Abstract
Aims: Femoral offset is routinely measured prior to total hip arthroplasty in order to recreate the position of optimum abductor function. We aim to determine how radiologically measured offset changes with hip rotation and to evaluate the clinical relevance of any changes. Methods: We took standardised radiographs of a proximal femur at ten degree increments of rotation and measured the offset derived in each position. We then measured the apparent offset obtained in full internal and external rotation in a series of twenty consecutive patients attending for hip arthroplasty. Results: The model demonstrated that femoral offset is maximal between ten and twenty degrees of internal rotation and that small changes in rotation can cause large changes in apparent offset. From the clinical series of elderly, arthritic patients we show that there is a signiþcant change (mean of 11.4mm or 29%) in measured offset between internal and external rotation. In our series this discrepancy would have led to a change in selected femoral prosthesis in almost half the cases. Conclusion: Femoral offset measurements are only accurate, and therefore useful, if taken with the hip in or close to þfteen degrees of internal rotation.
Theses abstracts were prepared by Professor Dr. Frantz Langlais. Correspondence should be addressed to him at EFORT Central Office, Freihofstrasse 22, CH-8700 Küsnacht, Switzerland.
