Geometric analysis of indications for minimally invasive distal metatarsal osteotomy in treatment of hallux valgus

TL;DR

This paper analyzes when a specific foot surgery is suitable based on geometric modeling of patient radiographs.

Contribution

The study introduces a geometric model to determine the suitability of minimally invasive distal metatarsal osteotomy for hallux valgus.

Findings

MIDMO requires the metatarsal neck to be at least 8 mm wider than the bunion eminence for sufficient fragment contact.

MIDMO may not correct all deformities within the IMA <20° and HV <40° range due to anatomical variations.

Patients with large bunion eminences and narrow metatarsals risk complications from insufficient fragment contact.

Abstract

Minimally invasive distal metatarsal osteotomy (MIDMO) is to be indicated for all patients with angles of IMA <20° and HV <40°, but many authors doubt whether this procedure is capable of correcting all types of hallux valgus deformities. The aims of this study were to perform a geometric analysis of MIDMO indications and to show which preoperative radiological parameters are necessary to achieve sufficient contact between bone fragments and sufficient correction with this operative technique.

A geometric mathematical model in AP and lateral radiographic plane was created based on preoperative measurements of the intermetatarsal angle (IMA), subcapital metatarsal width, medial bunion eminence, and metatarsal length. MIDMO was simulated with possible dorsal/plantar fragment displacement in order to assess postoperative contact between fragments (either 4–5 mm or half of the metatarsal width) and sufficient correction (postoperative IMA 8°).

The metatarsal neck should be at least 8 mm wider from the bunion eminence to achieve the minimally required contact between fragments. For sufficient correction, the metatarsal head translation should be at least 0.018 of the metatarsal length for every degree of IMA reduction. The medial bunion eminence, in comparison with metatarsal width/length size, determines whether MIDMO is a suitable procedure for a given patient.

MIDMO cannot sufficiently correct all deformations within the boundaries of IMA angle <20° and HV angle <40°. In patients with large eminences and narrow metatarsals, complications related to insufficient postoperative fragment contact can be expected, while sufficient hallux valgus correction in patients with small eminences and long metatarsals is questionable.

The online version of this article (doi:10.1186/s13018-015-0304-7) contains supplementary material, which is available to authorized users.

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