to counteract increased biomechanical forces. Moreover, the consideration of preoperative weight management may reduce both masticatory muscle force and soft tissue mass. Postoperative monitoring protocols should be more intensive for obese patients to detect early signs of hardware complications. The incidence of complications following orthognathic surgery in this study demonstrated a pattern similar to those reported in the literature. All complications, with the exception of bad split, exhibited a low incidence rate, remaining below 3%, thereby supporting the notion that orthognathic surgery is a relatively safe procedure. Furthermore, although a statistically significant difference in complication rates was observed when comparing outcomes across Body Mass Index (BMI) classifications, a limitation arose. Despite a large overall sample size, the absolute incidence of each specific complication was inherently low, resulting in an insufficient case count to conduct a robust statistical analysis. Moreover, data pertaining to major complications of orthognathic surgery, such as nerve injury and temporomandibular joint disorder, were excluded from this analysis due to incomplete records. This factor limited the ability to present a comprehensive association between BMI and all relevant complications. Therefore, future research should aim to overcome these limitations and enhance statistical power by expanding the sample size and conducting in-depth analyses based on the systematic recording of major complications. Conclusion This study demonstrates that distinct pathophysiological and biomechanical risks may be associated with different BMI categories in orthognathic surgery. It suggests that personalized clinical management could be beneficial: Physiological support, such as nutritional supplementation and close monitoring for hemoglobin level and clinical signs of anemia, is critical for underweight patients. Conversely the implementation of enhanced fixation strategies to withstand masticatory forces, coupled with consideration of preoperative weight management, is recommended for improving long-term stability in obese patients. Abbreviations BMI Body Mass Index BSSRO Bilateral Sagittal Split Ramus Osteotomy MMF Maxillomandibular Fixation SD Standard deviation WHO World Health Organization Declarations Ethics approval and consent to participate This study was approved by the Institutional Review Board (IRB) of Pusan National University Dental Hospital (IRB No. PNUDH-2024-034). Due to the retrospective nature of the study and the use of de-identified data, the requirement for informed consent was waived by the IRB of Pusan National University Dental Hospital. All methods were performed in accordance with the relevant guidelines and regulations (Declaration of Helsinki). Consent for publication Not applicable. (As no individual person’s data in any form are included in this study.) Availability of data and materials The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request. Competing interests The authors declare that they have no competing interests. Funding Not applicable. Author’s contributions JB was responsible for the study's conceptualization, performed the formal statistical analysis, and drafted the original manuscript. YDK served as the principal investigator, designed the research protocol, performed all surgical procedures for the 1309 patients, and critically revised the manuscript for important intellectual content as the corresponding author. CM, UK, CWL, and BC were involved in the acquisition of clinical data and perioperative management. JCB, SL, NRC, and JMS contributed to the long-term clinical follow-up, data curation, and interpretation of postoperative complications. All authors have read and approved the final version of the manuscript to be published. Acknowledgement The authors declare that there are no additional acknowledgements. Clinical trial number Clinical Research Information Service KCT0011570, February 3, 2026. Retrospectively registered. References Reyneke JP, Sullivan SM: Essentials of orthognathic surgery: Quintessence Publishing Company; 2003. Naran S, Steinbacher DM, Taylor JA: Current concepts in orthognathic surgery. Plastic and reconstructive surgery 2018, 141(6):925e-936e. Friscia M, Sbordone C, Petrocelli M, Vaira LA, Attanasi F, Cassandro FM, Paternoster M, Iaconetta G, Califano L: Complications after orthognathic surgery: our experience on 423 cases. Oral and Maxillofacial Surgery 2017, 21(2):171-177. Kim Y-K: Complications associated with orthognathic surgery. Journal of the Korean Association of Oral and Maxillofacial Surgeons 2017, 43(1):3-15. Zaroni FM, Cavalcante RC, da Costa DJ, Kluppel LE, Scariot R, Rebellato NLB: Complications associated with orthognathic surgery: a retrospective study of 485 cases. 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The American journal of medicine 1997, 102(3):277-283. Kamruzzaman M: Is BMI associated with anemia and hemoglobin level of women and children in Bangladesh: A study with multiple statistical approaches. PloS one 2021, 16(10):e0259116. Seo MH, Lee W-Y, Kim SS, Kang J-H, Kang J-H, Kim KK, Kim B-Y, Kim Y-H, Kim W-J, Kim EM: 2018 Korean society for the study of obesity guideline for the management of obesity in Korea. Journal of obesity & metabolic syndrome 2019, 28(1):40. Smadi Z, Lingam S, Muwalla R, Halayqeh S, Pereira D, Saleh K: Weight on the fixation: the influence of body mass index on lower extremity fracture fixation outcomes. Injury 2025:112864. Steenen S, Becking A: Bad splits in bilateral sagittal split osteotomy: systematic review of fracture patterns. International journal of oral and maxillofacial surgery 2016, 45(7):887-897. Jiang N, Wang M, Bi R, Wu G, Zhu S, Liu Y: Risk factors for bad splits during sagittal split ramus osteotomy: a retrospective study of 964 cases. British Journal of Oral and Maxillofacial Surgery 2021, 59(6):678-682. Porto OCL, Silva BSdF, Silva JA, Estrela CRdA, Alencar AHGd, Bueno MdR, Estrela C: CBCT assessment of bone thickness in maxillary and mandibular teeth: an anatomic study. Journal of Applied Oral Science 2020, 28:e20190148. Yasa Y, Buyuk SK, Genc E: Comparison of mandibular cortical bone among obese, overweight, and normal weight adolescents using panoramic mandibular index and mental index. Clinical Oral Investigations 2020, 24(8):2919-2924. Frisch N, Wessell NM, Charters M, Peterson E, Cann B, Greenstein A, Silverton CD: Effect of body mass index on blood transfusion in total hip and knee arthroplasty. Orthopedics 2016, 39(5):e844-e849. Drake T, Nepogodiev D, Chapman S, Glasbey J, Khatri C, Kong C, Claireaux H, Bath M, Mohan M, McNamee L: Multicentre prospective cohort study of body mass index and postoperative complications following gastrointestinal surgery. British Journal of Surgery 2016, 103(9):1157-1172. Seidelman JL, Mantyh CR, Anderson DJ: Surgical site infection prevention: a review. Jama 2023, 329(3):244-252. Mavili ME, Canter HI, Saglam-Aydinatay B: Semirigid fixation of mandible and maxilla in orthognathic surgery: stability and advantages. Annals of plastic surgery 2009, 63(4):396-403. Kobayashi R, Haga S, Umehara A, Takakaze M, Akatsuka K, Nakano H: Quantitative and qualitative evaluation of the masseter muscle by ultrasonography and correlation with whole body health status. Journal of Physical Therapy Science 2024, 36(3):136-141. Alrashidi HA, Almutairi MH, Almohaimeed SM, Homdi LA, Alharbi AF, Alazmi GS, Mesmeli RO, Alanazi AM, Muaini SA, Alraddadi KA: Evaluating post-surgical stability and relapse in orthognathic surgery: A comprehensive review. Cureus 2024, 16(10). Additional Declarations No competing interests reported. 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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-8704505","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":590981059,"identity":"b5074b80-3a7f-4c61-a1eb-02709eb0ab99","order_by":0,"name":"Junghwan Bae","email":"","orcid":"","institution":"Pusan ​​National University Dental Hospital","correspondingAuthor":false,"prefix":"","firstName":"Junghwan","middleName":"","lastName":"Bae","suffix":""},{"id":590981061,"identity":"c180f2b2-892f-4ed9-87ef-28b119aa8fe4","order_by":1,"name":"Chiho Moon","email":"","orcid":"","institution":"Pusan ​​National University Dental Hospital","correspondingAuthor":false,"prefix":"","firstName":"Chiho","middleName":"","lastName":"Moon","suffix":""},{"id":590981064,"identity":"6b1c24a1-3b20-4d40-b566-81110df02184","order_by":2,"name":"Ungang Kim","email":"","orcid":"","institution":"Pusan ​​National University Dental Hospital","correspondingAuthor":false,"prefix":"","firstName":"Ungang","middleName":"","lastName":"Kim","suffix":""},{"id":590981067,"identity":"26096b57-1763-4510-96ec-65d140bd4e36","order_by":3,"name":"Chung-woo Lee","email":"","orcid":"","institution":"Pusan ​​National University Dental Hospital","correspondingAuthor":false,"prefix":"","firstName":"Chung-woo","middleName":"","lastName":"Lee","suffix":""},{"id":590981068,"identity":"7373b160-3df4-4e98-8149-ad7b397d778d","order_by":4,"name":"Borim Choi","email":"","orcid":"","institution":"Pusan ​​National University Dental Hospital","correspondingAuthor":false,"prefix":"","firstName":"Borim","middleName":"","lastName":"Choi","suffix":""},{"id":590981069,"identity":"651ace26-14f4-46f8-8d49-60bc3392319f","order_by":5,"name":"Ji-Cheul Bae","email":"","orcid":"","institution":"Pusan National University Hospital","correspondingAuthor":false,"prefix":"","firstName":"Ji-Cheul","middleName":"","lastName":"Bae","suffix":""},{"id":590981070,"identity":"152a933a-4a19-4954-9b76-6079b4c84dce","order_by":6,"name":"Soobyung Lee","email":"","orcid":"","institution":"Pusan National University Hospital","correspondingAuthor":false,"prefix":"","firstName":"Soobyung","middleName":"","lastName":"Lee","suffix":""},{"id":590981071,"identity":"9127f4ff-94fa-4e8c-898c-b1d4f7c175c5","order_by":7,"name":"Na-Rae Choi","email":"","orcid":"","institution":"Pusan National University Hospital","correspondingAuthor":false,"prefix":"","firstName":"Na-Rae","middleName":"","lastName":"Choi","suffix":""},{"id":590981073,"identity":"fd106a43-bfec-49c5-8977-5229718e2258","order_by":8,"name":"Jae-min Song","email":"","orcid":"","institution":"Pusan ​​National University Dental Hospital","correspondingAuthor":false,"prefix":"","firstName":"Jae-min","middleName":"","lastName":"Song","suffix":""},{"id":590981075,"identity":"6b9b2cfe-8c8c-49e4-9b19-0847e4e53ed6","order_by":9,"name":"Yong-Deok Kim","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA4ElEQVRIiWNgGAWjYFCCNIYDDGzMDPwIETYitUg2kKKFAaTF4ACxWgyOpyUeulFmbW98u8f4w88dDPL8DWxpH/BqOfPswOGcc+mJ2+6cMZPsPcNgOOMA2+EZeLXcSG84nNt2OMHsRo4ZA28bA+MGBvZm/A6DarE3npFj/PFvG4M9EVrSDoC0MG6QyDGQBtqSuIGB7TBeLZJnniWA/TLjzrEyadk2ieQZh9mS8WrhO55m/DkHGGL8s5s3f3zbZmPb395mjFeLwgEYSwJGMuPVwMAg34CqZRSMglEwCkYBJgAAjA5NF6MkMGwAAAAASUVORK5CYII=","orcid":"","institution":"Pusan ​​National University Dental Hospital","correspondingAuthor":true,"prefix":"","firstName":"Yong-Deok","middleName":"","lastName":"Kim","suffix":""}],"badges":[],"createdAt":"2026-01-27 01:08:50","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8704505/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8704505/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":102962962,"identity":"1c08469e-5e4a-4fea-83bc-ac8b1f67072c","added_by":"auto","created_at":"2026-02-19 04:12:26","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":4845845,"visible":true,"origin":"","legend":"\u003cp\u003eIntraoperative bad split patterns during BSSRO.\u003c/p\u003e\n\u003cp\u003eLegend: Representative radiographs demonstrating buccal cortex fracture (a and b) and unfavorable fracture extending to the condylar process (c) encountered during the sagittal split.\u003c/p\u003e","description":"","filename":"Figure1.png","url":"https://assets-eu.researchsquare.com/files/rs-8704505/v1/ca6c363b91c1cf8b8869af1d.png"},{"id":102963157,"identity":"693a5cfc-224d-453d-b8ff-cf515caa4755","added_by":"auto","created_at":"2026-02-19 04:14:01","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":2358427,"visible":true,"origin":"","legend":"\u003cp\u003eClinical and radiographic examples of fixation hardware failure.\u003c/p\u003e\n\u003cp\u003eLegend: Images showing various hardware complications: mechanical plate fracture (a), plate dislocation from the original position (b), and unplanned plate removal necessitated by associated osteomyelitis (c) .\u003c/p\u003e","description":"","filename":"Figure2.png","url":"https://assets-eu.researchsquare.com/files/rs-8704505/v1/a290b0d9ca7c69c2dae9796d.png"},{"id":103056512,"identity":"52631e5a-d6c5-4503-b141-5944a8146ae8","added_by":"auto","created_at":"2026-02-20 09:12:39","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":1500461,"visible":true,"origin":"","legend":"\u003cp\u003eSkeletal relapse patterns following initial surgical correction.\u003c/p\u003e\n\u003cp\u003eLegend: Postoperative clinical outcomes illustrating common relapse types: anterior crossbite (a), anterior open bite (b), and facial skeletal asymmetry (c) .\u003c/p\u003e","description":"","filename":"Figure3.png","url":"https://assets-eu.researchsquare.com/files/rs-8704505/v1/16bbb5c247f21fdaff04da2f.png"},{"id":102963155,"identity":"be49fa5b-b36e-4588-861d-6c21196278b0","added_by":"auto","created_at":"2026-02-19 04:14:01","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":134334,"visible":true,"origin":"","legend":"\u003cp\u003eProportional distribution of major complications categorized by BMI.\u003c/p\u003e\n\u003cp\u003eLegend: Comparative analysis showing the incidence of complications across underweight, normal, overweight, and obese groups. Statistical significance was observed for transfusion rates in the underweight group and hardware failure in the obese group .\u003c/p\u003e","description":"","filename":"Figure4.png","url":"https://assets-eu.researchsquare.com/files/rs-8704505/v1/3b6c39823a0d564241b309f9.png"},{"id":103056982,"identity":"f721c68d-058a-4b58-a468-23e59ddc9468","added_by":"auto","created_at":"2026-02-20 09:27:22","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":9948480,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8704505/v1/0293acfa-3d55-4eea-a6da-9ef465797de5.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Differential Impact of Body Mass Index on Postoperative Complications in Orthognathic Surgery: A retrospective study of 1,309 patients","fulltext":[{"header":"Background","content":"\u003cp\u003eOrthognathic surgery is a surgical treatment designed to correct structural disharmonies of the maxillofacial skeleton to enhance both function and esthetics.[1, 2] Despite recent advancements in three-dimensional computed tomography imaging, virtual surgical planning, and patient-specific implants, complications remain a significant concern, ranging from early events such as hemorrhage, infection, bad splits, and hardware issues to long-term sequelae including skeletal relapse, malocclusion, and temporomandibular joint disorder.[3–5]\u003c/p\u003e \u003cp\u003eBody Mass Index (BMI) is recognized as a crucial independent predictor of perioperative complications across various surgical specialties. With the recent global increase in obesity prevalence, the influence of elevated BMI on surgical outcomes has become a major clinical concern.[6] According to previous studies, a high BMI increases the risk of postoperative complications across diverse surgical fields, where obese patients face a higher risk of thrombosis, infection, and readmission compared to normal weight individuals.[7, 8] This phenomenon is largely attributed to the synergistic effects of chronic inflammation associated with obesity, compromised blood flow, and reduced healing capacity in adipose tissue.[9, 10] Conversely, underweight patients carry a distinct risk profile, with an increased need for blood transfusion due to reduced preoperative blood volume. Both extremes of the BMI spectrum significantly influence clinical prognosis.[11]\u003c/p\u003e \u003cp\u003eDespite the established role of BMI in general surgery, its specific impact on orthognathic surgery remains inadequately characterized. Unlike general surgical procedures, orthognathic surgery involves unique biomechanical demands including precise bone repositioning, rigid fixation under masticatory forces, and complex soft tissue dynamics. Therefore, a comprehensive analysis of BMI-associated complications specific to orthognathic surgery is needed.\u003c/p\u003e \u003cp\u003eThis study retrospectively analyzes 1,309 cases performed by a single surgeon over 13 years to evaluate the incidence, types, and, most importantly, the association between BMI and the risk of postoperative complications. By meticulously examining these complication patterns, this analysis aims to enhance surgical safety and establish practical clinical guidelines for prevention and management.\u003c/p\u003e "},{"header":"Patients and methods","content":"\u003ch3\u003e1) Study Design and Patient Selection\u003c/h3\u003e\u003cp\u003eThis retrospective chart review study analyzed patients who underwent orthognathic surgery performed by a single surgeon over a 13-year period from January 2012 to December 2024. Patients were required to have a minimum postoperative follow-up period of 6 months. This study was approved by the IRB (Number: 2025-02-002), and a waiver of informed consent was granted due to the retrospective nature of the study.\u003c/p\u003e\u003ch3\u003e2) Inclusion and Exclusion Criteria\u003c/h3\u003e\u003cp\u003eInclusion Criteria:\u003c/p\u003e\u003cp\u003e- Patients who underwent orthognathic surgery for skeletal malocclusion and facial\u003c/p\u003e\u003cp\u003easymmetry.\u003c/p\u003e\u003cp\u003eExclusion Criteria:\u003c/p\u003e\u003cul\u003e \u003cli\u003e \u003cp\u003ePatients with congenital facial deformities.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003ePatients who underwent maxillofacial reconstructive surgery due to trauma history.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003ePatients with insufficient perioperative or follow-up periods below the required criteria.\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e\u003ch3\u003e3) BMI Measurement and Classification\u003c/h3\u003e\u003cp\u003ePreoperative BMI was calculated using the formula: Weight (kg) / Height (m)\u003csup\u003e2\u003c/sup\u003e. Patients were categorized into four groups based on the World Health Organization (WHO) Asia-Pacific Classification system, which is suitable for the study population:[12]\u003c/p\u003e\u003cul\u003e \u003cli\u003e \u003cp\u003eUnderweight: BMI \u0026lt; 18.5\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eNormal Weight: 18.5 ≤ BMI \u0026lt; 23.0\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eOverweight: 23.0 ≤ BMI \u0026lt; 25.0\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eObese: 25.0 ≤ BMI\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e\u003cp\u003e \u003cb\u003e4) Surgical procedure\u003c/b\u003e \u003c/p\u003e\u003cp\u003e- Bimaxillary surgery: The bimaxillary procedure, comprising a Le Fort I osteotomy followed\u003c/p\u003e\u003cp\u003eby a Bilateral Sagittal Split Ramus Osteotomy (BSSRO), was performed sequentially. Initially,\u003c/p\u003e\u003cp\u003ethe Le Fort I osteotomy was executed; after the down fracture, bony interference was\u003c/p\u003e\u003cp\u003eremoved, and the maxilla was positioned using an intermediate wafer and secured with\u003c/p\u003e\u003cp\u003eL-shape plates. Subsequently, the BSSRO was carried out using the Obwegeser-Dal Pont\u003c/p\u003e\u003cp\u003etechnique. The distal mandibular segment was repositioned according to the final wafer to\u003c/p\u003e\u003cp\u003ecorrect the deformity, after which interference between the proximal and distal segments was\u003c/p\u003e\u003cp\u003eremoved and the condyle was seated in a stable position. The mandibular segments were then\u003c/p\u003e\u003cp\u003efixed using sliding plates in a semi-rigid fixation method; if this was inadequate, alternative\u003c/p\u003e\u003cp\u003erigid (screw) or non-rigid fixation methods were considered. Finally, Maxillomandibular\u003c/p\u003e\u003cp\u003eFixation (MMF) was applied on the second postoperative day and maintained for seven days.\u003c/p\u003e\u003cp\u003e- Mandibular only surgery: This procedure involved a BSSRO and was performed identically\u003c/p\u003e\u003cp\u003eto the mandibular component of the bimaxillary surgery. MMF was applied immediately post-\u003c/p\u003e\u003cp\u003eurgery and maintained for five days.\u003c/p\u003e\u003ch3\u003e5) Definition and Classification of Complications\u003c/h3\u003e\u003cp\u003ePostoperative complications included all adverse outcomes occurring from immediately after surgery to the final follow-up. Based on detailed medical records, the following items were analyzed as dependent variables for association with BMI:\u003c/p\u003e\u003cul\u003e \u003cli\u003e \u003cp\u003eBad split [Figure \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e]: Unfavorable fracture deviating from the osteotomy line during BSSRO\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e\u003cul\u003e \u003cli\u003e \u003cp\u003eExcessive bleeding: Hemorrhage requiring either blood transfusion or surgical intervention\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e\u003ch3\u003e1) Transfusion: Administration of packed red blood cells necessitated by postoperative\u003c/h3\u003e\u003cp\u003ehemoglobin levels ≤ 7.0 coupled with clinical signs of acute anemia\u003c/p\u003e\u003ch3\u003e2) Surgical intervention: Procedures performed under local or general anesthesia for\u003c/h3\u003e\u003cp\u003eevacuation of hematoma and subsequent bleeding control\u003c/p\u003e\u003cp\u003e- Infection: A bacterial infection manifesting at the surgical site with clinical signs of\u003c/p\u003e\u003cp\u003einflammation, requiring admission for intravenous antibiotic therapy and surgical drainage\u003c/p\u003e\u003cp\u003e- Re-fixation: A subsequent corrective procedure performed under general anesthesia to\u003c/p\u003e\u003cp\u003eaddress malunion or significant malocclusion arising from the primary surgery\u003c/p\u003e\u003cp\u003e- Malnutrition: A state of postoperative nutritional deficiency shown by re-admission after\u003c/p\u003e\u003cp\u003edischarge due to systemic weakness, lethargy, or other signs resulting from restrictive diet\u003c/p\u003e\u003cp\u003e- Fixation hardware failure [Figure \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e]:\u003c/p\u003e\u003cp\u003e1) Plate fracture: Mechanical failure and breakage of fixation hardware\u003c/p\u003e\u003cp\u003e2) Plate dislocation: Displacement of fixation plates from original position\u003c/p\u003e\u003cp\u003e3) Plate removal: Unplanned surgical removal of hardware\u003c/p\u003e\u003cp\u003e- Relapse [Figure \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e]: Return of skeletal segments toward preoperative position after initial surgical correction\u003c/p\u003e\u003cp\u003e1) Anterior crossbite: Recurrence of Class III relationship after initial surgical correction\u003c/p\u003e\u003cp\u003e2) Anterior open bite: Recurrence of a vertical gap between the opposing anterior teeth\u003c/p\u003e\u003cp\u003e3) Asymmetry: Recurrence of facial skeletal asymmetry after initial surgical correction\u003c/p\u003e\u003ch3\u003e6) Limitation\u003c/h3\u003e\u003cp\u003eDue to insufficient objective and consistent documentation of nerve injury and temporomandibular disorder symptoms during the retrospective chart review process, these complications were excluded from the analysis. Therefore, the complication rates presented in this study are limited to the items defined above.\u003c/p\u003e\u003ch3\u003e7) Statistical Analysis\u003c/h3\u003e\u003cp\u003eUnivariate analysis was performed to determine the association between BMI categories and the occurrence of selected complications. The Chi-square test was used for this analysis, and Fisher's exact test was applied to calculate the accurate p-value when the assumption of the Chi-square test was violated. Furthermore, to compare the difference in continuous variables across three or more independent groups, One-way ANOVA test was used when the data satisfied the assumption of normal distribution, and the Kruskal-Wallis test was utilized to compare medians when the assumption of normal distribution was not met. To ensure adequate statistical power, only complications with at least 10 events were included in the analysis. The level of statistical significance for all analyses was set at p \u0026lt; 0.05. Statistical analyses were performed using SPSS version 23.0 (IBM Co., Armonk, NY, USA).\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eIn Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, the analysis of the 1,309 orthognathic surgery patients showed statistically significant differences in age, sex distribution and type of surgery across the four BMI categories. Mean age increased significantly with BMI, ranging from 22.0\u0026thinsp;\u0026plusmn;\u0026thinsp;4.3 years in the underweight group to 23.7\u0026thinsp;\u0026plusmn;\u0026thinsp;5.2 years in the obese group (p\u0026thinsp;=\u0026thinsp;0.0186). Sex distribution showed a highly significant association with BMI (p\u0026thinsp;\u0026lt;\u0026thinsp;0.0001), with females constituting the majority of the underweight group (69.6%), while males were predominant in the obese (69.2%) groups. Furthermore, the type of surgery differed significantly by BMI (p\u0026thinsp;=\u0026thinsp;0.0002). Bimaxillary surgery was most frequent in the underweight group (74.6%) but saw a steady decline, becoming the least frequent procedure in the obese group (55.0%). Conversely, mandibular only surgery increased consistently with BMI, peaking at 45.0% in the obese patient cohort. The mean operative time showed no statistically significant differences across BMI categories for either bimaxillary surgery (p\u0026thinsp;=\u0026thinsp;0.2060) or mandibular only surgery (p\u0026thinsp;=\u0026thinsp;0.3256).\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\u003eBaseline characteristics of 1309 patients undergoing orthognathic surgery stratified by Body Mass Index categories.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\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 \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCharacteristic\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eUnderweight\u003c/p\u003e \u003cp\u003e(\u0026lt;\u0026thinsp;18.5)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNormal\u003c/p\u003e \u003cp\u003e(18.5\u0026ndash;23.0)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eOverweight\u003c/p\u003e \u003cp\u003e(23\u0026ndash;25.0)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eObese\u003c/p\u003e \u003cp\u003e(\u0026ge;\u0026thinsp;25.0)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\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\u003e\u003cb\u003eN\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e138\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e748\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e212\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e211\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAge (years)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e22.0\u0026thinsp;\u0026plusmn;\u0026thinsp;4.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e22.7\u0026thinsp;\u0026plusmn;\u0026thinsp;5.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e23.0\u0026thinsp;\u0026plusmn;\u0026thinsp;5.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e23.7\u0026thinsp;\u0026plusmn;\u0026thinsp;5.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.017*\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"6\" nameend=\"c6\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSex\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMale, n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e42 (30.4%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e325 (43.4%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e146 (68.9%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e146 (69.2%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.000*\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFemale, n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e96 (69.6%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e423 (56.6%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e66 (31.1%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e65 (30.8%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"6\" nameend=\"c6\" namest=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSurgery type\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBimaxillary\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e103 (74.6%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e516 (69.0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e135 (63.7%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e116 (55.0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.000*\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMandibular only\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e34 (24.6%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e222 (29.7%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e76 (35.8%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e95 (45.0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eOperative time\u003c/b\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003e(minutes)\u003c/b\u003e\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=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBimaxillary\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e196.4\u0026thinsp;\u0026plusmn;\u0026thinsp;40.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e191.3\u0026thinsp;\u0026plusmn;\u0026thinsp;38.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e195.3\u0026thinsp;\u0026plusmn;\u0026thinsp;38.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e186.7\u0026thinsp;\u0026plusmn;\u0026thinsp;38.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.206\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMandibular only\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e107.4\u0026thinsp;\u0026plusmn;\u0026thinsp;29.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e111.6\u0026thinsp;\u0026plusmn;\u0026thinsp;35.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e105.8\u0026thinsp;\u0026plusmn;\u0026thinsp;29.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e104.8\u0026thinsp;\u0026plusmn;\u0026thinsp;36.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.325\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\u003eTable\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e Legend. Data are presented as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD or n (%). One-way ANOVA for continuous variables; Chi-square test for categorical variables. *p\u0026thinsp;\u0026lt;\u0026thinsp;0.05.\u003c/p\u003e \u003cp\u003eIn Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, among the 1,309 patients, 192 major postoperative complications were documented. Bad split was the most frequent complication (82 cases, 6.3%), followed by fixation hardware failure (34 cases, 2.59%). Infection occurred in 22 cases, with mandibular infections significantly outweighing maxillary infections (17 vs. 5 cases). Bleeding complications occurred in 19 cases (14 requiring transfusion, 5 requiring surgical intervention). Relapse was reported in 15 cases, presenting mainly as anterior crossbite (8 cases). Additional complications included re-fixation (15 cases) and malnutrition (5 cases).\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 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eIncidence and classification of postoperative complications\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eClassification\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eN\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eTotal (Incidence rate)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eBad split\u003c/b\u003e\u003c/p\u003e \u003cp\u003eRight mandible\u003c/p\u003e \u003cp\u003eLeft mandible\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e39\u003c/p\u003e \u003cp\u003e43\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e82 (6.3%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eFixation hardware failure\u003c/b\u003e\u003c/p\u003e \u003cp\u003ePlate fracture\u003c/p\u003e \u003cp\u003ePlate dislocation\u003c/p\u003e \u003cp\u003ePlate removal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e15\u003c/p\u003e \u003cp\u003e10\u003c/p\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e34 (2.6%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eInfection\u003c/b\u003e\u003c/p\u003e \u003cp\u003eMaxilla\u003c/p\u003e \u003cp\u003eMandible\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e5\u003c/p\u003e \u003cp\u003e17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e22 (1.7%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eBleeding\u003c/b\u003e\u003c/p\u003e \u003cp\u003eTransfusion\u003c/p\u003e \u003cp\u003eSurgical intervention\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e14\u003c/p\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e19 (1.5%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eRe-fixation\u003c/b\u003e\u003c/p\u003e \u003cp\u003eMaxilla\u003c/p\u003e \u003cp\u003eMandible\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3\u003c/p\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e15 (1.2%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eRelapse\u003c/b\u003e\u003c/p\u003e \u003cp\u003eAnterior crossbite\u003c/p\u003e \u003cp\u003eAnterior open bite\u003c/p\u003e \u003cp\u003eAsymmetry\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e8\u003c/p\u003e \u003cp\u003e6\u003c/p\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e15 (1.2%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eMalnutrition\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e5 (0.4%)\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\u003eTable\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e Legend. Complications were documented from immediately after surgery to the final follow-up period.\u003c/p\u003e \u003cp\u003eIn Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, among major complications, only transfusion and relapse showed significant associations with BMI category (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05).[Figure \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e] Transfusion risk was highest in the underweight group (3.6%, p\u0026thinsp;=\u0026thinsp;0.0181), significantly exceeding the rates in the normal (0.9%), overweight (0.5%), and obese (0.5%) groups. Conversely, relapse and fixation hardware failure showed significant association with high BMI (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05), occurring at a rate of 3.3% in the obese group compared to 0.8% in the normal group and 0.0% in the underweight group. Bad split, infection, and re-fixation showed no significant association with BMI (p\u0026thinsp;=\u0026thinsp;0.1913).\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 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eAssociation between BMI and the Incidence of postoperative complications\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\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\u003eUnderweight\u003c/p\u003e \u003cp\u003e(\u0026lt;\u0026thinsp;18.5)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNormal\u003c/p\u003e \u003cp\u003e(18.5\u0026ndash;23.0)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eOverweight\u003c/p\u003e \u003cp\u003e(23\u0026ndash;25.0)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eObese\u003c/p\u003e \u003cp\u003e(\u0026ge;\u0026thinsp;25.0)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003ep-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIntraoperative\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBad split\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e14 (10.1%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e43 (5.7%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e12 (5.7%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e13 (6.2%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.260\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTransfusion\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e5 (3.6%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e7 (0.9%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1 (0.5%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1 (0.5%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.018*\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003ePostoperative\u003c/b\u003e\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=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eInfection\u003c/p\u003e \u003cp\u003e Fixation hardware failure\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3 (2.2%)\u003c/p\u003e \u003cp\u003e1 (0.7%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e9 (1.2%)\u003c/p\u003e \u003cp\u003e13 (1.7%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3 (1.4%)\u003c/p\u003e \u003cp\u003e3 (1.4%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e7 (3.3%)\u003c/p\u003e \u003cp\u003e17 (8.0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.191\u003c/p\u003e \u003cp\u003e0.000*\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRe-fixation\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1 (0.7%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e8 (1.1%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1 (0.5%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e5 (2.4%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.273\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eLong-term\u003c/b\u003e\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=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRelapse\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0 (0.0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e6 (0.8%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1 (0.5%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e7 (3.3%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.005*\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 \u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e Legend. Data are presented as n (%). p-values from Fisher's exact test. *p\u0026thinsp;\u0026lt;\u0026thinsp;0.05.\u003c/p\u003e \u003cp\u003eIn Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, analysis of overjet changes demonstrated a mixed pattern concerning BMI categories. The initial surgical correction (T1-T0) showed a statistically significant difference among groups (p\u0026thinsp;=\u0026thinsp;0.001), with the magnitude of correction increasing as BMI increased, ranging from 10.1\u0026thinsp;\u0026plusmn;\u0026thinsp;5.5 mm (underweight) to 12.4\u0026thinsp;\u0026plusmn;\u0026thinsp;5.5 mm (obese). However, the post-surgical changes observed in the subsequent intervals (T2-T1, T3-T1 and T4-T1) were not statistically significant across the BMI categories (p\u0026thinsp;=\u0026thinsp;0.313, 0.759, 0.948, respectively).\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 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eCorrelation between BMI and overjet changes\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOverjet changes\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eUnderweight\u003c/p\u003e \u003cp\u003e(\u0026lt;\u0026thinsp;18.5)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNormal\u003c/p\u003e \u003cp\u003e(18.5\u0026ndash;23.0)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eOverweight\u003c/p\u003e \u003cp\u003e(23\u0026ndash;25.0)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eObese\u003c/p\u003e \u003cp\u003e(\u0026ge;\u0026thinsp;25.0)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\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\u003eT1-T0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e10.1\u0026thinsp;\u0026plusmn;\u0026thinsp;5.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e11.2\u0026thinsp;\u0026plusmn;\u0026thinsp;5.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e11.9\u0026thinsp;\u0026plusmn;\u0026thinsp;5.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e12.4\u0026thinsp;\u0026plusmn;\u0026thinsp;5.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.001*\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eT2-T1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e-1.04\u0026thinsp;\u0026plusmn;\u0026thinsp;1.88\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e-1.21\u0026thinsp;\u0026plusmn;\u0026thinsp;1.95\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e-1.41\u0026thinsp;\u0026plusmn;\u0026thinsp;2.07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e-1.41\u0026thinsp;\u0026plusmn;\u0026thinsp;2.17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.313\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eT3-T1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e-1.45\u0026thinsp;\u0026plusmn;\u0026thinsp;1.95\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e-1.33\u0026thinsp;\u0026plusmn;\u0026thinsp;2.10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e-1.44\u0026thinsp;\u0026plusmn;\u0026thinsp;2.16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e-1.52\u0026thinsp;\u0026plusmn;\u0026thinsp;2.22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.759\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eT4-T1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e-1.68\u0026thinsp;\u0026plusmn;\u0026thinsp;2.39\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e-1.58\u0026thinsp;\u0026plusmn;\u0026thinsp;2.36\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e-1.48\u0026thinsp;\u0026plusmn;\u0026thinsp;2.26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e-1.52\u0026thinsp;\u0026plusmn;\u0026thinsp;2.38\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.948\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\u003eTable\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e Legend. Data are presented as Mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD. T0: 2 weeks preoperatively T1: immediately after surgery, T2: 2 months postoperatively, T3: 5 months postoperatively, T4: 12 months postoperatively. p-values from Kruskal-Wallis test.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eBMI is widely recognized as a major risk factor for postoperative complications. In general surgery, high BMI increases the risk of prolonged operative time, extended hospital stays, readmission, reoperation, infection, and severe systemic complications such as renal failure, pulmonary embolism, and deep vein thrombosis.[7] Orthopedic surgery, which similarly involves open reduction and internal fixation to withstand mechanical load, has reported higher rates of malunion and hardware removal in obese patients.[13] In orthognathic surgery, previous study found that high BMI was associated with prolonged operative time and antibiotic use but showed no significant effect on overall outcomes.[9] However, these studies did not analyze specific complications such as bleeding, bad split, relapse or fixation hardware failure.\u003c/p\u003e \u003cp\u003eTherefore, comprehensive studies on BMI and complications specific to orthognathic surgery remain lacking. This study investigated the association between BMI and postoperative complications in orthognathic surgery. Our analysis demonstrates that BMI influences postoperative complications in orthognathic surgery through two distinct mechanisms: physiological reserve in underweight patients and biomechanical stability in obese patients. A comparison of patient baseline characteristics across BMI categories revealed statistically significant differences in the distribution of age, sex, and surgical type. Age tended to increase slightly with BMI, and men exhibited a higher average BMI than women, consistent with general population statistics. [12]\u003c/p\u003e \u003cp\u003eNotably, the incidence of mandibular only surgery significantly increased in the obese group. This reflects a conservative surgical choice driven by the clinical limitation that increased soft tissue thickness associated with high BMI compromises the accuracy of predicting postoperative soft tissue changes, making the esthetic impact of skeletal changes less noticeable to both the patient and the surgeon. The BMI category did not have a statistically significant effect on the operative time for either bimaxillary or mandibular only orthognathic procedures (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05). This suggests that anatomical factors such as increased soft tissue in obese patients did not meaningfully prolong the operative time.\u003c/p\u003e \u003cp\u003eThe overall complication rate for bad split defined as an unfavorable fracture of the mandible during BSSRO was within the conventional range.[14] However, the institution's educational environment, where residents and fellows performed osteotomies during BSSRO, likely contributed to this rate. The analysis of physiological vulnerability showed that the underweight group exhibited a higher incidence of bad split (10%) compared to other groups, though this difference did not reach statistical significance (p\u0026thinsp;=\u0026thinsp;0.2600). This trend may be linked to the thinner cortical bone thickness observed in low BMI patients, a known risk factor for bad split.[15\u0026ndash;17] Furthermore, the necessity for blood transfusion during surgery was significantly higher in the underweight group (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). Low BMI patients, who tend to possess lower absolute circulating blood volume and hemoglobin levels, quickly reach the transfusion threshold due to hemodynamic instability even with minor blood loss, suggesting their limited physiological reserve.[11, 18] This vulnerability is supported by the observation that three out of five patients readmitted due to malnutrition, belonged to the underweight group, potentially indicating their extreme sensitivity to poor nutritional intake during the MMF period.\u003c/p\u003e \u003cp\u003eInterestingly, contrary to many previous studies identifying BMI as a risk factor for infection, this study found no statistically significant association between BMI and postoperative infection.[6, 19] This may suggest that localized contamination factors specific to orthognathic surgery, such as oral hygiene challenges and food impaction due to orthodontic hardware and surgical wafer, may exert a greater influence on infection risk than systemic factors like poor blood supply in adipose tissue.[20]\u003c/p\u003e \u003cp\u003eA key finding on fixation hardware failure is the biomechanical instability observed in the obese group. The institution primarily utilizes semi-rigid fixation with a sliding plate during BSSRO to guide the condyle toward its physiological position and reduce excessive torque on the condyle.[21] The obese group exhibited significantly higher rates for fixation hardware failure, indicating that the forces acting on the fixation hardware exceeded the physiological tolerance of the plate. The forces exerted by the proximal and distal segments lead to a rapid shortening of the plate's fatigue life. Obese patient are known to possess developed masticatory muscles; during the recovery phase, the forceful action of these muscles imposes persistent biomechanical overload on the plate.[22]\u003c/p\u003e \u003cp\u003eThe consequence of this hardware failure appears to be reflected in long term outcome, where the incidence of relapse was statistically and significantly highest in the obese group (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). The heightened risk of relapse in obese group is attributed to the combined effect of their masticatory muscles exerting a greater propensity for regression than those in normal weight group, and the excessive mass of soft tissue around the face contributing to instability through gravitational forces.\u003c/p\u003e \u003cp\u003eDespite this finding of significantly higher relapse, the study's specific analysis of overjet regression revealed a complex pattern. This study, which excluded patients who underwent mandibular advance BSSRO, showed a difference in overjet quantity between pre-operative and immediate post-operative periods of approximately 11 mm. While previous studies reported overjet relapse following setback surgery to be up to 20%, the obese group in the current study demonstrated a regression of approximately 15%.[23] Critically, statistical analysis showed no significant difference in the amount of regression across the various BMI categories. This result suggests that the degree of overjet regression is independent of the patient's BMI category.\u003c/p\u003e \u003cp\u003eTherefore, to prevent relapse in obese patients, surgical strategies should consider enhanced fixation methods such as additional fixation points to counteract increased biomechanical forces. Moreover, the consideration of preoperative weight management may reduce both masticatory muscle force and soft tissue mass. Postoperative monitoring protocols should be more intensive for obese patients to detect early signs of hardware complications.\u003c/p\u003e \u003cp\u003eThe incidence of complications following orthognathic surgery in this study demonstrated a pattern similar to those reported in the literature. All complications, with the exception of bad split, exhibited a low incidence rate, remaining below 3%, thereby supporting the notion that orthognathic surgery is a relatively safe procedure. Furthermore, although a statistically significant difference in complication rates was observed when comparing outcomes across Body Mass Index (BMI) classifications, a limitation arose. Despite a large overall sample size, the absolute incidence of each specific complication was inherently low, resulting in an insufficient case count to conduct a robust statistical analysis.\u003c/p\u003e \u003cp\u003eMoreover, data pertaining to major complications of orthognathic surgery, such as nerve injury and temporomandibular joint disorder, were excluded from this analysis due to incomplete records. This factor limited the ability to present a comprehensive association between BMI and all relevant complications. Therefore, future research should aim to overcome these limitations and enhance statistical power by expanding the sample size and conducting in-depth analyses based on the systematic recording of major complications.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThis study demonstrates that distinct pathophysiological and biomechanical risks may be associated with different BMI categories in orthognathic surgery. It suggests that personalized clinical management could be beneficial: Physiological support, such as nutritional supplementation and close monitoring for hemoglobin level and clinical signs of anemia, is critical for underweight patients. Conversely the implementation of enhanced fixation strategies to withstand masticatory forces, coupled with consideration of preoperative weight management, is recommended for improving long-term stability in obese patients.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cdiv class=\"DefinitionList\"\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eBMI\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eBody Mass Index\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eBSSRO\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eBilateral Sagittal Split Ramus Osteotomy\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eMMF\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eMaxillomandibular Fixation\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eSD\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eStandard deviation\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eWHO\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eWorld Health Organization\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was approved by the Institutional Review Board (IRB) of Pusan National University Dental Hospital (IRB No. PNUDH-2024-034). Due to the retrospective nature of the study and the use of de-identified data, the requirement for informed consent was waived by the IRB of Pusan National University Dental Hospital. All methods were performed in accordance with the relevant guidelines and regulations (Declaration of Helsinki).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable. (As no individual person\u0026rsquo;s data in any form are included in this study.)\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.\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.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor\u0026rsquo;s contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eJB was responsible for the study\u0026apos;s conceptualization, performed the formal statistical analysis, and drafted the original manuscript. YDK served as the principal investigator, designed the research protocol, performed all surgical procedures for the 1309 patients, and critically revised the manuscript for important intellectual content as the corresponding author. CM, UK, CWL, and BC were involved in the acquisition of clinical data and perioperative management. JCB, SL, NRC, and JMS contributed to the long-term clinical follow-up, data curation, and interpretation of postoperative complications. All authors have read and approved the final version of the manuscript to be published.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that there are no additional acknowledgements.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical trial number\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eClinical Research Information Service KCT0011570, February 3, 2026. Retrospectively registered.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eReyneke JP, Sullivan SM: Essentials of orthognathic surgery: Quintessence Publishing Company; 2003.\u003c/li\u003e\n\u003cli\u003eNaran S, Steinbacher DM, Taylor JA: Current concepts in orthognathic surgery. Plastic and reconstructive surgery 2018, 141(6):925e-936e.\u003c/li\u003e\n\u003cli\u003eFriscia M, Sbordone C, Petrocelli M, Vaira LA, Attanasi F, Cassandro FM, Paternoster M, Iaconetta G, Califano L: Complications after orthognathic surgery: our experience on 423 cases. Oral and Maxillofacial Surgery 2017, 21(2):171-177.\u003c/li\u003e\n\u003cli\u003eKim Y-K: Complications associated with orthognathic surgery. Journal of the Korean Association of Oral and Maxillofacial Surgeons 2017, 43(1):3-15.\u003c/li\u003e\n\u003cli\u003eZaroni FM, Cavalcante RC, da Costa DJ, Kluppel LE, Scariot R, Rebellato NLB: Complications associated with orthognathic surgery: a retrospective study of 485 cases. Journal of Cranio-Maxillofacial Surgery 2019, 47(12):1855-1860.\u003c/li\u003e\n\u003cli\u003eYuan K, Chen H-L: Obesity and surgical site infections risk in orthopedics: a meta-analysis. International journal of surgery 2013, 11(5):383-388.\u003c/li\u003e\n\u003cli\u003eBamgbade OA, Rutter TW, Nafiu OO, Dorje P: Postoperative complications in obese and nonobese patients. World journal of surgery 2007, 31(3):556-560.\u003c/li\u003e\n\u003cli\u003eZusmanovich M, Kester BS, Schwarzkopf R: Postoperative complications of total joint arthroplasty in obese patients stratified by BMI. The Journal of arthroplasty 2018, 33(3):856-864.\u003c/li\u003e\n\u003cli\u003eShah S, Block-Wheeler N, Liu K, Weintraub MR, Williams WB: The association of body mass index and early outcomes following orthognathic surgery. Journal of Oral and Maxillofacial Surgery 2024, 82(7):782-791.\u003c/li\u003e\n\u003cli\u003eThomas EJ, Goldman L, Mangione CM, Marcantonio ER, Cook EF, Ludwig L, Sugarbaker D, Poss R, Donaldson M, Lee TH: Body mass index as a correlate of postoperative complications and resource utilization. The American journal of medicine 1997, 102(3):277-283.\u003c/li\u003e\n\u003cli\u003eKamruzzaman M: Is BMI associated with anemia and hemoglobin level of women and children in Bangladesh: A study with multiple statistical approaches. PloS one 2021, 16(10):e0259116.\u003c/li\u003e\n\u003cli\u003eSeo MH, Lee W-Y, Kim SS, Kang J-H, Kang J-H, Kim KK, Kim B-Y, Kim Y-H, Kim W-J, Kim EM: 2018 Korean society for the study of obesity guideline for the management of obesity in Korea. Journal of obesity \u0026amp; metabolic syndrome 2019, 28(1):40.\u003c/li\u003e\n\u003cli\u003eSmadi Z, Lingam S, Muwalla R, Halayqeh S, Pereira D, Saleh K: Weight on the fixation: the influence of body mass index on lower extremity fracture fixation outcomes. Injury 2025:112864.\u003c/li\u003e\n\u003cli\u003eSteenen S, Becking A: Bad splits in bilateral sagittal split osteotomy: systematic review of fracture patterns. International journal of oral and maxillofacial surgery 2016, 45(7):887-897.\u003c/li\u003e\n\u003cli\u003eJiang N, Wang M, Bi R, Wu G, Zhu S, Liu Y: Risk factors for bad splits during sagittal split ramus osteotomy: a retrospective study of 964 cases. British Journal of Oral and Maxillofacial Surgery 2021, 59(6):678-682.\u003c/li\u003e\n\u003cli\u003ePorto OCL, Silva BSdF, Silva JA, Estrela CRdA, Alencar AHGd, Bueno MdR, Estrela C: CBCT assessment of bone thickness in maxillary and mandibular teeth: an anatomic study. Journal of Applied Oral Science 2020, 28:e20190148.\u003c/li\u003e\n\u003cli\u003eYasa Y, Buyuk SK, Genc E: Comparison of mandibular cortical bone among obese, overweight, and normal weight adolescents using panoramic mandibular index and mental index. Clinical Oral Investigations 2020, 24(8):2919-2924.\u003c/li\u003e\n\u003cli\u003eFrisch N, Wessell NM, Charters M, Peterson E, Cann B, Greenstein A, Silverton CD: Effect of body mass index on blood transfusion in total hip and knee arthroplasty. Orthopedics 2016, 39(5):e844-e849.\u003c/li\u003e\n\u003cli\u003eDrake T, Nepogodiev D, Chapman S, Glasbey J, Khatri C, Kong C, Claireaux H, Bath M, Mohan M, McNamee L: Multicentre prospective cohort study of body mass index and postoperative complications following gastrointestinal surgery. British Journal of Surgery 2016, 103(9):1157-1172.\u003c/li\u003e\n\u003cli\u003eSeidelman JL, Mantyh CR, Anderson DJ: Surgical site infection prevention: a review. Jama 2023, 329(3):244-252.\u003c/li\u003e\n\u003cli\u003eMavili ME, Canter HI, Saglam-Aydinatay B: Semirigid fixation of mandible and maxilla in orthognathic surgery: stability and advantages. Annals of plastic surgery 2009, 63(4):396-403.\u003c/li\u003e\n\u003cli\u003eKobayashi R, Haga S, Umehara A, Takakaze M, Akatsuka K, Nakano H: Quantitative and qualitative evaluation of the masseter muscle by ultrasonography and correlation with whole body health status. Journal of Physical Therapy Science 2024, 36(3):136-141.\u003c/li\u003e\n\u003cli\u003eAlrashidi HA, Almutairi MH, Almohaimeed SM, Homdi LA, Alharbi AF, Alazmi GS, Mesmeli RO, Alanazi AM, Muaini SA, Alraddadi KA: Evaluating post-surgical stability and relapse in orthognathic surgery: A comprehensive review. Cureus 2024, 16(10).\u003c/li\u003e\n\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-oral-health","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ohea","sideBox":"Learn more about [BMC Oral Health](http://bmcoralhealth.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/ohea/default.aspx","title":"BMC Oral Health","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Orthognathic surgery, complication, Body mass index, Recurrence, Transfusion, Obesity, Underweight","lastPublishedDoi":"10.21203/rs.3.rs-8704505/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8704505/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground\u003c/strong\u003e: Body Mass Index (BMI) is a well-established predictor of postoperative complications in various surgical fields; however, its specific role in orthognathic surgery has not been sufficiently investigated. This study aimed to comprehensively analyze the association between BMI and postoperative complications in orthognathic surgery to enhance surgical safety and establish practical clinical guidelines.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods\u003c/strong\u003e: A retrospective study was conducted on 1,309 patients who underwent orthognathic surgery performed by a single surgeon from 2012 to 2024. BMI was classified according to the World Health Organization Asia-Pacific criteria: underweight (\u0026lt;18.5 kg/m²), normal (18.5–23.0 kg/m²), overweight (23.0–25.0 kg/m²), and obese (≥25.0 kg/m²). Complications were categorized into intraoperative events, such as bad split and excessive bleeding, and postoperative issues, including hardware failure, infection, and relapse. Statistical analyses were performed using Chi-square or Fisher’s exact tests for categorical variables and One-way ANOVA or Kruskal-Wallis tests for continuous variables.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults\u003c/strong\u003e: Statistically significant differences were observed in complication patterns across BMI categories. Among major complications, the transfusion rate was significantly highest in the underweight group (3.6%, p=0.0181). Conversely, fixation hardware failure (8.0%, p\u0026lt;0.001) and skeletal relapse (3.3%, p=0.0051) were significantly more prevalent in the obese group. While initial surgical overjet change increased with higher BMI (p=0.0011), postoperative overjet changes showed no significant differences among groups. No significant association was observed between BMI and infection rates.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusions\u003c/strong\u003e: This study suggests that distinct pathophysiological and biomechanical risk factors are involved according to BMI categories in orthognathic surgery. Underweight patients show an increased risk of transfusion due to reduced physiological reserve, while obese patients face elevated risks of hardware failure and relapse due to biomechanical instability. Personalized clinical management strategies based on BMI are necessary, including enhanced fixation methods and long-term follow-up for obese patients.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTrial registration: \u003c/strong\u003eClinical Research Information Service KCT0011570, February 3, 2026. 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