Evaluation of femoral prosthetic loosening using CT imaging.

Abstract

Arthrography, using either a radiopaque contrast agent or technetium-99m radionuclide, is the established technique for evaluating patients with painful loosening of hip prostheses [1-3]. Although offering the advantage of allowing simultaneous evaluation of painful hip prostheses for both loosening and infection, this technique is invasive and also painful. Although infection can occur at any time after prosthesis placement, the incidence of infection is low, particularly in patients without complicating medical problems [4-8]. Therefore, a noninvasive imaging technique to evaluate for loosening would benefit patients who develop pain in long-standing hip prostheses. Such a technique could be particularly useful for evaluating cementless prostheses, in which the value of arthrography is less established [9]. Fletcher et al. [10], in a recent symposium on the hip, suggested using CT for evaluating femoral component loosening of cementless prostheses. We know of no other published reports that describe the use of CT for this purpose. In our study, we evaluated the ability of CT to detect femoral loosening by applying torsional stress and then measuring angular displacement of the femoral stem within the femoral canal.