Avascular necrosis in sickle cell (homozygous S) patients: predictive clinical and laboratory indices

Pathogenetic mechanism as well as laboratory and clinical correlates of osteonecrosis in sickle cell have not been fully investigated. The aim of this study is to investigate the predictive value of the steady state white cell and platelet count as well as the frequency of bone pain crisis per annum to detect sickle cell patients who will eventually develop avascular necrosis (AVN).

A 5 year retrospective analysis of 122 homozygous S (HbSS) patients, aged 6-49 years (mean age 24.7 ± 7 years), out of which 16 patients (13.1%) had developed AVN within the years under review.

The prevalence of AVN in sickle cell patients was determined to be 13.1 per 1000. The steady state white cell count, platelet count, frequency of bone pain crisis and hematocrit, was compared in patients that develop AVN and those who had not over the period. Only the steady state platelet count was found to differ significantly ( P = 0.011) between these two patient groups and to correlate positively (Pearson correlation coefficient = -0.251) with development of AVN. The hematocrit, white cell count, and frequency of bone pain crisis were found neither to differ significantly nor correlate with the development of AVN.

In conclusion, patients with a raised steady state platelet count may have a higher tendency to develop AVN and may require closer orthopedic review and prophylactic intervention.