Early Weight Loss After Sleeve Gastrectomy Selectively Improves Intermetatarsal Angle Without Affecting Hallux Valgus Angle

Background/Objectives: While bariatric surgery is known to improve plantar pressure distribution and reduce foot-related symptoms, its impact on radiographic forefoot alignment parameters, such as the intermetatarsal angle (IMA) and hallux valgus angle (HVA), remains unclear, highlighting the need for further investigation. The aim of this study was to quantitatively evaluate changes of HVA and IMA in patients undergoing bariatric surgery and to determine whether weight loss-induced reductions in mechanical load are associated with differential changes of the forefoot. Methods: Weight-bearing anteroposterior foot radiographs of 102 patients who underwent laparoscopic sleeve gastrectomy were obtained preoperatively and at 6 months postoperatively. HVA and IMA were measured using standardized digital techniques. Changes in angular parameters were analyzed in relation to body mass index reduction. Results: Intra-observer reliability was excellent for all angular measurements (ICC: 0.987–0.999, p < 0.001). Radiographic evaluation demonstrated no significant change in HVA (p = 0.147), whereas IMA showed a significant decrease postoperatively (p < 0.001). No significant change was observed in HVA distribution (p = 0.341), and although the proportion of patients within the normal IMA range increased, this did not reach statistical significance (p = 0.091). Correlation analysis revealed significant associations of postoperative angles with age and body weight parameters (p < 0.05), while no significant relationship was found between changes in body weight or BMI and angular measurements (p > 0.05). Conclusions: Sleeve gastrectomy significantly improves biomechanically driven aspects of forefoot alignment (decrease in IMA), while structural deformities (HVA) remain unchanged in the short-term. These findings highlight that obesity-related forefoot pathology is predominantly linked to altered load distribution rather than fixed structural deformity, suggesting that radiographic parameters reflecting biomechanical loading are more sensitive to weight loss.