An evaluation of the anatomic basis of the O'Brien active compression test for superior labral anterior and posterior (SLAP) lesions.
Aim: To evaluate the anatomic basis of the O'Brien test for SLAP lesions (specifically, to quantify the active and passive tension in the long head of biceps during the O'Brien test).
Methods: Two complementary studies were performed, one evaluating the active and the other the passive tension in the long head of biceps. Each measured tension in the positive (shoulder flexion, horizontal adduction, and internal rotation) and negative (shoulder flexion, horizontal adduction, and external rotation) positions of the O'Brien test. To clarify the point of examiner contact each position was performed with resistance against the arm above the elbow and again below the elbow.
Active tension was studied in six female volunteers (mean age 21.2 (SD 1.7) years) and six male volunteers (mean age 23.5 (SD 3.7) years) with no history of shoulder problems using surface electromyography (EMG). Muscle recordings were taken from the long and short head of biceps, and the anterior and middle portions of deltoid. Passive tension was measured in three female cadavers (age 58-91 years) using a load cell directly attached to the proximal long head of biceps tendon.
Results: As measured by surface EMG the long head of biceps was more active in the negative than positive position of the O'Brien test in normal volunteers. This was found against both arm resistance (63% more active) and forearm resistance (88% more active). In the cadaveric specimens, passive tension in the long head of biceps was greater in the negative (201 g) than the positive position (-738 g).
Discussion: The study findings are contrary to the proposal by O'Brien et al (1998) that the positive position of the O'Brien test increases tension in the bicipitallabral complex. The increases in active and passive tension in the negative position have an anatomical basis. Shoulder external rotation brings the biceps onto the anterior aspect of the arm, allowing this muscle to actively contribute to shoulder flexion. It also lengthens the intra-articular path of the long head of biceps, thus increasing passive tension. The lack of support for the anatomical basis of the O'Brien test may partly explain variable reports of the clinical accuracy of this test.
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This excellent study takes a back-to-school approach to examining the O'Brien test for SLAP lesions, and reveals that the anatomical basis is not supported. For clinicians, this is both important and useful. Studies of clinical tests for SLAP lesions have shown poor accuracy, and considerable variability (Mirkovic et al 2005, Munro and Healy 2009). Historically, new tests have been developed and reported to have good accuracy, but researchers re-evaluating the same tests have not produced such good results (Munro and Healy 2009). With such findings, re-examining the validity of SLAP tests is highly appropriate.
Clinically, differential diagnosis of a SLAP lesion requires careful objective testing, as well as careful interpretation of the findings. New clinical tests for SLAP lesions are still emerging (Kim et al 2001, Myers et al 2005), but none has proven definitive. In this environment, evidence-based practice is less about applying the "best" test, and more about applying a reasoned approach to diagnosis. An understanding of the structures under stress during the physical examination is essential, as highlighted by Green et al (2008).
Clinicians utilising the O'Brien test in the diagnosis of SLAP lesions should find this article of interest. It provides a reasoned critique of the anatomical basis of the O'Brien test, and represents an opportunity to review your own differential diagnosis of SLAP lesions.
Ewan Kennedy, BPhty, PhD
Professional Practice Fellow, School of Physiotherapy, University of Otago
Journal of Shoulder and Elbow Surgery 17: 165-171. (Abstract prepared by Ewan Kennedy)
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|Title Annotation:||Clinically Applicable Papers|
|Author:||Green, R.A.; Taylor, N.F.; Mirkovic, M.; Perrott, M.|
|Publication:||New Zealand Journal of Physiotherapy|
|Date:||Jul 1, 2009|
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