Diagnostic Accuracy of the Resisted Anterior Drawer (RAD) Test for Lateral Elbow Instability in Lateral Epicondylitis.

BACKGROUND: Lateral epicondylitis (LE) is increasingly recognized as a multifactorial condition in which subtle lateral elbow instability may contribute to persistent pain. However, reliable clinical tests to detect such instability are lacking.

PURPOSE: To determine the diagnostic accuracy of the resisted anterior drawer (RAD) test for detecting lateral elbow instability in patients with LE.

METHODS: Consecutive adult patients diagnosed with LE underwent standardized clinical examination followed by magnetic resonance imaging (MRI). The RAD test was considered positive when pain during resisted wrist extension, with the elbow in extension, decreased by at least 1 point on a visual analogue scale (VAS) with anteromedial stabilization of the radial head. MRI-defined instability was defined as the presence of lateral collateral ligament (LCL) injury, posterior sagging, or ulnohumeral joint-line opening of grade ≥1. Diagnostic indices were calculated with 95% confidence intervals and likelihood ratios, and the continuous reduction in pain was evaluated with receiver operating characteristic (ROC) analysis.

RESULTS: A total of 500 elbows were analyzed (mean age: 51 years). MRI evidence of instability was present in 57.4% of elbows. The RAD test demonstrated a sensitivity of 95.8% (95% CI 92.8-97.6%), specificity of 82.2% (95% CI 76.5-86.7%), and overall accuracy of 90.0% (95% CI 87.1-92.3%), with positive and negative likelihood ratios of 5.4 and 0.05. The area under the ROC curve for the reduction in pain was 0.92 (95% CI 0.90-0.95). The magnitude of pain reduction during the RAD maneuver correlated with the severity of MRI-defined instability (Spearman ρ = -0.71). Increasing MRI severity was associated with a higher number of corticosteroid infiltrations, whereas symptom duration showed only a weak association with structural instability.

CONCLUSION: In this Level III diagnostic study, the RAD test showed high sensitivity and good specificity for MRI-defined lateral elbow instability in patients with LE, and the magnitude of pain reduction was correlated with MRI-defined severity. These findings suggest that the RAD test may be a useful screening maneuver for instability-related pain in patients with LE. A prospective, blinded cohort study with an independent reference standard is required to confirm its clinical utility.

LEVEL OF EVIDENCE: Level III, Diagnostic Study.