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Acetabulum-head index measured on arthrograms in children with Legg-Calvé-Perthes disease
A Moberg1, G Hansson, C Kaniklides
1Department of Orthopaedics, Hudiksvalls Hospital, S-824 81 Hudiksvall, Sweden.
Insights
The acetabulum-head index (AHI) effectively assesses femoral head displacement in Legg-Calvé-Perthes disease. Radiographs and arthrograms provide distinct AHI guidelines for detecting early subluxation in pediatric hip conditions.
Area of Science:
- Pediatric Orthopedics
- Radiology
- Biomechanical Assessment
Background:
- Legg-Calvé-Perthes disease affects the hip joint in children.
- Assessing femoral head stability is crucial for treatment.
- The acetabulum-head index (AHI) is a potential metric for evaluating hip joint alignment.
Purpose of the Study:
- To evaluate the acetabulum-head index (AHI) for assessing lateral femoral head displacement.
- To compare AHI measurements from plain radiographs and arthrograms in children with Legg-Calvé-Perthes disease.
- To establish diagnostic guidelines for early subluxation using AHI.
Main Methods:
- Retrospective analysis of 37 children with unilateral Legg-Calvé-Perthes disease.
- Measurement of AHI on plain radiographs and two types of arthrograms (I and II).
- Reproducibility assessment of AHI measurements on arthrogram II from unaffected hips.
Main Results:
- High reproducibility of AHI measurements on arthrogram II (root mean square error of 3.3).
- Plain radiographs suggest an AHI of ≤80 indicates early subluxation.
- Arthrogram I and II guidelines for subluxation were AHI ≤70 and ≤85, respectively.
Conclusions:
- The acetabulum-head index (AHI) is a reproducible measure for assessing femoral head position.
- Distinct AHI thresholds exist for plain radiographs and arthrograms in detecting subluxation.
- AHI offers a valuable tool for early diagnosis and management of Legg-Calvé-Perthes disease.
Abstract:
The acetabulum-head index (AHI), which can be used to assess the lateral displacement of the femoral head, was measured on both plain radiographs and arthrograms in 37 children with unilateral Legg-Calvé-Perthes disease. For the identification of the outermost part of the acetabulum on the arthrograms, two measuring points were used: A. the lateral border of the bony acetabulum (arthrogram I) and B. the lateral border of the labrum (arthrogram II). The reproducibility of the measurements, evaluated by duplicate calculations of the AHI on arthrogram II, which was obtained from the unaffected hips, was high; the root mean square error of the AHI was 3.3. On the plain radiographs, an AHI of 80 or less could be used as a 'guideline' to reveal early subluxation of the femoral head. The corresponding figures on arthrograms I and 11 were 70 and 85, respectively.