Comparison of three-dimensional translation of repaired and healthy menisci during partial weight bearing knee flexion
Meniscal tears form one of the most common pathologies treated by the knee orthopaedic surgeon. The primary objective of a meniscal repair is to restore meniscal function, maintaining appropriate loading throughout the joint and preventing long-term degenerative changes. However, an important characteristic of meniscal function is translation across the tibial plateau to match the dynamic pathways of tibiofemoral contact points. Despite its importance to meniscal function, little is known about meniscal translation in-vivo during weight-bearing, particularly movement other than anterior-posterior translation. The purpose of this study was to determine the relationship between meniscal condition (repaired vs uninjured),compartment (medial vs lateral), anatomical subregion (anterior horn, body, posterior horn) and flexion arc (0-60, 60-90, 90-max) on three-dimensional translation during weight-bearing knee flexion. The purpose of this study is
Materials & Methods
A cohort of 15 patients (9m; 26.5yrs range 16-52yrs), eligible for meniscal repair were recruited. A medial meniscal tear was repaired in 1 case and a lateral meniscal tear was repaired in 15, with simultaneous ACL reconstructions in 6 cases. A postoperative MRI was performed in an open bore MRI scanner (Upright Multipostional, Fonar, USA). Both knees were secured in carbon braces and scanned in the sagittal plane at 0°, 60°, 90°, and maximum flexion with ~20% body weight. The three-dimensional positions of the horns and body of the medial and lateral menisci were determined with manual image segmentation combined with a cubic spline fitted to the centroids of each meniscal region visible in each image. Translation was defined as the change in position between 0 and 60deg, 60 and 90deg and 90 and maximum flexion.
The anterior-posterior translation of the uninjured menisci occurred mostly during 0_60, but did not move uniformly across the range of motion. Further, the uninjured menisci demonstrated different patterns of movement between medial and lateral compartments. Regression models with meniscal status, meniscal region, knee compartment and flexion arc as predictors explained limited variance in anterior-posterior (R2 = 16%), medial-lateral (R2 = 2%) and superior-inferior (R2 <1%) translation. The lateral menisci translated posteriorly on average, with the most occurring in the anterior horn between 0 and 60° (mean 6.0mm, 95%CI 2.1 – 9.9mm), whereas the anterior (3.8mm, 1.0 – 6.7mm) and posterior horn (1.9mm, 1.2 – 2.6mm) of the medial menisci translated less during the same flexion arc. The repaired menisci demonstrated different patterns of anterior-posterior translation across the knee flexion range.
Meniscal mobility is highly specific to the individual and anatomical subregion in both healthy and repaired menisci. The lack of variance explained by the independent variables included in this study suggest that other factors may be important determinants of translation, which requires further study. The results confirm the importance of meniscal repair in preserving menisci function and protecting the chondral surfaces from inappropriate loads.