ABSTRACT
Objective:To investigate the changes in coronal spino-pelvis alignment in patients with developmental dysplasia of the hip (DDH) and effects of total hip arthroplasty on it.Methods:This study included 48 patients (6 males and 42 females) with DDH who underwent total hip arthroplasty from January 2009 to December 2019 at the Department of Orthopaedics, the PLA General Hospital. The average age of patients was 42.81±10.42 years (range, 22 to 61 years), whose follow-up time was 10.31±2.62 months (range, 3 to 18 months). Eleven cases underwent bilateral hip replacements and 37 cases underwent unilateral hip replacements, which included 13 hips in Crowe I, 7 hips in II, 4 hips in III, 35 hips in IV. The coronal spino-pelvic parameters were measured with all patients, including Cobb angle, coronal balance distance (CBD), sacral obliquity (SO), iliac obliquity (IO), hip obliquity (HO), L 5 obliquity (L 5O) and leg length. Results:The interobserver reliability of IO, SO, HO and L 5O in patients with DDH was 0.965, 0.875, 0.912 and 0.934. The interobserver reliability of IO, SO, HO and L 5O was 0.887, 0.889, 0.892 and 0.907. Thirty-three patients diagnosed with DDH had leg length discrepancy, which the incidence was 69% (33/48). The incidence of scoliosis of patients was 58% (28/48). The incidence of pelvic obliquity was 96% (46/48). The preoperative IO was 6.71°±4.62° and the postoperative IO was 3.52°±3.14°, the difference was statistically significant ( t=4.81, P<0.001). The preoperative SO was 6.38°±5.48° and the postoperative SO was 3.72°±3.38°, the difference was statistically significant ( t=3.91, P<0.001). The preoperative HO was 5.32°±5.83° and the postoperative HO was 3.71°±3.62°, the difference had not statistically significant ( t=1.85, P=0.071). The preoperative L 5O was 6.12°±5.46° and the postoperative L 5O was 4.33°±4.71°, the difference had statistically significant ( t=2.15, P=0.037). The preoperative Cobb angle was 11.05°±10.76° and the postoperative Cobb angle was 6.82°±7.76°, which had a statistically difference ( t=4.07, P=0.001). There is no significant difference of preoperative CBD and postoperative CBD, which was 14.22±10.64 mm vs. 13.73±12.58 mm ( t=0.24, P=0.821). Cobb angle was positively correlated with SO and IO ( r=0.61, P<0.001; r=0.57, P<0.001). Conclusion:Causes coronal pelvic obliquity in patients with DDH included leg length discrepancy and hip dislocation. Coronal pelvic obliquity can lead to compensatory scoliosis, which alters the overall coronal spino-pelvic alignment of patients with DDH. However, they can still maintain coronal balance. Total hip arthroplasty could improve the degree of coronal pelvic obliquity significantly and compensatory scoliosis in patients with DDH.