Carpo-metacarpal growth disturbance and the assessment of carpal narrowing in children with juvenile rheumatoid arthritis.

Second metacarpal length (M2), radio-metacarpal length (RM), and intermetacarpal width (W) were measured on 96 radiographs in 52 children with polyarticular juvenile rheumatoid arthritis (JRA), and compared with body height and skeletal maturation in order to: (1) differentiate between processes resulting in retardation of bone growth and those producing delay in skeletal maturation; (2) assess the severity and progression over time of such retardation; and (3) assess the impact of retardation of the second metacarpal on the assessment of carpal narrowing in children with JRA. All measurements were converted into z scores (the units of standard deviation above or below the normal mean for each measurement) based on published norms. Retardation of M2 (mean z scores -0.91) began earlier and was more severe compared with retardation of height (mean z score -0.25). This disproportion widened with increasing duration of disease. That this primarily represents a disturbance in M2 growth rather than a secondary effect due to altered maturation is suggested by the bone ages being normal (mean z score 0.14) and the absence of premature closure of the metacarpal physes. Z scores for RM/W (mean -3.53) were at least 1 Z more negative than for corresponding measurements of RM/M2 (mean -2.41) in 47 (90.4%) children and the mean difference between the z scores for RM/W was -1.12. This discrepancy between RM/W and RM/M2 was eliminated by correcting for the reduction in M2.