Total hip arthroplasty (THA) is an effective reconstructive procedure for treatment of osteoarthritis of the hip joint. It has been proven to improve hip function and patient quality of life (1). This procedure was initially designed to benefit patients with osteoarthritis and over 65 years of age. Recent studies report a broadening of the spectrum for age as well as pathological diagnosis. THA is being offered to young patients and patients with osteonecrosis, rheumatoid arthritis and end stage arthritis from paediatric hip conditions. Outcomes for young patients are not as good as compared to those over 65 years of age. Reports from follow up studies and joint registries show a higher revision rate for young patients (2). Improvement
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A similar study by Elting et al(7) with 67 patients followed up to a maximum of 5 years revealed promising results with only six failures and 93% of femurs showing graft incorporation and bone remodeling. Since then a number of reports have been published on outcomes of impaction bone grafting in revision hip arthroplasty (8-10). Most of the studies show a high incidence of early stem subsidence (11) and periprosthetic fractures of the femur (12). Interestingly, collared stems appear to reduce the early subsidence (13). A long-term study by Exeter group (14) argued that stem design is not the only factor for early subsidence. They found a direct relation between severity of bone loss and subsidence. Despite these concerns, developer centers have reported satisfactory results for femoral (14) and acetabular impaction grafting (5).
Impaction grafting is most commonly performed using fresh frozen allograft but its use is limited by inadequate availability. Other major concerns regarding the use of allograft are the risk of transmission of pathogens such as Hepatitis B and HIV (15). One method to reduce the risk of this transmission is to use irradiated bone (16). Multiple reports have cited deficient graft incorporation and less optimal bone remodeling following the use of irradiated bone graft for impaction grafting (17, 18). These problems have lead to a surge in the usage of synthetic bone grafts.
Hydroxyapatite (HA) and Tricalcium-phosphate (TCP) are