Functional capacity, bone mineral density and neoformation-resorption bone markers in patients under 18 years of age with reduced mobility.

Introduction: Prolonged immobilization associated with several neurological disorders causes se condary osteoporosis with pathological fractures and persistent bone pain.

Objectives: To establish the association between bone mineral density (BMD), neoformation and bone resorption markers and the degree of functional capacity in children under 18 years of age with reduced mobility. Pa tients and Method: Cross-sectional study conducted in Ciudad Real, Spain between January 1, 2016, and December 31, 2017 with patients aged between 6 and 18 years diagnosed with different neuro logical disorders. The following variables were analyzed: age, sex, pubertal stage, functional capacity according to the Functional Mobility Scale (FMS), which assesses the ability to walk from 5, 50 to 500 meters, BMD, 25-hydroxy-vitamin D, alkaline phosphatase and osteocalcin in blood, and N-terminal telopeptide crosslinks in collagen type I (NTX-I) in urine. BMD, alkaline phosphatase, osteocalcin, and NTX-I values are expressed in Z score according to reference values for age and sex. The Pear son and Spearman correlations were used for data analysis.

Results: 36 patients (52.7% girls) with an average age of 8.6±4.7 years. Mean FMS value: 5.3 out of 18. Mean BMD: -1.99 ± 1.7 standard deviations (SD), mean alkaline phosphatase: -2.64 ± 1.08, mean osteocalcin: -2.15 ± 1.39, and mean NTX-I: +3 ± 1.72. There was a significant association between BMD and FMS for 5 meters (r = 0.395; p = 0.017) and for total score (r = 0.365; p = 0.029). There were no significant differences according to the stages of pubertal development.

Conclusions: In this population, there was a decrease in BMD and bone neoformation markers, and an increase of bone resorption markers with no association with pubertal development. Patients with a lower degree of mobility present a lower BMD.