Nonoperative estimation of the soleus musculotendinous junction using magnetic resonance imaging

Although it is recognized as the muscle flap of choice for middle-third defects of the lower limb, the capability for even more distal transposition of the soleus muscle remains controversial. Such reach depends directly on the site of insertion of the muscle and previously has not been assessed convincingly without surgical intervention. Magnetic resonance imaging (MRI) may be a noninvasive alternative for determining the distal extent of the musculotendinous junction of the soleus muscle. In our last four patients, preoperative MRI scans were obtained prior to an elective soleus muscle transfer. The distance from the ankle joint to the most distal site of the soleus insertion was measured on the MRI scan and compared with the actual intraoperative measurement, which had a significant correlation (r = 0.98, p = 0.019). A retrospective review of 42 other sagittal ankle MRI scans predicted the mean of this distance to be 1.92 +/- 1.23 cm (range -0.4 to 4.5 cm), compared with gross anatomic dissections in 30 unrelated fresh cadavers, where this was 4.06 +/- 3.11 cm (range -0.7 to 12.5 cm). These additional data are pertinent because they reinforce recognition of the great variation in soleus anatomy, which would limit clinical applications for the distal third of the leg only for those individuals with very distal insertions. The MRI scan can reliably identify the soleus muscle and provides a nonoperative method for evaluation of potential feasibility for its use as a local muscle flap for distal lower extremity defects.