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Quantitative analysis of lower limb and pelvic deformities in children with X-linked hypophosphatemic rickets
Aurore Bonnet-Lebrun1, Agnès Linglart2, Marine De Tienda3
1Institut de biomécanique humaine Georges-Charpak, arts et métiers ParisTech, 151, boulevard de l'Hôpital, 75013 Paris, France.
Insights
Quantifying bone parameters in children with X-linked hypophosphatemia (XLH) rickets helps monitor leg deformities. Three-dimensional reconstructions reveal significant differences and variability in skeletal parameters, aiding diagnosis and management.
Area of Science:
- Orthopedics and Radiology
- Pediatric Endocrinology
- Skeletal Dysplasias
Background:
- X-linked hypophosphatemia (XLH) is a genetic disorder causing rickets, primarily manifesting as leg deformities in children.
- These deformities can progress with growth, impacting long-term skeletal health and mobility.
- Accurate documentation and monitoring of skeletal deformities are crucial for effective management of XLH.
Purpose of the Study:
- To hypothesize that quantifying bone parameters can aid in documenting and monitoring leg deformities in children with XLH.
- To investigate the utility of three-dimensional (3D) reconstructions from biplanar radiographs for assessing skeletal parameters in XLH patients.
- To compare skeletal parameters between XLH patients and a healthy control group.
Main Methods:
- A cross-sectional study included 35 growing children with XLH and 40 age-matched controls.
- Biplanar radiographs were acquired using an EOS system for 3D reconstructions of the pelvis and legs.
- Sixteen geometric parameters were calculated, with statistical analyses performed to identify significant differences and correlations.
Main Results:
- Significant differences (p<0.05) were observed in neck-shaft angle, femur/tibia length ratio, and HKS between XLH patients and controls.
- XLH patients exhibited a high prevalence of genu varum (23 legs), genu valgum (25 legs), and straight legs (22 legs).
- Strong correlations were found between femoral mechanical angle and femorotibial angle (r²=0.73), and between femoral mechanical angle and HKS (r²=0.69).
Conclusions:
- Quantitative radiological parameters from 3D reconstructions highlight that XLH-related deformities are primarily in the femoral shaft but exhibit significant inter-individual variability.
- Specific radiological parameters show potential utility in the diagnosis and ongoing monitoring of skeletal deformities in children with XLH.
- These findings support the use of advanced imaging techniques for a comprehensive assessment of XLH in pediatric populations.
Introduction:
X-linked hypophosphatemia (XLH) rickets mainly causes leg deformities in children that can worsen as they grow. We hypothesized that quantifying the bone parameters will help to document and monitor these deformities in children with XLH.
Methods:
Thirty-five growing children affected by XLH were included in this cross-sectional study. Biplanar radiographs were taken with an EOS system allowing three-dimensional (3D) reconstructions of the pelvis and legs. Sixteen geometric parameters were calculated for the legs and pelvis. A control group of 40 age-matched patients was used to define the reference values for these geometric parameters.
Results:
For the legs, significant differences (p<0.05) appeared between the XLH patients and the control group in the neck-shaft angle, femur/tibia length ratio and HKS. Among the 70 legs in the XLH group, 23 were in genu varum, 25 were in genu valgum and 22 were straight. There were significant differences between the genu varum and genu valgum subgroups in the femoral mechanical angle and the HKS. A strong correlation was found between the femoral mechanical angle and femorotibial angle (r2=0.73) and between the femoral mechanical angle and HKS (r2=0.69) The sacral slope and acetabular anteversion were significant different from the reference values.
Discussion:
Quantitative radiological parameters derived from 3D reconstructions show that the deformities in XLH patients are (1) mainly in - but not limited to - the femoral shaft; (2) highly variable from one person to another. Some of these radiological parameters may be useful for the diagnosis and monitoring of XLH patients.
Level Of Evidence:
III; case control study.
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