Difference between affected and unaffected sides of forearm bone length in children with congenital terminal transverse deficiencies at the level of carpal bone

The forearm of the affected sideis often shorter than that of the unaffected side in children with congenital terminal transverse deficiencies at the level of proximal or distal carpals. The aim of this study is to clarify the characteristics of forearm bone length in those children, especially to quantify the difference in forearm bone length between affected and unaffected sides. The subjects were children with carpal partial transverse deficiencies. The lengths of the radius and the ulna were measured in the radiographs. The lengths of affected and unaffected sides (A/U) were compared in order to quantify the discrepancy. The A/U ratio was defined as the length of the affected side divided by that of the unaffected side. The A/U ratios ranged from 77.1 to 99.0% in the radii and from 74.1 to 99.6% in the ulnae. In both the radius and ulna, the A/U ratios were significantly lower than the left/right ratios of normal adults. Additionally, the A/U ratios of the ulna were significantly lower than the A/U ratios of the radius. The forearm bones of affected side are significantly shorter than those of unaffected side. Although the cause remains unclear, it is possible that not only congenital factors but also acquired factors such as infrequent use of the affected upper limb are involved. A future longitudinal study is necessary to investigate whether length discrepancies can be reduced by using prostheses to increase the frequency of use on the affected limb.