Background How the hip dysplasia affects the spinopelvic alignment in developmental dysplasia of the hip (DDH) patients is unclear, but it is an essential part for the management of this disease. This study aimed to investigate the coronal and sagittal spinopelvic alignment and the correlations between the spinopelvic parameters and the extent of hip dysplasia or the low back pain in unilateral DDH patients. Methods From September 2016 to March 2021, 22 unilateral patients were enrolled in the DDH group with an average age of 43.6 years and 20 recruited healthy volunteers were assigned to the control group with an average age of 41.4 years. The Cobb angle, seventh cervical vertebra plumbline–central sacral vertical line (C7PL–CSVL), third lumbar vertebra inclination angle (L3IA), pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), thoracic kyphosis (TK), thoracolumbar kyphosis (TLK) and lumbar lordosis (LL) were measured on the standing anteroposterior and lateral full-length standing spine radiographs. Additionally, the Oswestry Disability Index (ODI) and Japanese Orthopaedic Association Back Pain Evaluation Questionnaire (JOABPEQ) were used to assess the degree of low back pain. Results Cobb angle (8.68 ± 6.21° vs. 2.31 ± 0.12°), L3IA (4.80 ± 5.47° vs. 0.83 ± 0.51°), C7PL–CSVL (1.65 ± 1.57 cm vs. 0.48 ± 0.33 cm), PT (15.02 ± 9.55° vs. 9.99 ± 2.97°) and TLK (7.69 ± 6.66° vs. 3.54 ± 1.63°) were significantly larger in DDH patients, whereas LL (37.41 ± 17.17° vs. 48.79 ± 7.75°) was significantly smaller (P < 0.05). No correlation was found between significantly different spinopelvic parameters and the extent of dysplasia. Statistical analysis revealed correlations between ODI and Cobb angle (r = 0.59, P < 0.01), PT (r = 0.49, P = 0.02), TK (r =  −0.46, P = 0.03) and TLK (r = 0.44, P = 0.04). Correlations between JOABPQE score and the Cobb angle (r = −0.44, P = 0.04), L3IA (r = −0.53, P = 0.01), PT (r = −0.44, P = 0.04), and TK (r = 0.46, P = 0.03) were also observed. Conclusions Cobb angle, L3IA, C7PL–CSVL in coronal plane and PT, TLK in sagittal plane increased, while LL decreased in unilateral DDH patients. These significantly different spinopelvic parameters have no correlation with the extent of dysplasia. Changes in coronal and sagittal plane including Cobb angle, L3IA, PT, TK and TLK were associated with the low back pain in the patients with unilateral DDH.

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Background: The observational study aimed to investigate the change and correlations of the spinopelvic parameters as well as the relationships with the related symptoms in unilateral developmental dysplasia of the hip (DDH) patients. Methods: The clinical data of 22 unilateral DDH patients and 20 healthy volunteers were collected from 2016 to 2021. All patients and volunteers were taken the antero-posterior pelvic radiograph and the frontal and lateral radiography of the whole spine as a routine examination. And the clinical symptoms, signs and functions were measured according to Oswestry Disability Index and Low Back Pain Scoring System. Then the t test and Pearson correlation were used to analyze the data. Results: The Cobb(8.68±6.21°), L3(4.79±5.47°), CB(1.65±1.57cm), PT(15.02±9.55°) and TLK (7.69±6.66°) were significantly larger in the DDH patients, whereas LL(37.41±17.17°) were significantly smaller (P＜0.05). As for the coronal spinopelvic parameters, CB was found to be associated with L3 (R=0.58, P＜0.01). Of the sagittal spinopelvic parameters, SS was found to be associated with LL (R=0.48, P=0.02), and TLK was found to be related to ST and TK, respectively (R=0.49, P=0.02; R=-0.45, P=0.04). In terms of relations between the spinal and pelvic parameters, PI were found to be related to the SS (R=0.58, P＜0.01). An analysis of relations revealed a correlation between the Oswestry Disability Index and Cobb(R=0.59, P＜0.01), PT(R=0.49, P=0.02), TK(R=-0.46, P=0.03) and TLK(R=0.44, P=0.04). Furthermore, an analysis of relations revealed a correlation between Low Back Pain Scoring System and Cobb (R=-0.44, P=0.04), L3(R=-0.53, P=0.01), PT (R=-0.44, P=0.04), TK(R=0.46, P=0.03) and TLK(R=-0.43, P=0.05). Conclusion: The parameters are related to each other and compensate each other to maintain the balance of the coronal and sagittal planes of the spine. In addition, the change of some parameters is closely related to the quality of life of the patients, and can provide some clues for the clinical diagnosis and treatment of DDH.