A chance observation of asymmetrical bone ages in a child with spastic hemiplegia stimulated a prospective gathering of bilateral hand radiographs in 33 hemiplegic patients, and on a single occasion in a control group of 23 patients with leg length discrepancy in the absence of neurological disorder. The bone age assessments according to Greulich and Pyle, which by convention has used the left hand only, were done by a single expert observer blinded to the clinical details.

13 hemiplegic patients (39%) had delayed bone ages of 6 months or more. When present it was always delayed on the hemiplegic side. The mean delay for the whole group was 2.5 months, whereas there was no mean difference in the control group (p = 0.001). The oldest bone age with asymmetry was 14.5 years in males and 12 years in females, indicating that when present the delay “catches up” in the last 2-3 years of growth.

In hemiplegia the percentage leg length discrepancy also tends to decrease during later growth, and after 80% of growth the hemiplegic side outgrows the normal leg by a mean of 0.3cm/year. No correlation could be found between the delay of bone age and the severity of either the neurological abnormality or the actual discrepancy of length. The implications for clinical management will be discussed.