Fractures or breaks of the bone above or around a total knee replacement (artificial joints or prostheses) are becoming more common over time. These are called peri- (around) prosthetic fractures. These mostly involve the distal femur or thigh bone. They can also involve the top of the tibia; but this is less common.
Very large muscles with good blood supply surround the femur or thighbone. This can help the bones heal. However, because the thigh has many large muscles, breaks can be very painful due to the muscle spasm or cramping. Sometimes breaks can occur between a total hip replacement and a total knee replacement.
Mechanism and Epidemiology
More than 350,000 total knee replacements occur each year in North America alone. Since total knee replacements are commonly put in people over the age of 50, these injuries are more common in older adults. Falls are the primary cause. These falls can be from standing height, from a chair, in the shower, or even getting out of bed. As you age, your bones can become weaker. This means a very short fall may cause a break. There is some evidence that parts of the bones may become weaker after a joint replacement. Other trauma such as a motor vehicle accident can also cause these fractures whether the bone is weak or not. Since people are living longer and getting more knee replacements, these types of injuries have become more common over time.
A break in the femur (thigh bone) is a serious injury. It generally means that you cannot put any weight on that leg and will require an ambulance to take you to the hospital. In the hospital, you may be given many tests that do not focus on your leg. These are important to make sure you do not have any other injuries or other medical problems. Other injuries may include broken bones or injuries to your head. It is important to tell the emergency team if you hit your head or if you do not remember what happened. This is to make sure your head, heart, and other body parts are uninjured.
In the emergency room, you may be placed in traction, in a brace, or in a splint. These are used to keep your injured leg from moving and becoming more damaged. Traction may require putting a pin into your leg bone. This pin will be attached to weights to pull on your leg to straighten it out. This helps decrease your pain while lying in bed, since it allows your muscles to relax and keeps them from cramping up and moving your bone. The decision to do this will be made with your treating physician.
You will likely be admitted to the hospital. You may even be transferred to another, more specialized hospital to take care of your other injuries or broken leg. More tests may be needed for you and your leg. These include x-rays, CT scans, and other tests for your heart and head.
Nearly all of these fractures require surgery. How the surgery is done depends on several things: where your fracture is in the thigh bone, if the break touches your knee replacement parts, what type of knee replacement you have, how strong or thick your bones are, or if you have a hip replacement above your knee replacement, and many other factors. Your surgeon will talk to you about the options. The three typical options are:
- a plate with screws or cables
- a nail that goes through part of your knee replacement and into the center of your thigh bone
- a new knee replacement that replaces part of your femur, or a combination of these options
All of these options are big operations, and your surgeon will pick the one they think will best to fix your specific fracture.
Sometimes the surgeon is limited by the type of knee replacement you have. Some knee replacements have metal portions in the femur that can make putting screws around them difficult, and some do not have a space for a nail to go through the middle. It can be very helpful to know the doctor’s name who performed your knee replacement. This allows your surgeon to contact them and try to find out what type of total knee they put in.
This can be a long surgery. Sometimes your surgeon may have help from another surgeon who specializes in joint replacements. It is also common to require a blood transfusion before, during or after surgery.
After surgery, your leg will be in pain. Your nurses and doctors will work with you to control your pain. It is likely that you will still have some pain, since too much pain medication can cause problems, including breathing issues, confusion, and difficulty peeing and pooping.
Depending on your particular fracture and how it was fixed, you may or may not be able to put weight on your leg. You may also be placed in a brace or splint to keep your knee from moving. This all depends on your specific injury, and what your surgeon thinks is needed to allow your break to have the best chance of healing. You will need to do physical therapy during your hospital stay. Physical therapists assess how safe you are doing activities. You may need to use a cane, walker, or even a wheelchair. Many patients cannot take care of themselves and need some time at a rehab facility or skilled nursing facility.
A good number of people with this injury are able to return to doing what they could do before the break. Many factors contribute to the long-term outlook after this injury. These include other injuries that happened at the same time, the strength of the person before and after their injury, as well as how fast they heal. It is common to need a cane or walker after this type of injury. It is extremely important to prevent future falls or injuries. It may be a good idea to get your bone health assessed to help prevent other fractures, and this may require seeing a bone health specialist. Talking to your surgeon and primary care doctor about the health of your bone is a good place to start.
Sometimes the plates and screws or nails used to fix the fracture need to be removed. That requires another operation. Sometimes the break does not heal and requires another surgery to try to get the bone to heal. Regardless of the injury, your knee replacement may wear out over time. Stiffness and weakness are also common. Because this break happens in an older population, it is often harder and/or takes longer for them to recover than young people.
Christopher Domes, MD
Edited by the OTA Patient Education Committee and Justin Haller, MD (section lead)
All x-rays and pictures taken from the personal collection of Dr. Domes