Summary

Nonanatomic medialized and anteriorized posterior root lateral meniscus repair of the lateral meniscus restores contact area and contact pressure to near-intact levels.

Abstract

Introduction

Complete avulsion of the posterior root of the lateral meniscus results in decreased contact area and increased contact pressure across the knee joint, potentially leading to rapid progression of osteoarthritis. Studies have shown that anatomic repair of the posterior root restores joint mechanics to near-normal levels. However due to the increased mobility of the lateral meniscus, compromised meniscal tissue quality, or difficulty locating or accessing the true anatomic insertion of the lateral meniscus root, surgical repair may fail to restore the lateral meniscus to its anatomic state. The purpose of this study was to biomechanically assess the effect of nonanatomic repair of the posterior root of the lateral meniscus in a cadaveric model.

Methods

Fifteen fresh-frozen human cadaveric knees were biomechanically tested using a previously described model. Specimens were excluded if there was evidence of meniscal damage or greater than Outerbridge 1 arthritic change. Five lateral meniscus conditions (intact, complete posterior root avulsion, anatomic repair, 5-mm medialized nonanatomic repair, and 5-mm anteriorized nonanatomic repair) were tested in 4 flexion angles (0?, 30?, 60?, and 90?). Repair states were randomized for each specimen. Contact area, mean contact pressure, and peak contact pressure were measured in both the medial and lateral compartments for each testing state.

Results

Complete avulsion of the posterior root of the lateral meniscus resulted in significantly decreased contact area in the lateral compartment compared to the intact and all repair states at all flexion angles, except in full extension (p<0.05). Complete avulsion also resulted in significantly increased mean and peak contact pressures compared to the intact and repair state at 30? and 60? of flexion. The medialized nonanatomic repairs resulted in significantly decreased lateral compartment mean contact pressures versus the intact state at 30? and 60?, as well as significantly decreased peak contact pressure versus the anatomic repair state at 30? and 60?. There were otherwise no statistically significant differences between repair states in the lateral compartment.

Discussion/Conclusion: Nonanatomic medialized and anteriorized posterior root repair of the lateral meniscus restores contact area and contact pressure to near-intact levels. Our results also demonstrate that medialization of the lateral meniscus root effectively decreases the functional circumference of the lateral meniscus. This decreases peak stress across the joint in mid-range of motion to levels lower than the anatomic state. While these findings might suggest to some that nonanatomic repair may be acceptable, we feel this most likely represents dramatic increases in the strain at the repair site and significantly increased risk of clinical failure.