[Validity of a novel arthroscopic test to diagnose posterolateral rotational instability of the knee joint: the lateral gutter drive-through test].

Objective: To assess the validity of the lateral gutter drive-through (LGDT) test in diagnosing posterolateral rotational instability (PLRI) of the knee joint.

Methods: Between October 2009 and February 2012, 115 consecutive patients were enrolled into this prospective diagnostic study. The tibia external rotation dial test was used as the gold standard for diagnostic reference. According to the dial test, the patients were divided into a study group (35 patients) and a control group (80 patients). The LGDT test was performed on all patients during arthroscopic surgery. The sensitivity and specificity of the LGDT test were calculated. The statistical difference of sensitivities in patient subgroups defined by injury patterns was tested using χ(2) test. And the correlation between the extent of tibia external rotational instability and the sensitivity of LGDT test was analyzed using logistic regression.

Results: The sensitivity and specificity of the LGDT test were calculated as 91.4% and 93.8%, respectively. The sensitivity of detection for acute PLRI was 9/10 vs. 92.0% in chronic cases (χ(2) = 0.036, P = 0.849). Popliteus femoral "peel off" lesions were detected with a sensitivity of 100% vs. 87.0% in cases of non "peel off" lesions (χ(2) = 1.712, P = 0.536). The sensitivity of detecting isolated external rotational instability vs. combined instability (rotational and varus) was 90.5% and 13/14, respectively (χ(2) = 0.062, P = 0.805). The sensitivity of the LGDT test was correlated with the extent of tibial external rotational instability (r = 1.000, P = 0.011).

Conclusions: The LGDT test is a reliable method to diagnose PLRI of the knee joint. The highest sensitivity is observed for patients with the femoral "peel off" injury pattern. The sensitivity of the LGDT test is correlated with the extent of tibia external rotational instability.