Watson's test

Watson's Test is a clinical examination procedure used to assess the integrity of the Scapholunate ligament in the wrist. This test is particularly important in diagnosing Scapholunate Dissociation (SLD), a condition where there is a tear or dissociation in the scapholunate ligament, leading to instability between the scaphoid and lunate bones of the wrist. The scapholunate ligament is crucial for maintaining proper movement and stability in the wrist joint, and its injury can lead to significant pain, decreased wrist function, and long-term complications such as osteoarthritis if left untreated.

Procedure

Watson's Test, also known as the Scaphoid Shift Test, is performed with the patient seated or standing. The examiner uses one hand to stabilize the patient's forearm and the other hand to hold the patient's thumb in slight extension. The examiner then applies a dorsal directed pressure on the scaphoid tubercle with the thumb while moving the patient's wrist from ulnar deviation to radial deviation and from a flexed position to an extended position. A positive Watson's Test is indicated by a painful clunk as the scaphoid subluxes over the dorsal rim of the radius, suggesting a potential scapholunate ligament injury.

Indications

Watson's Test is indicated in patients presenting with wrist pain, especially those with a history of trauma to the wrist, such as a fall on an outstretched hand. It is also indicated in patients who report symptoms suggestive of scapholunate instability, including weakness, decreased range of motion, and a clicking or clunking sensation in the wrist during certain movements.

Interpretation

A positive Watson's Test suggests scapholunate instability due to a compromised scapholunate ligament. However, it is important to note that a positive test does not definitively diagnose scapholunate dissociation. Further diagnostic imaging, such as X-ray, MRI, or arthroscopy, may be required to confirm the diagnosis and assess the extent of the injury.

Limitations

While Watson's Test is a valuable tool in the clinical assessment of scapholunate instability, it has its limitations. The test can be subjective and dependent on the examiner's technique and interpretation. Additionally, it may not be positive in all cases of scapholunate ligament injury, particularly in chronic or partial tears. False positives can also occur in individuals with lax ligaments or pre-existing wrist conditions.

Conclusion

Watson's Test is a clinically significant examination for assessing scapholunate ligament integrity and diagnosing scapholunate dissociation. Despite its limitations, when combined with a thorough patient history, physical examination, and appropriate diagnostic imaging, Watson's Test can be an effective component of a comprehensive wrist assessment strategy.

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