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Acetabular retroversion in Down syndrome
Wudbhav N Sankar1, Jonathan G Schoenecker, Matthew E Mayfield
1The Children's Hospital of Philadelphia, Philadelphia, PA, USA.
Insights
Children with Down syndrome have significantly more retroverted acetabula, a key factor in hip instability. This finding suggests axial imaging is crucial for planning corrective surgery in Trisomy 21 patients.
Area of Science:
- Orthopedics
- Genetics
- Radiology
Background:
- Hip instability in Down syndrome presents management challenges.
- Posterior acetabular wall deficiency is a common observation in Down syndrome hips, differing from typical anterolateral dysplasia.
- This suggests potential acetabular retroversion in Down syndrome hip dysplasia.
Purpose of the Study:
- To determine acetabular version in children with Down syndrome.
- To compare acetabular version in Down syndrome patients with matched normal and developmental dysplasia of the hip (DDH) control groups.
Main Methods:
- Retrospective case-control study (Level III).
- Matched cohorts of Down syndrome patients, normal controls, and DDH patients.
- Preoperative computed tomography (CT) scans used to measure acetabular version.
- Analysis of variance (ANOVA) used for statistical comparison.
Main Results:
- Mean acetabular version was 2±11 degrees in Down syndrome patients, indicating significant retroversion.
- This was significantly different from normal controls (13±5 degrees, P=0.02) and DDH patients (21±7 degrees, P<0.001).
- 10/16 Down syndrome patients exhibited severe acetabular retroversion, compared to 3/16 normal controls and 1/16 DDH patients (P=0.002).
Conclusions:
- Acetabula in patients with Down syndrome and hip instability are more retroverted than in normal or DDH populations.
- Axial imaging is recommended for evaluating acetabular version in Trisomy 21 patients with hip instability.
- This evaluation aids in planning optimal corrective osteotomies for acetabular deficiency.
Background:
The management of the unstable Down syndrome hip is challenging, and there is controversy about the anatomic factors that may contribute to the instability. It has been our observation that children with Down syndrome often have a deficient posterior acetabular wall. This is different from other congenital acetabular dysplasia where the anatomic deficiency is typically anterolateral. These observations suggest that the acetabulum in Down syndrome hip dysplasia may be relatively retroverted. The purpose of this study was to determine the acetabular version in children with Down syndrome and compare this with matched controls from both normal and developmental dysplasia of the hip (DDH) populations.
Methods:
A cohort of Down patients treated surgically for acetabular dysplasia and/or hip instability was matched by age, sex, and side to a group of normal controls and compared with a cohort of patients who had undergone periacetabular osteotomy for DDH. For all patients, preoperative computed tomography scans were used to measure acetabular version through the joint center. Statistical differences were determined using analysis of variance with α=0.05.
Results:
We identified 16 subjects in each cohort. The average acetabular version in the normal control group was 13±5 degrees and in the DDH cohort was 21±7 degrees. In contrast, the mean version in the group of patients with Down syndrome was 2±11 degrees, indicating increased acetabular retroversion; this result was significantly different from both the normal group (P=0.02) and those with DDH (P<0.001). According to the criteria described by Tönnis for computed tomography measured retroversion, 10/16 patients with Down syndrome were severely retroverted compared with only 3/16 normal controls and 1/16 patients with DDH (P=0.002).
Conclusions:
Patients with Down syndrome and hip instability seem to have more retroverted acetabula than normal controls and patients with DDH. In patients with Trisomy 21, axial imaging should be performed to evaluate acetabular version when planning the optimal corrective osteotomy for instability and/or acetabular deficiency.
Level Of Evidence:
Level III (prognostic, retrospective case-control).
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