Abstract
Introduction
Total hip arthroplasty (THR) with non-cemented or hybrid fixation remains one of the most successful procedures performed today. The aim of this study was to assess the safety and efficacy of a hydroxyapatite (HA) coated, hemispherical cup.
Material and Methods
Between 2003 and 2007, 223 THAs (210 patients) with peripheral self-locking (PSL) cup and highly cross-linked polyethylene (Crossfire, Stryker, Mahwah, NJ) with minimum 5 years clinical and radiographic follow-up (5–9 years) were analyzed. The mean age was 62.5 years ± 10.8 (range, 32.7 – 86.3) at the time of surgery and the predominant preoperative diagnoses was osteoarthritis (97.8%). 72% were solid cups without screw augmentation and 28% were multi-hole with screw. Clinical analysis included Hospital for Special Surgery (HSS) hip scores at latest follow-up. Detail radiographic analysis was carried out on anteroposterior and false profile views for evidence of osseointegration in all Charnley's zones. Osseointegration was assessed based on presence of Stress Induced Reactive Cancellous Bone (SIRCaB) with trabecular bone hypertrophy 5–15mm extending from the cup, and absence of radiolucency or demarcation. EBRA software was used to assess cup positioning.
Results
At final follow up, clinical result were excellent with average HSS score of 34.8. 4% underwent revision for following reasons: dislocation (1.34%), loose stem (0.89%), stem fracture (0.89%), pain/bursitis (0.45%), and infection (0.45%). There were no revisions for failures of fixation. In radiographic analysis, the average functional cup abduction angle and functional anteversion were 41.7° ± 5.2 (range, 30 – 52) and 16.8° ± 6.1 (range, 4 – 30). 96% of the cups were within the safezone of Lewinnek. There was no progressive radiolucency, migration or change in the cup position at final follow-up. The average overall SIRCaB and radial trabeculae in all 3 zones were 47% and 93%, respectively; both were most prevalent in Zone 1.
Conclusion
The hemispherical, peripheral press-fit, HA-coated PSL cup has excellent safety and efficacy, appropriate radiographic osseointegration with no mechanical failures at 5 – 9 years. PSL cup has 1 mm increase in the radius at the periphery of the shell to allow for an enhanced initial press fit. Based on our results, supplementary screw with this cup may not lead to better fixation.
