Biomechanical Comparison of Transtibial Pull-out Fixation Versus Suture Anchor Fixation for Repair of Medial Meniscus Posterior Root Tears

Abstract

Background: Posterior medial meniscus root tears are commonly treated with a transtibial pull-out (TO) repair, but significant postoperative meniscal extrusion has been reported. Recently, knotless adjustable suture anchor fixation has been introduced to treat root tears. This anchor-based fixation demonstrates less cyclic displacement than a TO repair. However, it is unknown how meniscal extrusion and contact mechanics compare between these 2 repair techniques when the meniscus endures cyclic tibiofemoral loading. Hypothesis: Suture anchor repair will demonstrate reduced meniscal extrusion and lower medial compartment pressure at the 1000th cycle compared with the TO repair. Study Design: Controlled laboratory study. Methods: Eight pairs of cadaveric knees were used to compare extrusion and contact pressure between transtibial fixation and suture anchor repair techniques for medial meniscus posterior root tears. Each specimen underwent cyclic compressive loading (0th, 100th, 500th, and 1000th cycles). Medial meniscal extrusion was assessed with the knee at full extension using ultrasound, and medial compartment contact pressures were evaluated using pressure sensors. Statistical analyses included paired t tests and repeated-measures analysis of variance with an alpha level set at .05. Results: The suture anchor repair technique demonstrated significantly lower absolute and relative medial meniscal extrusion compared with transtibial fixation repair after 500 and 1000 cycles of loading (P = .012 and P = .001, respectively). Similarly, mean medial compartment pressures were significantly lower in the suture anchor repair group compared with the transtibial fixation repair group after 1000 cycles (P = .028). No significant differences were found in peak pressures between the 2 repair techniques. Conclusion: The suture anchor repair demonstrated lower medial meniscal extrusion and reduced medial compartment contact pressures after time-zero cyclic loading. This biomechanical profile may be important for increasing the likelihood of healing and may translate to improved long-term outcomes for patients undergoing meniscus root repair. Clinical Relevance: Understanding the biomechanical differences between repair techniques at time zero may be crucial for optimizing surgical outcomes and minimizing the risk of long-term joint degeneration after meniscus root tears. Future clinical studies should further investigate these findings in live patient populations to validate their effect on root healing, functional outcomes, and long-term osteoarthritis progression.