Analysis Of Imaging Parameters Of Pelvis Acetabular Femur Of The Bony Ankylosis Of Hip Joint In Patients With Ankylosing Spondylitis

Background and ObjectiveAnkylosing spondylitis(AS)is a kind of inflammatory spondyloarthropathy with a variety of pathogenesis.Hip joint involvement is one of the most important characteristics.With the destruction of inflammation,hip motion gradually loses,and the late stage of the disease is not only osteotonic ankylosis of hip joint.Total hip arthroplasty is an effective method to reconstruct the ankylosing hip joint,relieve pain and improve the motion of the joint,because the patients with ankylosing spondylitis often have multiple deformities.Different from the conventional total hip arthroplasty,the angle of implant should be adjusted according to the angle of pelvis,acetabular and femur.Previous studies of pelvic sagittal parameters have focused on degenerative spinal degeneration,spinal deformities and hip and knee disorders.The changes of pelvic parameters in ankylosing spondylitis patients with ankylosis of hip joint were rarely studied.The imaging parameters of pelvis acetabular femur were measured in patients with ankylosing spondylitis and healthy subjects.To investigate the characteristics of the imaging parameters of ankylosing spondylitis patients with hip ankylosis and the correlation between the parameters,and to study the rule of pelvic tilt and acetabular parameter change.To provide a reference for total hip arthroplasty in patients with ankylosing spondylitis with ankylosis of hip joint.MethodsFrom November 2008 to October 2016,28 patients with AS hip ankylosis treated with THA and with complete imaging data were selected as AS group,and 30healthy volunteers as control group.All patients in both groups were routinely photographed the X-ray of the full length lateral position of spine and standing position of pelvis and CT of the hip joint.Mimics software was used to measure the full-length lateral radiographs of the spine:pelvis incidence angle(PI),pelvis tilt angle(PT),sacral slope angle(SS),and orthostatic radiographs in the pelvis:femoral neckshaft angle(NSA).Mimics software was used to reconstruct the original two dimensional CT images of the hip joint.The acetabulum was observed on axial,coronal and sagittal images by MPR.Measured on CT images with reference plane of human true pelvis and coronal plane:acetabular abduction angle(ABA),acetabular anteversion angle(AVA).Comparison of pelvic,acetabular and femoral parameters between as group and control group by t-test.Analysis of correlation between pelvis acetabular and femur parameters in as group and control group by Pearson,The effect of pelvic tilt on acetabular parameters in as group was analyzed.Taking acetabular parameters as dependent variables and influencing factors of acetabular parameters as independent variables,a simple regression fitting relationship between acetabular parameters and independent variables was established by linear regression analysis.ResultsCompared with the control group,the parameters PI and PT of pelvis sagittal position in AS group were significantly larger than those in control group(P<0.01),AVA in acetabular parameters increased significantly(P<0.01),but there was no significant difference in ABA between the two groups(P>0.05),and femur parameter(NSA)increased significantly(P<0.01)in AS group.In AS group,there was a positive correlation between PI and SS among pelvic parameters(r=0.701,P?0.01),negative correlation between PI and AVA,SS and AVA among pelvic and acetabular parameters(r=-0.676?r=-0.796,P?0.01),so changes in pelvic inclination can cause changes in acetabular parameters,but there was no correlation between femoral parameter(NSA)and pelvic and acetabular parameters(P>0.05).In control group,there was a correlation between PI and PT,PI and SS,PT and SS among pelvic parameters(P<0.01),between PI and ABA,PI and ABA,SS and ABA among pelvic and acetabular parameters(P<0.01),but there was also no correlation between femoral parameter(NSA)and pelvic and acetabular parameters(P>0.05).There was a clear linear regression model between pelvis parameter SS and acetabular parameter AVA in AS group(R~2=0.634,P?0.01),the anteversion of the pelvis can cause an increase in the acetabular anteversion angle,estimated simple linear regression equation is:AVA=-0.534SS+33.563°.Conclusion1.In patients with ankylosing spondylitis with hip ankylosis,the tendency of pelvic retroversion and acetabular anteversion was obvious,and the hip valgus of femur was significant.2.The imbalance of the pelvic sagittal plane in patients with ankylosing spondylitis with hip ankylosis can lead to abnormal postures,loss of correlation between the pelvis sagittal parameters,and decompensation pelvis showing loss of equilibrium.3.When total hip arthroplasty was performed in patients with ankylosing spondylitis with hip ankylosis,pelvic sagittal parameter sacral slope angle decreases every 10°,the acetabular anteversion angle increases 5°,and the implant has to be reduced by 5°.