A positive Elson test indicates a specific type of finger joint dysfunction, specifically related to the central slip of the extensor tendon.
Understanding the Elson Test
The Elson test is a physical examination maneuver used to assess the integrity of the central slip of the extensor tendon at the proximal interphalangeal (PIP) joint of a finger. The extensor tendon, which runs along the back of your finger, is responsible for straightening the finger joints. It has several parts, and the central slip plays a crucial role in extending the PIP joint.
How the Elson Test is Performed
The test involves the following steps:
- Patient Position: The patient's hand is placed palm down on a flat surface.
- PIP Joint Flexion: The examiner holds the PIP joint in a flexed (bent) position.
- Extension Attempt: The patient is then asked to extend their finger at the PIP joint against the examiner's resistance while the DIP joint is left free.
Interpreting the Results: Positive vs. Negative Elson Test
The key to understanding the test lies in observing the movement and strength at both the PIP and distal interphalangeal (DIP) joints:
| Test Result | PIP Joint | DIP Joint | Interpretation |
|---|---|---|---|
| Positive | Weak Extension | (Hyper)extension | Central slip injury/dysfunction. |
| Negative | Strong Extension | Floppy | Intact central slip, no issue. |
What Does a Positive Elson Test Mean?
A positive Elson test occurs when the patient cannot fully extend the PIP joint against resistance and there is simultaneous hyper or hyperextension at the DIP joint. This scenario suggests that the central slip of the extensor tendon is weak or disrupted.
The Logic Behind the Test
When the central slip is damaged, the force of extension is no longer concentrated at the PIP joint. The lateral bands of the extensor mechanism, which influence the DIP joint, can then cause extension (and often, hyperextension) at the DIP joint instead of the PIP joint.
Clinical Significance
A positive Elson test often points towards:
- A tear or rupture of the central slip.
- An imbalance in the extensor mechanism.
- A possible swan neck deformity if left untreated.
Treatment and Management
The treatment for a positive Elson test result will depend on the specific nature and severity of the injury. Often this involves:
- Splinting the PIP joint in extension to allow the central slip to heal.
- Hand therapy and exercises to regain full range of motion and strength.
- Surgical intervention for more severe injuries.
In Summary
In essence, a positive Elson test indicates that a patient demonstrates weak extension at the PIP joint while exhibiting (hyper)extension at the DIP joint, which is suggestive of central slip injury or dysfunction. This test is crucial for diagnosing certain extensor tendon issues that affect finger function.
