The terrible triad refers to a potentially devastating –and yet common– elbow injury.
Three bones meet at the elbow joint. The bone in the arm is called the humerus. The bones in the forearm are called ulna and radius. The articulating ends of the upper part of the ulna are called coronoid and olecranon. The articulating end of the upper part of the radius is called radial head. The radius and ulna behave as a retaining wall, preventing the lower part of the humerus (distal humerus) to jump over.
Proper joint function requires that the surfaces of the joint are smooth, and that the bones track perfectly during motion. Joint smoothness is provided by articular cartilage, a very specialized tissue layered at the articulating ends of bones. The friction between cartilage surfaces is less than the friction between two ice-cubes! Arthritis basically means articular cartilage degeneration, leading to pain and occasionally poor motion. Perfect tracking during motion requires that the shapes of the bones are normal, and that bones are kept assembled together by soft-tissues, namely ligaments and muscles. Ligaments are thick bundles of collagen fibers that connect bones to each other, preventing them from coming apart. In the elbow, there are two main ligaments, one on each side of the joint: the lateral collateral ligament and the medial collateral ligament.
What is an elbow terrible triad? “Triad” means three. A terrible triad combines three injuries: dislocation of the elbow, fracture of the radial head, and fracture of the coronoid. In some accidents, the elbow dislocates (the radius and ulna are pulled apart from the humerus) without any bones breaking; surgeons call this injury a “simple dislocation”. Elbow dislocation results in tearing of the lateral collateral ligament, and in many cases (not all) the medial collateral ligament. In a “terrible triad”, as the radius and ulna dislocate, they hit the humerus and sustain fractures.
The combination of the two fractures plus ligament tearing makes it almost impossible for the elbow to stay located: the bundles of collagen that used to keep the bones together are torn, and the fractured radial head and coronoid can easily escape under the distal humerus. Without surgery, and even with surgery when not perfectly performed, elbow instability may persist. Persistent instability will not only generate pain and inability to use the arm, but will also lead to rapid degeneration of the articular cartilage: the elbow can quickly become arthritic.
Evaluation – Terrible triads are pretty substantial injuries. Patients presenting right after the injury will have marked deformity and severe pain due to the dislocation and fractures. The first evaluation often takes place in an emergency room (ER). Due to the relatively small size of the fractures and overlapping of structures, computed tomography with three-dimensional rendering (3D-CT) is necessary in most of these injuries to visualize the fractures properly.
Management – Relocating the dislocated joint by manipulation should be performed as soon as possible. This procedure is called “closed reduction”, typically performed under sedation or anesthesia. The ER doctor or surgeon will move the forearm relative to the arm to place the elbow bones in the right position. Due to the fractures of the radius and coronoid, in terrible triads the elbow will want to come out of place again, although complete redislocation can be prevented in many circumstances by immobilizing the elbow bent beyond 90 degrees. Without surgery, terrible triads lead to a poor outcome most of the time.
The problem is that even with surgery, until relatively recently, reported outcomes were also poor in many, hence the term “terrible”. This was due to (1) difficulty fixing the very small fractured pieces, (2) failing to fix the coronoid fracture, and (3) poor healing of the lateral collateral ligament. Luckily, elbow specialists have come up with sound strategies to restore the best possible stability and function to the elbow joint after a terrible triad. Rarely, if the elbow is still somewhat unstable after all, the surgeon will apply a temporary external metal frame called external fixator that will be removed within the first few weeks, after some healing occur. If the radial head is fractured in too many pieces, there are metal replacements.
Care after surgery – Obtaining a good outcome after surgery for a terrible triad requires a balance between motion exercises –so that the elbow does not freeze and become stiff–, and protection –so that the fractures and ligaments heal properly. Right after surgery, most elbows are immobilized with a splint for 2 to 3 weeks. When motion is initiated, two aspects are essential to understand: (1) active motion is better than passive motion, and (2) gravity is our enemy. Why is active motion better? Well, when we activate our muscles to move the elbow, as they contract they also pull the joint together, protecting it from redislocation. And what about gravity? If you think about it, every time we lift an object with our hand, the combined weight of the forearm and the object will tend to stretch out the lateral collateral ligament.
Complications – These can include instability and stiffness. The former is more difficult to solve than the latter. Loss of motion to some extent is very common after terrible triads, but if most of the motion is recovered, you will feel you can perform most activities [elbow motion] even if your elbow does not come out fully straight or does not bend all the way up. Many individuals will develop some arthritis over time, although the radiographs may look worrisome for many patients, the elbow actually hurts very little, and function is good. With good surgical care, the terrible triad may not be as terrible anymore.
— I sigh every time I read this. My injury was even worse than this. You can read about it in the category ‘My Story’. You can start at the beginning here.