Heterotopic Ossification Following Primary Total Hip Arthroplasty

ObjectiveTo study the prevalence and important predisposing factors associated with heterotopic ossification(HO) after primary total hip arthroplasty(THA),and afford the proof to choose the patient who needed an efficient prophylaxis.Materials and methodsProspectively evaluated 249 consecutive patients with 292 primary THA for HO, the mean clinical and radiological follow-up was 36months,diagnosis was mainly based on anteroposterior X-rays of hips, the classification was according to Brooker system,clinical function was evaluated by Harris Score,and the data was analyzed using chi-quest test of independence and logistic regression(p < 0.05).ResultsHO was noted in 79 hips(27.1%), and was graded as Brooker I in 57 hips(19.5%), Brooker II in 15 hips(5.1%),Brooker III in 7 hips(2.9%),there was no Brooker IV.The prevalence of who had the predisposing factors of male gender, osteoarthritis, ankylosing spondylitis,previous hip surgery were 40.2 %,34.6%,39.1 %,45.5%,while the prevalence of whom suffered rheumatic arthritis was 9.7%. The mean preoperative Harris score was 45.5 compared with 94.2 of postoperation. There were not apparent difference in Harris score ofvariant Brooker group.The average range of flexion and abduction of non-HO were 92.1,29.4,while the Brooker IIP were 74.4,15.1.ConclusionThe prevalence of HO following THA was musch higher than considered.The following factors showed a significantly increased risk of HO: Male gender, osteoarthritis, ankylosing spondyritis and previous hip surgery. In patients undergoing total hip arthroplasty with these risk factors, an efficient prophylaxis against HO is of great importance ,while patients with rheumatic arthritis showed less HO.The exist of HO decreased little of the Harris score.The range of flexion and abduction of hip was apparently decreased in Brooker III.