Validation of the lateral anterior drawer test for examining posterior cruciate ligament integrity in cadaveric knees

Background: Clinicians are often unable to identify posterior cruciate ligament (PCL) ruptures through common clinical tests. This leads to undetected tears and potential degenerative changes within the knee joint (e.g. irreversible cartilage damage). The lateral-anterior drawer (LAD) test is distinguished from the more common clinical tests by its lateral-anterior testing force direction and has been proposed for the diagnosis of PCLruptures. However, it has not yet been validated. Purpose: To assess the construct and concurrent validity of the LAD test. Methods: Eighteen cadaveric knees (36-94 years old; mean = 79 years), embalmed according to the method of Thiel, were sectioned from pelvis to foot. With skin and subcutaneous tissue removed, threaded markers were inserted into the distal femur and proximal tibia. Each femur was stabilized and the tibia was translated in lateral-anterior direction for the LAD, versus straight posterior for the posterior sag sign (PSS). Each test was repeated three times with the PCL both intact and cut in that order. Digital images were captured at start and finish positions during each trial. Tibial marker translation during each trial was digitized using the MATLAB Program. Means and standard deviations were established for each condition. The PSS values were used as a reference standard for establishing LAD concurrent validity. Results: Tibial translation was significantly greater with the PCL cut versus intact during the LAD (u=-3.680; p<0.002) and PSS (u=-3.724; p<0.002) tests. There was no significant difference between the changes in tibial translation after the PCL was cut during the LAD versus PSS tests (t=2.029; p=0.07). Conclusion: The LAD test detected changes in tibial translation corresponding with changes in PCL integrity, supporting test construct validity. The LAD test was at least as effective for assessing PCL integrity as the PSS test, supporting test concurrent validity. The use of the LAD test may be best suited when: (1) joint end-feel is important to the diagnosis; (2) increased muscle tone accompanies the knee injury and hinders an accurate PSS test use; and (3) the tester is rather inexperienced. Furthermore, positive LAD and PSS tests could be clustered to strengthen PCL tear diagnostic suspicions. Further studies are needed to determine intra- and inter-tester-reliability of the LAD test. Implications: Adding the LAD test to the diagnostic algorithm in PCL tear diagnostic suspicions may be conducive to detect PCL tears more precisely and hence preserve patients from subsequently developing irreversible cartilage damage due to knee laxity.