This study should provide surgeons with the confidence that in an ACL + lateral meniscus deficient knee, in which there is often increased anterolateral rotatory laxity, it is safe to perform an ACL reconstruction with LET augmentation if appropriately indicated.
Lateral meniscus deficiency and injury to the anterolateral complex (ALC) have both been implicated as causes of increased rotatory laxity in combination with anterior cruciate ligament (ACL) rupture. Lateral extra-articular tenodesis (LET) has been proposed as a procedure of addressing persistent anterolateral rotatory laxity following ACL reconstruction; however, concerns remain in regard to the possibility of increasing lateral compartment contact pressures and therefore increasing the risk of osteoarthritis development. This concern is heightened in the presence of a lateral meniscus tear. Therefore, the purpose of this study was to determine whether the addition of a LET to ACL reconstruction would increase lateral compartment contact pressures, both in the intact and lateral meniscus deficient state.
Eight fresh-frozen cadaveric knee specimens (mean [SD] age = 60 [3.4] years) were utilized for this study, with specimen potted and loaded on an Instron materials testing machine. A Tekscan® pressure sensor was inserted into the lateral compartment of the tibiofemoral joint, and specimens were loaded at 0°, 30°, 60° and 90° of flexion in the following states: i) Baseline –ACL and anterolateral ligament deficient; ii) ACL reconstruction; iii) ACL reconstruction with an LET; iv) Partial meniscectomy – removal of 50% of the posterior third of the lateral meniscus; v) Subtotal meniscectomy - removal of 100% of the posterior third of the lateral meniscus; and vi) LET release. Mean contact pressure, peak pressure, and the center of pressure were analyzed with a one-way repeated measures ANOVA.
Across all flexion angles, there was no significant increase in the mean contact pressure or peak pressure following ACLR/LET with and without lateral meniscectomy compared to an isolated ACL reconstruction. There was a significant reduction in the mean contact pressure, from baseline, following subtotal meniscectomy (69.72 [19.27] % baseline) and LET release (65.81 [13.40] % baseline) at 0°, and in response to the addition of an LET at 30° (61.20 [23.08] % baseline). The center of pressure was observed to be more anterior following partial (0°,30°) and subtotal (0°, 60°) meniscectomy, and when the LET was released (0°,30°,60°).
This study has shown that in a weight bearing knee, the addition of an LET to ACL reconstruction does not increase lateral compartment contact pressures compared to the ACL reconstructed state. Furthermore, the absence of the lateral meniscus does not result in increased contact pressures, likely mitigated by physiological load bearing.
This study should provide surgeons with the confidence that in an ACL + lateral meniscus deficient knee, in which there is often increased anterolateral rotatory laxity, it is safe to perform an ACL reconstruction with LET augmentation if deemed to be indicated.