Arthro-kinematics of the elbow: study of the carrying angle

Abstract

The carrying angle of the elbow is usually assessed in full elbow extension, with a protractor goniometer, or derived from X-ray images. Substantial differences in carrying angle values have been reported, possibly explained by methodological differences. Carrying angles tend to show higher values in women than in men. The aim of this study was to confirm the previously described progressive decrease of the carrying angle as a function of increasing elbow flexion. After assessment of the carrying angle with a protractor goniometer and an electromagnetic tracking system (Flock of Birds) in extension, flexion-extension movements with the forearm held in supination were recorded by means of the latter system. Three recordings were averaged in both the left and the right elbows of 20 volunteers without a history of elbow pathology (10 males and 10 females; mean age 25 years). In extension, a mean (+/- SD) carrying angle of 11.6 +/- 3.2 degrees was found in the male and 16.7 +/- 2.6 degrees in the female subjects. The carrying angles progressively decreased with flexion, at the end changing into a mean (+/- SD) varus angle of 1.8 +/- 2.9 degrees in men and 1.6 +/- 2.3 degrees in women. Significant differences in carrying angles between the sexes were recorded in moving from 0 to 30 degrees of flexion (p < 0.03 for the left and p < 0.01 for the right elbows), but disappeared beyond 30 degrees . No statistically significant differences were found between the results of left and right elbows. Although statistically significant differences (p < 0.05 to p < 0.001) were found along the course of flexion and extension, these differences were small (<0.6 degrees ). The mean carrying angles at 0, 30, 60, 90 and 120 degrees of flexion revealed larger standard deviations in the male group than in the female group.