Metacarpophalangeal pattern profiles: Q-score for ages from birth to 7 years

The metacarpophalangeal pattern profile (MCPP) analysis is a widely used method of standardization of bone length measurements to quantify congenital skeletal dysplasia of the hands. A main source of inaccuracy is the prominent scatter in the values of the standard deviation (S.D.) of the reference length, which is used in the calculation of the standardized values (Z-scores). Other sources of error, especially when bone length measurements of younger children are evaluated, are the rather large variability in the age of appearance of the epiphyses of the different bones, and the use of tabulated reference data which are available only at one-year intervals. We have devised another method of standardization of bone length measurements, by calculating the Q-score. Its advantages are that no S.D. values are needed and that more accurate results are obtained. Moreover the interpretation of the Q-scores is more straightforward than the interpretation of the Z-scores. Q-scores for 3 patients with Sotos syndrome are presented. Use of the MCPP in the form of the Q-score, will probably make it an even stronger tool than before.