X-ray Manifestations And Related Factors Of Heterotopic Ossification After Total Hip Arthroplasty

Objective:To investigate the main risk factors of heterotopic ossification(HO)caused by total hip arthroplasty(THA),and to analyze the correlation between X-ray manifestations and risk factors of HO after THA and provide prevention、early diagnosis and prognosis evaluation of HO through X-ray follow-up observation of HO.Methods:A retrospective analysis included 342 patients(368 hips)which with THA from affiliated Zhongshan hospital of Dalian university,from January 2010 to September2018,and these patients included 132 males(143 hips)and 210 females(225 hips),aged36~90 years old,average age was 61.70 years,and the follow-up period was 6 to 89months.The collected cases were divided into two groups.The study group included 173patients(178 hips)with HO observed by the X-ray after THA,including 81 males(86 hips)and 92 females(92 hips),with average age was 63.40 years.The control group included169 patients(190 hips)without HO observed by the follow-up X-ray for more than 6months,including 51 males(57 hips)and 118 females(133 hips),with the average age was60.21 years.Observe and record the initial appearance time,location,number,range,length and diameter of HO on X-ray and the Brooker classification of the HO.χ~2 test,Mann-Whitney U test and Logistic regression analysis were used to analyze the risk factors of HO,including age,gender,side,history of ipsilateral and contralateral hip surgery,artificial joint material,operation time of surgery,intraoperative blood loss,length of surgical incision and use NSAIDs time.Spearman correlation analysis was performed between independent risk factors and Brooker classification to explore the correlation between risk factors and HO severity(X-ray manifestations).Results:Compared with the control group,the study group was older,more males,less intraoperative blood loss,and shorter time to use NSAIDs after surgery(P<0.05).There was no significant difference between the two groups in side,operation history of ipsilateral and contralateral hip,artificial joint material,operation time of surgery,length of surgical incision(P>0.05).Logistic regression analysis showed that intraoperative blood loss(P=0.189)did not show the increase of HO.Age,gender,and use NSAIDs time were statistically significant(P<0.05),which were the risk factor of HO.In this study,the incidence of HO was 48.3%(178/368).According to Brooker classification,HO was divided into four levels on the X-ray film:Brooker I:118 hips(66.3%),BrookerⅡ:47 hips(26.4%),BrookerⅢ:12 hips(6.7%),BrookerⅣ:1 hip(0.6%).HO usually located at:between the gluteus medius and gluteus minimus 113 hips(63.5%),the top of trochanter59 hips(33.1%),iliopsoas 6 hips(3.4%),beside lesser trochanter 11 hips(6.2%),beside acetabulum 4 hips(2.2%).The initial appearance time of HO observed on the X-ray was0.5~6 months,the average time was 1.90 months.At the last follow-up,the number of HOs was 1-7,and the average number was 1.51;the range was from 1.60 to 2251.60mm~2and the average range was 144.03mm~2;the maximum length was 0.74~95.60mm,and the average was 17.76mm.The number of HO in some patients was gradually increased,the number of HO were increased in 59 hips(33.1%)HO and the number of HO did not change in 119 hips(66.9%).The range of HO increased in 76 hips(42.7%),with no significant changed in 45 hips(25.3%)and reduced in 57 hips(32.0%).The shape and range of HO were no longer changed significantly from 1 to 15 months,and the average was 5.58 months.There was no significant difference in the initial appearance time between the mild HO group(Brooker I,II)and the severe HO group(Brooker III,IV)(P>0.05).Spearman correlation analysis was performed between gender,age,use NSAIDs times and Brooker classification,the results showed that gender and age were positively correlated with the severity of HO(P<0.05),use NSAIDs time was negatively correlated with the severity of HO(P<0.05).Conclusion:Old age,males were risk factors for HO after THA,and were associated with more serious HO.Postoperative application of NSAIDs could effectively reduce the incidence of HO and reduce the severity of HO.Intraoperative blood loss was related to the occurrence of HO,but it was not an independent risk factor.After THA,HO appeared within 6 months,so we considered that it would not appear again after more than 6 months after THA.In this study the imaging manifestations of most HO were longer changed significantly after 1 year,speculated that the progress of HO after THA was within 1 year.The severity of HO is not related to whether it can be observed early on the X-ray.HO after THA were mostly Brooker I and II,in the early stage,the range,length of the mild HO were smaller than that in severe HO.HO usually located in the hip outside where between the gluteus medius and gluteus minimus,and the top of trochanter.