A Short-Term Magnetic Resonance Imaging Analysis of Acetabular Adaptation in Developmental Dysplasia of the Hip by Open Reduction or Open Reduction Combined with Dega Osteotomy
Developmental dysplasia of the hip (DDH) is one of the most common limb deformities encountered in pediatric orthopedics. It is characterized by abnormal development of the hip joint, leading to instability, dislocation, and, if left untreated, long-term disability. For patients who cannot achieve closed reduction or maintain concomitant reduction, open reduction (OR) is often necessary. However, studies have shown that patients treated with OR alone are prone to continued acetabular dysplasia and dislocation. To address this, it is recommended that OR be combined with pelvic osteotomy, such as Dega osteotomy, to correct dysplasia, reduce the incidence of residual acetabular dysplasia, and lower the long-term reoperation rate. Dega osteotomy has gained popularity in recent years due to its wide indications, simplicity, low trauma, and lack of dependence on prior hip surgery history.
Most studies analyzing the outcomes of open reduction combined with Dega osteotomy (ORCWDO) have relied on X-ray imaging. However, X-rays have limitations in fully understanding the degree of reduction, particularly in visualizing posterior femoral positions and the details of fixed hips. Magnetic resonance imaging (MRI), with its superior soft tissue resolution, offers a comprehensive assessment of hip recovery after reduction and can identify factors hindering reduction. Despite its advantages, there is a paucity of international studies using MRI to evaluate ORCWDO outcomes. This study employs MRI to compare and analyze the short-term results of OR and ORCWDO, providing valuable insights for optimizing clinical treatment strategies for DDH in children.
The study was conducted at Shengjing Hospital of China Medical University and involved children with DDH who underwent either OR or ORCWDO between September 2012 and April 2017. The research protocol was approved by the hospital’s Ethics Committee, and informed consent was obtained from the parents of each child. The cohort included 15 children (16 hips) who underwent OR and 20 children (21 hips) who underwent ORCWDO. Among the OR group, one patient had bilateral dislocation, 10 had left hip dislocation, and four had right hip dislocation. In the ORCWDO group, one patient had bilateral dislocation, seven had left hip dislocation, and 12 had right hip dislocation.
MRI examinations were performed using a 3.0T superconducting MR scanner (Philips Ingenia 3.0T, Best, Netherlands). Children were placed in a supine position with their lower limbs in a neutral position. Anal anesthesia was induced using diluted chloral hydrate before the MRI. The bony and cartilaginous structures of the acetabulum were measured on MR images using a picture archiving and communication systems (PACS) imaging diagnosis workstation. Preoperative X-ray images were graded using the Tönnis criteria, and the acetabular index (AI) was measured. Postoperative outcomes were classified using the Severin imaging evaluation criteria, with satisfactory outcomes defined as Severin grades I or II and unsatisfactory outcomes as Severin grades III or IV.
Statistical analysis was performed using SPSS 24.0 software. Continuous variables were expressed as mean ± standard deviation, and categorical variables were described by frequency. Independent sample t-tests were used to compare measurement parameters between groups, while the Mann-Whitney U test was used to compare the degree of dislocation. Paired sample t-tests were used to compare measurement parameters within groups. COX regression analysis was employed to compare the prognosis of the two surgical methods, and receiver operating characteristic (ROC) curves were used to determine critical values for ORCWDO evaluation.
Preoperative X-ray Tönnis criteria revealed that two hips were classified as grade II, seven as grade III, and seven as grade IV in the OR group. Postoperatively, five hips had satisfactory recovery, while 11 had unsatisfactory recovery. In the ORCWDO group, nine hips were preoperative grade III, and 12 were preoperative grade IV. Postoperatively, 14 hips had satisfactory recovery, while seven had unsatisfactory recovery. The Mann-Whitney U test showed no significant difference in the degree of preoperative dislocation between the two groups (P = 0.275).
MRI measurements indicated that the improvement in cartilage structure was more pronounced than in bone structure. The ORCWDO group showed more significant improvement in both bony and cartilaginous structures compared to the OR group. The preoperative osseous acetabular index (OAI) was statistically significant between the two groups (P = 0.047), with the OR group having an OAI of 29.13 ± 4.33° and the ORCWDO group having an OAI of 32.67 ± 4.68°. ROC analysis determined that the critical value for ORCWDO on MRI was 27.50°, with an area under the ROC curve of 0.692 (P = 0.048, 95% CI: 0.520–0.864). On X-ray, the critical AI value was >30.50°, with an area under the ROC curve of 0.696 (P = 0.043, 95% CI: 0.526–0.867). COX regression analysis confirmed that the surgical method significantly affected the prognosis of hip dislocation (P = 0.035), with ORCWDO associated with a lower risk of poor prognosis compared to OR (95% CI: 1.078–8.802).
The study highlighted the importance of cartilage measurement as a prognostic indicator, as cartilage improvements were more evident than bony improvements in follow-up. The cartilage acetabular index (CAI) in the OR group improved from 18.81° preoperatively to 11.19° postoperatively, while the OAI improved from 29.13° to 22.75°. In the ORCWDO group, the CAI improved from 20.48° preoperatively to 8.95° at the last follow-up, and the OAI improved from 32.67° to 17.10°. These findings align with previous studies, such as that by Karlen et al., which reported an improvement in AI from 37.00° to 15.00° postoperatively in children with DDH.
The study also emphasized the biomechanical advantages of ORCWDO in restoring concentric reduction and hip function. The Dega osteotomy, which does not require internal fixation or secondary surgery for removal, offers additional benefits, such as the ability to correct bilateral dysplasia without causing leg length discrepancies. Long-term studies have shown that the reoperation rate for OR is 56.00%, compared to 11.00% for ORCWDO. Additionally, OR combined with pelvic osteotomy reduces the risk of avascular necrosis (AVN) of the femoral head and effectively treats residual acetabular dysplasia.
In conclusion, ORCWDO achieves more satisfactory imaging outcomes than OR alone. When the OAI is >27.50° (or AI > 30.50° on X-ray), ORCWDO should be performed in children with DDH to ensure normal acetabular cartilage development and sufficient femoral head coverage. ORCWDO is an effective method for correcting DDH in children, providing better long-term outcomes and reducing the need for reoperation. The use of MRI in evaluating DDH offers a noninvasive, high-resolution approach to assessing hip recovery and guiding clinical decision-making.
doi.org/10.1097/CM9.0000000000001583
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