Lever Sign Test: Is it Sensitive for the Diagnosis of Anterior Cruciate Ligament Disruption?

Fahmy Samir Fahmy, MD; Hossam Fathi, MD

Disclosures

Curr Orthop Pract. 2019;30(4):343-346. 

In This Article

Discussion

The main function of an intact ACL is resisting anterior tibial translation. Also, it has an important role in controlling rotational and valgus-varus stresses.[12,13] Most of the studies investigating the clinical tests of ACL disruption concluded that the Lachman test is the most sensitive, and the anterior drawer is the least sensitive in acute injuries.[14] A novel clinical manual test for diagnosis of ACL injuries was described by Lelli et al.[11] called the lever sign test. They stated that this test is suitable to detect all types of ACL tears (acute, chronic, partial, and complete) with better sensitivity than other clinical diagnostic tests.[11]

The rationale of this test is that an intact ACL enables the leg to act as a lever arm and resists the gravity acting on it. This makes the knee extend and the heel lift off the examination table when a downward force is applied to the distal femur. When the ligament is injured, this lever arm mechanism fails to overcome the gravity acting on the leg, and the heel will not lift off the table,[11] but there are no biomechanical studies supporting and proving the idea of this test.

Our study was done on 100 patients with complete chronic ACL disruptions, excluding acute ACL tears, partial ACL injuries, multiligamentous injuries, meniscal and chondral lesions to avoid the possible occurrence of false-negative results. Also, physical examination was done with patients under anesthesia and completely relaxed for the same reason. The clinical tests of ACL were done by two different clinical examiners.

Lelli et al.[11] were the first to study the lever sign test. They performed their study on 400 patients of ACL lesions categorized into four groups according to the time of injury (acute or chronic) and the MRI findings (partial or complete). They reported 100% sensitivity of the test in all groups. They concluded that the lever sign test had better sensitivity than other clinical tests, and it was helpful for diagnosis of different ACL injuries. Later, Thapa et al.[15] included 80 patients with knee trauma in their study. They reported the sensitivities of different clinical tests: Lachman test (91%), lever sign test (86%), anterior drawer (80%) and pivot-shift test (51%). The sensitivity of the lever sign test was lower than the Lachman test and lower than the values in the previous study. In a study by Deveci et al.[16] of 117 chronic ACL tears (partial and complete), four clinical tests were performed before and after anesthesia for ACL tear, including the lever sign test. The evaluated sensitivity of the lever sign test was higher than the sensitivity of Lachman test. They declared that this test was helpful in diagnosing ACL disruption and it was easily applicable. The last study done by Jarbo et al.[17] included 102 patients with acute knee injuries. Physical examination was done in the outpatient clinic and after anesthesia in the operating room. The accuracy of the lever sign test was 77%, with 63% sensitivity and 90% specificity. They were not in agreement with the 100% results recorded by the original author.

Despite the encouraging results of the lever sign test in the previous studies, there have been no biomechanical studies to prove these results and explain how it works.[17] Our study included 100 patients with chronic complete ACL tears examined under anesthesia. Contrary to the previous studies, the sensitivity of the lever sign test in our study (34%) was much inferior to other tests and had a high number of false-negative results (66 patients). Also, our results were lower than the results of the aforementioned studies. The sensitivities of the Lachman, anterior drawer, and pivot-shift tests were lower than expected. A possible explanation is that some patients in our study had bulky thighs and over-sized legs, which could have produced false-negative results.

A biomechanical study by Pandy et al.[18] demonstrated that the medial collateral ligament (MCL) is the primary stabilizer against anterior tibial translation, and the forces exerted on the intact ACL are shifted to the MCL when the ACL is torn. This may explain the false-negative results of the lever sign test recorded in our study. Future biomechanical tests will be needed to detect if there is a contribution from other knee ligaments in this clinical sign.

During arthroscopic reconstruction of our patients, we noticed that the ACL in patients with a false-negative lever sign test was torn and scarred to the posterior cruciate ligament, roof of the notch, or the wall of lateral femoral condyle (Figure 2; Video 2, Supplemental Digital Content 2, http://links.lww.com/COP/A29 shows the patient in Figure 2. The patient had a left ACL tear with a negative lever sign test). In the true positive cases, the ligament was not there. These arthroscopic findings should be considered for further biomechanical investigations to prove and explain this association.

Figure 2.

Arthroscopic view showing the torn anterior cruciate ligament scarrred to the wall of the lateral femoral condyle.

The limitations in our study were exclusion of acute and partial ACL injuries, lack of biomechanical investigations supporting the results of our study, and the study did not include patients with knee injury so the data required to measure test specificity were absent.

In conclusion, the lever sign test had a poor sensitivity compared to other diagnostic clinical tests. The accuracy of this test for the diagnosis of ACL disruption is still questionable, and further biomechanical work-up is needed to prove the efficacy of this test.

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