Chronic deltoid ligament insufficiency results in greater anterior translation and positive arthroscopic drive-through sign.

Background: Diagnosis and treatment of medial deltoid ligament instability is inconsistent.

Purpose: This biomechanical study evaluated arthroscopic drive-through sign as a viable and reproducible diagnostic method to determine chronic deltoid instability and determined the restorative potential of combined medial and lateral ligament repair on ankle stability.

Study design: Controlled laboratory study.

Methods: The proximal tibia (n = 5) was mounted in 20° plantar flexion. Anterior translation was simulated by loading specimens with 2 kg/3 kg/4 kg. Arthroscopic drive-through sign and anterior translation distance were evaluated at the following ligament release and repair phases: intact, lateral instability, dual-sided instability, dual-sided repair, and lateral repair alone. Arthroscopic drive-through was attempted with 2.0-5.0 mm diameter probes before each phase. A positive arthroscopic drive-through sign was defined as passage into the medial gutter.

Results: Positive arthroscopic drive-through sign for intact specimens were observed with 2.0 mm (4/5) and 2.5 mm (1/5) probes. In the dual-sided instability model, probe sizes ranged from 3.5 mm to 4.5 mm. Dual-sided repair restored the medial gutter distance to intact. The lateral repair alone did not restore to intact. Anterior translation in dual-sided instability was significantly greater than intact (14.3 ± 1.9 mm[12.6-16.0] vs. 7.4 ± 1.5 mm[6.1-8.7], P < 0.001). Dual-sided repair and lateral repair alone restored intact anterior translation (4.8±0.8 mm[4.1-5.5], P = 0.637; 7.0 ± 1.1 mm[6.0-8.0], P = 0.958).

Conclusion: The arthroscopic drive-through sign seems to be a reliable method to detect medial deltoid instability. Combined medial and lateral ligament repair effectively restores anterior translation to intact levels. Medial deltoid repair contributed to 23.2 % of the total anterior translation reduction from the dual-sided instability phase to dual-sided repair phase.