Contact pressures in the human hip joint

Abstract

In previous studies on the mechanics of the human hip joint (Afoke, Byers and Hutton 1980, 1984) it was found that the inter-cartilaginous space was variable in size and location, and that it changed shape with different positions of the joint. It was concluded that this space would be of limited value as a load-distribution mecha nism and that cartilage per se should be well able to distribute the applied load. If incongruity had any function, it seemed to be in promoting bulk fluid movement for the purpose of lubrication and nutrition (Afoke, Hutton and Byers 1984).To obtain a better understanding of the mechanics of the joint, it was thought advantageous to measure the pressure distribution at the cartilage interface during load-bearing. Previous pressure measurements in the hip have been carried out either directly or indirectly. Direct measurements have mostly involved the insertion of piezo-electrictransducersin the acetabulum(Christel, Derethe and Sedel 1976; Mizrahi et al. 1981; Adams and Swanson1985);in theseexperiments, a limited number of transducers were used and it was difficult to infer the pressure distribution over the whole of the cartilage surface. On the other hand, Rushfeld, Mann and Harris (1979), using an instrumented endoprosthesis, were able to obtain the pressure contours on the cartilage when the hip was loaded. However, the use of a prosthesis has its Requests for reprints should be sent to Dr P D Byers. body weight (BW), it would be oflimited value as a load distribution mechanism and that cartilage per se is able to distribute the applied load evenly. ©1987British Editorial Societyof Bone and Joint Surgery MATERIALS AND METHODSHip joints were obtained from routine necropsies and were stored in sealed polythene bags at â€" 20°Cuntil required. Before testing, they were thawed at room temperature and all the excess soft tissue and the labrum were removed. The disarticulated specimen was then mounted by first cutting the ilium and the femoral shaft in such a way that the direction of the applied force simulated that in vivo. The cut ends of the joint components were mounted in cups using quick-setting dental cement. Wood screws were inserted in the cortical bone to improve the fixing ofthe specimen to the cement. From The Polytechnicof Central LondonThe pressuredistribution between the cartilaginous surfaces in the humanhipjoint was measured using pressure-sensitive film. Five cadaveric hip joints (aged between 58 and 87 years) were measured at three @fions and loads, representing three instants in the stance phase of the walking cycle. The pressure distribution was not uniform, indicating that the cartilage did not, to any great extent, distribute the applied load. The maximum pressures recorded were about 10 MN/m2. The anterosuperiorsurface of the cartilage was identified as an area of high pressure.

Tribology of Hemiarthroplasty

“…When half of the porcine body weight was applied constantly to acetabulum with a range of FE radial clearances 0.05-3.45mm , the average contact stress on the acetabulum was found to be approximately 2.4-4.7 MPa , and the peak contact stress was approximately 3.9-7.2 MPa. This peak contact stress range is close to values in the literature of the hip peak contact stress measured by in-vitro pressure-sensitive film ; these are cited as approximately 2.90-9 MPa in human hip joint: 2.9-8 .6 MPa (Afoke et al, 1987), 4 .0-6.0 MPa (Say et al, 1997) , 7.5-9.0 (Hak et al, 1998), and 7.7 MPa (von Eisenhart et al, 1999 .…”

Pelvic orientation and assessment of hip dysplasia in adults

“…The underlying biomechanical concept hypothesizes that concentration of compressive stress in the reduced weight-bearing area of the dysplastic hip leads to accelerated degeneration of the articular cartilage. This hypothesis has been substantiated in mathematical, in vivo and in vitro studies (Afoke et al 1987, Hadley et al 1990, Bergmann et al 1993, Maxian et al 1995, Michaeli et al 1997. However, neither the prevalence of unrecognized hip dysplasia in the population at large, nor the natural history of untreated mild to moderate dysplasia is known.…”

Mature runt cow lumbar intradiscal pressures and motion segment biomechanics

“…In vivo loading in articular joints has been measured in both domestic mammals and humans [72][73][74][75][76][77][78][79][80]. Based on these studies, in vivo joint contact pressures are estimated to generally range from 1.0 to 2.5 MPa (and up to 10 MPa for peak loading).…”