Assessment of the appropriateness of tendon transfer procedures and the necessity for excising the posterior tibial tendon (PTT) in stage II PTT dysfunction.

12 patients undergoing surgical treatment for unilateral PTT dysfunction underwent magnetic resonance imaging of the tibialis posterior (TP) and flexor digitorum longus (FDL) muscle bellies.

All patients had atrophy of the TP muscle compared to the normal leg (mean 10.7%, p = 0.008). In those patients with a complete rupture of PTT there was replacement of the TP muscle by fatty infiltration. Conversely, the FDL muscle showed a compensatory hypertrophy (mean 17.2%, p< 0.002).

Treatment of stage II posterior tibial tendon (PTT) dysfunction remains controversial. These findings support the use of FDL as the tendon of choice for augmentation of PTT in stage II disease. This study also demonstrates that in the presence of a complete rupture, excision of the PTT is a reasonable surgical procedure and pure tenodesis will fail because the TP muscle belly undergoes fatty infiltration. In patients with a diseased but intact PTT there was no fatty infiltration and the TP muscle volume was at least 83% of the normal side in all cases. We therefore suggest that in the presence of an intact PTT the TP muscle may provide some useful function if used to augment the FDL transfer when the diseased tendon is excised.