Intermediate results of a straight stem prosthesis in primary total hip arthroplasty.

In a retrospective study of 130 primary total hip arthroplasties with a self-locking straight stem femoral component (Muller) and low profile cup, the average follow-up evaluation was 3.1 years (range, 2.0-4.6 years). According to the clinical rating system modified from Swanson and Evarts, there were 115 (88.3%) excellent, six (4.7%) good, four (3.1%) fair, and five (3.9%) poor results. Radiolucent lines at least 1 mm in width were noted in 12.8% of acetabula, mostly in Zones 1 and III. One cup has been revised and one is awaiting revision. Radiolucent lines greater than or equal to 1 mm were noted around 26.5% of femoral components. These were asymptomatic, unless associated with the presence of infection, subsidence greater than 5 mm, or symptoms of acetabular loosening. True femoral subsidence was pain free and nonprogressive in seven patients (6%) if less than or equal to 5 mm. Femoral loosening was roentgenographically observed as component migration or subsidence greater than 5 mm. By these criteria, three femoral components (2.6%) were loose, although none have been revised.