Sickle-cell hip necrosis and intraosseous pressure

Osteonecrosis of the femoral head (ONFH) is a frequent complication of sickle-cell disease. Numerous studies have demonstrated increased intraosseous pressure (IOP) in idiopathic necrosis and necrosis secondary to corticotherapy or alcohol poisoning. Several reports have testified to the clinical interest of decompression by drilling which, when performed in the early course of the pathology, can arrest or slow evolution. To the best of our knowledge, no studies have reported IOP increase in sickle-cell ONFH. The present study sought to show that intraosseous hyperpressure plays a role in the physiopathology of sickle-cell, like idiopathic, ONFH.

Sixteen intraosseous pressure (IOP) measurements were taken: eight in adult sickle-cell disease patients, four in sickle-cell trait carrying ONFH patients (AS) and four in non-sickle-cell ONFH patients (AA). Arterial blood-pressure equipment with bone-puncture needle was used to measure IOP in the great trochanter body. Three IOP measurements were made after zero calibration: before drilling (direct pressure: IOP-1), after hyperpressure test but before drilling (IOP-2), and after drilling (IOP-3).

The present, admittedly short, series displayed elevated predrilling IOP-1 and IOP-2, reduced after drilling (IOP-3). Abnormal IOP fell after drilling performed for evolutive symptomatic ONFH. Significant differences in IOP-1 and IOP-2 were found, these being higher in the "sickle-cell disease" and "sickle-cell trait carriers" groups (p<0.05). Only in the sickle-cell groups was there a significant correlation between pain score and hyperpressure level, with significantly reduced pain after drilling.

The elevated IOP levels found in symptomatic sickle-cell hips were comparable to those reported in the literature. Ischemia due to femoral head sinusoid occlusion by falciform globules with secondary intraosseous hyperpressure is the cause of the pain and of the onset and evolution of ONFH. The drilling tunnel acts as a safety valve, achieving real decompression of the segment involved and immediate postoperative reduction in or disappearance of pain.

Measuring pressure is of diagnostic interest in sickle-cell disease patients with symptomatic hips. Manometry can be performed independently of surgery, under local anesthesia, and provides early confirmation of ONFH in geographic regions in which MRI is not readily available. It can be carried out very straightforwardly, without pressure sensor, using a simple water column (physiological saline) and three-way tap. Peroperative comparison of IOP-1 and IOP-3 is a means of assessing the effectiveness of decompression drilling.