Watson Test | Scaphoid Shift Test

The Watson Test (or as it called scaphoid shift Test) examines the dynamic stability of the wrist, in particular the integrity of the scapholunate ligament. It detects abnormal motion between the scaphoid and the lunate bone, where application of a dorsally directed force attempts to shift the scaphoid from the lunate.

How do you perform the Watson Test?

• The patient should be sitting with the elbow flexed and supported on the table and the forearm and hand pointing up, resembling the starting position for arm wrestling.
• The elbow in approximately 90 degrees of flexion and the forearm slightly pronated.
• With the patient’s wrist in full ulnar deviation, the examiner flexes the scaphoid bone between his or her thumb and index finger, with the thumb pressed against the distal pole of the scaphoid (tubercle) such that the scaphoid is held in extension.
• The examiner uses the other hand to grasp the metacarpals and radially deviates the wrist, which normally would be accompanied by scaphoid flexion but which is now prevented by the thumb’s pressure on the scaphoid.
• As the wrist is brought passively into radial deviation, the normal flexion of the proximal row forces the scaphoid tubercle into an anterior (palmar) direction (into the examiner‘s thumb). The clinician attempts to prevent the anterior (palmar) motion of the scaphoid. When the scaphoid is unstable, its proximal pole is forced to sublux posteriorly (dorsally).
• Bilateral comparison is important because many patients have nonpathological but positive findings.
• This maneuver is best done with the patient’s wrist flexed, because this causes the scaphoid to be angled to such a degree that the proximal pole may be only partially constrained by the bony architecture of the dorsal lip of the radius.

See Also: Wrist Anatomy

What does a positive Watson Test mean?

• In the normal patient, this maneuver should produce smooth movement and minimal discomfort.
• The Scaphoid Shift Test is positive when the proximal pole of the scaphoid shifts to the dorsal rim of the scaphoid fossa, subluxates, and bumps against the examiner’s index finger. A ruptured SL ligament allows the proximal pole to move more dorsally and frequently rest on the dorsal lip of the radius.
• This “snap” is accompanied by pain, demonstrating damage to the scapholunate ligament; however, it does not give any information as to the severity of the lesion.

Sensitivity & Specificity

A descriptive study by LaStayo¹ for provocative tests used in evaluating wrist pain and compare retrospectively the results of these tests with the arthroscopic findings of three independent hand surgeons, he found that the Sensitivity & Specificity of Watson Test was as following:

• Sensitivity: 69 %
• Specificity: 66 %

Modified Watson Test

A slight modification to the Watson test has been described.

The patient positioning is similar to the Watson test except that the wrist is positioned in neutral to slight (0–10 degrees) radial deviation and neutral wrist flexion/extension. The clinician then quickly pushes the tubercle of the scaphoid in a posterior (dorsal) direction, noting a clunk, crepitus, or pain in comparison to the opposite wrist.

No diagnostic accuracy studies have been performed to determine the sensitivity and the specificity of this test.

Notes

Watson test is a provocative maneuver rather than a test, because it does not offer a simple positive or negative result, but rather a variety of findings, with emphasis being on asymmetry on bilateral examination.

It will also produce symptoms when an occult dorsal ganglion or an occult scaphoid fracture is present. Because the test produces a dorsal displacement of the scaphoid and traction on the SL ligament, if an occult dorsal ganglion is present, the test will generally be painful.

This test will produce a painful stimulus if any fracture exists, and should be considered a mandatory test for all cases diagnosed as “clinical scaphoid fracture”, because thumb pressure produces a force that begins on the tuberosity of the scaphoid and travels up the longitudinal axis of the scaphoid.

The degree of the Scaphoid shift is related to the amount of examiner pressure, the degree of scaphoid flexion, the amount of ligamentous laxity, and the status of the scapholunate (SL) ligament.

The watson’s test is usually considered a test for SL rupture and scaphoid instability; however, this test is also important for assessing the articular cartilage status of the proximal pole of scaphoid and radial facet, with a gritty sensation or clicking suggesting chondromalacia or loss of articular cartilage.

Perilunate Dislocation

• A perilunate dislocation results from disruption of the scapholunate ligament, then extension of the injury to the capitolunate articulation and the lunotriquetral ligament.
• Most carpal dislocations are of the perilunate variety with the lunate dislocating in an anterior (palmar) direction.
• This is accompanied by damage to both of the interosseous ligaments of the proximal row and possible injury to the median nerve.
• The usual mechanism of injury is hyperextension of the wrist.
• Physical examination is often limited, revealing swelling and a deformity, and the injury may be confused for a distal radius fracture.
• If the median nerve is involved, paresthesias or numbness in the median nerve distribution may be present.
• The dislocation is easily reduced if the intervention occurs soon after the injury.
• The reduction involves placing the wrist in extension and putting pressure on the lunate, after which the wrist is moved into flexion and immobilized.

Reference

1. P LaStayo, J Howell: Clinical provocative tests used in evaluating wrist pain: a descriptive study. J Hand Ther . Jan-Mar 1995;8(1):10-7. doi: 10.1016/s0894-1130(12)80150-5. PMID: 7742888
2. Wolfe SW, Gupta A, Crisco JJ III: Kinematics of the scaphoid shift test. J Hand Surg Am 22A:801–806, 1997.
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8. Lane LB: The scaphoid shift test. J Hand Surg Am 18:366–368, 1993.
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