Spring ligament tear decreases static stability of the ankle joint

Background: Spring ligament tear is often found in advanced adult acquired flatfoot deformity and its reconstruction in conjunction with the deltoid ligament has been proposed to restore the tibiotalar and talonavicular joint stability. The aim of the present study is to determine the effect of spring ligament injury and subsequent reconstruction on static joint reactive force using a non-invasive method of measurement. Methods: Ten fresh-frozen human cadaveric lower legs were disarticulated at the knee joint. Static joint reactive force of the tibiotalar and talonavicular joint were measured at baseline, after spring ligament injury, and after ligament reconstruction. Reconstruction consisted of a forked semitendinosis allograft with dual limbs to reconstruct the tibionavicular and tibiocalcaneal ligaments. Findings: The mean baseline joint reactive force of the tibiotalar and talonavicular joints were 37.2 N + 8.1 N and 13.4 N + 4.2 N, respectively. The spring ligament injury model resulted in a significant 29% decrease in tibiotalar joint reactive force. Reconstruction of the tibionavicular limb resulted in a significant increase in tibiotalar and talonavicular joint reactive force compared to those seen in the injury state. Furthermore, the addition of the tibiocalcaneal limb significantly increased tibiotalar joint reactive force compared to those results obtained from the injury state and the tibionavicular limb alone. Interpretation: This is the first study to demonstrate diminished tibiotalar static joint reactive force in a spring ligament injury model with subsequent joint reactive force restoration using two-limbed reconstruction of the deltoid and spring ligament.