The scaphoid shift Test (Watson 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).
How it’s Performed?
This test is performed with the patient sitting with the elbow resting on the table.
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).
The test are compared with the other hand.
What does a positive Watson Test (Scaphoid Shift 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.
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 (Scaphoid Shift Test) was as folowing:
Sensitivity: 69 %
Specificity: 66 %
Scaphoid shift 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.
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.
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
Wolfe SW, Gupta A, Crisco JJ III: Kinematics of the scaphoid shift test. J Hand Surg Am 22A:801–806, 1997
Clinical Tests for the Musculoskeletal System 3rd Edition.
Dutton’s Orthopaedic Examination, Evaluation, And Intervention 3rd Edition.