A Biomechanical Comparison of an Open vs. Arthroscopic Approach for the Treatment of Lateral Ankle Instability (SS-57)

Abstract

Introduction Ankle sprains are the most common musculoskeletal injury, accounting for 2 million emergency department visits annually. Most sprains involve the lateral ligament complex secondary to an inversion force on a plantar flexed foot. The diagnosis of chronic ankle instability is considered when repetitive sprains or persistent symptoms of giving way are present. The current clinical standard is the open modified Brostrom procedure (open). Many surgeries in orthopedics have evolved with minimally invasive approaches. The purpose of this study was to biomechanically compare a minimally invasive arthroscopic technique for the treatment of ankle instability to the open technique. Methods Twenty matched lower extremity cadaver specimens were tested (mean 40 ± 12 years). Specimens were examined for gross instability or anatomic lesions. Steinman pin wires were inserted into the tibia and the talus, and six sensors were rigidly affixed to each of the wires to establish relative planes of movement. Specimens were placed in a Telos ankle stress apparatus and loaded to 1.7 N-m in two orientations simulating the anterior drawer and talar tilt clinical exam tests. For each of these tests the ankle was held in three orientations: 15° plantar-flexion, neutral alignment, and 15° dorsiflexion. During testing, the movement of the sensors was measured in three separate planes using the Optotrak Computer Navigation System. The difference in translation between the talus and the tibia in the loaded anterior drawer test and the angle between the tibia and talus in the loaded talar tilt test were calculated and compared to the unloaded state to determine the differences in translation and angle. Following intact testing, the anterior talofibular ligament and the calcaneofibular ligament were both sectioned from the fibula to simulate an unstable ankle and retested in all test modes. Sectioned ligaments were then repaired using two 3.5mm diameter corkscrew suture anchors. One anchor was placed at the ATFL origin and the other at the CFL origin. Ten of the specimens were repaired using the standard open repair; while the remaining 10 contralateral specimens were repaired using an arthroscopic technique. All test modes were retested following repair. Statistically significant differences in displacement within treatment groups were analyzed using a repeated measures ANOVA. A paired t-test was used to determine differences between the open and arthroscopy groups. Results There was significantly more motion in the sectioned ankles compared to intact and both treated groups for all but one test mode (anterior drawer in dorsiflexion, p=0.054). The arthroscopic and open repair techniques were biomechanically similar with the exception of the inversion in plantar flexion. However, the difference in total combined motion was not statistically significant and both repair groups were statistically superior to the sectioned state. Conclusion Our findings suggest similar improvement in biomechanical function with both the arthroscopic and open repairs when compared to the sectioned state. Both techniques were shown to be comparable to the intact state suggesting that biomechanically effective ankle stabilizations may be able to be performed through a minimally invasive approach.