Intra-articular vertical dislocation of the patella: a case report of an irreducible patellar dislocation and unique surgical technique.

Intra-articular vertical dislocations of the patella are rare injuries that occur when a laterally or medially directed force is applied to the opposite patellar edge, causing it to rotate about its longitudinal axis. Diagnosis of this injury is not difficult with physical examination alone, but roentgenograms are necessary to rule out associated fracture and to define the direction of the articular surface. A Schanz screw is useful as a reduction tool to restore the patella to its normal relationship in the femoral groove if closed reduction proves impossible.