The offset V osteotomy versus the modified Austin with a longer plantar arm: a comparison of mechanical stability.

Abstract

Several studies have tested the strength and various fixation modalities of the long dorsal arm offset V osteotomy, and have proven it to be a stable construct when fixated properly. We believe that a modification of the traditional Austin cuts, with a slightly longer plantar arm, lends itself to greater stability because instead of ground reactive forces applying a distraction moment on the osteotomy, the ground actually compresses the osteotomy leading to greater stability and less chance of failure. We compared the mechanical stability of the long dorsal offset V osteotomy to the slightly longer plantar arm osteotomy using 20 sawbone models, 10 in each study group. The offset V osteotomies were all fixated with two 2.7-mm stainless steel screws through the dorsal arm of the osteotomy, and the longer plantar arm osteotomies were fixated with one 2.4-mm stainless steel screw through the plantar arm of the osteotomy. Results of testing with the 858 Mini Bionix materials testing device, showed a mean load at failure of the long dorsal arm osteotomies of 142.26 N (range 53.16-235.45 N). Mean load at failure of the longer plantar arm osteotomies was 280.07 N (range 184.91-337.39 N). There was a significant difference in the ultimate load at failure between the 2 groups (P < .0001). There was no significant difference in displacement (P = .18) or stiffness (P = .54). The results of our study indicate that the slightly longer plantar arm osteotomy is a more stable construct than the long dorsal arm offset V osteotomy.