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    Tips for Diagnosing Shoulder Instability and Its Direction

    Shoulder instability affects about 2% of the population, primarily as anterior shoulder instability caused by traumatic injury. Recurrent instability depends on age and activity level, with young individuals, males, and individuals who participate in contact sports at higher risk for recurrence. [1-3]

    Speaking at ICJR’s 6th Annual Shoulder Course, Eric T. Ricchetti, MD, from Cleveland Clinic, said that instability should be viewed as spectrum of disease. At one end is traumatic, unidirectional instability associated with less laxity, and at the other end is multidirectional, atraumatic instability associated with a higher degree of laxity.

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    Patients usually present with some baseline laxity, Dr. Ricchetti said, and it is important for surgeons to recognize this in their workup of the patient with suspected shoulder instability: The degree of laxity impacts treatment decisions and outcomes. Surgeons should also keep in mind that the history will be the key to diagnosing instability and determining if surgical intervention is necessary. The history should include:

    • Degree of trauma: major, minor (repetitive), or none
    • Dislocation versus subluxation
    • Position of the arm during the instability event: abduction external rotation versus adduction internal rotation versus mid-abduction (bone loss)
    • Frequency of instability events
    • Prior surgical treatment for instability

    The physical examination may be of limited value in some patients due to guarding and apprehension. But there are characteristic signs of instability the surgeon should consider. In acute dislocation, look for:

    • Acromial prominence due to dislocated humeral head
    • Anterior/posterior fullness
    • Arm position: Anterior instability, external rotation; posterior instability, internal rotation; luxatio erecta, abduction/elevation
    • Skin dimpling
    • Limited range of motion
    • Axillary nerve injury, which occurs in 5% to 18% of patients

    In recurrent instability, testing should be done to evaluate the extent and type of instability, but again, the results may be limited by guarding. The tests include:

    • Ligamentous laxity
    • Sulcus sign
    • Apprehension test/relocation test
    • Surprise test
    • Load-shift test
    • Jerk test

    Imaging studies are important for the diagnosis as well. With acute instability, pre-reduction anteroposterior and axillary radiographs will show the direction of the dislocation; post-reduction, these views will indicate whether the dislocation has been successfully reduced. Other modified views, such as the trans-scapular Y view, the Velpeau view, and the Stryker notch view, have been shown to detect associated pathology in shoulder instability patients. However, they are less commonly used now, Dr. Ricchetti said, due to the widespread availability of MRI to assess labral tears and other soft tissue injuries and CT scans to assess bony pathology such as glenoid and humeral head bone loss.

    Click on the image above to watch Dr. Ricchetti’s presentation and get more details on evaluating patients suspected of having shoulder instability.

    Disclosures

    Dr. Ricchetti has disclosed that he is a paid consultant and paid presenter/speaker for DJO Surgical.

    References

    1. Mather RC 3rd, Orlando LA, Henderson RA, Lawrence JT, Taylor DC. A predictive model of shoulder instability after a first-time anterior shoulder dislocation. J Shoulder Elbow Surg. 2011 Mar;20(2):259-66. doi: 10.1016/j.jse.2010.10.037.
    2. Owens BD, Duffey ML, Nelson BJ, DeBerardino TM, Taylor DC, Mountcasle SB. The incidence and characteristics of shoulder instability at the United States Military Academy. Am J Sports Med. 2007 Jul;35(7):1168-73.
    3. Robinson CM, Howes J, Murdoch H, Will E, Graham C. Functional outcome and risk of recurrent instability after primary traumatic anterior shoulder dislocation in young patients. J Bone Joint Surg Am. 2006 Nov;88(11):2326-36.