Bone Abstracts

We recruited 60 healthy volunteers ages 5 to 21 to perform scan-rescan precision tests on the XtremeCT II. Participants were positioned in a carbon fiber immobilization cast. iPad-based video content was used to facilitate motion-free compliance. Distal radius and tibia scans were acquired starting 2 mm proximal to the proximal margin of the growth plate or growth plate remnant. Diaphyseal radius and tibia scans were centered at an offset from the same landmark, corresponding to 30% of limb length. Repeat scans were performed following complete repositioning of the participant. Scans were assessed for movement and the image quality was on the standard 5-point scale. The manufacturer’s image analysis pipeline was optimized for pediatric distal and diaphyseal scans to measure bone density and structure, and to estimate bone strength by micro-finite element analysis (μFEA). Precision errors were calculated from the test-retest measurements using root mean square of the coefficient of variation (CV%). The success rates for acceptable quality scans based on extreme (image grade ≤1), strict (≤2), and moderate criteria (≤3), are reported in Table 1 by age group and scan site. Precision errors measured from paired scans meeting the moderate quality criterion (≤3) by scan site are reported in Table 2. These data demonstrate that performance of HR-pQCT scans is feasible in the majority of children and adolescents. The performance in younger children was improved with the use of a video to provide distraction. With the exception of distal cortical porosity, precision was outstanding and greater than reported in prior XtremeCT I reproducibility studies in adults. Diaphyseal measurements of cortical porosity offer superior precision to measurements immediately adjacent to the growth plate.

Disclosure: The authors declared no competing interests.