Capitellar fractures are rare and may only be encountered a few times over an orthopaedic surgeon’s career. However, with knowledge of the “pitfalls” that exist with these injuries, the surgeon can correctly diagnose and properly treat these fractures with fair to good results.

This article should be really be entitled “capitellar and trochlear fractures.” The most important message a treating surgeon should remember is that fractures of the capitellum commonly extend medially to include the trochlea. If this is not recognized, then the treating surgeon may be in for a surprise at the time of surgery.

Injury Mechanism and Pattern

Like many other injuries, understanding the injury mechanism and injury pattern is crucial. This has been best highlighted by two Canadian authors.1,2 Direct axial compression transmitted to the capitellum by the radial head with the elbow in a semiflexed position can create a shear fracture of the anterior portion of the capitellum. Displacement is often significant, resulting in a block to elbow flexion. A thorough evaluation of the shoulder and wrist should be completed to rule out concomitant injuries. In particular, radial head, interosseous membrane, and distal radial ulnar joint (DRUJ) injuries should be identified. It is important to assess if there is extension of the fracture into the trochlea, as this can affect implant selection and surgical approach.

AP, lateral, and radiocapitellar radiographs are recommended. The lateral X-ray will reveal the amount of displacement and the classically described “double arc” sign, which represents extension of the capitellum fracture into the trochlea. Even with high-quality X-rays, the injury pattern may not be fully appreciated. CT (3D is often helpful) should be performed in most cases (Figures 1a-3b).


Figure 1a


Figure 1b

Figures 1a and 1b. AP and lateral radiographs of an elbow with a comminuted fracture of the capitellum and trochlea. Note the “double arc” sign.


Figure 2. CT scan of the same injury.


Figure 3a.


Figure 3b

Figures 3a and 3b. AP and lateral radiographs of the same case at 6-month follow-up. Note fixation with multiple minifragment screws.

Dubberley et al classified capitellum fractures into three types and included a modifier (A or B) to indicate the absence or presence of posterior comminution

  • Type 1 fractures, are isolated to the capitellum.
  • Type 2 fractures have medial extension and include a significant portion of trochlea.
  • Type 3 fractures consist of separate capitellum and trochlea fragments. A type 3B fracture would indicate separate capitellar and trochlear fragments with posterior comminution.  

Type 2 and type 3 fractures require a larger exposure to gain access to both the capitellum and trochlea

ORIF by Fracture Type

Once the injury pattern is appropriately understood, then ORIF can be performed with more confidence. Type 1 fractures (capitellum only) can be exposed laterally through a separate or combined Kocher or EDC split approach. For small, unreconstuctible fragments (in the setting of an isolated injury), excision is an option, but fixation is favoured in most cases. Once a reduction is achieved, small screws, headless screws, and threaded wires can provide anterior to posterior fixation, whereas small fragment screws (with or without plate fixation) can offer posterior to anterior fixation.

Type 2 and 3 fractures (trochlear involvement) often necessitate a more extensile lateral approach. The anterior approach (EDC split or Kaplan) is extended proximally by releasing the extensor muscle origin off the supracondylar ridge and reflecting the capsule off the anterior humerus. The attachment of the LUCL at the lateral epicondyle should be preserved. If further exposure is required, LUCL release from the lateral epicondyle can be considered. Secure isometric repair of the LUCL is necessary. An olecranon osteotomy can also be considered, particularly when there is significant posterior comminution. Even with proper exposure and meticulous preoperative planning, achieving secure anatomical fixation can be difficult and frustrating.

Simple capitellar fractures can be straightforward to fix; but be aware of more complex fracture patterns. Proper preoperative assessment including CT (in most cases) will help you better assess the fracture, plan your fixation, and avoid any surprises.

References

  1. McKee MD, Jupiter JB, Bamberger HB. Coronal shear fractures of the distal end of the humerus. J Bone Joint Surg Am 1996 Jan;78(1):49-54.
  2. Dubberley JH, Faber KJ, Macdermid JC, Patterson SD, King GJ. Outcome after open reduction and internal fixation of capitellar and trochlear fractures. J Bone Joint Surg Am 2006 Jan;88(1):46-54.

Reprinted with permission from the Summer 2010 issue of COA Bulletin

Attachments:


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