Special Physical Examination Tests for Superior Labrum Anterior-Posterior Shoulder Tears: An Examination of Clinical Usefulness

COMMENTARY

Since 1995, the number of diagnosed superior labrum anterior-posterior (SLAP) lesions has increased in the recreationally active and athletic populations. Prevalence in studies usually ranges from 3.9% to 11.8%; the identification of SLAP lesions with and without biceps tendon involvement has increased due to the use of arthroscopy¹ and to some extent magnetic resonance imaging.² To aid the clinician performing the physical examination, an extensive number of tests have been described in the literature. However, shoulder pain in active and overhead athletes can be a diagnostic challenge because of comorbidities.^1–3 Furthermore, when shoulder pain is nonspecific² and the exact pathophysiology is unknown, no definitive maneuvers specifically identify the lesion, the gold standard can be suspect, and studies can be biased.^2–6 In addition, several classifications can be used. The 2 that appear the most often in the literature are the 4 types described by Snyder et al^1–3,5,6 and the 3 subtypes described by Morgan et al.^1,3

When evaluating diagnostic accuracy studies, one should consider sensitivity, specificity, positive and negative likelihood ratios (LRs), and confidence intervals (CIs).^2,7 Doing so helps to rule the condition in or out or predict that the condition does or does not exist. Sensitivity refers to the proportion of patients with a positive test who have the condition. A reference standard usually verifies the presence of the condition. Specificity refers to the proportion of patients with a negative test who do not have the condition. Again this is verified by a reference standard. The reference standard for SLAP lesions is arthroscopy,³ not magnetic resonance imaging or magnetic resonance arthrography. For most SLAP lesion tests, sensitivity is lower than specificity,⁴ except when the special test has been evaluated by the creator.³ For example, the active compression test developed by O'Brien had a sensitivity of 100% and specificity of 98.5%.² However, when the test was evaluated in another diagnostic accuracy study, those values decreased to 47% sensitivity and 55% specificity.² Because specificity is usually higher than sensitivity, the special tests are better at ruling a SLAP lesion out than in. One should be cautious, though, in interpreting the results; in most diagnostic accuracy investigations, assessors were not blinded, studies were uncontrolled, and populations having mixed symptoms² were included, with most patients being older than those commonly seen in a traditional athletic training setting.

Positive and negative LRs and CIs should be evaluated. The LRs combine sensitivity and specificity values to provide a ratio quantifying the posttest probability of having a condition once the index test results (arthroscopy) are obtained. A positive LR ranges from 1 to infinity.^5,7 Clinically, a positive likelihood ratio of 2.0 or more represents an increased likelihood that the patient has the condition.^5,6 Negative LRs range from 0 to 1; a value of 0.50 or less represents a decreased likelihood that the patient has the condition.^5–7 Both positive and negative LRs may give the athletic trainer more information than sensitivity and specificity alone, and they should be considered when a new special test is being evaluated for use. Calculating CIs may clarify the situation even further. When the CI for a positive or negative LR spans 1, the test result has a limited bearing on whether the patient has or does not have the condition.² For example, the CIs for the Speed (+LR = 0.5246, 3.0882, –LR = 0.653, 1.2987) and Yergason (+LR = 0.8427, 4.7465, –LR = 0.4788, 1.1045) tests cross 1, so the test is ineffective to rule the condition in or out.²

Orthopaedic special tests for SLAP lesions become suspect if the test dynamics are considered analogous to a torn knee meniscus in which a torn labrum may get caught in the joint. This is not the case, and tests designed to detect this have low sensitivity.³ Other tests evaluate the shear movement of the labrum across the glenoid, as in the anterior slide test. Again, low sensitivity has been reported. Another test for SLAP lesions, the active compression test, creates tension in the biceps tendon or labrum and may be considered more of a pain-provocation test for either a labral or acromioclavicular joint injury.³ Results of this test vary in the literature. Thus, physical examination should not be used in isolation because special tests do not identify SLAP lesions.^2–5 In the absence of a detailed patient history and other clinical findings, a single test rarely benefits the decision-making process.⁶ Furthermore, a cluster of tests does not improve or aid in the diagnosis.^3,5,6 Rather, a careful history should be taken, including the mechanism of injury; intensity, occurrence, and location of pain; and presence of a click, pop, or catch.^1,3,5 Cook et al⁶ stated that a click or catch may not be an acceptable criterion in diagnosing a SLAP lesion, but Michener et al⁵ indicated otherwise. In the latter study,⁵ the combination of a history of clicking, popping, or catching along with the anterior slide test yielded a high positive LR (6.0, 95% CI = 1.59, 22.71). Additional clinical studies are needed to determine which history questions, physical examination tests, and valid self-reported upper extremity disability, function, and symptom indexes⁶ should be included to clinically detect a SLAP lesion.

Because the results of static isometric SLAP lesion tests may be suspect, a dynamic movement that duplicates the pain may be more helpful in diagnosing a biceps tendon or SLAP lesion. Two new SLAP lesion dynamic tests, the upper cut⁴ and modified dynamic labral shear,⁴ may be of assistance to the athletic trainer. These tests were developed from the description of pain by patients performing this movement. The upper-cut test relies on isotonic muscle activity to create tension in the biceps with dynamic rotation of the arm, and the modified dynamic labral shear (MDLS) combines appropriate positioning of the humerus with dynamic arm motion to apply stress to the labrum. For the upper-cut test, the patient is asked to rapidly bring the hand up and toward the chin, replicating a boxing upper-cut punch.⁴ For the MDLS test, the examiner applies a shear load to the joint by maintaining external rotation and horizontal abduction and lowering the arm from 120° to 60° of abduction.⁵ The upper-cut test had equal sensitivity (73%) and specificity (78%) in detecting a biceps tendon injury, whereas the MDLS test had higher specificity (98%) than sensitivity (72%) and was better at detecting a labral injury than a biceps tendon injury. For both tests, the +LR was large: 3.38 for the upper cut to predict a biceps tendon injury and 31.57 for the MDLS test to predict a labral injury. The upper-cut test was better (–LR = 1.40) in not predicting a labral injury than a biceps tendon injury (–LR = 0.34), whereas the MDLS test was better in not predicting a biceps tendon injury (–LR = 1.54) than a labral injury (–LR = 0.29). Based on the results of Calvert et al,² no single test can effectively diagnose a SLAP lesion. Therefore, the athletic trainer should include history questions, dynamic orthopaedic special tests, and valid self-reported upper extremity disability, function, and symptom indexes. Understanding the positive and negative LRs along with their CIs may be more useful than relying on sensitivity and specificity alone. Further diagnostic accuracy studies performed by athletic trainers on populations in traditional athletic training settings are currently rare in the athletic training literature and are needed.