A 53 year old coach presented after an injury sustained falling down two stairs three months previously. He described experiencing a popping sensation followed by well localised pain around the medial side of his foot and ankle. On examination there was localised tenderness about the medial malleolus and navicular tuberosity, pain and weakness with resisted ankle inversion and an inability to perform single leg calf raises. His foot posture appeared grossly normal however his heel did not move into varus when performing a calf raise.
An x-ray series of the foot is within normal limits, with no significant loss of the medial arch and normal foot architecture. MRI sequences define a full-thickness tear of the tibialis posterior tendon 2.5 cm proximal to the navicular. The proximal tendon stump is retracted behind the medial malleolus, above the level of the ankle mortise. There is a 5 cm gap between the tendon ends. The proximal stump is thickened, measuring 12 x 10 mm. The entire tibialis posterior muscle has oedema with a fibrillary pattern.
After diagnosis this patient was seen by a sub-specialist foot and ankle surgeon. The tendon was not felt to be repairable based on the nature of the tendon, the location of the rupture and the delay from the injury. He underwent a flexor digitorum longus (FDL) tendon transfer with a calcaneal osteotomy. He is currently rehabilitating following surgery.
There is often a considerable delay in the diagnosis of this injury, with one case series highlighting an average time to treatment of 43 months. As a result a high level of suspicion is needed. The injury is generally associated with an eversion injury mechanism. Common presenting symptoms include pain along the course of the tendon, weakness of ankle inversion and a loss of the medial longitudinal arch. Patients generally find calf raises difficult, lack heel varus with calf raises and may display the “too many toes” sign (the appearance of more toes on the affected side when viewed from behind). Younger patients generally sustain an avulsion injury from the insertion into the navicular, while middle aged or elderly individuals general suffer a mid-substance tear (as seen here). In the acute phase x-rays are generally not helpful, with ultrasound or MRI being the most useful imaging modalities. Surgical treatment is usually required. Soft tissue procedures, including primary repair, are effective when the diagnosis is made promptly. In this case that was not possible. A tendon transfer is a good option however the FDL tendon is not as strong as the tibialis posterior and will weaken over time under that amount of load. As a result, further measures are needed to adjust the mechanics of the hindfoot. In this case a medial displacement calcaneal osteotomy, which reduces the lever arm on the tendon, was completed to try to ensure good long term function.
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