Capitellar Fractures

Steve Papp, M.D., FRCSC
Ottawa, ON

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.

Like many other injuries, understanding the injury mechanism and injury pattern is crucial. This has been best highlighted by two Canadian authors1, 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.

PAPPFigure1B

Figure 1(A/B) - AP and Lateral of elbow with a comminuted fracture of the capitellum and trochlea. Note the "double arc" sign.

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 trochlea1. 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. Dubberley et al. classified capitellum fractures into three types and included a modifier (A or B) to indicate the absence or presence of posterior comminution2. 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.  Both type 2 and type 3 fractures will require a larger exposure in order to gain access to both the capitellum and trochlea

PAPPFigure2

Figure 2: 3D-CT Scan of the same injury.

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 K-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.

PAPPFigure3A PAPPFigure3B

Figure 3(A/B) - AP/Lateral radiograph of the same case at six-month follow-up. Note fixation with mutiple minifragment screws.

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. Good Luck!

References

  1. McKee M.D., Jupiter J.B., Bamberger H.B. Coronal shear fractures of the distal end of the humerus. J Bone Joint Surg Am. 1996 Jan;78(1):49-54.
  2. Dubberley J.H., Faber K.J., Macdermid J.C., Patterson S.D., King G.J. Outcome after open reduction and internal fixation of capitellar and trochlear fractures. J Bone Joint Surg Am. 2006 Jan;88(1):46-54.

 

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