Forearm length - a new tool to standardize bone parameters of the forearm measured with peripheral quantitative computed tomography in individuals with disproportional growth of forearm length and body height.

AIM: To investigate the relationship of forearm length (FL) or height to bone parameters of the forearm of a normal pediatric population in comparison to individuals with osteogenesis imperfecta (OI). METHODS: Data on FL, height and peripheral quantitative computed tomography measurements of the forearm were collected from participants of the DONALD study (140 males and 156 females; age 5-19 years) and from 73 patients with OI (53 males; mean age +/- SD: 11.7 +/- 3.3 years). Bone mineral content (BMC) was transformed into standard deviation score (SDS) according to height or FL. RESULTS: Height and Tanner stages significantly predicted FL in males (R(2)(adjusted) = 0.960) and females (R(2)(adjusted) = 0.934). Height was a stronger predictor of FL than Tanner stages. Compared to controls, patients with OI were characterized by lower BMC-SDS(FL) and lower BMC-SDS(height) (-0.37 +/- 1.77 vs. 0.00 +/- 0.97, p = 0.002, and -0.15 +/- 5.0 vs. -0.02 +/- 1.01, p = 0.011, respectively). BMC-SDS(FL) was not significantly lower than BMC-SDS(height) in controls, and also not lower in patients with OI (p = 0.865 and p = 0.809). The height/FL ratio was significantly decreased in patients with OI (mean +/- SD: 6.34 +/- 0.38 vs. 6.45 +/- 0.21, p = 0.001) compared with controls. CONCLUSION: Because of disproportional growth, BMC may be overestimated in OI patients.