Lower Limb and Pelvic Deformities in Pediatric Patients with X-Linked Hypophosphatemic Rickets

Researchers, led by Aurore Bonnet-Lebrun, theorized that quantifying bone parameters in children with X-linked hypophosphatemia (XLH) rickets would help document and monitor the lower limb and pelvic deformities caused by XLH. Their quantitative analysis, published in Orthopaedics & Traumatology: Surgery & Research, found that deformities in XLH are primarily—though not exclusively—in the femoral shaft, and are highly variable from one patient to another.

The study enrolled 35 growing children with XLH for assessment, and a control group of 40 age-matched patients to define reference values for the parameters. Three-dimensional biplanar radiographs of patients’ legs and pelvis were analyzed for 16 geometric parameters.

In the leg parameters, significant differences were observed between patients with XLH and control patients for the neck-shaft angle, femur/tibia length ratio, and hip-knee shaft (HKS; p <0.05). Additionally, genu varum leg (n = 23/70) and genu valgum leg (n = 25/70) subgroups had significant differences in femoral mechanical angle and HKS. The investigators also observed a strong correlation between the femoral mechanical angle and femorotibial angle (r2 = 0.73), as well as between the femoral mechanical angle and HKS (r2 = 0.69). Lastly, the sacral slope and acetabular anteversion were significantly different than the reference parameters.

The quantitative analysis led the study’s authors to draw the aforementioned conclusions, and further theorize that “some of these radiological parameters may be useful for the diagnosis and monitoring of XLH patients.”