Distal radius in adolescent girls with anorexia nervosa: trabecular structure analysis with high-resolution flat-panel volume CT

Abstract

Purpose: To examine trabecular microarchitecture with high-resolution flat-panel volume computed tomography (CT) and bone mineral density (BMD) with dual-energy x-ray absorptiometry (DXA) in adolescent girls with anorexia nervosa (AN) and to compare these results with those in normal-weight control subjects.

Materials and methods: The study was approved by the institutional review board and complied with HIPAA guidelines. Informed consent was obtained. Twenty adolescent girls, 10 with mild AN (mean age, 15.9 years; range, 13-18 years) and 10 age- and sex-matched normal-weight control subjects (mean age, 15.9 years; range, 12-18 years) underwent flat-panel volume CT of distal radius to determine apparent trabecular bone volume fraction (BV/TV), apparent trabecular number (TbN), apparent trabecular thickness (TbTh), and apparent trabecular separation (TbSp). All subjects underwent DXA of spine, hip, and whole body to determine BMD and body composition. The means and standard deviations (SDs) of structure parameters were calculated for AN and control groups. Groups were compared (Student t test). Linear regression analysis was performed.

Results: AN subjects compared with control subjects, respectively, showed significantly lower mean values for BV/TV (0.37% +/- 0.05 [SD] vs 0.46% +/- 0.03, P = .0002) and TbTh (0.31 mm +/- 0.03 vs 0.39 mm +/- 0.03, P < .0001) and higher mean values for TbSp (0.54 mm +/- 0.13 vs 0.44 mm +/- 0.04, P = .02). TbN was lower in AN subjects than in control subjects, but the difference was not significant (1.17 mm(-3) +/- 0.15 vs 1.22 mm(-3) +/- 0.07, P = .43). There was no significant difference in BMD between AN and control subjects. BMD parameters showed positive correlation with BV/TV and TbTh in the control group (r = 0.55-0.84, P = .05-.01) but not in AN patients.

Conclusion: Flat-panel volume CT is effective in evaluation of trabecular structure in adolescent girls with AN and demonstrates that bone structure is abnormal in these patients compared with that in normal-weight control subjects despite normal BMD.

Supplemental material: http://radiology.rsnajnls.org/cgi/content/full/249/3/938/DC1.

Figure 1a:

(a) High-resolution flat-panel volume CT scan of distal radius in 15-year-old adolescent girl with AN (bone age, 16 years; BMI, 19.6 kg/m²) demonstrates rarefaction of trabeculae of distal radius and ulna. Note lack of subcutaneous and deep fat. BV/TV was 0.25%; TbTh, 0.31 mm; TbN, 0.8/mm⁻³; and TbSp, 0.9 mm. Total BMD was 1.156 g/cm²; z score, 1.399. (b) High-resolution flat-panel volume CT scan of distal radius in 16-year-old normal-weight control subject (bone age, 17 years; BMI, 24.2 kg/m²) demonstrates normal mineralization of distal radius and ulna. An increase was observed in trabeculae compared with trabeculae in AN subject in a. BV/TV was 0.54%; TbTh, 0.43 mm; TbN, 1.3/mm⁻³; and TbSp, 0.37 mm. Total BMD was 1.106 g/cm²; z score, 1.228.

Figure 1b:

(a) High-resolution flat-panel volume CT scan of distal radius in 15-year-old adolescent girl with AN (bone age, 16 years; BMI, 19.6 kg/m²) demonstrates rarefaction of trabeculae of distal radius and ulna. Note lack of subcutaneous and deep fat. BV/TV was 0.25%; TbTh, 0.31 mm; TbN, 0.8/mm⁻³; and TbSp, 0.9 mm. Total BMD was 1.156 g/cm²; z score, 1.399. (b) High-resolution flat-panel volume CT scan of distal radius in 16-year-old normal-weight control subject (bone age, 17 years; BMI, 24.2 kg/m²) demonstrates normal mineralization of distal radius and ulna. An increase was observed in trabeculae compared with trabeculae in AN subject in a. BV/TV was 0.54%; TbTh, 0.43 mm; TbN, 1.3/mm⁻³; and TbSp, 0.37 mm. Total BMD was 1.106 g/cm²; z score, 1.228.

Figure 2a:

Regression analysis between lumbar spine BMD and trabecular structure parameters. Positive correlation was observed between (a) anteroposterior (AP) lumbar spine BMD and BV/TV, (b) anteroposterior lumbar spine BMD and TbTh, (c) lateral lumbar spine BMD and BV/TV, and (d) lateral lumbar spine and TbTh in normal-weight control subjects but not in AN patients. * = significant.

Figure 2b:

Regression analysis between lumbar spine BMD and trabecular structure parameters. Positive correlation was observed between (a) anteroposterior (AP) lumbar spine BMD and BV/TV, (b) anteroposterior lumbar spine BMD and TbTh, (c) lateral lumbar spine BMD and BV/TV, and (d) lateral lumbar spine and TbTh in normal-weight control subjects but not in AN patients. * = significant.

Figure 2c:

Regression analysis between lumbar spine BMD and trabecular structure parameters. Positive correlation was observed between (a) anteroposterior (AP) lumbar spine BMD and BV/TV, (b) anteroposterior lumbar spine BMD and TbTh, (c) lateral lumbar spine BMD and BV/TV, and (d) lateral lumbar spine and TbTh in normal-weight control subjects but not in AN patients. * = significant.

Figure 2d:

Regression analysis between lumbar spine BMD and trabecular structure parameters. Positive correlation was observed between (a) anteroposterior (AP) lumbar spine BMD and BV/TV, (b) anteroposterior lumbar spine BMD and TbTh, (c) lateral lumbar spine BMD and BV/TV, and (d) lateral lumbar spine and TbTh in normal-weight control subjects but not in AN patients. * = significant.