Interpretations of the dial test should be reconsidered. A diagnostic accuracy study reporting sensitivity, specificity, predictive values and likelihood ratios

Abstract

ObjectivesTo determine the accuracy of the dial test, used alone and in combination with additional clinical tests, in the diagnosis of an isolated posterolateral corner (PLC) injury, combined PLC-posterior cruciate ligament (PCL) injury or medial knee injury.MethodsA retrospective analysis of consecutive patients who underwent arthroscopic and/or open knee ligament reconstruction surgery was conducted. The dial test was performed in an outpatient’s clinic as part of a routine knee examination. Examination under anaesthetic and intraoperative findings were used as the reference standard test to determine the diagnostic accuracy of the dial test used alone and in combination with other PCL and medial knee tests. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio (LR+) and negative likelihood ratio (LR−) were calculated with corresponding 95% CI.ResultsData from 87 patients were available and included in the data analysis. For an isolated PLC injury, the dial test sensitivity and specificity were 0.20 (95% CI 0.08 to 0.39) and 1.00 (95% CI 0.92 to 1.00). The PPV and NPV were 1.00 (95% CI 0.52 to 1.00) and 0.70 (95% CI 0.59 to 0.80). LR+ and LR− of the dial test detecting isolated PLC injury were infinity (95% CI calculation not possible, infinity) and 0.80 (95% CI 0.41 to 1.57). The diagnostic accuracy of the dial test, when used alone and in combination with other PCL and medial knee tests, was also calculated for combined PLC-PCL and medial knee injuries.ConclusionA negative dial test at 30° of knee flexion can rule out a PLC injury, while a test that is positive at 30° and negative at 90° indicates a PLC injury, without concomitant injury to the PCL or medial knee ligaments. A positive test at both 30° and 90° can indicate isolated PLC, combined PLC-PCL or medial ligament injuries, and other knee examination findings are required to differentially diagnose these injury patterns.Level of evidenceII.