PubMed · 15898255
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Elizabeth Sheldon. Hip replacement.. https://doi.org/10.7748/ns.19.34.68.s54
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In this paper an application of the boundary element method for simulating wear in total hip prosthesis is presented. Several examples including different update periods of the worn acetabular cup, various femoral head sizes and various materials for both the femoral head and the acetabular cup are simulated under the same variable loading conditions for up to 20 years of service. Moreover, two different femoral models are considered in order to investigate the influence of the femoral modelling. The analysis demonstrates that due to the boundary only modelling requirement, the computational time and storage remains low, allowing large service periods to be simulated. Generally, the results obtained are in good agreement with other researchers findings. Moreover, ignoring the bending of the femoral neck in the model, results in a small overestimation of the maximum wear depth, while the volumetric wear is slightly underestimated. However, these differences are trivial considering the reduction of the computational effort.
This study investigates receptor activator NF-kappaB (RANK), RANK ligand (RANKL) and tumour necrosis factor (TNFalpha), key factors regulating bone turnover, present in the tissues near peri-prosthetic osteolysis. Tissue was obtained from zones of peri-prosthetic osteolysis from 11 patients undergoing revision of total hip prostheses, analysed preoperatively by high-resolution spiral multislice CT using a metal artefact suppression protocol. Synovial tissue from 10 patients with osteoarthritis undergoing primary hip replacement was used as control tissue. Immunohistochemical analysis of formalin fixed tissue sections demonstrated that RANK, RANKL and TNFalpha were strongly expressed by large multinucleated cells containing polyethylene wear debris in revision tissues. Control tissue stained weakly for RANK, RANKL and TNFalpha. A strong statistical correlation (p<0.02) was found between the five parameters, volume of bone loss, polyethylene wear debris, RANK, RANKL and TNFalpha expression. Importantly, in vitro studies revealed that RANKL and TNFalpha synergise to increase the volume of bone resorbed, by more than seven fold, when compared to the effect of either cytokine treatment alone. This suggests that the interaction of TNFalpha and RANKL promotes osteoclast activity associated with polyethylene wear and therapies targeting TNF activity may be useful to treat peri-implant osteolysis.
INTRODUCTION: Anteroposterior pelvic radiographs are routinely used to monitor cup orientation in total hip arthroplasty (THA). Analysis of planar radiographs leads to a certain degree of measurement error for the cup anteversion (AV). With the current study, we wanted to clarify whether planar radiography can be used for accurate evaluation of the THA position. MATERIALS AND METHODS: The postoperative orientation of pelvic implants in 42 patients was analyzed according to five documented mathematical algorithms using planar radiographs. Postoperative computed tomography (CT) pelvis scans were available for all patients. A CT-based navigation system was used to determine AV. RESULTS: The comparison showed that all five formulas presented substantial variations for the AV angle. Of these, Widmer's algorithm presented the smallest difference compared to the CT. Misinterpretation of postoperative planar radiographs is a common problem in THA. CONCLUSION: Planar radiographs are too imprecise for exact evaluation of the correct cup AV after THA. CT-based analysis may be necessary if exact values are required.