Periprosthetic Fracture Knee

A prosthesis refers to an implant which is inserted into the body. In terms of orthopaedics this can relate to any metalwork such as screws, plates, pins and also joint replacement components. A fracture can range from a hairline crack through to complete displacement of the bone or fractures in multiple pieces. Periprosthetic fractures refers to a break in the bone surrounding an implant. These fractures may be close enough to the implant that they result in the implant becoming loose.

PERIPROSTHETIC JOINT REPLACEMENT FRACTURES

These types of fractures can occur around any type of joint replacement: shoulder, elbow, wrist, hip, knee or ankle as well the other less common joint replacement locations. The most common location is in the thighbone (femur) near either a total hip or a total knee replacement.

PERIPROSTHETIC PLATE, SCREW OR PIN FRACTURES

These types of fractures occur around plates, screws or pins which were generally put in previously to treat earlier fractures. They tend to occur at the ends of the plates or pins but can also result in the metalwork being broken also. Periprosthetic fractures are most often caused by:

• High energy injuries such as car or motorbike accidents
• Falling directly onto the body part
• Direct blows to the bone
• Where there has been non-union (no healing) of a previous fracture
• Where bone has been weakened due to wearing out of a joint replacement

Conditions that weaken the bone such as osteoporosis may increase the risk of fracture on injury. The symptoms of periprosthetic fractures to any bone include:

• Pain with weight bearing if the lower limbs are affected
• Swelling and bruising
• Localised tenderness
• Visible deformity
• Numbness or tingling of the affected body part

If you are experiencing any of the symptoms above following an injury, you should see your doctor or present to the emergency department. Your doctor will discuss your symptoms and nature of the injury and conduct a physical examination. Your doctor will refer you for an x-ray to view the affected bones. A CT (computed tomography) scan will often to be useful to better appreciate the fracture. An MRI (magnetic resonance image) scan will rarely be required to identify injury to other surrounding structures such as the ligaments. These fractures can be associated with damage to the nerves and vessels of the leg. If this is the case further investigations may be required. Fractures that are aligned can sometimes be immobilised with a cast or brace, and you may be  given instructions on non-weight bearing or restricted use for a period of time. The majority of periprosthetic fractures will require surgery. Treatment will depend on the cause of the fracture and also its severity. If they occur around joints replacements and the implants remain stable within the bone then usually the bone can be fixed using screws and plates. If the implants of a joint replacement are loose within the bone due to a fracture, then that may mean a new joint replacement needs to be inserted. A course of physiotherapy is also normally required following treatment of these injuries. Complications:

• Infection and wound breakdown
• Blood clots
• Damage to the blood vessels or nerves
• Prominence of the metal work, may require removal
• Failure of fixation – sometimes the bones are not strong enough to be held together with plates, screws or wires. This will often require further surgery
• Swelling and stiffness
• Nonunion – non-healing of the bone.

Factors increasing the risk of nonunion include:

• Smoking
• Osteoporosis
• Diabetes
• Infection