In adults, > 2mm of scapholunate distance (SLD) commonly suggests pathology. In contrast, SLD in children is naturally larger than 2 mm consequential to ossification of the carpal bones. The lunate is not present on x-ray until 4 years of age and the scaphoid until 5 years. The scaphoid also ossifies in an irregular fashion, which further complicates measurements. This study evaluated 119 posteroanterior wrist x-rays taken for bone age and from 6 to 14 years of age. Two physicians measured bone age and SLD. A significant age-based decline in SLD was noted. The SLD was larger in boys than girls of similar age. Linear regression revealed equations to calculate SLD for each sex.
Boys: SLD = -0.7 x chronological age (years) + 13.6
Girls: SLD = -0.6 x chronological age (years) + 10.4
This study provides values for SLD in the immature carpus. The SLD is considerably greater in younger children because of impending ossification. Girls reach adult values of 2 mm by age 11 and boys by age 12, which is expected as girls reach skeletal maturity earlier. Although scapholunate injury is uncommon in children, this study provides helpful normative values according to the age of the child.