# Female Radiological Metatarsal Morphometry and Diameter Suitability of Intramedullary Implants Used for Midfoot Charcot

## TL;DR

This study finds that female metatarsal anatomy may not be suitable for standard intramedullary implants used in midfoot Charcot treatment.

## Contribution

The study is the first to show a mismatch between female metatarsal dimensions and available implants for midfoot Charcot fusion.

## Key findings

- M5 metatarsal had higher inner width than M2, M3, and M4.
- M2 had higher outer width than M3 and M4.
- Most metatarsals were unsuitable for standard implant diameters based on cut-off values.

## Abstract

Radiological biometrics of the metatarsal have been reported in few studies but mostly with no relevance to clinical settings. The smaller female metatarsal diameter could be an impediment for intramedullary implants. This study investigates female radiological metatarsal morphometry for diameter suitability of intramedullary implants used for midfoot Charcot fusion.

Standing foot roentgenograms of 143 female patients were collected for radiological measurements. Cortical thickness at the metatarsal neck level was calculated by subtracting inner width from outer width values. After hypothetical reaming, inner width, outer width, and cortical thickness mean values were considered for suitability estimation. Implant suitability was deemed acceptable when (a) inner width values more than the cut‐off value of 6 mm and/or (b) cortical thickness more than the cut‐off value of 2 mm (1 mm on each cortex side).

The results were (a) inner width: M5 had a higher mean value when compared to M2, M3, and M4 (p < 0.00001) with no difference between central metatarsals and (b) outer width: M2 showed a significantly higher outer width than M3 and M4 (p < 0.00001) with no difference with M5. Based on the cut‐off values, the simulated reaming width values to accept implant diameter were found unsuitable for M2, M3, and M4 and the estimated cortical thickness values were found unsuitable for M3, M4, and M5.

Our study indicates for the first time a mismatch between the inner width of the lateral metatarsals at the neck level with the commercially available Charcot‐specific IM implants for female patients.