Watson Test / Scaphoid Shift Test | Scapholunate Instability

The scaphoid shift test is a provocative maneuver used to examine the dynamic stability of the scaphoid and reproduce a patient's symptoms. It is used to diagnose scapholunate interosseous ligament instability (SLIL).

Scaphoid Shift Test

Purpose

Watson first described the test to the American Research in General Orthopedics conference in New Orleans in March 1978. The test is found helpful during the examination of the wrist and more specifically the scaphoid. Beside the stability, the examiner will also be able to reflect the quality of the adjoining articular surfaces.

Scaphoid Shift Test

Clinically Relevant Anatomy

The ligaments that are thought to provide the principle support to the scaphoid are the radioscaphocapitate ligament, the scaphoid-trapezoid-trapezium ligament and the scapholunate interosseous ligament.

The scapholunate interosseous ligament(SLIL) is the link between carpal scaphoid and lunate bone. It ensures stability of the scapholunate joint and helps keep the entire wrist stabilized.
The scapholunate interosseous ligament is an intra-articular structure (ie, synovial) composed of three regions:

Dorsal ligament: transversely oriented collagen fibers providing primary restraint for distraction and torsional/translational movements

Palmar ligament: provides rotational stability

Proximal fibrocartilage: negligible contribution to restraint of abnormal motion

Technique

• To perform the scaphoid shift test, the patient should rest his arm with his elbow on the table and his forearm lifted.

• The examiner sits across the table and places his arm next to the patient's arm (like in an arm wrestling position right to right or left to left).

• The patient's hand is slightly pronated and the examiner places his thumb on the palmar side of the scaphoid (on the scaphoid tubercule), his other fingers are wrapped around the back of the wrist at the distal part of the radius.

• This will allow the examiner to put pressure on the scaphoid with his thumb. With his other hand the examiner holds the patient's hand at the metacarpal level.

• The hand is put into ulnar deviation and in slight dorsal flexion; in this position the scaphoid lies almost 'in line' with the ulna.

• From this position the hand is moved passively by the examiner into radial deviation and slight palmar flexion.

• Meanwhile a constant pressure is given by the thumb on the scaphoid tubercule. During the radial deviation and slight palmar flexion, the distal part of the scaphoid tilts forward and thereby pushes against the examiner's thumb (which is pushing in the opposite direction) causing stress on the joints.

• This stress is overcome in a normal wrist (minimal movement can be tolerated), but results in a dorsal displacement ('shift') of the scaphoid in relation to the other carpal bones in the wrist of a patient with ligamentous laxity.

• When the thumb force is then abruptly taken away the shift will be reduced and the scaphoid will fall back in its normal position, this may result in a painful 'thunk'.

• It is important to perform this technique on both wrists and compare them.

Interpretation

Positive test: A palpable and/or audible reduction of the subluxed scaphoid and elicitation of symptomatic pain, usually on the dorsal side.


Negative test: Scaphoid moves normally, pushing back on the examiner's thumb with ulnar deviation of the wrist, and there is no symptomatic pain.

Though Watson HK. has described this test more as a provocative then a test with a positive and negative result. An experienced examiner should be able to conclude a variety of findings from this test, the mobility itself should not directly be considered pathological because it may be caused by hypermobility syndrome.

Though unilateral hyper mobility is rather suspicious. Pain similar to the patients symptoms during a dorsal shift indicates a symptomatic subluxation of the scaphoid, pain which is less localised combined with normal or limited movement may point in the direction of periscaphoid arthritis or scapho-Iunate advanced collapse pattern.

A gritty, clicking or smooth sensation gives you an idea about the state of the articular cartilage and bony form of the joint. When there are doubts and to have clear results about the actual shift, a radioscopy and mostly a fluoroscopy are used to get clear images and information about the shift test.

Reliability

As mentioned earlier, the scaphoid shift test is more a provocative then a test and needs to be interpreted carefully.

This is also the conclusion made by most trials about the scaphoid shift test, several trials have shown us that around 32-36% of the uninjured population have a painless positive scaphoid shift test (only mechanical parameters where measured to determine whether the test is positive or negative during the trial); note that a high correlation between asymptomatic subluxable scaphoid and generalised ligamentous laxity has been noticed.

In the test, an examiner with great experience has been able to predict the presence of absence of the scaphoid shift with an accuracy of 82 and 88% respectively.

A study has shown that the pain associated with the subluxation is significant (p<0,05) to diagnose pathological dynamic scaphoid instability.

This confirms that the scaphoid shift test should be interpreted with great care, that the patients history, pain and feel of the movement are of more importance then the actual shift and therefore experience of the examiner is of great importance to evaluate the results.