MENISCAL TIBIAL SLOPE - COMPARISON WITH BONY SLOPE

Purpose of the study X-ray measurements of the proximal tibial slope o nly study bony structures, without considering cartilage and meniscii thickness. It is well known that the posterior horn of the meniscii is thicker than the anterior one, and this could decrease the bony poste ro-distal slope. The aim of this study was to measure the meniscal slo pe, including cartilage and meniscii, and to compare it to the usual b ony slope. Material and methods 19 knee cadaver specimens without meni scal or chondral lesions were studied. Four metallic clamps were inser ted at the most anterior or posterior part of the medial or lateral me niscosynovial border. Lateral plain X-ray was taken for each knee. The bony proximal tibial slope and the medial and lateral meniscal slopes were measured and compared for each knee. Paired Wilcoxon T-test and correlations were calculated with a 5 per cent significant limit. Resu lts The mean paired difference between bony slope and medial or latera l meniscal slope was -6 degrees : the actual meniscal slope was less o blique than the bony slope, and it was almost perpendicular to the pro ximal tibial axis. There was a very significant correlation between bo ny and medial meniscal slopes. There was no correlation between bony a nd lateral meniscal slopes, nor between medial and lateral meniscal sl opes. Discussion These results suggest that the proximal tibial menisc al slope, which is the mechanically active one, is less oblique than t he usually measured bony slope. Medial meniscal slope and bony slopes are very strongly correlated for one given knee. But medial and latera l meniscal slopes can be very different for one given knee. Conclusion These results could have an influence on the design of total or unico ndylar knee replacements : the polyethylene slope of the tibial surfac e, which should reconstruct the natural articular design, should repro duce the meniscal, and not the bony slope. The medial and lateral slop es, should perhaps be individually reconstructed.