The Lever Test for Diagnosing ACL Injuries
/Guiraud, K. et al. Higher sensitivity with the lever sign test for diagnosis of anterior cruciate ligament rupture in the emergency department. Arch. Orthop. Trauma Surg. 142, 1979–1983 (2022).
Clinical Question: Does the lever sign provide improved sensitivity to the diagnosis of acute ACL tear in the ED?
Background
The anterior cruciate ligament (ACL) is one of the most commonly injured knee ligaments, with nearly 200,000 injuries annually in the US, with ~100,000 requiring reconstruction. The ACL prevents anterior translation of the tibia relative to the femur and is a secondary restraint to tibial and varus/valgus rotation. Accurately diagnosing ACL injuries in the ED after an acute knee injury remains difficult. The diagnosis is complicated because clinical tests are performed on an acutely injured knee, which is likely swollen and painful, leading to muscle contractures and patient apprehension. As Emergency Medicine physicians, we must have some confidence in suspicion of an ACL tear because not all patients can or should be referred for prompt orthopedic follow-up.
Traditional clinical evaluations for ACL injuries include the Lachman test and/or anterior drawer test, but several small studies have suggested that the lever sign has better test characteristics.
The lever sign test inflicts less pain on patients and requires only passive knee mobilization.
The lever test is performed in 3 steps:
The patient is placed supine on a bed with the knee fully extended
The provider's closed fist is placed at the level of the tibial tuberosity (just below the knee) on the back side of the leg on the bed, thus causing the knee to bend slightly
Downward pressure is applied to the distal femur, thus creating a lever from the patient's leg, with the fist as the fulcrum. If the ACL is intact, the foot rises off the bed (the lever is working), but if the ACL is torn, the foot remains on the bed (the lever is broken).
Study Design
A prospective study from a single ED in Belgium enrolled adults presenting to the ED within eight days after an acute injury with negative X-ray findings and a positive lever sign, Lachman test, or anterior drawer test, thus indicating clinical suspicion of ACL injury.
Exclusion Criteria
Patients excluded from the study include those who had:
Segond fracture (avulsion type fracture of lateral proximal tibia at attachment of the ACL) or tibial spine fracture on X-ray
Complete rupture of knee extensor mechanism or patella dislocation
Methods & Definitions
Patients presenting to the ED for acutely traumatic knee pain underwent evaluation by either an Orthopedic or Emergency Medicine resident who received training in performing and interpreting a Lever test. Every patient with a positive Lever sign, Lachman test, or anterior drawer test were enrolled in the study, totaling 52 patients. The mean time between injury and admission at the ED was 53 (1–192) hours. 41 out of 52 patients (79%) presented a sport-related etiology. All patients received an MRI within three weeks of ED evaluation (gold standard).
Results
Of the 52 patients, 40 had an ACL rupture confirmed by MRI (77%), and the lever sign performed better, with a sensitivity of 92.5%. In contrast, the Lachman and anterior drawer tests had 54% and 56% sensitivity, respectively. The Lachman test could not be performed on 2 patients (4%), and an anterior drawer test could not be performed on 7 patients (14%) because of pain or swelling.
The lever test had a sensitivity of 92.5%, specificity of 25%, PPV of 82%, and NPV of 50%. Of the 40 ACL ruptures, 12 (30%) were diagnosed exclusively with a positive lever sign test.
There were a total of 9 patients in the intact ACL group, meaning they had a normal MRI with a positive lever sign (false negative):
1 (8.3%) had a sprained collateral ligament,
1 (8.3%) had a combined meniscus and collateral ligament injury
2 (16.6%) had an isolated femoral condyle oedema.
1 (8.3%) partial rupture of the quadriceps tendon
2 (16.6%) had a bucket handle tear of the meniscus.
2 (16.6%) presented a compartmental mirrored bone marrow oedema which could be a potential case of false negatives on MRI.
Takeaway
Although this study represents a small sample of patients, it is a study that was performed in an ED on acutely traumatic knee injuries and showed the superiority of the Lever sign in comparison to the Lachman and anterior drawer in the diagnosis of acute ACL injuries.
Quantifying the significance of this test comes down to the provider's perspective on managing knee injuries and the resources available to them. Suppose prompt outpatient Orthopedic follow-up is available to all of their patients, and all patients with traumatic knee pain receive Orthopedic follow-up. In that case, the test may provide a small benefit. However, for those practicing in lower resource communities or without readily available Orthopedic follow-up, the Lever test can be another tool to guide them in patient management.
Given how easy the lever test is to perform and interpret and how it can be performed on patients in which other traditionally taught exams cannot be completed secondary to pain/swelling, it should be used to examine an acutely injured knee in the ED.
Authorship
Written by Casey Glenn, PGY-3, University of Cincinnati Department of Emergency Medicine
Peer Review and Editing by Jeffery Hill, MD MEd, Associate Professor, University of Cincinnati Department of Emergency Medicine.
Cite As: Glenn, C. Hill, J. The Lever Test for Diagnosing ACL Injuries. TamingtheSRU. www.tamingthesru.com/blog/journal-club/lever-test. October 20, 2023
