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Evolution of concentricity after closed reduction in developmental dysplasia of the hip
Weizheng Zhou1, Wudbhav N Sankar2, Fangfang Zhang1
1Department of Pediatric Orthopedics, Shengjing Hospital of China Medical University, Shenyang City, China.
Insights
Closed reduction for developmental dysplasia of the hip (DDH) can lead to concentricity over time, even if not achieved immediately. Most hips treated before age two become concentric within one year.
Area of Science:
- Orthopedic surgery
- Pediatric orthopedics
- Developmental dysplasia of the hip (DDH)
Background:
- Closed reduction (CR) is a treatment for DDH aiming for concentricity.
- The acceptable degree of non-concentric reduction post-CR remains debated.
- Dynamic evolution of hip joint space after CR requires further investigation.
Purpose of the Study:
- To investigate the dynamic changes in hip joint space after CR in DDH using MRI.
- To assess the rate and timing of concentricity achievement post-CR.
- To evaluate the influence of limbus presentation (inverted vs. everted) on joint space evolution.
Main Methods:
- Prospective study of 35 hips in 30 children with DDH undergoing CR.
- Reduction accepted if safe and stable, regardless of immediate concentricity.
- Concentricity defined as superior joint space (SJS) and medial joint space (MJS) < 2 mm on MRI.
- Mean follow-up of approximately four years.
Main Results:
- Only 8.6% of hips were concentric immediately post-CR.
- Concentricity was achieved in 68.6% by six months and 77.1% by one year.
- Significant decrease in SJS from 3.51 mm to 0.79 mm at six months (p=0.001).
- Everted limbus group showed smaller SJS/MJS than inverted group throughout follow-up.
Conclusions:
- Stable, non-concentric reductions in DDH treated before age two can improve over time.
- Nearly 80% of hips achieve concentricity by one year post-CR.
- Early CR in DDH, even if initially non-concentric, can lead to favorable long-term outcomes.
Aims:
The goal of closed reduction (CR) in the treatment of developmental dysplasia of the hip (DDH) is to achieve and maintain concentricity of the femoral head in the acetabulum. However, concentric reduction is not immediately attainable in all hips and it remains controversial to what degree a non-concentric reduction is acceptable. This prospective study is aimed at investigating the dynamic evolution of the hip joint space after CR in DDH using MRI.
Methods:
A consecutive series of patients with DDH who underwent CR since March 2014 were studied. Once the safety and stability were deemed adequate intraoperatively, reduction was accepted regardless of concentricity. Concentricity was defined when the superior joint space (SJS) and medial joint space (MJS) were both less than 2 mm, based on MRI. A total of 30 children, six boys and 24 girls, involving 35 hips, were recruited for the study. The mean age at CR was 13.7 months (3.5 to 27.6) and the mean follow-up was 49.5 months (approximately four years) (37 to 60). The joint space was evaluated along with the interval between the inverted and everted limbus.
Results:
Only three hips (8.6%) were fully concentric immediately after CR. During follow-up, 24 hips (68.6%) and 27 hips (77.1%) became concentric at six months and one year, respectively. Immediate SJS after CR decreased from 3.51 mm to 0.79 mm at six months follow-up (p = 0.001). SJS in the inverted group decreased from 3.75 mm to 0.97 mm at six months follow-up. SJS or MJS in the everted group were less than those in the inverted group at each time of follow-up (p = 0.008, p = 0.002).
Conclusion:
A stable, safe but non-concentric reduction achieved before the age of two years appears to improve over time with nearly 80% of hips becoming fully concentric by one year. Cite this article: Bone Joint J 2020;102-B(5):618-626.
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