Assessing the Usability of Flexor Digiti Minimi Muscle for Opponensplasty: An Anatomic Study

The abductor digiti minimi (ADM) and flexor digiti minimi (FDM) muscles have a similar vascular and nerve supply. The purpose of this study was to assess the feasibility of transferring the FDM instead of ADM for thumb opposition.

Thirty cadaver hands were dissected under loupe magnification to assess the presence of the ADM and FDM muscles as well as their blood and nerve supply. The length of these muscles and their location in relation to the radial aspect of the thumb metacarpophalangeal joint were assessed.

The ADM muscle was present in all cadavers whereas the FDM muscle was absent in 33% of hands. When the dimensions were suitable (53%), the more radially located FDM muscle reached the thumb metacarpophalangeal joint more easily.

Although the dissections revealed considerable variability in FDM anatomy, when present, it can have positional advantage over the ADM for opponensplasty.

In some cases with radial longitudinal deficiency, preservation of ADM function is essential. In these children, the FDM can potentially be explored and transferred if it is found to be suitable.