factors associated with the course of femoral head osteonecrosis; a retrospective study

background: an increased incidence of osteonecrosis of the femoral head (onfh) has recently been observed in iran, likely associated with the introduction of an illegal, steroid-containing opioid drug, temgesic. the correlation of risk factors associated with the course of onfh has yet to be determined.objectives: the purpose of the present study was to assess the effects of etiologic factors on the course of onfh after emergence of symptoms.patients and methods: we retrospectively assessed patients with untreated onfh due to one of the four etiologies of steroid medication, temgesic abuse, trauma and idiopathic. patients with multiple risk factors and those without collapse at the last follow-up visit were excluded. the effect of age, gender, etiology of osteonecrosis, opium addiction and smoking on the time interval between pain onset and radiologic collapse were investigated.results: in total, 110 patients (174 hips) were categorized into four etiologic groups. the average time between onset of pain to radiologic collapse in different etiologic groups was 12.8 months for all groups, 12.4 months for steroid, 8.7 months for temgesic, 18.5 months for trauma and 16.6 months for idiopathic groups. thirteen hips had collapse in less than six months. patients who used steroid and temgesic had shorter time interval to collapse, which was statistically significant (p values < 0.001 and < 0.001, respectively). smoking had a statistically significant association with the time to femoral head collapse (p value = 0.003).conclusions: steroid medications and temgesic abuse are associated with shorter time interval to femoral head collapse. smoking is also a factor associated with shorter time interval to collapse. these factors should be considered in any joint preserving treatments for patients with fhon.