Minggu, 07 Oktober 2007

Shoulder Instability Tests

From University of Washington

Laxity Tests

  • These tests examine the amount of translation allowed by the shoulder starting from positions where the ligaments are normally loose.

  • These are tests of laxity, not tests for instability : Many normally stable shoulders, such as those of gymnasts, will demonstrate substantial translation on these laxity tests even though they are asymptomatic.

  • The amount of translation on laxity testing is determined by the length of the capsule and ligaments as well as by the starting position (i.e. more anterior laxity will be noted if the arm is examined in internal rotation - which relaxes the anterior structures, than if it is examined in external rotation - which tightens the anterior structures).

  • Use the contralateral shoulder as an example of what is 'normal' for the patient.

1. Drawer Test

The patient is seated with the forearm resting on the lap and the shoulder relaxed. The examiner stands behind the patient. One of the examiner's hands stabilizes the shoulder girdle (scapula and clavicle) while the other grasps the proximal humerus. These tests are performed with (1) a minimal compressive load (just enough to center the head in the glenoid) and (2) with a substantial compressive load (to gain a feeling for the effectiveness of the glenoid concavity). Starting from the centered position with a minimal compressive load, the humerus is first pushed forward to determine the amount of anterior displacement relative to the scapula. The anterior translation of a normal shoulder reaches a firm end-point with no clunking, no pain and no apprehension. A clunk or snap on anterior subluxation or reduction may suggest a labral tear or Bankart lesion. The test is then repeated with a substantial compressive load applied before translation is attempted to gain an appreciation of the competency of the anterior glenoid lip. The humerus is returned to the neutral position and the posterior drawer test is performed, with light and again with substantial compressive loads to judge the amount of translation and the effectiveness of the posterior glenoid lip, respectively.(Silliman and Hawkins, 1993)

2. Sulcus Test

The patient sits with the arm relaxed at the side. The examiner centers the head with a mild compressive load and then pulls the arm downward. Inferior laxity is demonstrated if a sulcus or hollow appears inferior to the acromion. Competency of the inferior glenoid lip is demonstrated by pressing the humeral head into the glenoid while inferior traction is applied.

3. Push-Pull Test

The patient lies supine with the shoulder off the edge of the table. The arm is in 90 degrees of abduction and 30 degrees of flexion. Standing next to the patient's hip, the examiner pulls up on the wrist with one hand while pushing down on the proximal humerus with the other. The shoulders of normal, relaxed patients often will allow 50 per cent posterior translation on this test.

Stability Tests

  • These tests examine the ability of the shoulder to resist challenges to stability in positions where the ligaments are normally under tension.

1. Fulcrum Test

The patient lies supine at the edge of the examination table with the arm abducted to 90 degrees. The examiner places one hand on the table under the glenohumeral joint to act as a fulcrum. The arm is gently and progressively extended and externally rotated over this fulcrum. Maintaining gentle passive external rotation for a minute fatigues the subscapularis, challenging the capsular contribution to the anterior stability of the shoulder. The patient with anterior instability will usually become apprehensive as this maneuver is carried out (watch the eyebrows for a clue that the shoulder is getting ready to dislocate). In this test, normally no translation occurs because it is performed in a position where the anterior ligaments are placed under tension.

2. Crank or Apprehension Test

The patient sits with the back toward the examiner. The arm is held in 90 degrees of abduction and external rotation. The examiner pulls back on the patient's wrist with one hand while stabilizing the back of the shoulder with the other. The patient with anterior instability usually will become apprehensive with this maneuver. As for the fulcrum test, no translation is expected in the normal shoulder because this test is performed in a position where the anterior ligaments are placed under tension.

3. Jerk Test

The patient sits with the arm internally rotated and flexed forward to 90 degrees. The examiner grasps the elbow and axially loads the humerus in a proximal direction. While axial loading of the humerus is maintained, the arm is moved horizontally across the body. A positive test is indicated by a sudden jerk as the humeral head slides off the back of the glenoid. When the arm is returned to the original position of 90-degree abduction, a second jerk may be observed, that of the humeral head returning to the glenoid.

Strength Tests

The strength of abduction and rotation are tested to gauge the power of the muscles contributing to stability through concavity compression. The strength of the scapular protractors and elevators are also tested to determine their ability to position the scapula securely.

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