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.
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). 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. 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. Because of disproportional growth, BMC may be overestimated in OI patients.