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

Abstract

Background: 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.

Purpose: To determine the ability of surgical intervention on syndesmosis and SLs with suture repair and ligament bracing to restore intact external rotation ankle stability.

Study design: Controlled laboratory study.

Methods: 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.

Results: 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 (P < .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 (P < .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.

Conclusion: 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.

Clinical relevance: Knowledge of specific syndesmotic and DL repair patterns in rotational stability is crucial for appropriate surgical intervention in treating unstable ankles.

Keywords: ankle stability; augmentation; biomechanical testing; deltoid ligament; suture repair.