Diagnosis of closed central slip injuries. A cadaveric analysis of non-invasive tests.

Four non-invasive tests for central slip integrity were analysed using 20 fresh frozen cadaver fingers. A pre-boutonnière deformity was simulated by dividing the central slip. A passively correctable boutonnière was simulated by dividing the central slip, triangular ligament and oblique fibres of the extensor expansion. The test described by Boyes, which evaluates distal interphalangeal joint flexion, was found not to be reliable for the diagnosis of either injury. The test described by Elson, which evaluates distal interphalangeal joint rigidity while actively extending the flexed proximal interphalangeal joint, was the only manoeuvre which was able to discern central slip integrity in both simulated injuries. The central slip tenodesis test and testing resistance of active proximal interphalangeal joint extension should be performed with the proximal interphalangeal joint in flexion to weaken the effectiveness of the lateral bands.