Abstract
Background
Although the tribological characteristics are excellent, cup fixation has been one of the limitations in alumina-on-alumina total hip replacement (THR), so different types of materials and surfaces have been developing. We analysed the clinical and radiological outcome of two different uncemented cups for the same alumina-on-alumina THR.
Methods
679 hips were prospectively followed for at least 5 years. 342 had a hydroxyapatite (HA)-coated relatively smoothed tri-radius cup, implanted between 1999 and 2005 (group 1), and, 337 had a HA-coated macotextured tri-radius implanted between 2006 and 2009 (group 2). Dysplastic hips were more frequently observed in group 2. We compared screw use in both groups as primary fixation, the clinical results, and the radiological appearance of cup loosening.
Results
Multivariate analysis showed that group 1, osteopenic and dysplastic acetabulae and women had a higher risk of screw use (p=0.004, HR: 1.68,95% CI: 1.18 to 2.41; p<0.001, HR: 2.25 95%, CI: 1.55 to 3.38; p<0.001, HR: 4.95, 95% CI: 2.83 to 8.64; p=0.011, HR: 1.58, 95% CI: 1.11 to 2.25, respectively). Although the pre-operative clinical score was worse in group 2, the post-operative results were better (p<0.001). There were no complications related to alumina. 15 cups were revised for loosening in the group 1 and 2 in the group 2. The cumulative probability of not having a revision for cup loosening at 15 years for the whole series was 93.3 % (95% CI: 89.6 to 96.9). The probability of not having cup loosening was 93.3% (95% CI: 89.7 to 96.9) in group 1 and 97.5% (95% CI: 93.5 to 100) in group 2.
Conclusions
Despite worse pre-operative conditions, the macrotextured surface of the cup in the second group improved bone fixation in this series. Continued follow-up will be required to determine if reduction in wear between the alumina-on alumina bearings results in less osteolysis and loosening.
