Arthroscopic Quantification of Syndesmotic Instability in a Cadaveric Model.

PURPOSE: To investigate whether arthroscopy or stress radiography can identify instability resulting from single-ligament injury of the ankle syndesmosis and to determine whether either modality is capable of differentiating between various levels of ligament injury.

METHODS: Syndesmotic/deltoid ligament sectioning was performed in 10 cadaver legs. Arthroscopic evaluation and fluoroscopic stress testing were completed after each sectioning. In group 1 (n = 5), sectioning began with anteroinferior tibiofibular ligament (AITFL), then interosseous membrane (IOM), posteroinferior tibiofibular ligament (PITFL), and deltoid. In group 2 (n = 5), this order was reversed. Measurements were made by determining the largest-sized probe that would fit in the anterior and posterior syndesmosis. Radiographic parameters included tibiofibular overlap/clear space and medial clear space.

RESULTS: No radiographic measurement proved useful in distinguishing between intact and transected AITFL. Anterior probe (AP) size reached significance when distinguishing between intact and AITFL-transected specimens (P < .0001). AP detected significant differences comparing single with 2-, 3-, and 4-ligament (AITFL, IOM, PITFL, deltoid) disruptions (P = .05, <.0001, and <.0001, respectively). Significant differences were observed between 2- and 3/4-ligament (P = .02) transections. Posterior probe (PP) size detected significant differences between intact and single-, double-, triple-, and complete ligament transections (P values .0006, <.0001, <.0001, <.001, respectively). PP detected significant differences between single- and double-, triple-, and complete ligament transection models (P = .0075, .0010, and .0010, respectively). PP distinguished between 2- and 3/4-ligament (P = .03) transections.

CONCLUSIONS: Stress radiography did not distinguish between intact and single-ligament disruption, and was unreliable in distinguishing between sequential transection models. Arthroscopy significantly predicted isolated disruption of the AITFL or deltoid ligaments. Also, probing was able to differentiate between most patterns of ligament injury, including sequential transections.

CLINICAL RELEVANCE: These data can aid surgeons during arthroscopy of the ankle when attempting to correlate intraoperative syndesmotic evaluation findings with the extent of ligament injury.