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.

Comparison of screw-fixation stabilities of first metatarsal shaft osteotomies: a biomechanical study.

OBJECTIVES: Although metatarsal shaft osteotomies have become popular in the surgical treatment of moderate or advanced hallux valgus owing to better reduction and stability, they present fixation problems as the angular correction increases. The purpose of this biomechanical study was to evaluate the effects of widely used metatarsal shaft osteotomies and a newly defined osteotomy modification on the stability of screw fixation at greater angular corrections. METHODS: Upon evaluation of known problems of shaft osteotomies, a new osteotomy type was designed that might provide an adequate contact area while allowing a greater angular correction, increased stability, and safer osteosynthesis. In our new modification of the Mau osteotomy, the proximal plantar notch that was defined for the Sammarco's modification to increase the contact area was created more proximally making an angle of about 50 degrees with the osteotomy, and the osteotomy was extended until 5 mm to the distal joint surface, aiming to increase the contact area and intrinsic stability. For biomechanical analysis, 30 standard metatarsal bone models (Sawbones) were divided into five groups equal in number for the following osteotomy methods: Myerson's modification of the Ludloff osteotomy, Mau osteotomy, scarf osteotomy, offset V osteotomy, and the new modification of the Mau osteotomy. Osteotomies were performed with a standard correction of 10 degrees in the intermetatarsal angle, followed by appropriate osteosynthesis with fixation by two Acutrak compression screws. The relationship between osteotomies and osteosynthesis in terms of stability was assessed by the three-point bending test. RESULTS: The mean stiffness of the Ludloff osteotomy was significantly lower than all the other osteotomy groups (p<0.05). Stiffness of the Mau group was significantly greater than three groups (p<0.05), but the difference from the offset V group did not reach significance. Stiffness of the new Mau modification was significantly greater than the scarf group (p=0.016), but did not differ significantly from the offset V group. Osteotomy groups with and without notching had similar stiffness values (p=0.582), whereas single notching was associated with a significantly greater stiffness compared to double notching (p=0.031). CONCLUSION: Our findings suggest that the new modification to the proximal shaft osteotomies moves the center of rotation of angulation more proximally and provides sufficient stability of screw fixation.