Imaging Study Of Pelvic Lateral Tilt In Adult Patients With Developmental Dysplasia Of The Hip

Background and Objective:In clinical practice,researchers have found out that patients with Developmental dysplasia of the hip(DDH)has the phenomenon of pelvic lateral tilt in the coronal plane.However,previous studies have never described this phenomenon.This study aims to explore patients with DDH through three parts:(1)the distribution of pelvic lateral tilt and the contribution from pelvis and lower extremities;(2)The internal relationship between pelvic lateral tilt and scoliosis.(3)Using Finite element analysis(FEA)to explore the biomechanical characteristics of pelvic lateral tilt.Methods:We retrospectively collected imaging data of unilateral DDH patients from January 2018 to December 2020.The first study collected full-length weight-bearing phase of both lower extremities or standing EOS radiographs in 86 patients.There were 10 males(11.6%)and 76 females(88.4%).The mean age of onset was 42±14.8 years old.We analyzed the influencing factors of pelvic lateral tilt,and the distribution of pelvic lateral tilt and the contribution of each bone component were also measured.The second study included 42 patients with their spinal imaging data.We explored the internal connection between pelvic lateral tilt and lumbar scoliosis.Moreover,we analyzed the coronal balance distance distribution of spine and search for anatomical markers which is related to lumbar scoliosis.The third study included pelvic CT scans of 9 patients for FEA to explore the biomechanical mechanism of pelvic lateral tilt.Results:(1)Coronal imaging studies of pelvis and lower extremities showed that the incidence of pelvic lateral tilt in patients with DDH was about 58.1%-76.9%,and the ratio of patients with lateral tilt to the affected side and the unaffected side was about 1.8-2.8:1.iliac crest,sacroiliac joint,tear drop and ischium tubercle are good reference points for the determination of pelvic lateral tilt.Side was an influence factors of pelvic lateral tilt(P=0.026),and pelvic lateral tilt is more common to the left side.Both pelvis and lower extremities contributed to pelvic lateral tilt,and the lower extremities' contribution was greater than the pelvis',and the contribution of lower extremities mainly came from femur.(2)Coronal imaging studies of the spine showed that the incidence of lumbar scoliosis in patients with unilateral DDH was 59.5%;Scoliosis tended to be more toward the lower side of the pelvis(88.0%vs 12.0%);Most of the patients(92.9%)could achieve compensatory balance on the coronal plane of their spine.The tilt of upper iliac crest,lower sacroiliac joint,lower tear drop and lower ischium tuberosity were highly positively correlated with the tilt of L4(r>0.7,P<0.001).(3)The results of finite element analysis showed that in patients with DDH,there existed differences in VON MISE stress distribution between the affected and unaffected side of the pelvis.Compared with the unaffected side,the more the affected pelvis sinks,the greater the maximum stress on the acetabulum and femur on the affected side.The maximum stress of the acetabulum and femur on the affected side in the pelvic sinking group were higher than those in the pelvic lifting group.Compared with the affected side sinking group,the area of high stress in the affected side elevation group was more lateral to the acetabulum.Conclusion:Pelvic lateral tilt is widespread in patients with DDH,and the tilt direction may be related to the leg dominance.Both pelvis and lower extremities contributed to the formation of pelvic lateral tilt.Patients with pelvic lateral tilt often accompanied with lumbar scoliosis,but most of the scoliosis could be compensated completely on the coronal plane.FEA is an important method to explore the biomechanical characteristics of pelvic lateral tilt.