Introduction: Two major complications of hip resurfacing arthroplasty are avascular necrosis of the femoral head and femoral neck fracture. Both are thought to be precipitated by disruption of the blood supply to the femoral head and neck during the approach to the hip joint. Ganz et al have described their technique of approaching the hip joint using a “trochanteric flip” osteotomy. This has the theoretical advantage of preserving the medial femoral circumflex artery to the femoral head. The aim of this study was to compare the intra-operative femoral head blood flow during the Ganz flip osteotomy to the blood flow during a posterior approach for resurfacing arthroplasty of the hip.

Methods: The intra-operative measurements of blood flow were performed using a DRT laser Doppler flow-meter with a 20 mW laser and a fibreoptic probe. The probe was introduced into the lateral femoral cortex and threaded into the femoral head under image intensifier control. Measurements were recorded before the approach to the hip was performed, after the approach was performed but before the head was dislocated, and after the head was dislocated.

Results: Our initial results indicate that there is on average a 50% drop in the blood flow to the femoral head after a posterior approach to the hip joint. In contrast, the trochanteric flip osteotomy produces a much smaller fall of around 18%. We have used these results to inform a sample size calculation, and are currently recruiting further patients to achieve a total of 42 in order to confirm a statistically significant effect.

Conclusion: The Ganz trochanteric flip osteotomy appears to produce less damage to the blood supply to the femoral head during resurfacing arthroplasty than the posterior approach. This study will inform surgeons in deciding on their preference for a routine approach for hip resurfacing.

Background: Hip resurfacing preserves bone stock on the femoral head. Some authors believe that this is at the expense of sacrificing more bone on the acetabulum and they point out two main reasons for this. Since resurfacing tends to be used in younger and more active individuals a larger head to neck ratio seems desirable in order to provide a better range of movement before impingement. In addition, the acetabular component has to be a minimum of 5 mm thick to prevent deformation on implantation and the subsequent compromise in the congruency of the bearings.

Method: We report the average size of the acetabular components of 220 Cormet resurfacings and 199 Pinnacle cups implanted in our department over a period of 18 months. From these sizes we estimated the mean acetabular bone loss for each procedure.

Results: The mean cup size was 53.7 mm for Cormet and 54.1 mm for Pinnacle i.e. the acetabular component of the resurfacing was smaller than the equivalent uncemented total hip replacement.

Conclusions: These figures show that resurfacing arthroplasty does not necessarily lead to greater acetabular bone loss than a total hip replacement. In our practice, we concentrate upon preserving acetabular bone rather than establishing a large head to neck ratio. In spite of this approach, the occurrence of impingement and dislocation among our patients seems to be as rare as in other comparable series.