The functional outcome of posterior tibial tendon transfer for foot drop in leprosy. The results of one to 5 years follow up.

Neuropathy is the hallmark of leprosy, with Mycobacterium leprae affecting primarily skin and peripheral nerves and leads to motor, sensory and autonomic alterations. – 6 In the lower limbs, tibial and the peroneal nerves are frequently involved and may result in permanent loss of the protective sensibility of the sole as well as equinovarus deformity and drop foot. To correct the equinovarus deformity Srinivasan, Mukherjee, Subramaniam proposed a surgical technique that consists in transferring the tibial posterior tendon. The tendon was identified through an incision in the navicular bone then detached from its insertion. After that it was pulled out by a longitudinal incision close to the medial border of the tibia and then split into two tails. Two transverse incisions were made on the dorsum of the foot over the extensor hallucis longus and extensor digitorum longus tendon to attach the lateral and the medial slip respectively. After operation, a below knee cast is applied with the ankle in a maximum dorsiflexion for 6 weeks. It is well documented that posterior tibial tendon transfer by circuntibial or interosseous route has been used to treat foot drop and correct the equinovarus deformity in leprosy patients. According to literature the results of these techniques vary in strength and total range of motion but the tendon transposed forward works well as dorsiflexor irrespective of the method used and in general have a good outcome in restoring function and gait. However there is no conformity in literature about which are the most important criteria or a standardised evaluation to assess the postoperative results of tibial tendon transfer. Some studies used active dorsiflexion, foot posture, necessity of orthesis and gait pattern. The absence of a consensus makes the comparison of the postoperative results between previous studies difficult. – 15 In an unpublished study, for assessment of the results of tibial tendon transfer in 13 leprosy patients, a specific scale proposed by Yeap, Singh and Birch was used: the Stanmore system. The Stanmore system is an objective score table divided in seven sections: pain, need for orthosis, wearing normal shoes, activities of daily living (functional outcome), muscle power, degree of active dorsiflexion and foot posture. Each section has a specific score and the total is 100. For the sake of classification, the results are: excellent for scores between 85 and 100, good for scores between 70 and 84, fair for scores between 55 and 69, and poor if the score was less than 55. In this study the results of the posterior tibial tendon transfer assessed using the Stanmore system was: five (38, 4%) patients had excellent results; five (38, 4%) had good results; two (15, 3%) fair and one (7, 6%) had poor. The average score was 78, 6.