Periacetabular stress distributions during normal gait cycle and its guiding function in acetabular reconstruction of THA / 医用生物力学

Objective To study the basic regular patterns of stress distributions inside and outside periacetabular districts during normal gait cycle of healthy adults, so as to provide clinical guidance for acetabular reconstruction of total hip arthroplasty (THA). Methods Based on CT scans of a male and a female healthy adult volunteer, The three-dimensional model including pelvis and proximal femur was reconstructed. By using an inhomogeneous material distribution scheme which was based on CT data to calculate elastic modulus and convergence analysis, each element was given a corresponding material attribute. The dynamic change of hip contact force during a normal gait cycle was used as the load condition to the model. Von Mises stress of the nodes inside and outside the model was considered as the criterion to assess the results. Results During normal gait, the stress on the hip surface of two volunteers was mainly transmitted from postersuperior part of acetabulum to auricular surface along posterolateral of iliac wing, and the maximum stress was at the district near greater sciatic. As for the superior, middle and inferior section of two volunteers' acetabulum, the stress was distributed both on cortical and cancellous bone of postersuperior part. However, in terms of acetabular anterior and posterior column, the stress distribution was mainly found on cortical bone. Conclusions According to the observed acetabular stress distribution pattern of health adults during normal gait cycle, choosing acetabular component with more suitable size and controlling the placement of acetabular component with more accuracy could obtain some acetabular reconstruction plan better in accordance with stress distributions during normal gait.

Influence from acetabular component orientation on stress distributions of periacetabulum / 医用生物力学

Abstract： Objective To study the influence from different placement angles of acetabular component on inner and outer stress distributions of periacetabulum in acetabular reconstruction of total hip arthroplasty (THA), so as to explore proper orientation for improving stability of acetabular component after THA. Methods Based on model with inhomogeneous material property assignment, nine THA models with acetabular component at different anteversion angles(15°, 20°, 25°) and abduction angles(40°, 45°, 50°) as well as one normal hip model were constructed. The maximal hip contact force in phase of single leg stance during normal gait cycle was chosen as the loading condition. In addition, according to the qualitative and quantitative principle, inner and outer stress distributions on 9 THA models were analyzed and compared with the normal hip model as control. Results When abduction angle of acetabular component was the nearest to anatomic angle (19° anteversion, 46° abduction) of acetabulum, the phenomenon of stress shielding on periacetabulum was the most obvious. When abduction angle of acetabular component was placed at 45° and anteversion angle changed from 15° to 25°, no significant influence was exerted on the whole stress distributions of THA models. Meanwhile, when anteversion angle of acetabular component was 15°, the THA model had good stability in stress distributions, and the phenomenon of stress shielding on cortical and cancellous bone was obviously improved. Conclusions For patients who have normal anatomic acetabulum and need to be treated with THA, the abduction angle of acetabular component should be placed at 45°, as that of normal acetabulum; the anteversion angle should be 5° smaller than that of normal acetabulum and between 15° and 20°.

Trochanteroplasty for the Treatment of Uncontrolled Infected Total Hip Arthroplasty: A Case Report

Trochanteroplasty is a salvage procedure that is normally performed in septic infant hips. The procedure can provide a stable, painless, functional hip, and reduce any leg-length discrepancy. The authors describe a case of revisional total hip arthopalsty performed on a 65 year-old male patient 4 years after trochanteroplasty for an uncontrolled infection after total hip arthoplasty. The available literature on trochanteroplasty was reviewed. The authors provide a feasible strategy for treating adult hip infections with deficient bone stock in the proximal femur.