What is Periprosthetic Distal Femur Fracture?
Total knee replacement provides a solution for people suffering from knee osteoarthritis. Advances in surgery methods, pain management, patient suitability, and implant design now allow a wider range of people to undergo this treatment, sometimes even as an outpatient procedure. By 2030, it’s estimated that the number of knee replacements will shoot up to about 3.5 million, a staggering 673% increase when compared to 2005.
Thanks to advancements in medical treatment and science, people are now living longer than before. As a result, the demand for knee replacements has surged, resulting in a rapid increase in fractures that occur around the space where the implant was placed. This type of fracture is one of the most challenging surgeries an orthopedic surgeon has to perform. Therefore, detailed preparation before surgery and referring patients to a highly skilled surgeon is absolutely crucial for a successful operation.
What Causes Periprosthetic Distal Femur Fracture?
Periprosthetic fractures, which are breaks that occur around the area of a bone implant, are more common in certain situations. These include:
– Being female, often due to hormonal imbalances
– Suffering from Osteoporosis or Osteopenia, conditions that weaken bones
– Having Neuromuscular diseases such as Parkinson’s, epilepsy, or ataxia
– Having a cognitive disorder like dementia
– Using some certain medications for a long time, like steroids
– Living with inflammatory joint diseases like rheumatoid arthritis or osteoarthritis
– Having infections
– Having had a total knee replacement (as this can cause notching in the femur, or bone stress)
– Some specific characteristics of the implant, like its level of constraint or if it causes wear to the polyethylene component.
Risk Factors and Frequency for Periprosthetic Distal Femur Fracture
Periprosthetic fractures, or breaks around a joint replacement, occur about 300,000 times a year, making up 0.3% to 2.5% of all fractures. When a total knee replacement surgery is redone, it can increase the risk of these fractures to as high as 38%. These complex procedures are best handled by orthopedic surgeons with training in trauma or joint replacement. They can use careful techniques and a variety of treatment options to manage these cases.
- There are around 300,000 cases of periprosthetic fractures a year, accounting for 0.3% to 2.5% of total fractures.
- Revision total knee replacement surgery can raise the risk of these fractures to 38%.
- Orthopedic surgeons with trauma or arthroplasty training are best equipped to handle these complicated surgeries.
- These surgeons use careful techniques and numerous treatment options during the procedures.
Signs and Symptoms of Periprosthetic Distal Femur Fracture
People who come to the hospital with broken bones near the knee joint often won’t remember any major accidents. Instead, they might tell the doctors about a small stumble or twist that brought them there. These patients may also mention past fractures or falls, offering hints about the state of their bones. In most cases, they’ll report pain in the affected leg and trouble walking. During the physical check-up, doctors generally don’t see any obvious deformity. However, the patients usually react strongly to movement or touch at the knee and the lower thigh bone area.
Some common features include:
- Small stumble or twist
- History of fractures or falls
- Pain in the affected leg
- Difficulty in walking
- Strong reaction to knee movements or touch on the lower thigh bone
Testing for Periprosthetic Distal Femur Fracture
If you’re suspected of having a fracture around the knee joint area, doctors usually start by getting a complete x-ray of your leg, from hip to ankle. It’s essential to take a good look at the hip and knee as this helps doctors figure out what types of medical devices they can use for treatment. They need to check whether the medical device or implant has moved from its original position; this is very important as it could affect the treatment options.
One common method is using a ‘retrograde intramedullary nail’, a special kind of metal rod inserted inside the bone. However, if the implant is poorly positioned or not compatible with this method, then it might not be a suitable option. Existing metal devices from previous treatments within the body could also limit the choices of treatment. Sometimes, just an x-ray might not be sufficient, and a CT scan also is required.
CT scans give finer detail and can even allow 3D reconstruction of the fracture. A possible complication could be an infection around the knee joint. If signs of infection exist, doctors need to carry out additional tests to confirm this even before they decide on the final course of treatment. Knowing the exact kind of implant used during previous surgeries can help doctors plan the treatment more effectively.
In the world of orthopedics, doctors use specific systems to classify fractures – think of these as categories based on how severe the fracture is. The classification system aids them in deciding the best treatment. There are various such systems, like the ‘Neer’, ‘Lewis and Rorabeck’, and ‘Su’ systems, each one categorizing fractures based on parameters like the extent of displacement (movement from the original place) and the condition of the implant.
For instance, in the ‘Neer’ system:
– Type I represents a non-displaced (<5mm) fracture.
- Type II indicates a displaced fracture, with further categories whether it's displaced medially or laterally.
- Type III describes a fracture involving the area above the knee and the shaft of the femur.
Doctors choose the course of treatment depending on the category of the fracture, which could range from fixing the fracture where it is, replacing the femur's end, or in extreme cases, amputating the leg above the knee.
Treatment Options for Periprosthetic Distal Femur Fracture
When someone suffers a fracture in the lower part of the thighbone where a prosthetic knee is attached (a periprosthetic distal femur fracture), the first priority is to immobilize the area. This could involve using a knee brace or long leg splint, depending on factors such as the extent of the displacement, the patient’s discomfort, and body shape. In severe cases where the surrounding tissue or nerves are at risk, emergency stabilization with an external device may be needed.
While non-surgical treatment is rarely recommended, some patients who are unable to undergo surgery may have to take this route. Such patients are often bed-bound and would require regular check-ups to ensure there is no tissue damage around the fracture. They might be treated with a cast, knee brace, or other device, but there is a significant risk that the bone may not heal correctly (nonunion), which might necessitate surgery in the future.
Operative fixation is the preferred treatment for these types of fractures that have been displaced, i.e., bones separated at the fracture site. Advances in technology have improved surgical options aiming at limited incision and enabling the patient to put weight on the leg sooner after surgery.
Different types of devices are used depending on the fracture type and the presence of a prosthesis. Conventional and locking plates are often used for stable fractures when the prosthetic knee components do not interfere. On the other hand, intramedullary nails can offer another treatment option that may require less soft tissue dissection and allow the patient to bear weight earlier.
If there’s enough existing bone, a revision total knee replacement might be performed, particularly for severely unstable fractures. However, in the most serious cases, other measures might be necessary. For instance, if the bone stock is inadequate and the prosthetic knee is unstable, the lower part of the thighbone might be replaced. While this can be complex and costly, it can also shorten surgery time, allow immediate weight-bearing, and reduce the risk of complications due to immobilization. In critically ill patients with infection and an unstable prosthetic knee, an above-knee amputation might be necessary.
What else can Periprosthetic Distal Femur Fracture be?
Before using X-ray or other imaging techniques to examine a patient, doctors will consider several possible causes of the patient’s symptoms. These include:
- Fracture around the joint implant
- Loosening of the joint implant without infection
- Infection in the joint implant
- Ligament injury
- Breakage of the implant, which could involve either the metal or plastic parts
- Bruising
- Dislocation of the knee
- Blood clot in the veins, also known as venous thromboembolism
- “Hidden” fracture that’s not immediately visible
Once these possibilities are considered, the appropriate tests can be conducted for a correct diagnosis.
What to expect with Periprosthetic Distal Femur Fracture
Distal femur fractures and hip fractures are known to have a significant mortality rate of 30%. Between 1992 and 2009, a study analyzed the medical cases of 92 patients, most of whom were women (78%), and aged around 77.9 years. The vast majority of these fractures were closed (95%) and did not extend to the joint (76%). In over half of the cases (52%), the fractures occurred around an artificial knee joint. After ten years, the overall mortality rate was seen to be 38%.
The mortality rate was noted to increase at specific time intervals – 30 days, six months, and one year – with respective rates of 6%, 18%, and 25%. The report also highlighted several factors that could affect patient outcomes. Patients who were already in poor health before surgery, were very old, and had limited mobility, often had a difficult time recovering after surgery with many related medical complications. Additionally, complex fractures involving significant bone loss were best treated by surgeons who had extensive experience in tackling such challenging issues.
Possible Complications When Diagnosed with Periprosthetic Distal Femur Fracture
There are a number of complications that can occur with surgical bone repair. These troubles can include delayed healing, the bone failing to join back together, issues with the surgical hardware, or infection. This issue of the bone not joining, termed “nonunion,” is a problem in both surgeries and non-surgical treatments. Some research suggests not opting for a particular closed treatment for fractures near artificial knee joints, as about 20% and 23% of patients experienced nonunion and painful malunion (incorrect bone healing), respectively.
Further studies showed that a considerable 35% of patients who opted against surgery ended up needing a revision arthroplasty (a second surgery) due to nonunion. The utilisation of locking technology alongside plates technology has shown promise, particularly in more fragile bones. This method has indicated lower rates of incorrect bone healing (at 20%) and only slightly higher rates of nonunion (4.2%) when compared to another surgical approach.
However, when comparing methods, the other surgical approach of using intramedullary nails had a lower nonunion rate than the locking plate method, at 5.1% versus 11.3% respectively. Infections were found in up to 9% of cases when using plate fixation. This method also involved a larger surgical approach, potentially bringing more trauma to the bone and surrounding soft tissue.
Additionally, plate fixation on fractures near artificial knee joints has the risk of surgical screws failing. This eventually may lead to bone misalignment. Adding to complications, there can be extreme stiffness of the knee, injuries to nerves or blood vessels, and further wound complications in some surgical cases.
Common Complications:
- Delayed healing
- Nonunion
- Hardware failure
- Infections
- Painful malunion
- Revision arthroplasty for nonunion
- Higher trauma in in-situ plate fixation
- Surgical screw failure
- Extreme stiffness of the knee
- Neurovascular injuries
- Wound complications
Recovery from Periprosthetic Distal Femur Fracture
The ideal situation after any bone-related surgery is for the patient to bear weight immediately. The introduction of devices called intramedullary nails, which help to distribute the weight placed on the bone, has significantly reduced the number of patients who require restrictions on weight-bearing. Advances in these implant technologies have also expanded its use for breaks or fractures towards the end of the bone.
Intramedullary nail fixation is one of these devices and allows patients to bear weight immediately after surgery. This means they can walk sooner and begin targeted physical therapy earlier, which helps to limit problems that can arise from not being able to move or bear weight.
However, some specific fractures, like those around a joint replacement in the lower thigh bone (distal femur), which are treated exclusively with a method called plate fixation, may require the patient to limit weight-bearing for weeks to even months. Needless to say, making a patient immobile for a long period after surgery can significantly increase the risk of complications, which is why surgeons aim to avoid this as much as possible.
Preventing Periprosthetic Distal Femur Fracture
Preventing falls is key to avoiding bone breakages. Both family doctors and surgeons should focus on improving the health of the patient’s bones and reducing any factors that might lead to falls. It’s important to follow the U.S. Preventive Services Task Force’s advice on Dual-energy x-ray absorptiometry, often known as DEXA scans. Also, supplements and medicines may be required, depending on what the medical team thinks is best for the patient. If a person feels unstable when walking alone, using supportive devices can help.
