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.

Fourteen hips with osteoarthritis had femoral head blood flow measured with laser Doppler flowmeter while undergoing during total hip replacement through a modified lateral approach. Mean age sixty-five years (48–77); eight males & six females. Two measurements were taken within the femoral head one after anterior hip dislocation and one after simulated notching of the femoral neck. All hips had a significant decrease in blood flow with a median percentage decrease of 76% (range 4.4–90.4). During surface arthroplasty of the hip, notching of the femoral neck may not only mechanically weaken the bone but also put the femoral head at risk of osteonecrosis.

To evaluate femoral head blood supply in patients with osteoarthrtis of the hip undergoing simulated notching of the femoral neck during total hip replacement and its potential implications in hip resurfacing.

During surface arthroplasty of the hip, notching of the femoral neck may not only mechanically weaken the femoral neck but also put the femoral head at risk of osteonecrosis and subsequent femoral loosening.

It would appear that the retinacular vessels (extraosseous blood supply) are as important in the arthritic femoral head as they are in the nonarthritic state, contradicting the notion that arthritic femoral heads in humans rely mainly on an intraosseous blood supply.

Fourteen hips with a diagnosis of degenerative arthritis had femoral head blood flow measured with laser Doppler flowmeter while undergoing during total hip replacement through a modified lateral approach. With the femoral head exposed and leg in neutral position, a 3.5mm drill hole was made into the anterior lateral quadrant and the fiber optic probe of the laser Doppler flowmeter (Moor Instruments, Wilmington Delaware, 20mW laser, wavelength 780nm) was inserted. Mean age was sixty-five years (48–77). Eight males and six females. Two measurements were taken one after anterior hip dislocation and one after simulated notching of the femoral neck. All but four hips had a significant decrease of more than 50% in blood flow after neck notching with a median percentage change of 76% (range 4.4–90.4), p< 0.001.

During hip resurfacing arthroplasty, excessive valgus positioning or surgical technique can result in notching of the femoral neck. Although mechanical weakening and subsequent fracture of the femoral neck are well described, the potential damage to the retinacular vessels leading to an ischaemic event is relatively unknown. Using laser Doppler flowmetry, we measured the blood flow in 14 osteoarthritic femoral heads during routine total hip replacement surgery, before and after notching of the femoral neck. In ten hips there was a reduction in blood flow of more than 50% from the baseline value after simulated notching of the femoral neck. Our results suggest that femoral head vascularity in the osteoarthritic state is similar to the non-arthritic state, where damage to the extraosseous vessels can predispose to avascular necrosis. Surgeons who perform resurfacing arthroplasty of the hip should pay careful attention to these vessels by avoiding excessive dissection around the femoral neck and/or notching.