Hip Resurfacing Arthroplasty (HRA) is a surgical technique that has become more popular in recent years for the treatment of hip osteoarthritis in young patients. For these patients, an HRA offers the advantages of preserving the physiologic anatomy of a patient's femoral head size and neck offset, which has been theoretically suggested to improve range of motion and muscle function, as well as preserving bone stock for future revision surgeries. Although the improvements in quality of life outcomes in patients undergoing total hip arthroplasty (THA) are well-documented, there is a lack of literature documenting the improvements in quality of life in patients undergoing HRA. One hundred and four consecutive patients presenting for elective HRA at our institution were recruited between 2004 and 2008 for participation in this study, which was approved by the Ethics Review Board at our institution. The mean age was 51±6y, male:female ratio 79:24 and mean BMI of 29.7±4.4 Preoperative computed tomography (CT) scans were used to preoperatively plan each procedure, and intraoperative procedures were performed using individualized templates [Kunz M, Rudan JF, Xenoyannis GL, Ellis RE. Computer assisted hip resurfacing using individualized drill templates. J Arthroplasty 2010;25(4):600–6]. Surgery time was 90±28 min including time for intraoperative verification of templating accuracy. Mobilization with physiotherapy began within 24 hrs of surgery and continued until the patient was discharged, usually within 2–3 days of surgery. Each patient completed the modified Harris Hip Score (HHS), the UCLA activity rating, the SF-36 mental and physical health score and the Western Ontario and McMaster University Osteoarthritis Index (WOMAC) questionnaires at their preoperative appointment, then at 6 months, 1 year and 2 years postoperative. In addition, radiographs were taken at these appointments to confirm component position, and to check for signs of loosening or heterotopic ossification. Chi-square and t-tests were used for within and between group comparisons on selected variables and across times. Only four patients required revision to THA, with one case of avascular necrosis of the femoral head, one femoral neck fracture and two infections. The mean of the preoperative modified Harris Hip Scores was 51±19.7 with a significant improvement in the mean score at 6 months, 1 and 2 years postoperative (p<0.01). The preoperative UCLA activity index averaged 4 (range 2–9), improving to a mean of 6 at 6 months (p<0.001) then at 1 to 2 years to 7 (p<0.001). Mental state and further assessment of physical function were performed using the SF-36 scores, with the physical score initially 27.5 and improving to 45.2 after 2 years (p<0.01). The mental component score (MCS) means were almost unchanged, from 50.3 preoperatively to 51.5 after 2 years (p<0.21). Further data processing showed that patients who began with a below-average mental score also had significantly worse WOMAC scores for pain, stiffness and function; these patient showed a significantly higher MCS at 2 years (p<0.05). Those whose MCS were above average preoperatively showed little difference after 2 years.MATERIALS AND METHODS
RESULTS
T cells have been implicated in the pathogenesis of osteolysis. The goal of this study was to compare the ratios of CD4+ T cell populations in total hip arthroplasty (THA) patients with and without osteolysis. We found no significant differences in the frequency of peripheral blood CD4+CD25+ regulatory and effector T cells, serum IL-10 and TGF-β concentrations, and immuno-suppressive ability of regulatory T cells from patients with osteoarthritis prior to THA, and THA patients with and without radiographic evidence of osteolysis. CD4+ T cells are critical in regulating immune-mediated conditions. This study compared the frequency of CD4+ T cell subpopulations in the peripheral blood of patients with and without osteolysis following total hip arthroplasty (THA). Numbers of CD4+CD25hi regulatory T cells, CD4+CD25moderate effector T cells, and CD4+CD25+ T cells in the peripheral blood of thirty patients with osteoarthritis prior to primary THA, thirty patients with asymptomatic THAs and no radiographic evidence of osteolysis, nineteen patients with asymptomatic THAs with radiographic evidence of early osteolysis (not requiring revision surgery) and nine patients scheduled for revision THA for osteolysis were determined by flow cytometry. Serum IL-10 and TGF-β levels were measured using ELISA kits. Results were compared by t-test and rank sum test. CD4+ CD25hi regulatory T cells and CD4+ CD25neg T cells were isolated from blood using a MACS cell isolation kit, co-cultured for three days, and T cell proliferation determined by [3H]-thy-midine uptake. The frequency of CD4+CD25hi regulatory T cells, CD4+CD25moderate effector T cells, and CD4+CD25+ T cells were similar in each study group. Regulatory T cells from patients with and without osteolysis had a normal functional ability to inhibit CD4+ T cell proliferation. Serum levels of the regulatory T cell-derived cytokines IL-10 and TGF-β were also comparable between groups. Our data suggests that CD4+ T cell immune responses are normal in THA regardless of the level of osteolysis, in contrast to previous studies that have implicated T cell hypersensitivity in the pathogenesis of osteolysis surrounding THA.
