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

Abstract

Diagnosis and treatment of medial deltoid ligament instability is inconsistent. 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. Controlled laboratory study. 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. 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). 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.