Fracture of the Capitellum

 

Fractures of the capitellum are rare and usually occur in the coronal plane and can be difficult to diagnose. Fracture of the capitellum is similar to Hoffa fracture of the distal femur. Both fractures are coronal, difficult to diagnose, and the x-ray may miss the fracture. failure to diagnose this fracture and treat it appropriately can lead to a poor patient outcome. The Bryan and Morrey Classification has four types. Type I is a large fragment of bone and articular cartilage sometimes with trochlear involvement. Type II is a shear fracture of the articular cartilage. The articular cartilage is separated with a small shell of bone. Type III is a comminuted fracture of the capitellum. Type IV is the Mckee Modification; it is a coronal shear fracture that extends medially to include the capitellum and trochlea. You can see double bubble or a double arc on the lateral x-ray of the elbow. One arc represents the capitellum, and the other arc is the lateral ridge of the trochlea. The double arc sign is a pathognomic finding of the capitellar fracture and is usually seen in the lateral elbow x-rays. In more than 50% of the time, capitellum fracture may be associated other injuries such as radial head fracture or lateral ulnar collateral ligament injury. Fracture of the capitellum can cause mechanical block to movement of the elbow. The fracture can be seen on the lateral x-ray of the elbow, however CT scan is helpful in showing the fracture adequately. Nonoperative treatment for nondisplaced fracture is to give the patient a splint for less than 3 weeks followed by range of motion. Open reduction internal fixation is done for displaced fractures. We rarely excise the capitellum, but you may get into this situation if the fragment is displaced and causing symptoms and if most of the fragment is cartilage attached to a thin piece of bone and the fragment could not be fixed. You will try to fix it first before you excise it. Excision is done for Type III fractures, for comminuted and displaced fractures, especially if there is a block to movement of the elbow. Small displaced, insignificant fractures can be excised if it is causing pain or mechanical block to elbow motion. Excision of a large fragment of the capitellum can create a problem of developing arthritis or instability, especially if the medial collateral ligament is injured. Do total elbow arthroplasty when there is a comminuted fracture of the capitellum that extends to the medial column and the fracture is unreconstructable and the patient is old. For open reduction internal fixation, the ideal visualization of the fracture is usually provided by a lateral approach (Kaplan or Kocher approach). The patient is usually in the supine position. Elevate the common extensor tendons and the capsul anteriorly off the lateral column and use headless compression screws from anteriorly to posteriorly. The fracture is partial articular and vertical shear. Going anteriorly to posteriorly will allow excellent compression and stability of the fracture. Countersink the screws. Bury the screw heads beneath the articular cartilage anteriorly. Try to avoid destabilizing the lateral ulnar collateral ligament and try to make the dissection more anterior to the equator of the radial head. Try to avoid disruption of the capitellum blood supply that comes from the posterolateral area. Stay anteriorly to avoid these two problems. A complication of capitellar fractures is elbow stiffness. Surgery to fix the capitellar fracture will help in gaining the functional range of motion, but the patient will have residual stiffness. Surgery is probably better than no surgery, but the reoperation rate is high due to the residual stiffness of the elbow.