Isolated lateral extra-articular tenodesis in ACL-deficient knees: in vivo knee kinematics and clinical outcomes

Purpose To carry out an in vivo kinematic analysis of isolated modified Lemaire lateral extra-articular tenodesis (LET) to explore its ability to modify the stability of anterior cruciate ligament (ACL) deficient knees. The secondary aim was to look at the clinical outcomes of the isolated LET to analyze whether biomechanical changes have an influence on clinical improvement or not. Methods A total of 52 patients who underwent an isolated modified Lemaire LET were prospectively studied. Twenty-two were over 55-year-old patients with ACL rupture and subjective instability (group 1). They were followed up for 2 years postoperatively. Thirty were patients underwent a two-stage ACL revision (group 2). They were followed up for 4 months postoperatively (up to the second stage of the ACL revision). Preoperative, intraoperative, and postoperative kinematic analyses were carried out using the KiRA accelerometer and KT1000 arthrometer to look for residual anterolateral rotational instability and residual anteroposterior instability. Functional outcomes were measured with the single-leg vertical jump test (SLVJT) and the single-leg hop test (SLHT). Clinical outcomes were evaluated using the IKDC 2000, Lysholm, and Tegner scores. Results A significant reduction of both rotational and anteroposterior instability was detected. It was present both with the patient under anesthesia ( p < 0.001 and p = 0.007 respectively) as well as with the patient awake ( p = 0.008 and p = 0.018 respectively). Postoperative analysis of knee laxity did not show any significant variation from the first to the last follow-up. Both the SLVJT and SLHT improved significantly at the last follow-up ( p < 0.001 and p = 0.011 respectively). The mean values of both the IKDC and Lysholm and Tegner scores showed an improvement ( p = 0.008; p = 0.012; p < 0.001). Conclusion The modified Lemaire LET improves the kinematics of ACL-deficient knees. The improvement in the kinematics leads to an improvement in subjective stability as well as in the function of the knee and in the clinical outcomes. At the 2-year follow-up, these improvements were maintained in a cohort of patients over 55 years. Following our findings, to reduce knee instability, an isolated LET in ACL-deficient knees may be used when ACL reconstruction in patients over 55 years is not indicated. Level of evidence Level IV