Smaller and thinner long bones in children and adolescents with cerebral palsy and other neuromotor impairments

Erin Hodgson^1,2,3,4,5*Elizabeth Grace Condliffe^2,3,4,5,6Leigh Gabel^1,2,5,7*

• ¹McCaig Institute for Bone and Joint Health, University of Calgary, Calgary, Canada
• ²Alberta Children’s Hospital Research Institute, University of Calgary, Calgary, Canada
• ³University of Calgary, Faculty of Kinesiology, Calgary, Canada
• ⁴Hotchkiss Brain Institute, University of Calgary, Calgary, Canada
• ⁵Department of Biomedical Engineering, University of Calgary, Calgary, Canada
• ⁶Departments of Clinical Neurosciences and Pediatrics, University of Calgary, Calgary, Canada
• ⁷Faculty of Kinesiology, University of Calgary, Calgary, Canada

This study quantified bone and muscle health in children and adolescents with cerebral palsy (CP) and other neuromotor impairments across all five gross motor function classification system (GMFCS) levels. Peripheral quantitative computed tomography (pQCT) scans of both tibiae were acquired at the 3%, 38%, and 66% of tibia length in 22 children and adolescents (4-17 years old) diagnosed with CP and “CP-like” neurodevelopmental conditions causing motor impairment. Age-, sex-, and ethnicity-matched Z-scores were generated in reference to a normative typically developing population for total bone mineral content (BMC), trabecular and cortical bone mineral density (Tb.BMD, Ct.BMD), cortical BMC (Ct.BMC), cortical area (Ct.Ar), cortical thickness (Ct.Th), periosteal and endosteal circumference, cortical section modulus (Z), and muscle cross-sectional area (MCSA). Tibial total BMC, Tb.BMD, Ct.BMC, Ct.Th, Ct.Ar, periosteal circumference, Z, and MCSA were significantly lower in children with CP and CP-like conditions compared to typically developing peers (median Z-scores ranged from -2.66 to -1.09; p = 0.019 to <0.001) and showed greater deficits in children and adolescents with lower levels of motor function than those with higher functional abilities (GMFCS I-II vs III-V; p = 0.042 to <0.001). Endosteal circumference was not different from zero (p = 0.756) but was smaller in children and adolescents with lower levels of motor function (p = 0.042). Ct.BMD did not differ compared to typically developing youth (p = 0.202) or between functional abilities (p = 0.168). Results reveal that bone and muscle size, total and cortical content, and trabecular density are impaired in children with CP and CP-like conditions; however, cortical mineralization is not impaired. Therefore, the heightened risk of fragility fractures in children and adolescents with CP and CP-like conditions is likely due to smaller and thinner bone structure. Future investigation into bone microarchitecture is warranted.