Comparison of contact surface areas of metatarsal diaphyseal osteotomies for correction of hallux valgus: Experimental study.

OBJECTIVE: This study aimed to determine, pre-correction, the potential change in the osteotomy-site bony contact surface area that would occur during standard metatarsal diaphyseal procedures with the Baran-Unal modification of Mau osteotomy and then to compare it, post-correction, with the actual osteotomy-site bony contact surface area changes for a standard degree of deformity correction. METHODS: A total of 30 standard, same sized, biomechanically equivalent, left first metatarsal sawbones were included in this experimental study. They were divided equally into five groups for each of the planned osteotomy techniques: Myerson's modification of Ludloff, Mau, scarf, Offset V, and Baran-Unal modification of Mau osteotomy. The normal osteotomy for each sample was considered as the control, while the corrective osteotomy was the test. Computerized tomography scans and three-dimensional (3D) reconstruction imaging were performed for objective and accurate measurements. The techniques of the osteotomy and post-corrective osteotomy bony contact surface areas were investigated by the two independent research assistants. RESULTS: There was a statistically significant difference between the contact surface area changes of all pre- and post-corrective osteotomy groups (P<0.05). When the pre- and post-correction contact surface areas of any one group were compared with the other groups, the differences were or were not statistically significant. Mean differences between pre-correction and post-correction areas for Ludloff, Mau, scarf, Offset V, and Baran-Unal osteotomies were 180.7, 122.3, 226.2, 191.9, and 68.9 mm2, and the percentages of area loss were 22.9%, 15.5%, 28.6%, 24.3%, and 8.7%, respectively. The most bony contact area was found in the scarf osteotomy group (mean pre-correction area: 490.5 mm2 and mean post-correction area: 264.3 mm2), but the Baran-Unal modification group has significantly the highest post-correction bony contact area among the all other groups (mean pre-correction area: 413.3 mm2 and mean post-correction area: 344.4 mm2). CONCLUSION: Metatarsal diaphyseal osteotomies for hallux valgus deformity have the potential not only for deformity correction, but also for contact surface area preservation. This study reaffirms the considerable potential of this new Baran-Unal modification to confer outstanding contact surface area values, even with the operative correction of hallux valgus deformity.