FEMORAL BLOOD FLOW DURING HIP RESURFACING: A COMPARISON OF TWO APPROACHES USING LASER DOPPLER FLOW MEASUREMENT

Abstract

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.