The Effect of Humeral Rotation on Elbow Range-of-Motion Measurements
In 84 patients (85 elbows), a standard goniometer was used to measure elbow flexion and extension with the forearm in 2 positions: full supination (humeral condyles parallel to floor) and neutral forearm rotation (ulnohumeral joint in relative internal rotation). All measurements were made by the same surgeon with a standardized technique.
Mean absolute difference in elbow extension measurements was 8°. There was no difference in flexion between measurement positions. Mean difference between neutral and supinated measurements was 6° in extension. There was no difference in flexion for patients with contractures between 0° and 29°. In patients with flexion contractures of more than 30°, mean difference between neutral and supinated measurements was 12° in extension; there was no difference in flexion. Elbow goniometer extension measurements taken in neutral humeral rotation underestimated the degree of elbow hyperextension and elbow flexion contracture.
We recommend taking elbow flexion arc measurements in the true plane of motion, with the humerus externally rotated by fully supinating the forearm, such that the distal humeral condyles are parallel to the floor.
In the clinical setting, elbow flexion arc measurements are a major factor in treatment decisions and often dictate whether to proceed with operative interventions such as capsular release. In addition, ROM measurements are crucial in determining the success of treatments and the progression of disease. Erroneous elbow extension measurements can have significant consequences if they falsely indicate functional ROM when taken in neutral position. This is particularly true for patients with elbow flexion contractures of more than 30°, in whom differences in humeral rotation resulted in about 12° of variance between measured values. For instance, a patient with a true 40° flexion contracture in the externally rotated position could be determined to have functional ROM based on measurements made in the neutral position.
Limitations of this study include those involving goniometer reliability and intraobserver variability (already described) and the validity of goniometer measurements compared with radiographic measurements.
Conclusion
Because elbow goniometer extension measurements taken in neutral humeral rotation underestimate both the degree of elbow hyperextension and the degree of elbow flexion contracture, we recommend taking elbow flexion arc measurements in the true plane of motion, with the humerus externally rotated by fully supinating the forearm, such that the distal humeral condyles are parallel to the floor.
