Syndesmosis Repair Affects in Vivo Distal Interosseous Tibiofibular Ligament Elongation Under Static Loads and During Dynamic Activities

Abstract

Background: Ligamentous ankle injuries are the most common injuries sustained by athletes and by the general population, with an incidence of approximately 2 million per year in the U.S. Injuries to the ankle syndesmosis (i.e., "high ankle sprains") are generally treated operatively. Although cadaveric studies can evaluate syndesmosis fixation strength, they cannot predict how healing, neuromuscular adaptation, or dynamic loading will affect in vivo biomechanics. Using dynamic biplane radiography (DBR), we tested the hypothesis that syndesmosis repair would restore ankle kinematics and ligament elongation during static and dynamic loading.

Methods: A convenience sample of 6 male patients who had undergone fixation (2 screw, 3 suspensory, 1 hybrid) of syndesmosis injury were assessed with use of DBR during forward running, backpedaling, a 45° angled single-leg hop, and 1 static standing trial at 2 to 4.5 years postoperatively. Three-dimensional ankle kinematics and elongation of the distal interosseous ligament, anterior inferior tibiofibular ligament, and the posterior inferior tibiofibular ligament were measured bilaterally. Comparisons were made between the operative and uninjured sides. Clinical outcomes were evaluated with use of the Foot and Ankle Ability Measure.

Results: Static load increased the lengths of the distal interosseous ligament (p = 0.02 to 0.05) and middle segment of the anterior inferior tibiofibular ligament (p = 0.02) in the operative ankle. The distal syndesmosis length was greater on the operative side during the static unloaded and loaded conditions (p = 0.02). Length of the distal syndesmosis on the operative side was greater than the corresponding healthy syndesmosis length during all 3 dynamic activities. On average, the operative ankle was in less dorsiflexion over the support phase of the angled hop (p = 0.05) and running (p < 0.01). The average Foot and Ankle Ability Measure Activities of Daily Living and Sports subscale scores were 95 and 88, respectively.

Conclusions: This study provides the first in vivo evidence of post-fixation changes in biomechanics after syndesmosis repair. Syndesmosis repair fails to restore healthy static and dynamic distal tibiofibular anatomy, even in patients who report good to excellent clinical outcomes.

Level of evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.