INFLUENCE OF LOWER-LIMB TORSIONAL DEFORMI TIES ON THE DEVELOPMENT OF FEMOROTIBIAL DEGENERATIVE ARTHRITIS

Purpose of the study Frontal deformation of the knee is certainly not the only factor involved in the occurence of lateralised tibio-femoral arthrosis. The aim of the study was to analize if any kind of tibial torsion or femoral torsion could be able to induce lateralized arthros is. Material and methods Femoral torsion, tibial torsion and tibio-fem oral index (tibial torsion minus femoral torsion) have been measured o n 59 knees with lateral arthrosis (8 knees) or with medial arthrosis ( 51 knees), For each knee, two frontal deformations were measured : 1) the actual arthrosis deformation was calculated on a hip knee ankle ra diograph, 2) the pre arthrosis deformation is the arthrosis deformatio n minus the angle made by the femoral condyle tangent and the tibial p lateau tangent. A knee has no frontal deformation if the angle between the mechanical axis of the femur and the mechanical axis of the tibia is between 178 degrees and 182 degrees; there is a varus deformity if the angle is inferior to 178 degrees; there is a valgus deformation i f the angle is superior to 182 degrees. Results Out of the 8 knees wit h lateral arthrosis, 2 showed initialy no frontal deformation and 6 ha d a valgus deformation; out of the 51 knees with medial arthrosis, 34 showed initialy no frontal deformation, 6 had a valgus deformity and 1 1 a varus deformity. The tibio-femoral index in lateral FT arthrosis w as statistically different from those in medial FT arthrosis (p 0,0001 ). When a lateral arthrosis appeared whatever the pre arthrosis deform ation was the index was always negative (tibial torsion lower than fem oral torsion); when a medial FT arthrosis appeared, whatever the pre a rthrosis deformation was, the index (except for two cases) was always positive (tibial torsion higher than femoral torsion). Conclusion Femo ral and tibial torsions play a part in lateralised arthrosis occurence together with frontal mechanical factors. Perhaps troubles in torsion explain some spontaneous or post-therapeutic evolutions not explained by frontal mechanical factors.