First metatarsal proximal crescent and chevron shaft osteotomies stability comparison

Abstract

Objective: The treatment of the bunion deformity usually require an osteotomy of the first ray. The kind and the site of the osteotomy have being discussed among the orthopaedic surgeons. The purpose of this study was to compare the stability of chevron shaft and proximal crescentic osteotomies, techniques recommended for correction of moderate and severe bunion deformities. The classic chevron was used as gold standard, eventhough the technique is recommended for correction of mild bunion deformities, it is recognized by its high intrinsic stability. Methods: The stability of the chevron shaft, proximal crescent and distal chevron osteotomies, performed in sawbone models and fixated as clinically recommended was compared. The three osteotomy/fixation techniques were performed on 15 sawbone first ray. The models were loaded to failure at the fixation site by applying a load through the plantar surface of the first metatarsal head. Force versus displacement curves were obtained to calculate the failure load. Statistical differences among the three groups were determinated by the Kruskal-Wallis test. Results: The crescent osteotomy group was less stable than either the distal chevron osteotomy or the chevron shaft osteotomy group. The fact that the chevron shaft osteotomy group was more stable than the proximal crescent osteotomy group is very important, once they both are indicated for moderate and severe deformities. Conclusion: Based on sawbones models, the chevron shaft osteotomy fixated with three mini screws is more stable than the proximal crescentic osteotomy fixated with a single 3.5mm screw. The clinical use of chevron shaft osteotomy for correction of moderate to severe bunion deformities may decrease the incidence of dorsal malunion and transfer metatarsalgia.