Purpose: The purpose of this study was to assess the reliability of a new objective measurement tool to measure the valgus stress laxity of the ulnar collateral ligament (UCL) of the elbow, the "Elbow Tester". The anterior oblique portion of the ulnar collateral ligament (UCL) of the elbow is the primary static restraint to valgus stress during the overhead throwing motion. The main research question was if the "Elbow Tester" that we have developed was reliable and reproducible for further use in research and daily practice.
Methods: Three different examiners tested both elbows of 11 volunteers for UCL laxity. Each elbow was tested 5 times using a standard 2 Nm valgus load, and 3 times using a manual maximum valgus load. One examiner tested the volunteers again 1 week later. The outcomes of elbow valgus laxity were compared between examiners. The intraobserver reliability was assessed using an intraclass correlation coefficient (ICC) and interobserver reliability was also assessed with a mixed model repeated ANOVA test.
Results: The device demonstrated a high level of intraobserver reliability with both the 2 Nm valgus force and manual maximum valgus force, using a minimum of three trials as determined by an ICC > 0.9 for all examiners. The interobserver reliability was moderate using the 2 Nm valgus load with an ICC value of 0.72 and significant different outcomes of elbow valgus laxity amongst examiners (p < 0.01). A high interobserver reliability (ICC value of 0.90) was observed using manual maximum valgus force and no differences between outcomes (p > 0.53).
Conclusion: The noninvasive valgus elbow tester demonstrates high interobserver and intraobserver reliability using manual maximum valgus force and can be used for further research and daily practice.
Keywords: Elbow; Elbow tester; Pitchers elbow; Ulnar collateral ligament; Valgus laxity; Valgus stress; Valgus stress insufficiency.