A patellar fracture is a break in the patella, or kneecap, the small bone that sits at the front of your knee. Because the patella acts as a shield for your knee joint, it is vulnerable to fracture if you fall directly onto your knee or hit it against the dashboard in a vehicle collision. A patellar fracture is a serious injury that can make it difficult or even impossible to straighten your knee or walk.
Some simple patellar fractures can be treated by wearing a cast or splint until the bone heals. In most patellar fractures, however, the pieces of bone move out of place when the injury occurs. For these more complicated fractures, surgery is needed to restore and stabilize the kneecap and allow for the return of function.
The patella can fracture in many ways. A fracture may be a simple, clean, two-piece break or the bone can break into many pieces.
A break can occur at the top, center, or lower part of the bone. Sometimes, fractures occur in more than one area of the kneecap.
TYPES OF PATELLAR FRACTURES
This type of fracture is nondisplaced. The pieces of bone may remain in contact with each other or be separated by just a millimeter or two. In a stable fracture, the bones usually stay in place during healing.
In a displaced fracture, the broken ends of the bone are separated and do not line up correctly. The normally smooth joint surface may also be disrupted. This type of fracture often requires surgery to put the pieces of bone back together.
In this type of fracture, the bone shatters into three or more pieces. Depending on the specific pattern of the fracture, a comminuted fracture may be either stable or unstable.
In an open fracture, the bone breaks in such a way that bone fragments stick out through the skin or a wound penetrates down to the bone. An open fracture often involves damage to the surrounding soft tissues and may take a longer time to heal.
Open fractures are particularly serious because, once the skin is broken, there is a higher risk for infection in both the wound and the bone. Immediate treatment is required to prevent infection.
The most common symptoms of a patellar fracture are pain and swelling in the front of the knee. Other symptoms may include:
Inability to straighten the knee or keep it extended in a straight leg raise
Inability to walk.
Patellar fractures are most often caused by:
Falling directly onto the knee
Receiving a sharp blow to the knee, such as might occur during a head-on vehicle collision if your kneecap is driven into the dashboard
The patella can also be fractured indirectly. For example, a sudden contraction of the quadriceps muscle in the knee can pull apart the patella.
If the pieces of bone are not out of place (displaced), you may not need surgery. Your doctor may apply a cast or splint to keep your knee straight and help prevent motion in your leg. This will keep the broken ends of bone in proper position while they heal.
Depending upon your specific fracture, you may be allowed to bear weight on your leg while wearing a cast or brace. With some fractures, however, weight bearing is not allowed for 6 to 8 weeks. Your doctor will talk with you about restrictions on weight bearing.
If the pieces of bone are out of place (displaced), you will most likely need surgery. Fractured patellar bones that are not close together often have difficulty healing or may not heal. The thigh muscles that attach to the top of the patella are very strong and can pull the broken pieces out of place during healing.
TIMING OF SURGERY.
If the skin around your fracture has not been broken, your doctor may recommend waiting until any abrasions have healed before having surgery.
Open fractures, however, have an increased risk of infection and are scheduled for surgery as soon as possible, usually within hours. During surgery, the cuts from the injury and the surfaces of the bone are thoroughly cleaned out. The bone will typically be repaired during the same surgery.
The type of procedure performed often depends on the type of fracture you have. Before the surgery, your doctor will discuss your procedure with you, as well as any potential complications.
These two-part fractures are most often fixed in place using screws or pins and wires and a “figure-of-eight” configuration tension band. The figure-of-eight band presses the two pieces together.
This procedure is best for treating fractures that are located near the center of the patella. Fracture pieces at the ends of the kneecap are too small for this procedure. Breaks that are in many pieces can be over-compressed by the tension band.
Another approach to a transverse fracture is to secure the bones using small screws or small screws and small plates.
In some fractures, the top or, more commonly, the bottom of the patella is broken into several small pieces. This type of fracture occurs when the kneecap is first pulled apart from the injury, and is then crushed when the patient falls on it. Because the bone fragments are too small to be fixed back into place, your doctor will remove them. He or she will then attach the loose patellar tendon back to the remaining patellar bone.
If the kneecap is broken in many pieces at its center and the pieces are separated, your doctor may use a combination of wires and screws to fix it. Removing small portions of the kneecap that cannot be reconstructed may also have good results. Complete removal of the kneecap is a last resort in treating a comminuted fracture.
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