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Physical diagnostic tests for assessing ruptures of the anterior cruciate ligament.

Description

Anterior drawer test: This test is performed with the knee flexed to approximately 90 degrees. Ideally, the patient's foot should point straight ahead and be secured by sitting directly on the toes of the patient. The examiner's hands are placed around the proximal tibia with the thumbs placed on the tibial tubercle. A gentle to and fro rocking motion is performed to determine the degree of anterior translation of the tibia compared to the femur. It is essential to ensure that the patient has completely relaxed the hamstrings to prevent a potential false negative result. Increased anterior translation of the injured knee (compared to the normal contralateral knee) would be indicative of a potential anterior cruciate ligament (ACL) rupture, deficient posterior horns of the menisci, or meniscocapsular tears (or any combination of these).

Lachman test: This test is performed in the same way as the anterior drawer test, but with the knee flexed to 20 degrees. Again, it is important to ensure that the patient's hamstrings are completely relaxed to reduce the chance of a false negative test result. The examiner should pay attention to two aspects. 1) In a knee with an intact ACL one should feel a solid thud, or an endpoint, at the end of the force application to the tibia, which indicates that the ACL is intact and has not been torn. This solid thud should be felt in both knees. 2) If the ACL has been ruptured, a subjective increase of the translation of the tibia compared to the distal femur will be felt which is soft and in effect has no 'endpoint'. Also, in this test it is important to compare the injured knee to the uninjured knee to ensure that the patient doesn't have a normal variant of increased anterior translation.

Pivot shift test: The pivot shift test is a dynamic test which also tests the integrity of the ACL. In this test, the examiner stretches the patient's knee and lifts the leg with the hip and knee in full internal rotation. The knee is gently flexed to about 40 degrees. In a patient with an ACL tear, the joint starts out subluxed in full extension and then is forced back into its normal position by the action of the iliotibial band pulling the anterolaterally subluxed tibia back against the femur when the knee courses through approximately 30 degrees of flexion. This test is quite difficult to perform, making it less attractive for an inexperienced examiner, eg a primary care physician.

Commentary

The diagnostic accuracy of these physical diagnostic tests was assessed in a systematic review (Scholten 2003). 17 studies met the inclusion criteria. None of the studies was conducted in general practice, none of them assessed the index test and reference test independently (with blinding), and all but two displayed verification bias (ie patients whose physical test results were abnormal were more likely to undergo the gold standard reference test--a factor that inflates sensitivity and decreases specificity). Summary estimates of sensitivity and specificity were 62% (95% CI 42 to 78) and 88% (95% CI 83 to 92) for the anterior drawer test, 86% (95% CI 76 to 92) and 91% (95% CI 79 to 96) for the Lachman test. No summary estimates could be calculated for the pivot shift test (due to a lack of available studies). Data from four studies show that the sensitivity and specificity ranged from 0.18 to 0.48, and 0.97 to 0.99, respectively. The pivot shift test had the highest positive predictive value, and the Lachman test the highest negative predictive value. The anterior drawer test was of little diagnostic value.

It was concluded that physical diagnostic tests may be useful in the diagnosis of ACL ruptures. The clinical relevance of the test results, however, depends on the prior probability of the presence of such a rupture and is therefore different for general practitioners and specialists/physiotherapists. If the prior probability is low (say 10%, eg in general practice), a negative Lachman test will almost rule out an ACL rupture (probability decreasing from 10% to 2%), whereas a (difficult to perform and, therefore, less suitable) positive pivot shift test will result in referral to secondary care for further investigation (probability increasing from 10% to more than 60%). If the prior probability is high (say 50%, eg in secondary care or physiotherapy practice), a positive pivot shift test will almost confirm the clinical diagnosis of ACL rupture without further imaging investigation (probability increasing from 50% to more than 90%), whereas a negative Lachman test cannot rule out an ACL rupture (probability decreasing from 50% to 10%).

Obviously, elements from the medical history (eg, type of trauma, nature of the complaints) will increase the prior probability and, therefore, improve the predictive values.

In summary, in general practice a negative Lachman test almost rules out an ACL rupture, whereas in specialised care a positive pivot shift test will practically confirm the clinical diagnosis of an ACL rupture.

Wim Opstelten

Dutch College of General Practitioners, The Netherlands

Rob JPM Scholten

Dutch Cochrane Centre, The Netherlands

References Scholten RJ et al (2003) J Fam Pract 52: 689-695.
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Title Annotation:Appraisal: Clinimetrics
Publication:Australian Journal of Physiotherapy
Geographic Code:8AUST
Date:Dec 1, 2007
Words:859
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