Stability of the ankle joint in anatomical or non-anatomical anterior talofibular ligament repair

Abstract

Category: Ankle Introduction/Purpose: Chronic ankle instability (CAI) often needs surgical treatment if conservative treatment is ineffective. Recently, arthroscopic surgeries have become widely used to treat CAI. Although it is crucial to accurately ascertain the anterior talofibular ligament (ATFL) attachment site under arthroscopy, previous study showed that it might not be feasible to thoroughly observe the ATFL attachment site, and repair or reconstruction position were often unintentionally carried out proximal to the ATFL attachment site at the fibula as a result. Currently, there are few reports about stability of the ankle joint by different repair position of ATFL. The aim of this study was to evaluate the stability of the ankle joint by different repair position of ATFL. Methods: Six fresh-frozen human cadaveric ankles with the mean age of 83.5 ± 7.3 years were used. The ankles were tested using a six-degrees of freedom robotic system. The following ankle states were evaluated: intact, ATFL transection, ATFL anatomical repair, and ATFL non-anatomical repair. ATFL was transected at fibular attachment. Anatomical repair was performed at the center of original ATFL attachment of the fibula. Non-anatomical repair was set 8mm proximal from anatomical ATFL attachment of the fibula. At each state, laxity of anterior translation under 60 N load, inversion under 1.7 Nm load, and internal rotation under 1.7 Nm load were evaluated. Each test was performed at 30 degrees plantarflexion (PF), 15 degrees PF, 0 degree, and 15 degrees dorsiflexion (DF). The one-way repeated measures analysis of variance (ANOVA) with post hoc pairwise comparisons with Dunnett’s test was adopted. A P value of 0.05 was chosen as the level of significance. Results: Anterior translation under 60 N load was significantly increased in transection condition at 30 degrees PF compared with the intact condition (P=0.005). Anatomical repair and Non-anatomical repair did not show significant differences. Inversion under 1.7 Nm load was significantly increased in transection condition at 30 and 15 degrees PF compared with the intact condition (P=0.004, =0.049). Anatomical repair and Non-anatomical repair did not show significant differences. Internal rotation under 1.7 Nm load was significantly increased in transection condition at 30, 15 degrees PF and 0 degree compared with the intact condition (P<0.001, <0.001, and <0.001). Although anatomical repair did not show significant differences, non-anatomical repair showed significant increase at 30 and 15 degrees compared with the intact condition (P=0.006, =0.026). (Fig. 1). Conclusion: Anatomical repair did not show significant difference in all three loads with the intact condition. In non-anatomical repair, anterior translation and inversion did not show significant difference, but internal rotation significantly increased at 30 and 15 degrees PF compared with the intact condition. Compared with anatomical repair, non-anatomical repair might become more vertical ligament running because its attachment site of the fibula was more proximal. This difference might affect stability of the ankle joint. Anatomical repair of the ATFL might be essential to obtain the stability of the ankle joint like the intact condition.