MEASUREMENT OF PLANTAR PRESSURE DISTRIBUT ION DURING GAIT FOR DIAGNOSIS OF FUNCTIONAL LATERAL ANKLE INSTABILITY

Chronic functional instability of the lateral ankle may be difficult t o distinguish from mechanical instability when radiological stress tes t reveal only small ligamentous defects. When a decision for or agains t surgical reconstruction of the ligaments has to be made it can be he lpful to use additional information on joint function. Therefore, a pr ospective study of 65 patients (mean age 24.1+/-4.6 years) with long-s tanding chronic ankle instability was conducted to demonstrate that th e dynamic measurement of plantar pressure distribution tan identify pa tients with functional ankle instability. Plantar pressure patterns we re measured during gait by means of a capacitive platform, the EMED-SF system. The impurses at eight points of the foot were calculated intr aindividually and compared with those in a group Of 100 healthy subjec ts. On the basis of clinical criteria alone, the two groups of patient s were distinguished, 35 with functional instability and 30 with mecha nical instability. The patients with functional instability showed sig nificantly increased lateral loading of th; unstable foot (P=0.01), wh ereas the group with mechanical instability tended to walk more on the medial side of the unstable foot. This finding is explained by a defi cit or peroneal strength during the stance phase, based on a proprioce ptive deficit after trauma. The new technique provides additional info rmation, which is relevant and sufficiently important to help in makin g decisions about the individual patient with chronic instability.