Elson Test for Central Slip Injury

The Elson test is a hand special test used to evaluate the integrity of the Central Slip (Extensor Hood Rupture) of the hand.

See Also: Extensor Tendon Injury of the Hand

How it’s Performed?

• The patient flexes the finger to 90 degrees at the proximal interphalangeal joint (PIP) joint over the edge of the table.
• The patient is then asked to extend the PIP joint while the clinician palpates the middle phalanx.

What does a positive Elson Test mean?

• The absence of extension force at the PIP joint, and fixed extension at the distal joint, indicates complete rupture of the central slip (Positive Elson Test).
• If the PIP joint is tight in extension and distal interphalangeal joint (DIP) is supple, then the Elson test is negative.

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

Central Slip Injury

Damage to the central slip insertion requires extra effort to extend the joint, causing hyperextension at the DIP joint. The failure of the lateral bands to be connected to the central slip allows these bands to drift forward. Eventually they pass the axis of rotation of the PIP joint, and instead of extending this joint, they act as flexors while still hyperextending the distal joint.

Such destruction also results in the loss of the influence of the interosseous muscles, ED longus, and lumbrical muscles on the PIP joints. Simultaneous with the loss of this muscle influence, the lateral bands of the extensor mechanism slide anteriorly. The realignment of the extensor mechanism, coupled with the loss of certain muscle influence, produces a deformity of extension of the MCP and DIP joints and flexion of the PIP joint. This is the classic boutonnière deformity.

Reference

• Elson RA: Rupture of the central slip of the extensor hood of the finger: a test for early diagnosis. J Bone Joint Surg Br. 1986;68:229–231. PMID: 3958008
• Louis Christopher Grandizio and Joel Christian Klena:Sagittal band, boutonniere, and pulley injuries in the athlete. Curr Rev Musculoskelet Med. 2017 Mar; 10(1): 17–22. PMID: 28101826
• Dutton’s Orthopaedic Examination, Evaluation, And Intervention 3rd Edition.