Deltoid and Syndesmotic Ligaments, Part 2. The Value of Ligament Repair and Augmentation in Restoring Biomechanical Rotational Ankle Stability.

Abstract

Despite studies on syndesmotic and deltoid ligament (DL) repair, the biomechanical role of (partial or full) ligament repair and bracing in unstable ankles to regain rotational stability remains unclear. To determine the ability of surgical intervention on syndesmosis and SLs with suture repair and ligament bracing to restore intact external rotation ankle stability. Controlled laboratory study. A total of 24 cadaveric lower extremities were divided into 3 equal groups with anterior inferior tibiofibular ligament internal brace (AiTFL-IB), interosseous ligament (IOL) suture button repair, and superficial DL (SDL) and deep DL (DDL) suture anchor repair or bracing (DL-IB) performed in varying orders to assess their contribution to restoring rotational ankle stability. Individual external rotation angles (α_2.5 to α_7.0), determined from the intact time-zero load curve at 2.5, 4.0, 5.5, and 7.0 N·m, were used for rotation-controlled cycling performed sequentially (1000 cycles in total) for each surgical condition. Peak torque and stiffness were analyzed. Either IOL or SDL+DDL repair had the largest effect on restoring rotational stability (23% to 12% across α_2.5 to α_7.0) but showed a completely loose state with the lowest resistance to external rotation compared with the intact state. The contribution of SDL+DDL was higher (<i>P</i> < .009) than that of isolated SDL or DDL repair (except for SDL at α_7.0). Additional AiTFL-IB stabilized the ankle in the 7% to 13% range across all rotation angles. Ankles with full ligament repair (IOL+AiTFL-IB+SDL+DDL) approached native peak torque restoration (104% to 76% across α_2.5 to α_7.0) and were significantly more stable (<i>P</i> < .05) than IOL+DDL repair. IOL repair with different DL-IB configurations achieved similar levels of ankle stability and stiffness to full ligament repair. Higher construct stiffness of DL-IB and the full repair groups became similar to the intact condition with increasing rotation and approached native ankle function, except at the largest rotation. An isolated deltoid or syndesmosis repair was unable to restore rotational ankle stability. A combined repair or a combination of repair and bracing closely restored rotational stiffness and ankle stability in case of a multiligamentous ankle injury in a cadaveric model. Knowledge of specific syndesmotic and DL repair patterns in rotational stability is crucial for appropriate surgical intervention in treating unstable ankles.