Longitudinal Assessment of Bone Density and Structure in an Incident Cohort of Children With Crohn's Disease

Background & Aims

The impact of childhood Crohn's disease (CD) on volumetric bone mineral density (vBMD), bone structure, and muscle mass have not been established. The objective of this longitudinal study was to assess musculoskeletal outcomes in an incident cohort of children with CD using peripheral quantitative computed tomography (pQCT).

Methods

Tibia pQCT was performed in 78 CD subjects (ages, 5–18 years) at diagnosis and in 67 over the subsequent year. pQCT outcomes were converted to sex- and race-specific z scores based on reference data in over 650 controls. Multivariable linear regression models identified factors associated with changes in bone outcomes.

Results

At diagnosis, CD subjects had significant deficits in trabecular vBMD (z score, −1.32 ± 1.32; P < .001), cortical section modulus (a measure of bone geometry and strength) (z score, −0.44 ± 1.11; P < .01), and muscle (z score, −0.96 ± 1.02; P < .001) compared with controls. Over the first 6 months, trabecular vBMD and muscle z scores improved significantly (both, P < .001); however, section modulus worsened (P = .0001), and all 3 parameters remained low after 1 year. Increases in muscle z scores were associated with less severe declines in cortical section modulus z scores. Improvements in trabecular vBMD z scores were greater in prepubertal subjects. Glucocorticoids were associated with increases in cortical vBMD.

Conclusions

Substantial deficits in trabecular vBMD, cortical bone geometry, and muscle were observed at CD diagnosis. Trabecular vBMD improved incompletely; however, cortical deficits progressed despite improvements in muscle. Glucocorticoids were not associated with bone loss. Therapies to improve bone accrual in childhood CD are needed.

Abbreviations used in this paper: BMD, bone mineral density, CD, Crohn's disease, CortBMD, cortical volumetric bone mineral density, CSA, cross-sectional area, DXA, dual energy x-ray absorptiometry, GC, glucocorticoid, PCDAI, Pediatric Crohn's Disease Activity Index, pQCT, peripheral quantitative computed tomography, TrabBMD, trabecular volumetric bone mineral density, vBMD, volumetric bone mineral density, Zp, polar section modulus