Which of the 3 ACL diagnostic tests is for the best for assessing a patient with a potential Anterior cruciate ligament rupture?

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Answered by: Dan, An Expert in the By Injury Category
There are 3 main ACL diagnostic tests that exist when considering how to assess a potential ACL rupture (or partial rupture) from a physiotherapist's point of view. The Lachmans' test, the anterior draw test, and the pivot shift test are 3 ways in which a therapist can gain an indication of potential injury without any scans or other medical equipment. It has long been debated which one of these tests is the most effective and so a review of the current literature would be beneficial.

Scholten et al (2003) conducted a systematic review into which of the three tests was the most effective; they suggested that of the literature reviewed, the pivot shift test had the most favourable positive predictive value, and the Lachman test had the most favourable negative predictive value. Ostrowski (2006) also agreed with with this notion, which already begins to suggest that a range of diagnostic tests should be used to assess ACL injury as it may not be as simple to say “test x is the most effective”.

Ostrowski (2006) did draw another conclusion however and it was based on the sensitivity and specificity values; he stated that the Lachman test was the most effective overall for ruling in or ruling out ACL ruptures suggesting that it may be the most effective single test to use. Both of the previously mentioned articles also stated that the effectiveness of the anterior draw test is unproven, which casts doubt as to whether it is effective at all.

The literature suggests the anterior draw test is the least effective at assessing ACL injuries as its sensitivity can be disputed. Benjaminse et al (2006) stated that this might be the case because the protective spasm caused by the hamstrings could decrease the amount of tibial translation. If this protective spasm is present at the time of testing then the test would return a false-negative result meaning tibial translation appears normal, but it does so due to the aforementioned structures and not because of the supposed intact ACL.

Scholten et al (2003) were not alone in their findings, as Solomon et al (2001) reported much of the same when considering the sensitivity of the three diagnostic tests (both studies used arthroscopy as the reference standard and so are comparable in this respect). They reported that the mean sensitivity value for the Lachman test was 82%, adding to the argument that this is a good diagnostic test to use. Interestingly they also noted the sensitivity of the pivot shift test was a lowly 38%, which contradicts Scholten et al (2003) who observed the opposite, stating that the pivot shift was a highly sensitive test. One explanation for the difference in these findings is the lateral pivot shift test is one that requires considerable experience and skill to perform and so the results may vary from therapist to therapist.

Considering the results of Benjaminse et al (2006) however it would appear that Solomon et al’s (2001) argument seems to hold merit, as the former also reported a low sensitivity of just 32% for the pivot shift test (they did however find that it has a very high specificity value of 98%). These results suggest that because of the difficulty of performing this test (hence the low sensitivity value) it can only be used effectively when the therapist has considerable experience/skill to perform it correctly.

Regarding the Lachman test, Benjaminse et al (2006) notes that it has a specificity value of 94% and a sensitivity value of 85%, adding that it appears to have good diagnostic accuracy. This seems to coincide with the views of Scholten et al (2003) and Solomon et al (2001), who also suggested that the Lachman test was the best ‘all round’ one to use.

In summary then it would appear that not one of the ACL diagnostic tests discussed should be seen as the gold standard when assessing the integrity of the ACL and multiple tests should be used as part of the assessment process. The outstanding test however does seem to be Lachman’s due to its combined high specificity and sensitivity values, whereas the pivot shift test holds a very high specificity value but because of its difficulty to perform provides a low sensitivity value. It has also been shown that the anterior draw test is the most inaccurate test however it is the easiest to perform and so may be useful as an indicator should the other two tests not provide conclusive evidence.

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