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.
The data were reanalyzed after being stratified into 3 groups based on extent of elbow flexion contracture measured in supination.
The 9 elbows in group 1 (hyperextension) had mean extension of –2° (range, 10°-2°) and mean flexion of 141° (range, 130°-145°) in the neutral position. In external rotation, mean extension was –9° (range, –12° to –1°), and mean flexion was 141° (range, 130°-145°). When the 2 measurement positions were compared, group 1 had mean elbow ROM differences of –6° (range, –14° to 0°; P = .0033) for elbow extension and 0° for elbow flexion (Figure 3A).
The 50 elbows in group 2 (0°-29° flexion contracture) had mean extension of 7° (range, 0°-20°) and mean flexion of 138° (range, 100°-145°) in the neutral position. In external rotation, mean extension was 13° (range, 0°-26°), and mean flexion was 138° (range, 100°-145°). Mean difference between neutral and external rotation measurements was 6° (range, 0°-20°; P < .0001) in extension and 0° in flexion (Figure 3B).
The 26 elbows in group 3 (≥30° flexion contracture) had mean extension of 33° (range, 0°-72°) and mean flexion of 124° (range, 72°-145°) in the neutral position. In external rotation, mean extension was 45° (range, 30°-87°), and mean flexion was 124° (range, 72°-145°). Mean difference between neutral and external rotation measurements was 12° (range, 0°-30°; P < .0001) in extension and 0° in flexion (Figure 3C).
Discussion
Elbow flexion arc measurements are crucial for patient outcomes and activities of daily living. Commonly cited as functional ROM, the 30°-to-130° flexion arc often is used to guide clinical decisions in patients with elbow disorders.1 However, our data indicate that humeral position can alter elbow ROM measurements. Specifically, because of neutral forearm pronosupination, measurements made with the humerus in neutral rotation underestimate both the extent of elbow hyperextension and the degree of flexion contracture (Figures 4A, 4B). The more severe the flexion contracture, the more values are altered by measurements taken in this position. The same does not apply for elbow flexion measurements, as varying humeral rotation did not significantly affect those values.
Our results indicate that patients evaluated with the arm in neutral humeral rotation had flexion contractures underestimated by a mean of 8°, while there was a negligible difference in flexion measurements. Stratifying our data into 3 groups, we found that neutral humeral rotation kept elbow extension measurements closer to 0° for patients with both hyperextension and contractures. With increasing severity of flexion contractures in groups 2 and 3, the measurement errors were magnified. The differences in extension measurement values between these 2 groups based on humeral rotation increased more than 4°—an indication that, as flexion contracture severity increases, so does the degree of measurement error when elbow extension is measured with the humerus in neutral rotation rather than external rotation.
Our literature review found no studies on ROM value differences based on position of humeral rotation. Most texts, in their descriptions of elbow ROM and biomechanics, make no reference to position of pronosupination at time of flexion arc measurement.5-8 Although many elbow authorities recommend taking elbow ROM measurements in full external rotation, we found no corroborating evidence.
Other investigators have evaluated the reliability of goniometer measurements.2,3 Rothstein and colleagues3 concluded that elbow and knee goniometric measurements are highly reliable in the clinical setting when taken by the same person. In particular, intratester reliability for elbow extension measurements was high. Armstrong and colleagues2 specifically examined intratester, intertester, and interdevice reliability and found that intratester reliability was much higher than intertester reliability for universal goniometry. In our study, all patients were measured with the same technique by the same orthopedic surgeon to eliminate any intertester reliability error. Armstrong and colleagues2 also found that intratester changes vis-a-vis extension measurements are meaningful when goniometric differences are more than 7°. In our study, the difference in extension measurements between the 2 humeral positions averaged 8° overall and 12° in group 3. This suggests that the data reported here reflect a true difference dependent on humeral rotation and are not a result of goniometer intratester variability.
Other studies have examined measurement devices other than the standard universal goniometer. Cleffken and colleagues4 found that the electronic digital inclinometer was reliable for elbow ROM measurements. Blonna and colleagues9 used digital photography–based goniometry to measure patient outcomes without doctor–patient contact at tertiary-care centers and found it to be more accurate and reliable than clinical goniometry in measuring elbow flexion and extension. Chapleau and colleagues10 compared the validity of goniometric elbow measurements in radiographic methods and concluded that the maximal error of goniometric measurements in extension was 10.3°. However, they also found high intraclass correlation coefficients for goniometric measurements. With the accepted clinical reliability of universal goniometry,2-4,10 we believe it to be the best clinical tool for this study because of its availability, minimal cost, and ease of use.
