[Criteria for radiologic evaluation of cement-free hip endoprostheses exemplified by the Spotorno shaft].

Roentgenographic evaluation of total hip arthroplasty is based on changes in the marginal zones and in position. The changes in the marginal zones are not subject to any general rule. They are characteristic for the type of prosthesis. In a retrospective study, the roentgenographic findings of 431 spotornofemoral components were evaluated. We analyzed the X-ray pictures of 15 explanted spotornostems in comparison to the pictures of 15 spotornostems that were known to be stable because of revision surgery. We used this method to establish signs of stem loosening. Regression of more than 2 mm and a change in position toward varus or valgus were observed only in loose prostheses. We therefore considered these radiological changes to be an indication of loosening. Radiolucent lines up to 2 mm wide are typical for the spotornostem in the area of the prosthesis shoulder and the calcar region; when they appear in the mid- or distal section, they are also considered an indication of loosening. Radiolucent lines more than 2 mm wide indicate loosening in any case. Early in the postoperative course, the parameter of the femoral canal is already much lower in loose prostheses than in stable prostheses. An ill-fitting position in the femoral canal therefore shows a poor prognosis. Local hypertrophy of the femoral cortex or a base formation were more common in loose spotornostems. We also considered these changes to be indicator of an unfavorable prognosis.