Purpose of the study: During resurfacing arthroplasty, excessive valgus of the femoral neck or an insufficient surgical technique can lead to formation of a notch in the femoral head. Although the mechanisms weakening the femoral neck and subsequent fractures are well described, the effects of altered blood supply via the retinacular vessels on potential ischemia of the femoral head are largely unknown. The purpose of our study was to assess blood supply to the femoral head when a notch occurred in the femoral neck during total hip replacement surgery and to deduct possible implications concerning the resurfacing procedure.

Material and methods: Blood supply to the femoral head was measured with laser Doppler fluorometry in 14 hips undergoing total hip replacement for osteoarthritis via a lateral approach with anterior dislocation. An optical laser probe for the fluorometry (Moor Instruments, Wilmington Delewar, 20 mW laser, probe length 780 nm) was introduced via a 3.5 mm hole drilled in the antrolaeral quadrant of the femoral head (leg in neutral position). The position of the probe was checked on the x-ray of the femoral head after resection. A notch was simulated in the lateral posterior portion of the femoral neck using a bone gouge.

Results: Mean patient age was 65 years (range 48–77 years). There were eight men and six women. Two measurements were made: one after dislocation of the hip and the second after simulating the notch. A significant decrease in blood supply measured at more than 50% was observed in all but four hips after simulating the notch. The median decrease in blood flow was 76% (4.4–90.4, p< 0.001).

Conclusion: The retinacular vessels appear to be equally important for the blood supply for osteoarthritic and non-osteoarthritic femoral heads. A notch occurring during hip resurfacing would not only weaken the mechanical resistance of the neck but would also increase the risk of osteonecrosis and subsequent loosening of the femoral component. Consequently, approaches compromising retinacular blood supply (for example the posterior approach) would add a supplementary danger for the integrity and viability of the femoral head.