Which tendon graft to choose for anatomical ligament reconstruction in chronic lateral ankle instability? A biomechanical study.

Background: The need for anatomic lateral ligament reconstruction of the ankle continues to grow. This procedure usually requires a gracilis autograft or in some cases an allograft. Siegler et al. reported the mechanical characteristics of the collateral lateral ligaments of the human ankle: 231 ± 129 N for the ATFL and 307 ± 142 N for the CFL. The objective of this study was to evaluate the mechanical properties of different tendon grafts available for ATFL and CFL reconstruction. We hypothesized that the properties of the tested grafts are not inferior to the published values of those of the original ligaments on the lateral side of the ankle.

Methods: This was a comparative biomechanical study using 6 cadaver specimens (108 grafts): The biomechanical properties of nine types of grafts were determined using validated tensile testing methods: Gracilis, SemiT, EHL, FHL, Plantaris, Peroneus longus and brevis, TA and TP. The main outcome measure was the comparison of the mechanical properties of each single-stranded tendon with each other and with the known values ​​for the ATFL and CFL, during a uniaxial static rupture test.

Results: The mean load to failure for the gracilis was 257.5 ± 52.9 N. The groups had similar mean values in terms of the maximum load that they could withstand before failing except for the plantaris (137.9 ± 33.7 N) which was statistically lower than all other tested tendons (p < 0,01). The mean load to failure values of the grafts tested were equal or higher than that of the ATFL and CFL reported by Siegler et al. [14]: 231 ± 129 N for the ATFL and 307 ± 142 N for the CFL, while the grafts tested here had mean failure load between 258 ± 53 N and 464 ± 136 N.

Conclusion: The gracilis, peroneus longus/brevis, EHL, FHL, TA, TP and semiT are legitimate grafts for combined ATFL and CFL reconstruction in the ankle. These tendons have mechanical properties (load to failure, maximum strain at failure and stiffness) that are equal to or higher than the native ligaments on the lateral side of the ankle, except the plantaris.

Clinical relevance: This study validates the current use of the gracilis autograft for the anatomical reconstruction of the ATFL and CFL, and even provides proof that other tendons would be suitable for this anatomical reconstruction of the lateral ankle ligament by auto or even allograft under certain conditions.

Level of evidence: Descriptive laboratory study.