A Closer Look at Elbow Replacements
Elbow fractures, specifically radial head bone fractures, make up about five per cent of all fractures and are frequently caused by falling on an outstretched arm. If the fractured bones are aligned enough that they can heal on their own, the elbow is protected for a period of time, followed by physical therapy for full return to function. If the fractured bones are not well aligned then surgeons must go in and stabilize the bones with hardware.
The elbow joint is made up of three bones, the ulna, radius (both forearm bones), and the humerus (your upper arm bone). The end of the radial bone is shaped like a disc and articulates with the end of the humerus at a divot called the capitulum. Because of the unique shape of the radial head and the combined movements of the ulna and the radius, our elbows not only bend and straighten but our forearms are able to rotate as the radial head spins.
Advancements in technology and surgical techniques now allow for actual replacement of the radial head. This is appropriate in cases where the radial fracture is so bad that it cannot be reconstructed, incidences of elbow instability, poorly healed fractures, elbow arthritis, or when there is a combination of elbow dislocation and radial head fracture.
Several types of radial head implants are now available. Loose fitting prosthesis anatomically mimic the original radial head and are placed “loosely” in the radial bone. They are thought to stabilize the joint by acting as a block between the joint. The loose fitting prosthesis is not believed to be able to further loosen or cause pain from implant placement and has a full arc of articulation with the capitulum. Out of 13 patients with a loose fitting prosthesis placement queried at 38 months after surgery, eight reported excellent results, three good, and two fair results. Press-fit stems are another option. These are also modeled after the radial head in design. They are fitted as tightly as possible in the radial bone. Press fit stems tend to have good to excellent results but there is greater chance of implant loosening than with a loose fitting prosthesis. A bipolar implant consists of a fixed stem but a mobile head, which melds the two previously mentioned implants. The greatest benefit of a bipolar implant is the improved arc of contact between the implant and the capitulum, however the greatest complication is the implant can dislocate.
Complications from radial head replacement can include elbow stiffness, nerve damage, bone deposition in soft tissue, and pain. Authors point out, however that most of these reported complications are most likely due to the original trauma and not the elbow replacement surgery. Wear and tear on the neighboring bone, the capitulum, is a long-term complication that is currently unavoidable.
Rehabilitation following surgery focuses on restoring functional motion. The elbow is splinted for seven to 10 days followed by full active and assisted movement of bending and straightening the elbow. Elbow rotation (supination, pronation) is allowed with the elbow bent to 90 degrees. If patients are lacking full range of motion at the six-week mark, then physical therapy is prescribed. Elbows with instability are only allowed to move through a specific range prescribed by the surgeon for three weeks, followed with unrestricted movement after that time period.
As implants and surgical techniques improve, success rate of radial head replacement surgery ultimately lies with the skill and knowledge of the surgeon and an excellent understanding of implant designs and indications.
References: Daniel C. Acevedo, MD. et al. Radial Head Arthroplasty: State of the Art. In Journal of American Academy for Orthopedic Surgeons. October 2014. Vol. 22, No 10. Pp. 663-642.Back