Abstract
This study utilised NJR primary hip data from the 6th Annual Report to determine the rate and indication for revision between cemented, uncemented, hybrid and resurfacing prosthetic groups. Regression analysis was performed to identify the influence of gender and ASA grade on these revision rates. Validity of the data was interrogated by exploring for episodes of misclassification.
Results
We identified 2,264 misclassified episodes within the four groups (Misclassification rate 2.7% primary, 4.3% revision procedures). Analysis was performed using the “reclassified dataset”.
The Kaplan-Meier revision rates at 3 years were 0.9% (95%CI: 0.8%-1.0%) for cemented prostheses, 1.9% (95%CI: 1.8%-2.0%) for uncemented hips, 1.2% (95%CI: 1.0%-1.4%) for hybrids and 3.0%, (95%CI: 2.7%-3.3%) in the resurfacing group. The trends in revision rates were comparable to those published in the NJR (6th Edn.) with significant differences across all groups (p< 0.0001). Revision rates in the under 55 year age group showed an identical hierarchy with cemented and hybrid arthroplasty having the lowest revision rates.
Cox Regression analysis indicated that both the prosthesis group in isolation and the interaction between prosthesis group and ASA grade significantly influenced the rate of failure (p< 0.001).
Indications for revision showed significant differences in rates for, pain, aseptic loosening, dislocation and malalignment between prosthesis types (p< 0.001). The indications including Aseptic loosening, pain, malalignment and dislocation all demonstrated similar trends in revision rates between prosthetic groups with cemented hips having the lowest rates followed by ascending rates for hybrid, uncemented and resurfacing groups. The exception being dislocation with resurfacings having the lowest revision rates.
Discussion
This study provides important baseline revision rates by indication for each prosthetic group from which future comparisons can be made. Areas of misclassification within the NJR dataset have been reported back for future annual analysis.
