Biomechanical substantiation of the algorithm for choosing the type of corrective osteotomy of the fifth metatarsal bone in the treatment of tailor’s bunion

Abstract

Background. Joint deformity between the main phalanx of the fifth toe and the fifth metatarsal bone is called tailor’s bunion. Its treatment is most often surgical. At the same time, there is no unified single approach regarding the use of osteotomies, their type and localization on the metatarsal bone (distal, diaphyseal, and proximal). Goal: based on the biomechanical studies, to substantiate the corrective possibilities of Weil and chevron distal osteotomies to correct valgus deformity of the fifth metatarsal bone depending on its geometric parameters. Materials and methods. Two types of corrective osteotomies were modeled: Weil and chevron osteotomy. We determined the maximum possible values of valgus deformity of the fifth metatarsal bone, which can be eliminated with the help of these osteotomies, depending on the geometric parameters of the fifth metatarsal bone. To determine the latter, radiometry was performed on 39 digital radiographs of the patients’ feet. Results. Taking into account the relatively small angular deviation of the fifth metatarsal bone whose value is most often observed in the range from 10 to 15° at the norm of 8°, the angular deformity can be compensated by linear displacement of the head of the metatarsal bone. Since the head displacement is performed in the horizontal plane, both osteotomies in this case work equally. The zone of maximum possible correction for deformity is determined within the range from 12°, with a length of 60 mm and a diameter of 8 mm, to 15.5°, with a length of 45 mm and a diameter of 12 mm. Given that there is some balance between bone length and diameter, the maximum deformity that can be corrected with Weil and chevron corrective osteotomies is a deformity of up to 14°. Conclusions. Weil and chevron corrective osteotomies can be used to correct the fifth metatarsal valgus deformity (tailor’s bunion) and are effective when the M4M5 angle does not exceed 14°. In cases where the M4M5 angle exceeds 15°, it is advisable to use proximal corrective osteotomies of the fifth metatarsal bone for the treatment of tailor’s bunion.