Review Question - QID 220889

This is a 40-year-old female with an acute capitellum fracture after a fall. Posterior comminution is associated with a higher complication rate and less favorable outcomes compared to cases without posterior comminution (answer 3).

Capitellum fractures are intra-articular elbow injuries involving the distal humerus. They account for approximately 6% of all distal humerus fractures and occur after a low-energy fall onto an outstretched hand. The direct, axial compression with the elbow in a flexed position produces shear forces in the capitellum. These are associated (up to 60%) with other elbow injuries, including radial head and/or LUCL injuries. These are diagnosed on plain radiographs, with the lateral x-ray demonstrating a "double arc" sign created from subchondral bone in the capitellum and the lateral portion of the trochlea. CT scans can also be obtained for advanced imaging of the articular surface. Treatment relies on the fracture pattern, amount of displacement, and patient factors. Nonoperative treatment can be in the form of posterior elbow immobilization for fractures displaced <2mm. In those with >2mm of displacement, open reduction and internal fixation (ORIF), arthroscopic-assisted ORIF, fragment excision, and total elbow arthroplasty (TEA) are potential treatment options. Worse outcomes and higher complication rates have been associated with the presence of posterior comminution in capitellar fractures, as they typically require TEA or olecranon osteotomies for more extensive exposure.

Marinelli et al. conducted a retrospective cohort study to investigate the impact of posterior comminution in capitellum fractures on treatment and prognosis. They included 45 patients (17 without posterior comminution and 28 with it) from 2007 to 2015 at a single center. In this study, all type A fractures (without posterior comminution) were treated via a lateral elbow approach and screw fixation. In contrast, the type B (with posterior comminution) fractures were treated with elbow arthroplasty or olecranon osteotomy. They reported that Mayo Elbow Performance Index scores and range of motion were significantly better postoperatively in the type A group compared to the type B group, with considerably fewer complications (29% vs 64%, respectively). In conclusion, the presence of posterior comminution in capitellar fractures predicts significantly poorer results compared to those without comminution.

Carroll et al. reviewed capitellar and trochlear fractures. They explained the importance of thorough assessments due to their high association with other injuries. Surgical treatment (open or arthroscopic) is indicated in those with displacement and comminution. In conclusion, the ultimate goal of treatment is to obtain a stable, anatomic reduction with early range of motion.

Figure A is a lateral radiograph of the elbow demonstrating a displaced capitellum fracture with the characteristic "double arc" sign.

Incorrect Answer Choices:
Answer 1: A single fragment with >2mm of initial displacement demonstrates better outcomes with ORIF, typically in the form of headless compression screws. These injuries tend to have better outcomes compared to those treated with TEA or procedures requiring an olecranon osteotomy, such as in the case of fractures with posterior comminution.
Answer 2: Coronal shear patterns typically shear off as a single fragment and therefore demonstrate better outcomes with ORIF, typically in the form of headless compression screws. These injuries tend to have better outcomes compared to those treated with TEA or procedures requiring an olecranon osteotomy, such as in the case of fractures with posterior comminution.
Answer 4: 5mm of vertical/proximal displacement following reduction is an indication to fix this fracture. Given the pattern of displacement, this is likely a coronal shear fracture and is better fixed with ORIF. This treatment strategy typically does not predispose these fractures to worse outcomes when compared to posterior comminution.
Answer 5: Fractures extending into the lateral portion of the trochlea can be fixed appropriately with ORIF and headless compression screws. This does not typically predispose these fractures to worse outcomes when compared to posterior comminution.