Rupture or Division of the Central Slip

Clinical presentation

Zone III injuries may involve rupture or division of the central slip (as in the image) and if unrecognised can result in the boutonnière deformity – characterised by flexion at the PIPJ and hyperextension at the DIPJ and caused by the unopposed action of FDS and volar displacement of the lateral bands. Direct visualisation in an open laceration is the easiest way to confirm and treat this injury. A simple suture followed by six weeks splintage of the PIP joint in extension is usually satisfactory.

Closed rupture of the central slip over the PIPJ is easily missed. The history may be of axial loading or forced flexion with the PIPJ in extension, or after a volar dislocation of the PIPJ. Clinically, presentations may be variable – patients may present with an acute boutonniere deformity, with an unreduced volar dislocation or, most commonly, with a painful, swollen PIPJ.

Clinical management

Examination

Examination should look specifically for maximal localised tenderness over the dorsal aspect of the PIPJ, at the insertion of the central slip. Bruising may be noticed in the area.

Active extension at the PIPJ does not exclude a rupture as, in the acute setting, full extension may still be achieved by the lateral bands.

Elson’s test

Various clinical, non-invasive tests have been described for early diagnosis of closed central slip rupture including the test described by Elson [20].

Elson’s test is performed with the PIP joint of the injured finger flexed 90° over the edge of a table. The patient then tries to extend the PIP joint of the injured finger against resistance. The absence of extension force at the PIP joint and fixed extension at the DIP joint are signs of complete rupture of the central slip.

However, the test will not demonstrate a partial rupture, and may be limited by pain and the patient’s cooperation.

See here for a video demonstration.

Boutonnière deformity

X-ray may show an avulsion fracture, and sometimes gives the first clue to a developing boutonnière deformity.

Treatment

If a central slip rupture is known or strongly suspected, the PIPJ should be splinted in a static extension splint, leaving the DIPJ free.

Further follow-up in a hand clinic is required. The swollen, painful PIPJ with full active extension should be followed up in an ED clinic at 2-3 days for senior clinician re-assessment for possible central slip injury.