Comparison of two manual tests for ankle laxity due to rupture of the lateral ankle ligaments.

BACKGROUND

Assessment of ankle laxity can be both subjective and difficult, especially in less-experienced hands. The commonly-practiced anterior drawer test can mislead practitioners in the diagnosis of ankle instability due to subtalar joint motion. A manual stress test, focusing on tibiotalar translation, may be required.

OBJECTIVE

To evaluate the validity, reliability, and diagnostic accuracy of the modified manual stress test--the anterolateral drawer test (ALDT)--compared with the original anterior drawer test (ADT) in two groups of examiners with different levels of experience.

METHODS

A cadaveric study was performed at University Research Laboratory. Nine below the- knee specimens were randomized into three groups to simulate different degrees of lateral ligament injury. Two groups of examiners (Group A was four athletic training students; Group O was four senior orthopaedic trainees) performed ADT and ALDT while direct anatomical measurement (DAM) of tibiotalar translation was used as a reference under controlled load (Telos device). Ankle translation from DAM, ADT, and ALDT was recorded in millimeters. Measurements were compared using a paired t-test. Pearson correlation was used to determine linear relationship between groups. Inter- and intra-rater reliability was identified using ICC (intraclass correlation coefficient). The diagnostic threshold was determined by a receiver operating characteristic curve.

RESULTS

Both groups of examiners demonstrated excellent intra-observer reliability (0.94 for ADT and 0.80 for ALDT) and fair-to-good inter-observer reliability (0.52 for ADT and ALDT). There was no difference in the mean of measurement between group A and group O except for the ALDT on intact specimens (P = 0.01) and the ADT on the ATFL+CFL cut specimens (P = 0.02). Correlation with the DAM was superior in the ALDT (r = 0.73) compared to the ADT (r = 0.57). When using 4 mm or more as a diagnostic threshold, sensitivity and specificity (respectively) were found to be 100% and 66.67% for the ADT and 100% and 66.67% for the ALDT.

CONCLUSION

For diagnosis of ankle ligament injuries, this cadaveric study demonstrated high sensitivity, reliability and correlation with the gold standard using ADLT, regardless of the examiner's experience.