Effects of elbow flexion and forearm rotation on valgus laxity of the elbow

Clinical evaluation of valgus elbow laxity is difficult. The optimum position of elbow flexion and forearm rotation with which to identify valgus laxity in a patient with an injury of the ulnar collateral ligament of the elbow has not been determined. The purpose of the present study was to determine the effect of forearm rotation and elbow flexion on valgus elbow laxity.

Twelve intact cadaveric upper extremities were studied with a custom elbow-testing device. Laxity was measured with the forearm in pronation, supination, and neutral rotation at 30 degrees, 50 degrees, and 70 degrees of elbow flexion with use of 2 Nm of valgus torque. Testing was conducted with the ulnar collateral ligament intact, with the joint vented, after cutting of the anterior half (six specimens) or posterior half (six specimens) of the anterior oblique ligament of the ulnar collateral ligament, and after complete sectioning of the anterior oblique ligament. Laxity was measured in degrees of valgus angulation in different positions of elbow flexion and forearm rotation.

There were no significant differences in valgus laxity with respect to elbow flexion within each condition. Overall, for both groups of specimens (i.e., specimens in which the anterior or posterior half of the anterior oblique ligament was cut), neutral forearm rotation resulted in greater valgus laxity than pronation or supination did (p < 0.05). Transection of the anterior half of the anterior oblique ligament did not significantly increase valgus laxity; however, transection of the posterior half resulted in increased valgus laxity in some positions. Full transection of the anterior oblique ligament significantly increased valgus laxity in all positions (p < 0.05).

The results of this in vitro cadaveric study demonstrated that forearm rotation had a significant effect on varus-valgus laxity. Laxity was always greatest in neutral forearm rotation throughout the ranges of elbow flexion and the various surgical conditions.

The information obtained from the present study suggests that forearm rotation affects varus-valgus elbow laxity. Additional investigation is warranted to determine if forearm rotation should be considered in the evaluation and treatment of ulnar collateral ligament injuries of the elbow joint.