PIP joint volar rotatory dislocation: An anatomical study to explore extensor system lesions and the Stener effect.

Volar rotatory dislocation of the proximal interphalangeal joint results from volar rotation of the condyle around an intact opposite collateral ligament. A cadaveric study was preformed to better understand the mechanisms of this injury. Thirty-two long fingers (II to V) were studied. After partial section of the triangular ligament, the radial collateral ligament was cut (partly or completely, at proximal or distal insertion) and volar rotatory dislocation was induced. We studied the incidence of a fixed dislocation, the distal extension of the triangular ligament lesion, and the Stener lesion of the radial collateral ligament. A buttonhole lesion was produced by a dislocated lateral band in all cases with complete section of the collateral ligament. When the lesion of the triangular ligament extended distally, dislocation became irreducible. A Stener effect (interposition of the lateral band between the condyle and the collateral ligament) was observed after reduction in 21% of cases with proximal lesions of the radial collateral ligament.