Bone Abstracts

Objectives: Dual Energy X-ray Absorptiometry (DXA) is commonly used to monitor changes in bone mineral density (BMD). Small changes in BMD can be clinically meaningful; therefore precision-error calculations are needed to estimate true changes in BMD. The few published studies of precision errors in children with cerebral palsy (CP) are diverse in terms of ethnicities and medical comorbidities. Application of these estimates is inappropriate to our particular Midwest American cohort. Statutes in our state also limit precision studies in children. Therefore, a research project was undertaken to calculate the BMD precision error at multiple skeletal sites in the CP patients seen at our institution.

Methods: Ten of the required 30 participants aged 3–18 years with CP (GMFCS I-III) underwent two DXA scans (Hologic) by the same technologist with repositioning. BMD was measured at spine, hip, left/right distal femur, and whole body. Precision error and least significant changes were calculated according to ISCD recommendations.

Results: Ten participants (15±4 years, range 7–18 years, 6 male) have undergone repeated DXA scans. An additional 10 patients are scheduled, and all 30 subjects are expected to be complete by April. Three patients had low bone mineral density for age. Preliminary calculations of Least Significant Change using bootstrapping approach indicated a value of 0.034 g/cm² for the whole body (minus the head) and 0.178 g/cm² for the lateral distal femur. These preliminary values are expected to change once we reach the required 30 patients, and also allow for error calculations at each skeletal site.

Conclusion: Despite the significant heterogeneity in our Midwest CP population, especially in regard to their neuromuscular effects upon bone health, useful estimates of precision error were obtained at a number of regions of interest. This will allow us to continue to use DXA as a tool for long term bone health management. We conclude, therefore, that DXA BMD precision estimates can (and should) be done on the typical cerebral palsy pediatric population seen at each center or use estimates from geographically similar sites. We anticipate the need for similar studies in children with GMFCS classification IV–VI. This work was supported by Gillette Children’s Hospital Foundation.

Disclosure: The authors declared no competing interests.