Three-Dimensional Analysis of the First Metatarsal Bone in Minimally Invasive Distal Linear Metatarsal Osteotomy for Hallux Valgus

Abstract

Background: Modified Bösch osteotomy (distal linear metatarsal osteotomy [DLMO]) is one of the minimally invasive correctional surgeries for hallux valgus. The 3-dimensional correctional angles and distances of the first metatarsal bone in DLMO have not been clarified. The purpose of this study was to analyze the 3-dimensional postoperative morphological changes of the first metatarsal bone in DLMO. Methods: Twenty patients (30 feet) who underwent DLMO were enrolled. Preoperative plain radiographs and computed tomography (CT) scans of the feet were examined. Postoperative radiographs and CT scans were also obtained after bone union. The surface data of the pre- and postoperative first metatarsals were reconstructed from the CT data. The positions of the distal ends of the first metatarsals described with respect to the proximal ends were calculated using CT surface-matching technique. Results: The distal end of the first metatarsal after DLMO was significantly supinated (10.2 ± 6.0 degrees, P < .001), adducted (6.0 ± 11.8 degrees, P = .004), dorsiflexed (11.1 ± 10.9, P < .001), shortened (7.4 ± 2.5 mm, P < .001), elevated (2.3 ± 3.1 mm, P = .001), and laterally shifted (8.2 ± 3.0 mm, P < .001) compared to the preoperative metatarsal distal end. Supination correction demonstrated a significant correlation with adduction correction ( r = 0.659, P < .001) on correlation analyses between these parameters. Conclusion: The 3-dimensional corrections of the first metatarsal bone after DLMO were evaluated. Pronation and abduction were successfully corrected. Furthermore, adduction correction might be an important factor affecting correction of pronation. Level of Evidence: Level IV, retrospective case series.