A periprosthetic fracture is a broken bone that occurs in or around an existing joint replacement implant. It can happen during the surgery itself or, more commonly, months to years afterward. These fractures most often affect the hip, knee, and shoulder, and they represent one of the more serious complications of joint replacement surgery. After a primary hip replacement, the risk ranges from 0.1% to 18%, depending on patient factors. After knee replacement, rates fall between 0.3% and 5.5%, and after shoulder replacement, between 0.5% and 3%.
Why These Fractures Happen
The bone surrounding a joint implant is not the same as healthy, untouched bone. Over time, the implant changes how mechanical forces travel through the bone, and areas that no longer bear normal loads can gradually thin and weaken. This process, called stress shielding, leaves the bone more vulnerable to fracture. Add osteoporosis, aging, or loosening of the implant, and the risk climbs further.
Many people who experience a periprosthetic fracture don’t recall any significant fall or trauma. A large number sustain the break during ordinary daily activities: standing up from a chair, stepping off a curb, or turning in bed. This pattern reflects the underlying fragility of the bone rather than the force of the injury. A history of previous fragility fractures is common in these patients.
Specific risk factors include older age, female sex, obesity, smoking, diabetes, low bone mineral density, and implant loosening. Obesity increases mechanical stress at the bone-implant interface, which can accelerate loosening. Revision surgeries (a second or third replacement of the same joint) carry substantially higher fracture rates: 4% to 11% after revision hip replacement, and up to 30% after revision knee replacement.
Symptoms and How It’s Diagnosed
The most common symptom is sudden, severe pain in the thigh or leg along with an inability to walk or bear weight. Some people, though, have a more subtle presentation: a vague, persistent ache in the thigh while still being able to get around. This less dramatic version can delay diagnosis.
Doctors typically order X-rays of the entire limb, from the hip down to the ankle, to see the full length of bone surrounding the implant. This wide view helps determine exactly where the fracture is in relation to the implant and whether the implant itself has shifted or loosened. In some cases, a CT scan provides finer detail and three-dimensional reconstruction that helps with surgical planning.
How Periprosthetic Fractures Are Classified
Surgeons use classification systems to decide the best treatment. For hip fractures, the Vancouver system is the most widely used. It divides fractures into three types based on location and implant stability:
- Type A: Fractures around the bony bumps (trochanters) at the top of the thighbone. These are usually stable and often heal without surgery.
- Type B: Fractures near or just below the stem of the implant. This is the most critical category because it depends on whether the implant is still firmly fixed (B1), loose with good surrounding bone (B2), or loose with poor bone quality (B3). Each scenario requires a different surgical approach.
- Type C: Fractures well below the tip of the implant, essentially treated as a standard broken bone.
For knee replacements, the Rorabeck classification considers whether the fracture is displaced and whether the implant is still functioning. A Type I fracture is undisplaced with an intact implant. Type II is displaced but the implant is fine. Type III involves a loose or failing implant, displaced or not, which changes the treatment plan entirely.
Treatment Options
Treatment depends almost entirely on whether the implant is still solidly attached to the bone. When it is, surgeons typically repair the fracture with plates, screws, and sometimes pieces of donor bone to reinforce the area. This approach, called open reduction and internal fixation, leaves the existing implant in place and focuses on healing the bone around it.
When the implant has loosened, the fracture alone can’t be fixed without also addressing the failed implant. In these cases, revision surgery replaces the original implant with a longer-stemmed version that bypasses the fracture site and anchors into healthier bone further down the limb. If the surrounding bone is severely weakened, structural bone grafts or specialized implants originally designed for bone tumors may be needed to rebuild the area.
The choice between fixation and revision also factors in the patient’s overall health. Fixation is a less invasive procedure and tends to be chosen for patients who are frailer or have significant medical conditions. Younger patients may also benefit from fixation when possible, because preserving healthy bone gives surgeons more options if another revision is ever needed down the road.
Recovery Timeline
Recovery varies by fracture type and treatment. Minor fractures around the trochanters (Type A) that don’t require surgery are typically managed with protected, limited weight-bearing for 6 to 12 weeks, followed by a gradual return to full activity. For fractures treated with revision surgery, patients are often allowed to put weight on the leg as tolerated much sooner, since the new implant provides immediate structural support.
Regardless of the approach, rehabilitation is a slow process. Most patients need physical therapy to regain strength and mobility, and a full return to pre-fracture function isn’t guaranteed, particularly for older adults. The fracture itself, combined with the period of immobility, can lead to significant muscle loss and deconditioning.
Serious Risks and Mortality
Periprosthetic fractures carry real danger, especially for older patients. One-year mortality following a periprosthetic femur fracture is roughly 17% to 18%, with 80% of those deaths occurring within the first three months after injury. Age is the strongest predictor of this risk. In-hospital complications include kidney failure, respiratory failure, and serious infections.
These numbers are comparable to the mortality seen after standard hip fractures in elderly patients, reinforcing that periprosthetic fractures are not minor complications. They demand prompt treatment and careful postoperative management.
Reducing Your Risk
The single most impactful thing you can do to protect a joint replacement is to maintain bone health. A large study of over 35,000 patients who had hip replacement for a fracture found that those who received osteoporosis treatment within a year of surgery had a 10-year fracture rate of 3.9%, compared to 5.9% for those who went untreated. After adjusting for other factors, treatment reduced the risk of a periprosthetic fracture by about a third.
Fall prevention matters just as much. Removing trip hazards at home, improving lighting, maintaining leg strength through regular exercise, and managing medications that cause dizziness all reduce the chance of the kind of low-energy falls that cause these fractures. Since many periprosthetic fractures happen during routine activities rather than dramatic accidents, even small improvements in balance and bone density make a meaningful difference.