The Research Of Femoral Head Offset Degree Measurement In Diagnosis Adult Acetabular Dysplasia

Objective: Acetabular dysplasia is a kind of developmental anomaly. Wiberg first described acetabular dysplasia concept, centre edge angle≤ 20 ℃was used to diagnose adult acetabular dysplasia. Acetabular dysplasia can not cover the femoral head completely, which changed the hip joint loading state, aggravated the articular cartilage cataplasia, and lead to hip joint osteoarthritis at last. References reported that 20%~50% hip joint osteoarthritis patients have acetabular dysplasia. Acetabular dysplasia play an important role in the incidence of osteoarthritis. Acetabular dysplasia patients haven’t obvious symptoms in the early stage. Patients gradually had the symptoms in 20-40 years. The majority of patients had the more severe osteoarthritis when they found the acetabular dysplasia, which made it difficult for the treatment of acetabular dysplasia. In orde to diagnosed acetabular dysplasia in the early stage, and made effective intervention, the research of acetabular dysplasia were paid more and more attention at present. The adult acetabular dysplasia’ imaging diagnosis have variety methods, but there were no standard method. Each measurements had their limitations. Different measure index diagnosed acetabular dysplasia may have completely different conclusions in the same patient. We applied x-ray measured adult acetabular by four different methods, included centre edge angle, acetabular angle of Sharp, acetabular head index and acetabular index, meanwhile we established a new measurement method, femoral head offset degree.The new method used teardrop as reference. We used ratio method to meaure the horizontal and vertical offset degree of femoral head. We diagnosed acetabular dysplasia by observed the femoral head outwards and upwards degrees of dislocation. Our study analyzed the advantages and disadvantages by compared the concordance of different measurement methods, and screened the more reliable diagnostic index to diagnose acetabular dysplasia.Methods: A total of 402 patients were enrolled this study through anteroposterior pelvic X-ray examination in the third hospital of Hebei medical university from July 2014 to December 2014. X-ray examined by the same group of peoplep. The radiology examination standard: Patient was prostration, double leg straight, the first tip toe moved close to each other and vertical examining bed,the patients also shoud keep the pelvis no rotation and slope, the distance between film and pipe ball was 100 cm. Enrolled criteria: all patients were identification normal people or acetabular dysplasia by two radiologia expert and orthopaedics expert. Exclusion criteria includede patients with neuromuscular disease, associated with the other deformity, severe hip joint osteoarthritis complicated obviously hyperplasia of the acetabulum outer edge, severe pelvic tilt, palvic fracture and severe femoral head necrosis and femoral head collapse. There were 199 male and 211 female patients among 402 cases, the average age was 51.1 years(range 18–91 years), the average body weight was 65.1 kilograms(range 42.5–98 kilograms), the average body height was 167 centimeters(range 150–185 centimeters).We used centre edge angle,acetabular angle of Sharp acetabular head index, and the femoral head horizontal and vertical offset degree measured 804 patients’ s hip joint respectively. The distance between the femoral head center and the same side teardrop middle point vertical line’s vertical distance called ‘a’. The distance between acetabulum outside edge and teardrop middle point vertical line’s vertical distance called ‘b.’The femoral head horizontal offset degree was defined as a/b. The distance between the femoral head center and the bilateral teardrop’ lowest point vertical distance called ‘c’. The distance between acetabulum outside edge and the bilateral teardrop’ lowest point vertical distance called ‘d’. The femoral head vertical offset degree was definedn as c/d. The normal hip joint were assessed as CE angle and Sharp angles within normal range. The 496 patients hip joint were confirmed normal, there were 308 patients with acetabular dysplasia. Kappa test was used to compare the femoral head offset degree and ce angle, Sharp angle, AHI, AI respectively. Compared with ce angle, the sensitivity and specificity of femoral head offset degree mesurement to diagnose acetabular dysplasia was observed, and further analyzed the validity of femoral head offset degree mesurement.Results:There were 496 patients with normal hip joint, they were both ce angle> 20 o and Sharp angle< 45 o, the sample was’ t normal distribution, the method of 95% percentiles were applied to definite femoral head offset degree normal reference range. The femoral head horizontal offset degree reference range was <80.08%, the vertical offset degree range was <45.15%.The adult femoral head offset degree larger than any normal value were diagnosed acetabular dysplasia. According to the femoral head offset degree, the hip joint were judged as normal or acetabular dysplasia. By Kappa analyzed, the three methods had good diagnostic consistency, but no significant differences in diagnostic positive ratio were found among femoral head offset degree, ce angle and Sharp angle measurement groups.(Kappa value =0.565,P=0.353; Kappa value =0.401, P=0.152).Compared with ce angle method, the sensitivity and specificity of femoral head offset degree assay were 66.67% and 88.89%,the sensitivity and specificity of Sharp angle assay were 68.86% and 86.11%.The AHI, AI femoral head offset degree assay had bad diagnostic consistency( Kappa value =0.470, P=0.000; Kappa value = 0.090,P=0.000) the sensitivity and specificity of AHI assay were 90.7%% and 66.84%. the sensitivity and specificity of AI assay were95.17% and19.27% AI had the lowest specificity.Conclusions:1.The femoral head offset degree assay was a good method to diagnose acetabular dysplasia. The normal range of femoral head horizontal offset degree was <80.08%, the vertical offset degree range was <45.15%.The adult femoral head offset degree larger than any normal value were diagnosed acetabular dysplasia.2.The femoral head offset degree assay was a simple method to diagnose acetabular dysplasia, We established a new reliable diagnositic method to identified acetabular dysplasia.3 The AI had the largest measurement error and worst diagnositic validity. Ce angle and AHI reflected outward dislocation status. The Outward and upward dislocation tendency of femoral head can be comprehensive evaluated by the femoral head horizontal and vertical offset degree. The new method had less affecting factors, such as osteophytosis, and so on. The femoral head offset degree assay had significantly preponderance in diagnosis acetabular dysplasia.