Abstract
Introduction: THR is still the standard of care for young arthritic patients. However, failure rates remain high at 10 years follow-up, with rates of up to 33% in all cemented designs and 10.5% in cementless designs. With the arrival of new, more wear-resistant bearings, Surface Arthroplasty (SA) has become a viable and promising solution for this patient population. The purpose of the present study was to investigate the results of a metal-on-metal (M/M) hybrid SA and identify appropriate criteria for patient selection.
Method: The first 400 hips (of 620) in 355 patients underwent M/M hybrid surface arthroplasty. Mean age 48.2; 73% males, 27% females; 198 Charnley Class A; 139 Class B and 18 Class C. Diagnosis at surgery: OA 64%, DDH 11%, ON 9%, Post-traumatic 8%, Inflammatory arthritis 3%, SCFE and LCP 4%, Melorheostosis 0.3%.
Results: Mean follow-up 5.2 years (3.9–7.8). Average UCLA hip scores post-op: pain 9.4, walking 9.5, function 9.4, and activity 7.7. The SF-12 physical and mental components were respectively, 31.2 and 46.8 pre-op and 50.1 and 53.0 post-op. Fifteen hips were converted to THA (nine in the first 102): two neck fractures, 10 femoral loosenings, one socket protrusio due to over-reaming, one subluxation due to impingement and one sepsis. The three most important risk factors for femoral loosening and radiolucencies were large cyst formation (p=0.0067), female gender (p=0.0001), and lighter weight in male patients (p=0.0003). The occurrence of femoral loosening or lucency was 18% for the first 100 cases, 9% for the second, 8% for the third, and 1% for the last 100 cases.
Conclusion: Clinical results are excellent, despite very high activity levels. The experience with SA of all cemented metal/UHMWPE bearing demonstrated failure rates of 15 to 33% at three years. At longer follow-up, the preliminary experience is encouraging (3.75% failure rate). Dislocation is rare, and acetabular fixation secure. Initial femoral fixation is critical, as the fixation area is small, especially with osteopenia and cystic degeneration. Cementing the femoral metaphyseal stem appears as a meaningful technical improvement towards the prevention of early femoral radiolucencies. None of the 59 cemented metaphyseal stem had any radiolucency at last review.
These abstracts were prepared by Editorial Secretary, George Sikorski. Correspondence should be addressed to Australian Orthopaedic Association, Ground Floor, The William Bland Centre, 229 Macquarie Street, Sydney, NSW 2000, Australia.
At least one of the authors is receiving or has received material benefits or support from a commercial source.
