The shear fractures of the capitellum are rare fractures both in children and adult patients. Due to the anatomical features of the elbow, their diagnosis can be often missed or delayed. For this reason, in the pediatric literature, these fractures have been grouped among the so-called TRASH injuries, an acronym that stands for “The Radiographic Appearance Seemed Harmless”, including also osteochondral fractures of the radial head and lateral condyle, incarcerated medial epicondylar and unossified medial condylar fractures, transphyseal separations of the distal humerus, and Monteggia lesions (1). The anatomy of the pediatric elbow is characterized by six ossification centers, merged in radio-transparent physes, which fuse during adolescence in a sequential order, beginning from the capitellum, trochlea and olecranon around the age of 14 (2). Consequently, any injury before the fusion of the ossification centres can cause chondral or osteochondral fragments that can be missed on radiographs, especially if small in size.

Capitellar shear fractures account for less than 1% of elbow fractures in both pediatric and adult patients (3–7). In children, they usually affect adolescents around the age of 14, just before the fusion of the ossification centre (8, 9). These fractures are generated by an axial load towards the humeral paddle with an elbow in extension or semiflexion, as in a fall on the outstretched arm (10–12). Depending on the flexion or extension of the elbow at injury, the fracture fragment can be anterior or posterior. These fractures can also be generated by a posterolateral elbow dislocation or subluxation, due to the impact of the radial head and coronoid against the capitellum (10–12). Even though in many cases they are isolated, the capitellar shear fractures can be associated with other injuries of the lateral column, such as radial head or neck fractures, lateral condyle fractures, lateral collateral ligament complex avulsion, but also medial condyle and olecranon fractures (13).

There are two main classifications of capitellar shear fractures in use for children and adults, the modified Bryan-Morrey and Dubberley (4, 14). The Bryan-Morrey classification distinguishes these injuries into three types, mainly depending on the fracture size of the fragment (4). Type 1, also called Hahn-Steinthal fracture, is an isolated fracture of the capitellum, characterized by a single fracture fragment including both the chondral and subchondral component of the capitellum, eventually extended to the lateral trochlear ridge. Type 2, the Kocher-Lorenz fracture, is a thin articular cartilage fragment of the capitellum. Type 3, also called Broberg-Morrey fracture, has the same extension as Type 1 but is comminuted. McKee added a fourth type to the Bryan-Morrey classification, that extends up to the trochlear groove (4).

Dubberley classified capitellar fractures into three types, differentiated by the extension in the trochlea, each one distinguished in type A and B, according to a more anterior or posterior involvement of the capitellum on the sagittal plane (14). In this classification, Type 1 is like a Hahn-Stenthal fracture, involving the lateral trochlear ridge, Type 2 describes a capitellar fragment that extends in the trochlear groove, and Type 3 is comminuted, with at least a capitellar and a trochlear fragment.

Due to the anatomy and the timing for the ossification of the pediatric elbow, the capitellar shear fracture diagnosis can be missed or delayed. In clinical practice, distinguishing these patterns of injuries requires not only a radiological diagnosis but also high clinical suspicion. The reason stands in the high cartilaginous component of the pediatric elbow, making impossible a direct radiographic diagnosis of small chondral fragments. Radiographs rather show a double contour sign, when the fracture involves the subchondral bone or just a fat pad sign in the case of a small chondral fragment (11). What leads clinicians to further investigate the injured elbow is the clinical appearance of a swollen and tender elbow, eventually accompanied by hematoma. The limitation of motion is not only related to pain but also to a mechanical blockage of the elbow amplitude related to the interposition of the fragment. In these cases, investigations are usually pursued with a computed tomography scan (CT) or magnetic resonance imaging (MRI) of the elbow, to characterize the fracture pattern and plan the surgery. The surgical approach and osteosynthesis or fragment excision are planned based on the imaging, leaving margins for the intraoperative adaptation of the strategy. Since there is no consensus on the best management, we aimed to describe two cases treated in our institution and provide a narrative review of available pediatric literature.

We carried out a narrative review of the pediatric literature for capitellar shear fractures (shown in Table 1). Most of the literature consists of case reports (5–8, 13, 16, 17, 20–23, 25–27, 29–31, 33, 38), followed by a smaller number of retrospective case series (9, 18, 19, 24, 28, 32, 34–37). The retrieved literature showed a bimodal distribution of these fractures, with a first peak in childhood (<10 years) (7, 17, 20, 31) and a second one, the most representative, in pre-adolescents and adolescents (5–9, 13, 16, 18, 19, 21–25, 27–30, 32–38). The most frequent associated injury was the ipsilateral elbow dislocation, followed by the involvement of the medial or lateral condyle, or an olecranon or radial head fracture (5, 16, 17, 21, 31, 37, 38).

The radiographs are the baseline exam for diagnosis, accompanied by a clinical suspicion. Before the advent of CT and MRI, arthrography was perioperatively used in selected cases or oblique radiographs were carried out to better visualize the fragments (7, 20). The use of CT and MRI has improved the diagnosis of capitellar shear fractures, allowing us to visualize them early and plan the treatment. According to the time elapsed between the accident and the management, it is possible to distinguish between fractures that are diagnosed early in the acute post-traumatic period or whose diagnosis is delayed. The availability of CT and MRI, within the first weeks from the injury, allowed setting a threshold of two weeks between the acute and delayed diagnosis (36). In fact, in most of the studies on the delayed finding of capitellar shear fractures, the diagnosis was stated between five post-traumatic weeks up to three years, with most of the cases between 3 and 6 months from the accident (8, 13, 21, 22, 30, 37).

As far as the classification is concerned, the most used one was the Bryan-Morrey, followed by the Dubberley. A few studies published in the 80ies and 90ies were rather descriptive in the definition of the fracture or used the Salter-Harris classification (6, 7, 16, 17). An orthopedic surgery team from Harvard provided their classification, based on the sagittal appearance of the capitellar shear fractures (9). By reversing the perspective provided by Dubberley, they proposed a classification distinguishing between anterior (Type 1) and posterior (Type 2) osteochondral fractures of the capitellum and chondral fractures (Type 3) (9). The perspectives offered by the mentioned classifications open the discussion for surgical planning. One of the most important elements for the planification of the surgical approach is a coronal extension of the fracture and any associated injury requiring surgical management (13, 18). The available literature shows that the most used approach is the lateral, especially through the Kocher interval between the anconeus and extensor carpi ulnaris (also called the posterolateral approach) (39). This allows a good exposure of both posterior and anterior fractures of the capitellum. For most anterior fractures, the options are the lateral approach through the Kaplan interval, between extensor carpi radialis brevis and extensor digitorum communis, but in rare cases also the anterior and anterolateral approach, especially for large fragments anteriorly displaced and with medial extension or in case of associated injuries to the lateral column (13, 18). To a lesser extent, also bilateral approaches or the posterior (eventually transolecranon) approach have been used (16, 17, 32, 36, 37).

The most used devices for osteosynthesis are screws and Kirschner wires. The latter were usually percutaneously fixed, allowing the removal between three to eight postoperative weeks (5, 6, 17, 20, 33). The headless screws, put on the sagittal plane of the fractures, have taken the place of the cancellous screws, not requiring another surgery for hardware removal, and being well tolerated in most of the cases. Some authors have also used osteosuture (22) or bioabsorbable pins (26, 35, 37). In the case of small fragments generating a mechanical blockage in the joint, whose size does not allow any fixation, these fractures are accessible for excision by an open or even arthroscopic approach (9). Finally, capitellar shear fractures can also be accessible to the conservative treatment for non-displaced fractures (9, 18, 21, 24, 30). In brief, the surgical indication lies in a symptomatic displaced fracture of the capitellum, where the most relevant determinant for surgical management is a mechanical blockage to the elbow range of motion.

When considering the timing of diagnosis, most of the cases with a prompt diagnosis were managed with open reduction and internal fixation. This was probably related to the fact that the fractures characterized by a remarkable displacement were promptly diagnosed on conventional radiographs. The fractures whose diagnosis was delayed were susceptible to all treatment strategies, from a conservative attitude when the clinical status allowed, rather than fragment excision or fixation (8, 13, 21, 22, 30).

In many cases, the treatment allows good and uneventful clinical and radiological outcomes. Among the postoperative complications, we can distinguish between the clinical manifestations with limitation of function, especially extension, persistent pain and even blockage. On one hand, the limitations to the elbow amplitudes can be related to soft tissue contractures, eligible for arthrolysis when the functional arc of motion is affected. On the other, pain and blockage can be the epiphenomenon of radiocapitellar osteoarthritis, capitellar necrosis and, in rare cases, loose fragments or cartilage defects, requiring surgical management (5, 9, 21, 30, 32, 36, 37). When distinguishing between the early and delayed diagnosis, the available literature showed that there was not a propensity for radiocapitellar osteoarthritis and capitellar necrosis in delayed cases, but these seemed to be equally distributed. One case of malunion requiring a corrective osteotomy was also described in the literature (21).

Our case report showed the story of two adolescents with a capitellar shear fracture Type 1 and 4 according to Bryan-Morrey classification, surgically treated with open reduction and internal fixation by headless screws and K-wires, respectively, with complete recovery of function and radiological union at follow-up. According to our experience and the review of the literature, the diagnostic and therapeutic work-up of the pediatric shear fractures of the capitellum starts with a clinical and radiologic suspicion, based on the double contour sign or indirect signs of elbow injury (joint effusion, soft tissue edema) on standard radiographs. In pre-adolescents and adolescents, the diagnostics should be pursued to the CT, which not only allows the confirmation of the diagnosis, but also the choice of the treatment strategy, conservative or surgical. The CT scan also provides relevant information as the site where the fragment is displaced, which will guide the choice of the surgical approach, and its size, useful in the planning of the fixation method (Figure 3). The CT scanner is more widely available compared to MRI, that should be used for children due to the higher cartilaginous component, or in pre-adolescents and adolescent to clear associated injuries (ligamentous lesions, for instance).

The narrative review is limited by the impossibility of drawing statistical conclusions due to the predominance of case reports in the pediatric literature. The predominance of case reports has justified the performance of a narrative review rather than a systematic one. The description of complications and sequelae could be affected by the follow-up time of individual studies, varying between 4.5 months to 8 years. The limitation of retrospective case reports or case series are mainly represented by the recall and selection bias as well as the missing data related to the retrospective collection. To overcome these limitations, future research should rather aim to produce prospective studies, testing clinical guidelines and collecting predetermined clinical-radiologic variables and outcome measures, in the setting of multicenter studies. These data could aid to clearly define the diagnostic strategy that avoids the delayed diagnosis and treatment of these fractures, and standardize their management.

The interest in pediatric capitellar shear fractures lies not only in their challenging diagnosis and treatment but also in the sequelae that can develop and their further management. Future research should prospectively study these pediatric fractures, not only to draw decisional trees but also to find out the predictors of outcome, especially for the development of severe sequelae such as radiocapitellar osteoarthritis and osteonecrosis of the capitellum.