REDUCING OF STRESS IN THE HIP JOINT ARTICULAR SURFACE IN SKIING

Abstract

INTRODUCTION - It was recently shown that too high contact stress in the articular surface of the hip joint can accelerate the arthrosis development in the hip joint ( Hadley et al., 1990). Increased contact stress in the hip joint articular surface can result from too small hip joint articular surface andlor from too high resultant hip joint force. Since the resultant hip joint force. Since the resultant hip -joint force is permanently increased during sport activities it is understandable that the incidence of the hip arthrosis among people with high exposure to sport is significantly higher compared to those with low exposure (Vingard et al., 1993). The acetabular dysplasia in sportsmen, i.e, small femoral head coverage, additionally increase the probability of hip arthorsis development. During skiing changes in the position of the upper body occur. They are associated with varying degrees of pelvic tilting, which influence the hip joint contact stress distribution (Iglic et al., 1994). The aim of this work was to determine how acetabular dysplasia and pelvic tilt affect the hip joint contact stress distribution after shifting of the upper part of the body towards the weight-bearing leg in slow skiing. METHODS - A three-dimensional model of the hip joint articular surface is used in order to calculate hip joint contact stress distribution (Iglic et al., 1993a). the resultant hip joint force for various body positions is calculated separately by using a static three-dimensional model of the adult hip in the one-legged stance (Iglic et at., 1993b, lglic et al., 1994). RESULTS - It is shown that the decrease of the hip joint contact stress after the shifting of the upper part of the body towards the supporting leg is more effective in the case of large inclination of the pelvis during the shifting og the of the upper part of the body towards the supporting leg hip the stress can be in the case of severe acetabular dysplasia and small inclination of the pelvis even increased in spite of the fact that the resultant hip joint force is considerably reduced. CONCLUSIONS - In accordance with the results of this study it can be concluded that the subjects with borderline acetabular dysplasia should be encouraged to turn during skiing with increased pelvic tilt on the side of the non-weight-bearing leg with simultaneously shifting of the upper part of the body towards the weight-bearing leg. In this way the dysplastic hip is unloaded to an optimum degree. consequently, the risk for arthrosis development is decreased. REFERENCES - Hadley N.A., Brown T.D., Weinstein S.L. (1990) J. Orthop. Res. 8:504-513. lglic A,, Kralj-lglic V., Antolic V., Srakar F., Stanic U. (1993a) IEEE Trans. Rehab. Engr. 1 :207-212. lglic A,, Srakar F., Antolic V. (1993b) Clin. Biomech. 8:223-224. lglic A,, Kralj- lglic V., Antolic V. (1994) Acta Chir. Orthop. Traum. Cech. 61.268- 270. Vingard E., Alfredsson L.. Goldie I., Hoghstedt C. (1 993) Am.J.Sports Med. 21.195-200.