Lateral Ligament Repair and Reconstruction Restore Neither Contact Mechanics of the Ankle Joint nor Motion Patterns of the Hindfoot

Ankle sprains, particularly lateral ankle sprains, are the most common athletic injuries1-3. It is well established that these injuries damage the lateral ankle ligaments and also may damage the osteochondral tissues of the ankle joint4-10. In fact, osteochondral lesions of the ankle are being recognized as an increasingly common injury and may occur in association with as many as 50% of acute ankle sprains and fractures, particularly among patients with sports injuries11-13. Lateral ankle sprains involve sudden, forceful inversion of the hindfoot. This is associated with aberrant hindfoot kinematics and impaction of the articulating surfaces of the ankle joint, possibly altering the load-transfer patterns across the joint surfaces. Abnormal contact mechanics could damage the osteochondral tissues and predispose the patient to premature ankle osteoarthritis10. However, studies have only explored contact behavior during simulated stance14 in the presence of compromised lateral ligaments, not under inversion loading conditions. A connection between altered contact mechanics and inversion loading has not yet been established, despite the potential role of this association in the development of osteochondral injury to the articular surfaces of the ankle joint during the inversion injury. When nonoperative treatment fails, ankle instability frequently requires operative treatment. The Brostrom procedure, a direct repair of the anterior talofibular and calcaneofibular ligaments, can restore hindfoot kinematics if viable ligamentous tissue allows this repair15. The Gould modification of the Brostrom procedure involves the same direct repair of the ruptured lateral ligaments with reinforcement of the repair with use of the inferior extensor retinaculum16, providing additional support against inversion loads17. More recently, reconstruction of the lateral ligaments with free tendon grafts has been advocated15,18-20. Surgeons may resort to this option when the quality of the torn ligament tissue is insufficient for direct repair21. These techniques have been associated with improved stability of the hindfoot as shown by in vitro biomechanical15 and clinical studies22,23. Previous studies15,17-20,22,24,25, however, have focused on the effect of ligament reconstruction on primary motions in the direction of the applied load. Coupled motions, or motions in directions other than the applied load, are seldom explored26, although they form an important component of normal hindfoot motion27,28. In addition to quantifying the degree to which lateral ligament repairs and reconstructions improve hindfoot stability, it is important to characterize their ability to restore native load-transfer properties at the ankle joint because altered contact mechanics may be an important factor in the development of premature ankle osteoarthritis14. For example, following tenodesis procedures, there is an onset of radiographic findings consistent with osteoarthritis29,30 over a five to fifteen-year period after surgery31-36. Ideally, lateral ankle ligament repair or reconstruction techniques should restore contact mechanics at the tibiotalar joint and should remove joint laxity without restricting ankle motion15. To examine the ability of these surgical techniques to achieve these goals, we defined four objectives for this study: (1) to determine whether inversion loading in the presence of ruptured lateral ligaments causes abnormal ankle contact mechanics, (2) to examine whether the Brostrom repair could restore normal hindfoot kinematics and ankle contact mechanics, (3) to assess whether the Gould modification of the Brostrom procedure provided additional hindfoot support without altering coupled hindfoot motion patterns and ankle contact mechanics, and (4) to determine whether graft reconstruction may be an alternative to direct repair by comparing hindfoot motion patterns and contact mechanics resulting from a graft reconstruction with those obtained with the Brostrom-Gould procedure.