Coronoid Process Fractures and Monteggia or Monteggia-Like Lesions

Complex instability of the elbow has been defined by Morrey as “instability caused by a traumatic injury to the articular surface and to ligamentous structures.” The main factors contributing to elbow stability include: the coronoid and the radial head, which serve as an anterior buttress against posterior forearm dislocation; the coronoid process is the keystone of elbow stability, the lateral ulnar collateral ligament, which together with the coronoid process provides a restraint against posterolateral rotation forces, the anterior bundle of the medial collateral ligament, which provides valgus stability to the elbow, while the radial head is the secondary stabilizer. This chapter describes the coronoid fracture in complex instability in acute and chronic lesions, the clinical presentations, diagnostic imaging and tests, and the treatment options. The combination of ulnar fracture and radial head dislocation gives rise to a set of injuries known as Monteggia lesions. Monteggia lesions are generally characterized by anterior or posterior radial head displacement relative to the distal humerus. In this chapter, we also describe the Monteggia and Monteggia-like lesions, the clinical presentations, diagnostic imaging and tests, and the treatment options.