Abstract
The concept of two-stage revision of infected total hip arthroplasties is well established in the literature. What has been lacking has been a user friendly, simple, safe, cost-effective interim prosthesis which can achieve hip stability, maintain ambulatory status and still deliver antibiotics at high local concentrations. Other commercially available products are expensive, difficult to implant and prone to dislocation. We have developed a modular, antibiotic-laden spacer hemiarthroplasty of the hip which has been fully bench tested. The prosthesis consists of a head/neck module utilising antibiotic impregnated bone cement (PMMA) as the bearing surface and a stainless steel neck. This can be assembled onto a polyacetal (Delrin) stem of varying lengths and diameters. Bone defects are accommodated with hand moulded PMMA at the time of implantation.
We have inserted 47 of these implants in the period 9/97 to 5/2000. 28 of these have been retrieved and submitted for biomechanical analysis at the Royal Perth Hospital Implant Retrieval Laboratory.
This paper presents the concept of the implant, the clinical results, the results of retrieval analysis and elutional studies on antibiotic release from the implant.
We have analysed the retrieved implants and there have been no implant failures. Two implants have been fractured during extraction and one has dislocated secondary to subsidence. Wear analysis has shown polishing of the PMMA in the weightbearing area of the head.
Elution studies are ongoing but suggest that antibiotic release is continuing for up to 8 weeks post implantation providing ambulation is encouraged. Clinical results indicate success rates comparable to other published reports of infected total hip arthroplasties.
This implant in the hands of a variety of orthopaedic surgeons has proven itself simple to use and to maintain ambulatory status to patients whilst maximising antibiotic delivery to the infected hip.
The abstracts were prepared by Professor Jegan Krishnan. Correspondence should be addressed to him at the Flinders Medical Centre, Bedford Park 5047, Australia.
