Correct positioning for hip radiographs allows reliable measurement of hip displacement in cerebral palsy
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Published on: February 27, 2018
Lucy Cliffe1, Don Sharkey, Grace Charlesworth
1Nottingham Children's Hospital, Nottingham University Hospitals NHS Trust, Queens Medical Centre Campus, Nottingham, UK. lucy.cliffe@nuh.nhs.uk
Insights
Pelvic radiographs reliably measure hip displacement in children with cerebral palsy (CP) when performed correctly. Experienced radiologists and proper positioning ensure accurate migration percentage calculations for effective monitoring.
Area of Science:
- Pediatric Orthopedics
- Radiology
- Cerebral Palsy Research
Background:
- Cerebral palsy (CP) often involves hip displacement, a condition monitored using pelvic radiographs.
- The migration percentage is a key radiographic measure, but its reliability has been questioned.
- Accurate assessment is crucial for managing hip stability in children with CP.
Purpose of the Study:
- To evaluate the reliability of radiographic assessment of hip displacement in children with CP.
- To determine the impact of positioning and radiologist experience on measurement accuracy.
- To validate the migration percentage as a reliable surveillance tool.
Main Methods:
- 20 children (40 hips) with severe bilateral spastic CP (GMFCS IV-V) underwent two standard pelvic radiographs.
- Migration percentage was measured twice by two independent, experienced radiologists 3 months apart.
- Inter-observer and intra-observer reliability were assessed.
Main Results:
- Mean migration percentage showed high consistency across measurements.
- Intra-observer measurements (same observer, same time vs. 3 months apart) were 3.2% and 3.3%.
- Inter-observer measurements (different observers, 3 months apart) were 3.7%.
Conclusions:
- Reliable migration percentage measurements are achievable with correct positioning and experienced radiologists.
- Radiographic assessment of hip displacement is a valid method for surveillance in pediatric CP.
- Clinical decisions should account for a small, expected error margin in hip displacement measurements.
Aim:
The pelvic radiograph in children with cerebral palsy (CP) can inform the degree of hip displacement by calculation of the migration percentage. However, concerns have arisen about the reliability of this measurement. The present study examined the reliability of radiographic assessment of displacement and the importance of positioning and reporting experience.
Method:
Two pelvic radiographs, taken at least an hour apart, were performed in 20 children (total 40 hips) in the standard position by a trained paediatric radiographer. Children (13 males, seven females) were aged 30 months to 10 years with severe bilateral spastic CP in Gross Motor Function Classification System levels IV (n=10) and V (n=10). The migration percentage of each hip was measured on two occasions 3 months apart by two experienced radiologists independently. Comparisons of migration percentage were made in three ways by (1) the same observer at the same time, (2) the same observer 3 months apart, and (3) different observers 3 months apart.
Results:
Migration percentage (mean [SD]) was (1) 3.2% (3.5), (2) 3.3% (3.2), and (3) 3.7% (3.8) respectively.
Interpretation:
Reliable measures of migration percentage can be obtained with correct positioning and if reported by suitably experienced radiologists, making this a valid surveillance method. Clinical decisions can be made taking into account an expected error in hip displacement measurements.
