Quantitative computer-assisted osteodensitometry in total hip arthroplasty.

Several factors can cause bone loss and fixation failure following total hip arthroplasty (THA), including polyethylene wear debris, implant micromotion and stress shielding. Various techniques have been used in an effort to detect bone density loss in vivo, all with varying success. Quantitative computed tomography (qCT)-assisted osteodensitometry has been shown to be useful in assessing the in vivo structural bone changes after THA. It has a high resolution, accuracy and reproducibility, thereby making it a useful tool for research purposes, and it is able to differentiate between cortical and cancellous bone structures and assess the bone/implant interface. This technique also provides valuable information about the pattern of stress shielding which occurs around the prosthesis and can show early bony changes, which may prove informative about the quality of implant fixation and surrounding bone adaptation. In conjunction with finite-element analysis, qCT is able to generate accurate patient-specific meshes on which to model implants and their effect on bone remodelling. This technology can be useful to predict bone remodelling and the quality of implant fixation using prostheses with different design and/or biomaterials. In the future, this tool could be used for pre-clinical validation of new implants before their introduction in the market-place.