American Journal of Roentgenology, Vol 173, 719-722, Copyright © 1999 by American Roentgen Ray Society
Femoral growth lines: bony birthmarks in infants
RL Teele, GD Abbott, N Mogridge and DW Teele
Department of Radiology, Christchurch Hospital and Christchurch School of Medicine, University of Otago, New Zealand.
OBJECTIVE: During a study of infants who were being examined for antenatal
renal dilatation, we noted that many had growth lines in their proximal
femur on postnatal radiographs. We decided to determine the prevalence of
growth lines in healthy infants. MATERIALS AND METHODS: Voiding
cystourethrograms of 791 neonates and infants, 0-6 months old, were
reviewed. All who had documented severe illness or no reasonable view of
the proximal femur were excluded, resulting in a cohort of 633 healthy
infants. Each study was coded for presence or absence of a growth line in
the proximal femur, and the distance of the growth line from the
metaphyseal edge was measured to the nearest 0.5 mm. Radiographs were
obtained on a unit with fixed tube-film distance. Data on the mode of
delivery were collected for 136 infants. RESULTS: Of 633 eligible infants,
247 (39%) of 633 had a discernible growth line. The distance of the growth
line from the metaphysis, in millimeters, correlated significantly with age
in days (r = .81, p < .01). Infants delivered vaginally were more likely
to have a growth line than were those born by cesarean delivery (p = .049).
CONCLUSION: A growth line in the proximal femur is common in healthy
infants. The rate of longitudinal growth of the proximal femoral
metaphysis, on radiographs, is approximately 1 mm per 11 days (1 mm per 13
days when corrected for magnification). Approximation of the timing of
prenatal and postnatal stressful events that result in a growth disturbance
line may be possible.
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