Assessment of Bone Mineral Density in Children with Developmental Dysplasia of the Hip Joint: Possible Risk Factors for Osteopenia and Osteoporosis

Background and Objectives: Developmental dysplasia of the hip (DDH) in children can result in long-term skeletal complications, including a reduced bone mineral density (BMD) and an increased risk of osteoporosis. This study aimed to evaluate BMD in children with DDH and to identify clinical, functional, and nutritional factors associated with reduced BMD. Materials and Methods: A cross-sectional study was conducted on 25 children aged 5–10 years with confirmed DDH. Bone mineral density was measured at the total body, subtotal, and lumbar spine using dual-energy X-ray absorptiometry (DXA), and Z-scores were calculated. Functional assessments included isometric muscle strength, weight-bearing symmetry, and physical activity measured via accelerometry. Demographic data and daily calcium intake were recorded. Correlation and multiple linear regression analyses were performed to determine predictors of BMD. Results: Most participants exhibited normal growth and mobility, with mild asymmetries in limb strength and length. The mean total BMD was within normative ranges, whereas the lumbar spine Z-score (−1.41 ± 1.72) was mildly reduced. BMD positively correlated with age, anthropometric measures, weight-bearing capacity, and calcium intake, and negatively correlated with a family history of osteoporosis. Multiple regression analysis identified the muscle strength symmetry index as the strongest independent predictor of BMD across all sites (subtotal Z-score: β = 1.000, p < 0.001; total Z-score: β = 0.425, p = 0.023; lumbar Z-score: β = 0.499, p = 0.014). Physical activity levels showed no significant associations with BMD. Conclusions: Children with DDH generally demonstrate preserved overall BMD; however, mild lumbar spine deficits may occur. Muscle strength symmetry appears to be the most influential modifiable factor for optimizing bone health in this population, highlighting the importance of targeted physiotherapy interventions.