The biomechanical parameters of the hip joint articular surface were analysed in 141 adult hips after Legg-Calve Perthes Disease, and 114 contralateral unaffected hips (controls), by using HIPSTRESS ...mathematical models. Geometrical parameters, assessed from anteroposterior and axial radiograms, were used as input to models for resultant hip force and contact hip stress. Results confirm previous indications that head enlargement after the Legg-Calve-Perthes Disease compensates the values of hip stress. Furthermore, it was found that an increased risk for coxarthritis development after the disease is secondary to concomitant hip dysplasia, with considerable and statistically significantly lower centre-edge angle and unfavourable distribution of stress.
Summary Objective The aim of our study was to explore whether earlier hip arthroplasty for idiopathic osteoarthritis (OA) might be explained by enlarged contact stress in the hip joint, and to what ...amount can that be attributed to obesity and biomechanical constitution of the pelvis. Method Fifty subjects were selected from a list of consecutive recipients of hip endoprosthesis due to idiopathic OA; standard pelvic radiographs made years prior to surgery were the main selection criteria. For 65 hips resultant hip force and peak contact hip stress normalized to the body weight ( R /Wb and pmax /Wb) were determined from the radiographs with the HIPSTRESS method. Body weight and body mass index (BMI) were obtained with an interview. Regression analysis was used to correlate parameters of obesity (body weight, BMI), biomechanical constitution of the pelvis ( R /Wb, pmax /Wb) and mechanical loading within the hip joint ( R , pmax ) with age at hip arthroplasty. Results Younger age at hip arthroplasty was associated with higher body weight ( P = 0.009), higher peak contact hip stress normalized to the body weight – pmax /Wb (P = 0.019), higher resultant hip force – R ( P = 0.027) and larger peak contact hip stress – pmax ( P < 0.001), but not with BMI ( P = 0.121) or R /Wb ( P = 0.614). Conclusion Our results suggest that enlarged contact stress (pmax ) plays an important role in rapid progression of hip OA with both obesity (increased body weight) and unfavorable biomechanical constitution of the pelvis (greater pmax /Wb) contributing.
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