In this report, two orthopedic surgeons from the University of Michigan help other surgeons classify and manage a rare fracture of the elbow. The fracture is called a coronal shear fracture of the distal humerus.
Distal humerus refers to the bottom end of the upper arm bone, which forms the top half of the elbow joint. This lower end of the humerus bone is shaped with a round knob called the capitellum. Next to this knob is a spool-shaped area called the trochlea. A coronal shear fracture tells us that the fracture has separated one or both of these two areas of the bone.
Classification of the fracture is based on severity and is important to help guide treatment. 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).
The classification scheme has an additional subgrouping to describe a clean fracture or one with tiny bone fragments (called communition). The fracture may be impacted (bony ends pushed together) or displaced (bony ends separated). If the fracture is displaced, the bone may be shifted posteriorly (back away from the humerus). X-rays and CT scans are used to identify all areas of damage and determine the type of classification. This information is essential in making treatment decisions.
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). In fact, it is estimated that good-to-excellent results are obtained in more than 90 per cent of all cases treated with ORIF. Patients end up with a stable, durable joint with smooth joint function. There can be complications (e.g., arthritis, stiffness, infection, nonunion or malunion), but these are rare.
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.
Surgeons interested in treatment approaches and best methods of fixation to achieve optimal outcomes will find this article helpful. The authors provide drawings, descriptions, and X-rays to help the surgeon visualize the potential problems and create a plan of care for each patient.
Although research has not been done to reach agreement on the optimal method of fixation, they recommend a variable-pitch, headless compression screw. They also offer advice regarding placement of screws and avoidance of complications like damage to nerves and/or blood vessels.