Classification/Spectrum of Injury
Jose Luis Bado first described the widely used Bado classification in Uruguay, which was subsequently translated into English in 1967 (Supplemental Figure 1, Supplemental Digital Content 1, https://links.lww.com/JAAOS/A513). His system was determined by the direction of the radial head dislocation in the anterior (type I), posterior (type II), or lateral direction (type III). Type IV describes proximal ulna and radius fractures with an associated radiocapitellar dislocation in any direction. The original manuscript emphasized the level of the ulna fracture, the angulation of the fracture deformity, and the direction of the radiocapitellar dislocation.
Anterior dislocations of the radial head (Bado type I) have three potential mechanisms: (1) hyperpronation of the forearm resulting in the radial head dislocation and ulna fracture; (2) hyper-extension of the elbow causing strong contraction of the biceps leading to dislocation of the radial head, which is then followed by the ulna fracture; or (3) direct trauma to the posterior ulna that then forces the radial head anteriorly until it dislocates.[4,5] Posterior dislocations (Bado type II) are associated with a longitudinal force applied to a supinated and partially flexed ulna, resulting in fracture. There is also a hypothesis that patients with long-term corticosteroid use may be at increased risk for these injuries because of bone weakness resulting in their bone failing before their ligaments in the elbow. Lateral dislocations (Bado type III) occur by direct trauma with a varus force acting on an extended elbow. This type of Monteggia fracture is associated with posterior interosseous nerve (PIN) palsies, although these are only reported in case studies and primarily in pediatric populations. There currently is no literature that describes the overall incidence of nerve palsies with Monteggia fractures. At the time of Bado's publication, the treatment of Monteggia fractures was generally conservative in both adults and children. Therefore, reduction maneuvers in the opposite direction of the producing mechanism were paramount to treating these injuries.
In 1991, Jupiter et al developed a subclassification within the posterior Monteggia fracture group (Bado type II) based on the severity of the coronoid fragment and radial head fracture. The authors recognized the importance of the triangular or quadrangular fracture fragment at the level of the coronoid, which affects the functional disability of the injury when it is inadequately reduced. Specifically, there was a concern that the loss of the anterior cortex of the ulna at the coronoid process would result in treatment failure unless a plate is applied to the dorsal surface of the ulna. The contoured plate, acting as a "tension band plate," allows the opportunity to secure the anterior cortical fragments and resist the tendency of the proximal ulna to angulate anteriorly.
The Jupiter subclassification includes four main groups (Figure 1) based on the proximal ulna fracture pattern. Type IIA includes distal olecranon and triangular coronoid process fractures. In type IIB fractures, the proximal ulna fracture is at the metaphyseal-diaphyseal junction distal to the coronoid. Type IIC is a purely diaphyseal ulna fracture. The more complex type IID pattern includes an ulna fracture that extends from the trochlear notch, including the coronoid fragment, to the metaphyseal region with notable comminution. The Jupiter classification also includes an associated radial head fracture that is further subdivided by the number of fragments. Ten of 13 patients in this series had a radial head injury, and seven of these were comminuted. No discussion existed about how the radial head fracture and subsequent surgical management affected the outcomes.
Schematic drawing of the Jupiter subclassification of Type II Monteggia fractures. A, Type 2A includes distal olecranon and triangular coronoid process fractures, (B) Type 2B includes a proximal ulna fracture at the metaphyseal-diaphyseal junction distal to the coronoid, (C) Type 2C includes a purely diaphyseal ulna fracture and (D) Type 2D includes an ulna fracture that extends from the trochlear notch including the coronoid fragment to the metaphyseal region often with notable comminution.
In our experience, the Jupiter classification more accurately determines the complexity of the surgical reconstruction and prognosticates clinical outcome. There are three main variables that directly affect the complexity of the injury: (1) coronoid fracture, (2) radial head fracture, and (3) ulnohumeral instability.[9–11]
The Mason classification of the radial head and the number of fracture fragments is commonly considered by the surgeon to determine treatment. No clear treatment consensus exists, and the choice is often deferred to the surgeon's preference. The outcomes for isolated radial head open reduction and internal fixation (ORIF) and radial head arthroplasty are favorable.[13,14]
J Am Acad Orthop Surg. 2020;28(19):e839-e848. © 2020 American Academy of Orthopaedic Surgeons