Pelvic Sagittal Rotation in Patients With Hip Joint Disease

Objective: The functional orientation of the acetabular cup depends on the pelvic orientation when standing. Therefore, predicting the standing orientation of the pelvis after total hip arthroplasty( THA )is important to the preoperative plan. This study aimed to explore the rule suitable for different categories of patients. Methods: A total of 262 patients who had undergone hip arthroplasty in our hospital from 2011 to 2019 were retrospectively analyzed. Based on the spine and hip joint, they were divided into 5 categories: no flexion contracture of the hip joint - good lumbar range of motion (group A); no flexion contracture of the hip joint - limited lumbar motion (group B: B1, tanterior pelvic plane tilt (APPt)>0 °; B2, APPt<0 °); hip flexion contracture - good lumbar range of motion (group C); and hip flexion contracture - limited lumbar motion (group D). Changes of the pelvic sagittal parameter before and after THA were analyzed. Results: In group A, there was no significant difference in pelvic incidence (PI) and sagittal vertical axia (SVA) between preoperation and postoperation (P>0.05), but the mean value of sacral slope (SS) (from 44.99 °to 40.50 °), lumbar lordosis( LL) (from 51.42 to 47.45), pelvic tilt (PT) (from 8.71 °to 11.91°), and tanterior pelvic plane tilt (APPt) (from 4.5 °to 1.27 °) had statistic difference (P0.05); In group C, significant difference was not observed in PI (P>0.05), but found (P<0.05) in LL (from 52.17° to 43.43°), SS(44.90° to 38.34°), PT (from 5.70° to 13.36°), APPt (from 9.18° to 2.18°), and SVA (from 3.46cm to 1.16cm). In group D: the pelvis was in supination state before and after operation, and the spine sagittal position was imbalanced. Neither was there significant difference in SVA, PI, SVA, SS, ll and APPt between preoperation and postoperation (P>0.05). In addition, Harris scores of different groups changed accordingly. Conclusion: The sagittal rotation of the pelvis caused by different conditions of the spine-hip has a certain change law after total hip arthroplasty.