Pablo Wagner1, Cristian Ortiz2, Omar Vela3, Paul Arias4, Diego Zanolli2, Emilio Wagner2. 1. Clínica Alemana-Universidad del Desarrollo, Foot and Ankle Surgeon, Chile. Electronic address: pwagner@alemana.cl. 2. Clínica Alemana-Universidad del Desarrollo, Foot and Ankle Surgeon, Chile. 3. Clínica Alemana-Universidad del Desarrollo, Orthopaedic Surgeon, Chile. 4. Second Year Resident, Orthopaedic Surgery, Clínica Alemana-Universidad del Desarrollo, Chile.
Abstract
BACKGROUND: Tibialis posterior (TP) tendon transfer through the interosseous membrane is commonly performed in Charcot-Marie-Tooth disease. In order to avoid entrapment of this tendon, no clear recommendation relative to the interosseous membrane (IOM) incision size has been made. OBJECTIVE: Analyze the TP size at the transfer level and therefore determine the most adequate IOM window size to avoid muscle entrapment. METHODS: Eleven lower extremity magnetic resonances were analyzed. TP muscle measurements were made in axial views, obtaining the medial-lateral and antero-posterior diameter at various distances from the medial malleolus tip. The distance from the posterior to anterior compartment was also measured. These measurements were applied to a mathematical model to predict the IOM window size necessary to allow an ample TP passage in an oblique direction. RESULTS: The average tendon diameter (confidence-interval) at 15cm proximal to the medial malleolus tip was 19.47mm (17.47-21.48). The deep posterior compartment to anterior compartment distance was 10.97mm (9.03-12.90). Using a mathematical model, the estimated IOM window size ranges from 4.2 to 4.9cm. CONCLUSION: The IOM window size is of utmost importance in trans-membrane TP transfers, given that if equal or smaller than the transposed tendon oblique diameter, a high entrapment risk exists. A membrane window of 5cm or 2.5 times the size of the tendon diameter should be performed in order to theoretically diminish this complication.
BACKGROUND: Tibialis posterior (TP) tendon transfer through the interosseous membrane is commonly performed in Charcot-Marie-Tooth disease. In order to avoid entrapment of this tendon, no clear recommendation relative to the interosseous membrane (IOM) incision size has been made. OBJECTIVE: Analyze the TP size at the transfer level and therefore determine the most adequate IOM window size to avoid muscle entrapment. METHODS: Eleven lower extremity magnetic resonances were analyzed. TP muscle measurements were made in axial views, obtaining the medial-lateral and antero-posterior diameter at various distances from the medial malleolus tip. The distance from the posterior to anterior compartment was also measured. These measurements were applied to a mathematical model to predict the IOM window size necessary to allow an ample TP passage in an oblique direction. RESULTS: The average tendon diameter (confidence-interval) at 15cm proximal to the medial malleolus tip was 19.47mm (17.47-21.48). The deep posterior compartment to anterior compartment distance was 10.97mm (9.03-12.90). Using a mathematical model, the estimated IOM window size ranges from 4.2 to 4.9cm. CONCLUSION: The IOM window size is of utmost importance in trans-membrane TP transfers, given that if equal or smaller than the transposed tendon oblique diameter, a high entrapment risk exists. A membrane window of 5cm or 2.5 times the size of the tendon diameter should be performed in order to theoretically diminish this complication.