Irreducible Ankle Fracture Dislocation Because of Tibialis Posterior and Flexor Digitorum Longus Tendon Entrapment in the Interosseous Membrane: A Case Report.

CASE: We describe the case of a 63-year-old man with anterior ankle dislocation and fracture confirmed by x-ray. Postreduction x-ray and computed tomography (CT) revealed Arbeitsgemeinschaft für Osteosynthesefragen/Orthopaedic Trauma Association (AO/OTA) type 44C3 and Lauge-Hansen pronation-external rotation-type ankle fractures. CONCLUSION: This was a rare case of ankle fracture dislocation because of entrapment of the tibialis posterior and flexor digitorum longus tendons in the interosseous membrane. Tendon entrapment should be suspected in cases of high-energy injuries, Weber type C fractures, Lauge-Hansen pronation-external rotation fractures, syndesmosis widening, and irreducible fractures using manual closed reduction. Fractures and soft tissues should be evaluated by changing the CT settings.

[Injuries of the tibialis posterior tendon: diagnosis and therapy]. / Verletzungen der Sehne des M. tibialis posterior. Diagnostik und Therapie.

Complete traumatic rupture of the tibialis posterior tendon is absolutely rare. From the scarce case reports in the medical literature a extreme pronation-abduction or pronation-external rotation mechanism according to the Lauge-Hansen classification can be presumed, leading to a malleolar fracture because of forced pronation, external rotation and dorsiflexion of the foot. With primary suture the prognosis is favorable. Traumatic dislocations, mostly with luxatio pedis sub talo, are treated by atraumatic reduction and refixation of the retinaculum. Again, the prognosis is favorable. Incomplete traumatic rupture of the tibialis posterior tendon with development of posttraumatic pes plano valgus, according to case reports and our own experience result from severe pronation-external rotation-soft tissue injuries as well as with pronation-abduction or pronation-external rotation-type ankle fractures. In these cases no macroscopic rupture of the tendon is evident, however occult interstitial micro-ruptures can occur because of excessive stretching, which can be determined histologically. If conservative measures fail, a modified Evans osteotomy to lengthen the lateral foot column is indicated. Degenerative complete and incomplete ruptures of the tibialis posterior tendon are predominantly seen in women more than 42 years old. Staging of this entity can be achieved with clinical tests (muscular force, external rotation), ultrasound, weight-bearing x-rays, CT and MRT. According to the degree of decompensation of tendon function, treatment consists of augmentation, modified Evans procedure or triple arthrodesis of the hind-foot.