Our family has come up against what we’ve been told is a “rare” problem: a coronal shear fracture of the elbow. The surgeon is going to put some compression screws to hold it all together until healing takes place. We’ve been warned that there could be some complications and problems down the road but that this is rare. What kind of problems are we talking about here?

Coronal shear fractures of the elbow describes a break in the lower end of the humerus (upper arm bone). The elbow has some unusual and very individual anatomy that can make a difference after injuries. Fractures and dislocations can alter the normal bumps and grooves that give the elbow joint its alignment. So it might help you to have a little idea of the anatomy in this area to appreciate some of the possible complications.

The elbow is a hinge joint with its major point of axis for movement and rotation where the bones of the forearm insert into the humerus. The bottom of the humerus called the trochlea is spool-shaped. The top of the ulna (one of two bones in the forearm) wraps around this spool to form the hinge.

There is also the humeroradial joint where the humerus meets the radius (the second bone in the forearm). This joint is formed by a knob and a shallow cup. The knob on the end of the humerus is called the capitellum. The capitellum fits into the cup-shaped end of the radius, also called the head of the radius.

There are three basic types of fractures, depending on whether the fracture affects the medial side of the capitellum (type one), the capitellum and trochlea broken off as one piece (type two), or there is a fracture line on either side of the trochlea making three separate pieces (type three).

Treatment for any of these types of coronal shear fractures of the distal humerus requires surgery. Studies show too many problems develop when the nonsurgical approach is taken. Without surgical correction, patients end up with chronic pain, painful clicking of the elbow, and mechanical instability.

Surgery to pin the bones together with metal plates and screws or just screws alone has the best results. This procedure is called open reduction and internal fixation (ORIF). The goals of surgery are to match up the joint surfaces, allow for early joint motion, and reduce the risk of posttraumatic problems. Matching up joint surfaces (called restoring articular congruity) can be a challenge because the bottom of the humerus (where it meets the other half of the elbow) has five different shapes. Each of those five surfaces must slide and glide evenly to provide normal motion and prevent wear and tear and eventual joint degeneration.

Complications occur if the bones don’t heal properly causing either malunion (mismatch of the bone edges) and subsequent deformity or nonunion (failure to heal). Joint instability, painful motion, limited movement, and loss of function are natural consequences of these kinds of problems. Other complications (though rare as mentioned) are possible such as infection, stiffness, or joint contracture (joint can no longer move through its full range of motion but gets “stuck” after only going so far). That all sounds very dire but in fact, it is estimated that good-to-excellent results are obtained in more than 90 per cent of all cases treated with surgery. Most patients end up with a stable, durable joint with smooth joint function.