Application and evaluation of biomechanical models and scores for the planning of total hip arthroplasty.

Intimate knowledge of the biomechanics of a given individual hip joint provides a potential advantage during the planning of total hip arthroplasty, and would thus have a positive influence over the outcome of such an intervention. In current clinical practise, the surgical planning is based solely on the status of the individual hip and its radiographic appearance. However, additional information could be gathered from the radiography to be used as input data for biomechanical models aimed at calculating the resultant force FR within the hip joint. An investigation of the biomechanical models by Pauwels, Debrunner and Iglič was performed, where the magnitude of FR calculated by the models showed a favourable comparison to the in-vivo data from instrumented prostheses by Bergmann. The Blumentritt model returned abnormally high results. The computational results showed large variations for FR orientation, which tends to depend more on the model used than on patient-specific parameters. Furthermore, a discrepancy was found between the data gathered from instrumented prostheses and the Standing Human Model within the 'AnyBody Modeling System™' software by AnyBody Tech. Additionally, the variations in inter-rater and intra-rater errors made while localizing radiographic landmarks were analysed with respect to their influence on Babisch-Layher-Blumentritt (BLB)-scoring using the Blumentritt hip model.