An abbreviated scale for the assessment of skeletal bone age using radiographs of the knee

Hand and wrist radiographs are the most common means for estimating skeletal bone age. There is no widely used scale for estimating skeletal bone age using knee radiographs. Do skeletal bone age estimates from knee-maturity scales correlate sufficiently with both chronologic age and estimates from a hand-wrist scale to potentially substitute for estimates from the latter? The authors reviewed the records of 503 patients 6 to 19 years old who had hand and knee radiographs obtained within 30 days of each other. They analyzed radiographs using the O'Connor knee scale (based on 10 maturation markers) and a new, abbreviated version of the O'Connor scale (based on 7 markers). The authors also analyzed radiographs of the hands of boys 12.5 to 16 years old and girls 10 to 16 years old using the shorthand method. Multivariate linear regression was used for analysis. Inter- and intrarater reliabilities were assessed. Skeletal bone age derived from the O'Connor and abbreviated knee scales correlated with chronologic age (adjusted R²=0.88 and 0.90, respectively). Compared with estimates from the hand-wrist scale, estimates were lower by a mean of 0.91 years for boys and 0.38 years for girls when using the O'Connor scale and 0.96 years for boys and 0.52 years for girls when using the abbreviated scale. Inter- and intrarater reliabilities were very good (κ=0.82 and 0.90, respectively) and were substantial at each bony landmark measured. Knee radiographs can be used to estimate skeletal bone age using an abbreviated knee scale.