Abstract
Introduction
The use of screws is frequent for additional fixation, however, since some disadvantages have been reported a cup press-fit is desirable, although this can not always be obtained. Cup primary intraoperative fixation in uncemented total hip replacement (THR) depends on sex, acetabular shape, and surgical technique. We analyzed different factors related to primary bone fixation of five different designs in patients only diagnosed with osteoarthritis, excluding severe congenital hip disease and inflammatory arthritis, and their clinical and radiological outcome.
Materials y Methods
791 hips operated in our Institution between 2002 and 2012 were included for the analysis. All cases were operated with the same press-fit technique, and screws were used according to the pull-out test. Two screws were used if there was any movement after the mentioned manoeuvres. Acetabular and femoral radiological shapes were classified according to Dorr et al. We analyzed radiological postoperative cup position for acetabular abduction angle, the horizontal distance and the vertical distance. Cup anteversion was evaluated according to Widmer and the hip rotation centre according to Ranawat.
Results
Screws were required in 155 hips (19.6%) and were more frequently used in women and patients with a type A acetabulum (p<0.001, p=0.021, respectively). There were no differences among the different cups evaluated. The need for screws was more frequent in hips with a smaller version of the cup and with a distance greater than 2 mm to the approximate femoral head centre from the centre of the prosthetic femoral head (p=0.022, 0.012, respectively). Adjusted multivariate analysis revealed that female patients (p<0.001, Odds Ratio (OR): 2.063; 95% Confidence Interval (CI) 1.409–3.020), cups with a smaller version (p=0.012, OR: 0.966, 95% CI 0.94–0.992), and a greater distance to the rotation hip center (p<0.005, OR: 1.695; 95% CI 1.173–2.450) had a higher risk for screw use. No hips needed revision for aseptic loosening.
Conclusions
Cup press-fit depends on gender and surgical technique in hips without significant acetabular abnormalities or inflammatory arthritis. Contemporary uncemented cups provide similar primary fixation and mid-term outcome.
