Body Mass Index Changes and Muscle Loss After Orthognathic Surgery: A Prospective Study.

Background: Orthognathic surgery is routinely performed to correct malocclusion and dentofacial deformities. However, postoperative morbidities, such as nutritional deficiencies and consequent muscle loss, can arise.

Purpose: This study aimed to estimate body mass index (BMI) changes and muscle loss in patients following orthognathic surgery.

Study design, setting, and sample: This prospective cohort study involved patients who underwent bimaxillary surgery at the Erciyes University Oral and Maxillofacial Surgery Hospital from April 2022 to April 2023. Exclusion criteria were contraindications for bioelectrical impedance analysis (eg, cardiovascular stents, pacemakers, joint prostheses, and severe peripheral angiopathy), refusal to participate, or systemic steroid treatment.

Predictor variables: The predictor variable was time, coded as T0 (baseline), T1 (first month), T2 (third month), and T3 (sixth month) postoperatively.

Main outcome variable(s): The primary outcome variable in this study was BMI, assessed at T0, postoperative T1, T2, and T3. Secondary outcomes were muscle loss, body fat percentage, measurements taken using the bioelectrical impedance analysis device (TANITA RD-545, Tanita Corp., Tokyo, Japan), handgrip strength, skinfold measurements and blood concentration levels (vitamin D3, glucose, triglycerides, albumin, ferritin, folic acid, and vitamin B12).

Covariates: The study's covariates were age and sex.

Analyses: Descriptive statistics and 1-way analysis of variance were used for data analysis, with statistical significance set at a P value ≤ .05.

Results: The study included 60 subjects (median age: 23.0 years [interquartile range: 21.0 to 28.7]), with 18 (30%) male and 42 (70%) female participants. Preoperative weight averaged 62.47 ± 1.55 kg, with women at 59.1 ± 9.9 kg and men at 70.3 ± 13 kg (P < .001). Preoperative mean BMI was 22.14 kg/m², dropping to 21.15 kg/m² in T1 and gradually increasing to 21.83 kg/m² by T3, with statistically significant differences across time points (P < .001). Muscle mass decreased statistically significant in the postoperative period, showing a maximum mean reduction of -1.79 kg at T1 (P < .001). Although partial recovery was observed by T3 (-0.71 kg compared to baseline), preoperative levels were not fully restored.

Conclusion and relevance: Weight and muscle loss persisted below preoperative levels at T3. The patient-specific nutritional plans may contribute to optimize postoperative recovery.