Monteggia Fractures: Pearls and Pitfalls RobertD3XX Cole Turner, MD,D4XX † and ChristineD1XX A. Ho, MDD2XX * The entity of Monteggia fractures describes a spectrum of fracture-dislocations in which the radiocapitellar joint becomes disrupted in association with an ulnar shaft fracture. While these injuries are relatively uncommon in the pediatric population, they pose both a diag- nostic and therapeutic challenge, as the constellation of these injuries can be subtle and difficult to identify. As such, they are often missed or neglected in the setting of a minimally displaced ulnar shaft fracture in which the radiocapitellar dislocation goes unrecognized. There is a wide spectrum of treatment strategies for pediatric Monteggia fractures, from closed reduction and immobilization in the acute setting to extensile open reconstructive techniques for chronic cases. Outcomes can be variable depending on the time of treatment and age of the patient. The most important principle for management of these injuries is early recognition and close follow-up to prevent poor outcomes. Oper Tech Orthop 29:34-42 © 2019 Elsevier Inc. All rights reserved. KEYWORDS monteggia, elbow, pediatric Introduction and therefore under-recognizes plastic deformation (Fig. 1). It is critical to restore this anatomical relationship between the proxi- fi iovanni Monteggia rst described in 1814 two cases with a mal radius and ulna to the distal humerus when treating Mon- G combined a proximal third ulna fracture and an associated teggia fractures. In the pediatric population, this relationship is 1 anterior radiocapitellar dislocation. It was not until the 1960s most often driven by the character of the ulna; however, other that Jose Bado coined the eponym known today as the Monteggia soft tissue structures may impede the restoration of the normal lesion; in his seminal manuscript, he observed other variants of anatomical architecture. the Monteggia lesion, describing ulna fractures in locations other than the proximal third and describing posterior and lateral radial head dislocations.2,3 His classification is still used today. As multiple variants of Monteggia fractures exist, it is most Epidemiology accurately described as a forearm fracture with dislocation of the 4 Pediatric Monteggia fractures are relatively uncommon. Their proximal radioulnar joint. Subtle bowing of the ulna shaft with true incidence is likely unknown, but Letts et al reported an asssociated radiocapitellar dislocation may be missed by the only 33 cases over the course of 5 years at their children's inexperienced clinician who is looking for a forearm fracture hospital in Winnipeg, Canada.5 The peak incidence in their series was in children aged 7-10. More recently, Joeris et al *Department of Orthopaedic Surgery, Texas Scottish Rite Hospital for Chil- performed a comprehensive pediatric classification of long dren and Children's Health Dallas, University of Texas Southwestern bone fractures out of Switzerland over a 2-year period. Out Medical School, Dallas, TX. y of 2292 upper extremity fractures in children, 26 were Mon- Department of Orthopaedic Surgery, Tripler Army Medical Center, teggia fractures, comprising 1.1% of cases.6 Ninety-six per- Honolulu, HI. Grant support: None cent of these were children younger than 11 years old. Institution: From Texas Scottish Rite Hospital for Children and Children's Medical Center, Dallas, Texas Financial disclosures: No conflict of interests is disclosed. Address reprint requests to Christine A. Ho, MD, Department of Orthopaedic Anatomy Surgery, Texas Scottish Rite Hospital for Children and Children's Health Dallas, University of Texas Southwestern Medical School, E2300-E2.01, 1935 The anatomical relationship of the radius and ulna is crucial Medical District Drive, Dallas, TX 75235. E-mail: [email protected] for proper rotational motion. They are held together along 34 https://doi.org/10.1053/j.oto.2018.12.007 1048-6666/© 2019 Elsevier Inc. All rights reserved. Monteggia Fractures: Pearls and Pitfalls 35 diastasis of the PRUJ, in addition to radiocapitellar incongru- ence, is necessary to diagnose a Monteggia fracture.8,9 Because of their intimate association, displaced proximal or midshaft forearm fractures of one bone frequently result in a fracture or dislocation of the other due to the nature of the high energy mechanism.4 Figure 1 Anteroposterior (AP) forearm radiographic view of an 18- The muscular anatomy contributes to the deforming forces month-old child who fell from the couch. Note the subtle apex of Monteggia fractures. In hyperextension mechanisms, the anterior bow of the ulna with radiocapitellar dislocation; this Bado biceps brachii acts to pull the proximal radius anterior rela- Type I Monteggia lesion is easily underappreciated. tive to the capitellum, which is the most common Monteggia fracture-dislocation, a Bado Type I.7 their length, distally by the distal radioulnar ligamentous Surrounding neurovascular structures may also experience complex, by the interosseous membrane along their shafts, either compression or traction injuries after Monteggia fractures, and the proximal radioulnar joint (PRUJ) at the level of the which usually result in a transient neurapraxia. Because of its rel- elbow (Fig. 2). Altering the osseous structure or any of their atively closer proximity to the radial head and neck, the poste- connections along the length of the forearm can be detrimen- rior interosseous nerve is at particular risk. tal to regaining functional arcs of motion. Specifically for cases of Monteggia fractures, the quadrate and annular liga- ments are crucial structures for maintaining reduction of the PRUJ and radiocapitellar joint.7 Some even argue that the Classification Originally described as a proximal third ulna fracture with anterior dislocation of the radial head,1 Bado was the first to thoroughly describe the 4 distinguished types of Monteggia fracture-dislocations in the series of 40 patients that he treated.2,3 In his description, the type was defined by the direction of the radial head dislocation, which is always in the direction of the apex ulnar deformity (Table 1). In Bado's series (which included both adults and chil- dren), type I was the most common at 60%, followed by type III (20%), then type II (15%), and lastly type II. In chil- dren, the majority (>60%) are type I,6,10 followed by type III; types II and IV are relatively rare in children.10,11 Bado also described several Monteggia type I equivalents; the most common of these include a fracture of the ulnar shaft associated with a fracture of the proximal radial epiphy- sis or radial neck12; and another is a pure anterior dislocation of the radial head, which likely is associated with plastic ulnar deformation.7 Mechanism of Injury Each Bado type is associated with a different type of mecha- nism of injury. Type I Monteggia fractures alone have multi- ple proposed mechanism: a direct posterior blow to ulna,1,13 body rotation around a fixed and hyperpronated forearm,3 and hyperextension during which the biceps pulls the radial Table 1 Bado’s Classification of Monteggia Fracture- Dislocations Type I Radial head is dislocated anteriorly Type II Radial head is dislocated posteriorly Type III Radial head is dislocated laterally; the ulna frac- ture is often a proximal metaphyseal green- stick fracture Type IV Radial head is dislocated anteriorly, but both the Figure 2 Volar view of the multiple ligamentous structures connec- radius and ulna are fractured ting the radius and ulna. 36 R.C. Turner and C.A. Ho head anteriorly and the ulna fractures from bearing the full problem faced in treating these children because it may lead weight of the body.14 to missed or delayed diagnosis.9,10 This is true both in the Type II fracture-dislocations occur after a flexed elbow is acute setting as well as during the follow-up period. Weis- longitudinally loaded.12 Type III result from a varus exten- man et al described 2 delayed diagnoses of Monteggia frac- sion force at the elbow.3,9 tures: initially both were isolated ulnar fractures with congruent radiocapitellar joints, but as the ulna angulated in the cast, the radial head followed and dislocated from the radiocapitellar joint.18 Diagnosis While some Monteggia patterns may show obviously dis- Evaluation of children with Monteggia fractures usually placed ulnar fractures and radiocapitellar dislocations, care reveal an obvious deformity about the proximal forearm and should be taken when assessing for subtle dissociation of the elbow.7 The child will likely have limited range of motion in proximal radioulnar joint or incongruity of the radiocapitel- both flexion-extension and pronation-supination. Depending lar joint. on the amount of radiocapitellar dissociation, there may be a Classic dogma has taught that a line drawn down the longitu- palpable radial head. It is important to have a high index of dinal axis of the radius should pass through the center of the suspicion for associated ipsilateral upper extremity injuries, capitellum in all views regardless of the amount of flexion or especially in children with Bado type II lesions.15,16 Exami- extension of the elbow.13,18 This has been described as the nation of skin should be thorough to rule out possible open radiocapitellar line, or RCL. However, the RCL may not be as fractures, and prereduction neurovascular status is important reliable as originally thought to predict the congruence of the to compare to postreduction or postoperative findings. Pedi- radiocapitellar joint and defineaMonteggiafractureoranequiv- atric patients with missed or neglected Monteggia fractures alent thereof. Silberstein et al state that the RCL may miss the may not present until they are adults. In such cases, there capitellum completely on the anteroposterior (AP) view in may be obvious elbow deformities and neurologic deficits, young child.19 Likewise, Miles and Finlay recommend caution such as cubitus valgus and tardy ulnar nerve palsy.17 in using the RCL as they identified 5 normal pediatric elbows in which this line did not intersect the capitellum.20 These authors recommend limiting the use of the RCL to the lateral radiograph.