Postnatal growth of the clavicle: birth to 18 years of age.

BACKGROUND

The purpose of our study was to perform a large cross-sectional study aimed at determining the postnatal growth pattern of the clavicle from birth to 18 years of age.

METHODS

We analyzed the digital chest radiographs of a convenience sample of 961 individuals between birth and 18 years of age. Malrotated radiographs were excluded. Right and left clavicle lengths were measured in millimeters from the most lateral ossified border to the most medial ossified border of each clavicle. Study patients were divided into 19 subgroups with the first group being labeled as "birth to 11 months of age" followed by 1-year-olds, 2-year olds, etc. Patients were also grouped by sex. There was a minimum of 25 patients in each group.

RESULTS

At 18 years of age the mean+/-SD clavicle length for females was 149+/-12 mm and for males it was 161+/-11 mm. Although a statistically significant difference (P=0.049) was noted between the length of right and left clavicles it was not clinically significant (0.036 mm). A steady growth rate was noted for both genders from birth to the age of 12 years (8.4 mm/y). Above the age of 12 years there were significant differences in the growth of the clavicles of girls (2.6 mm/y) versus boys (5.4 mm/y) (P<0.001). Our data suggest that females achieve 80% of their clavicle length by 9 years of age and boys by 12 years of age.

CONCLUSION

This cross-sectional study establishes that relatively little clavicle growth (20%) remains for girls beyond age 9 years and for boys beyond 12 years. The length of one clavicle may be properly judged by comparing it with the contralateral clavicle.

CLINICAL RELEVANCE

Remodeling of the clavicle shaft fractures is currently believed to be proportional to remaining growth. Our study questions the capacity of the clavicle to re-establish normal length beyond the age thresholds we have identified.