SUBTALAR ANKLE INSTABILITY - A REVIEW

The aetiology of chronic functional lateral ankle instability is fairl y well understood. Pathophysiological factors such as mechanical insta bility, proprioceptive deficit and peroneal muscle weakness have been demonstrated. Subtalar instability has been in focus during the last y ears as one of the possible factors behind chronic functional instabil ity of the foot. The exact aetiology and the true incidence of subtala r ligament injuries remain unknown. Most subtalar ligamentous injuries probably occur in combination with injuries of the talo-tibial articu lation. Subtalar instability can have the characteristics of chronic l ateral instability or recurrent ankle sprains. Patients with chronic s ubtalar instability typically complain of 'giving way' symptoms and a history of recurrent sprains. Clinical examination including increased inwards rotation and forward displacement of the calcaneus may not be sufficient for the differentiation between ankle and subtalar instabi lity. Radiographic imaging using stress radiographs may be necessary t o assess subtalar instability. Subtalar instability can be defined as chronic functional instability with increased values of talar tilt and talo-calcaneal displacement as measured with standardised stress radi ographs. Few authors have addressed the treatment of subtalar instabil ity and the condition has not been clearly defined. Subtalar instabili ty can be treated either with a tendon transfer or tenodesis procedure , such as the Chrisman-Snook or triligamentous tenodeses, or with an a natomic ligament reconstruction using the calcaneo-fibular, lateral ta lo-calcaneal and cervical ligaments combined with a reinforcement of t he inferior extensor retinaculum. There have been no studies comparing anatomical and non-anatomical reconstructions and the long term resul ts after ligamentous stabilisation are unknown. The focus of this arti cle is on subtalar instability causing chronic functional ankle instab ility.