Natural History Of Osteonecrosis Of Femoral Head After Affected With SARS And Analysis Of Risky Factors In Progression

Avascular necrosis of femoral head(ANFH)is a common and intractable disease in orthopaedics. Its pathogenesis is unclear.The known risky factors of collapse assicated with ANFH are size of necrotic lesion and the location of lesion of it. We had an excellent chance to explore the prognosis of ANFH in cases affected with SARS. Some risky factors of collapse will be analysed in this paper.Understanding prognosis of ANFH has an importance and guidline for therapy of it. This study shows our results of following-up of them.Objective: Observing the imaging changes with time of osteonecrosis of femoral head, understanding the characteristics of alterations in the femoral head from onset of ONFH , analyzing the risky factors of collapse of femoral head. giving a classification of osteonecrosis of femoral head,and understanding its natural history . Observing the imaging changes of procollapse and postcollapse of bilateral osteonecrosis of femoral head and understanding its prognosis and finding the risky factors of collapse.Materials and methods: From July2003 to June 2007,we conducted a continuous screening in 539 medical staff patients with SARS. With MRI, radiography and physical examination three to six months later after steroid therapy, At the imaging studies included anteroposterior, frog-like lateral radiographs , and CT and MRI of both hips, All the cases with osteonecrosis of femoral head from patients with SARS were diagnosized by the medical team that consisted of the senior doctors from dept. Orthopaedics and Radiography. In Jan.2005,May 2006,Sept 2006,and July2007,the medical staff cases affected with SARS took MRI,CT or radiography organized by the Healthy Administration.The classification system depended on the ARCO system .Results: We diagnosized 130 cases with osteonecrosis of femoral head(222hips affected)from cases with SARS who all had used steroids as a therapy.In all the patients without osteonecrosis in the primary screening,there were no new cases with osteonecrosis in the reexaminations after six months stopping use of corticosteriod .The incidence of ONFH was 23.6% in our group.The mean period from start to use corticosteriod to ARCO stage I was 8.84(5-25)weeks ,and that to ARCO stage II was 8.71(2-18)months .We collected imaging materials of 117cases(203hips) from 130 cases with osteonecrosis of femoral head.There were 28 cases( 33hips) progressing to ARCO stageIII after from six to fiftyth months from start using corticosteriods. The surgery of preserving femoral head/arthroplasty were performed on 28 cases (45hips)with ANFH. These operations were performed on 2 hips with ARCOstageIIA,11 hips with ARCO stageIIB,and 32 hips with ARCO stageIIC.There were no surgery on 85 cases (158 hips ) with ANFH.They included33 hips with ARCOstageIIA, 61 hips with ARCO stageIIB,and 66 hips with ARCO stageIIC.By statistical analysis,for the natural collapse of femoral heads,there were significant differences in ARCO stages, locations of lesion of femoral head,MRI types,and CT types (P<0.01).Results were expressed by Kaplan-Meier estimates of hip survival.There were no significational differences in ages and genders. We observed that most of the collapsed femoral heads had the open shape of low signal band on the biggest Coronal T1-weighted imaging section of procollapse of femoral head in which the line connected the both dots that low signal band contacted with the subchondral bone was the longest axis in the necrotical lesion(we call this as Open type),The ratio of collapsed and uncollapsed in the Open type was 31/91 . However in the shape of low signal band on the biggest Coronal T1-weighted imaging section of procollapse of femoral head in which the line connected the both dots, that low signal band contacted with the subchondral bone was not the longest axis(we call this as Contained. type), The ratio of collapsed and uncollapsed was2/67,31 femoral head (ARCO-IB/IIB 4hips and ARCO-IC/IIC27hips) within 58 with lateral type had collapsed .2 femoral head (ARC0-IC/IIC2hips) within 51 with central type had collapsed. There were one hip(ARCO-IC/IIC) collapse in the medial type. According to the imaging changes on CT,we find that four types in lesions:a.there is sclerotic band around the necrotic lesion,moreover forming a continuous sclerotic band beneath subchondral bone(22hips).b. there is no sclerotic band around osteonecrotic lesion(4hips)c.there is an uncontinous scleritic band beneath subchondral bone(91hips).d.there is no obvious sclerotic band beneath subchondral bone(17hips). According to the classification on CT,there were no hip with type-a,4with type-b , 18with type-c and 5 with type-d collapsed.By statistical analysis,for the natural collapse of femoral heads,there were significant differences in sizes of lesion, locations of lesion of femoral head,MRI types,and CT types (P<0.01) .There were no significational differences in ages and genders.Six lesions with small area got smaller and one ANFH with small area (A) reduced.Conclusions : Besides of size of necrotic lesion,the location of lesion of osteonecrosis of femoral head has an influence on its prognosis;those with lateral type tend to collapse earlier;The open-type on MRI has more possibility to collapse than the contained-type. Some small lesions have tendness to shrink in size.