Fracture after Knee Replacement

Fractures after knee replacement surgery are a rare complication that may require revision knee replacement. Periprosthetic knee fracture may occur as a result of a fall/trauma after the surgery or may occur without any history of trauma/fall as a result of a loose component or mal-aligned component.

Fractures around the prosthetic knee joint that are not displaced may be treated with nonsurgical treatment options, however, displaced fractures usually require surgical treatment.

A knee replacement surgery is done after all nonsurgical methods of treatment have been tried for knee arthritis. The surgery involves cutting the diseased ends of the bones forming the knee joint. The lower part of the thigh bone (femur) is cut and replaced with a femoral component. Similarly, the upper part of the shin bone (tibia) is cut and replaced with a tibial component. The undersurface of the kneecap is usually resurfaced and a plastic component is fixed to it.

The periprosthetic fracture after knee replacement may occur during the surgery, immediately after the surgery, or days/weeks/years after the surgery. The fracture may occur in the femur, the tibia, or the patella. There may be certain risk factors associated with periprosthetic knee fracture such as:

• Inflammatory arthritis such as rheumatoid arthritis increases the chances of fracture after knee replacement.
• Elderly patients who may have a metabolic bone disorder such as osteoporosis are at an increased risk for periprosthetic fractures.
• Long-term steroid use may weaken the bones and to periprosthetic fractures after knee replacement.
• Certain neurological diseases such as Parkinson’s disease, epilepsy, polio, etc. may increase the risk for fracture.
• Localized factors such as stiffness of the knee, aseptic osteolysis, infection increase the chance of periprosthetic fracture.

Femoral periprosthetic fractures

The fracture inner side of the lower end of the femur (medial femoral condyle) occurs mostly during the surgery. The management of femur periprosthetic fractures depends upon the location of the fracture and the stability of the prosthesis.

Non displaced stable periprosthetic fractures may be managed with nonoperative methods use as braces or casting. Fractures above the prosthesis with a stable prosthesis may be fixed with a nail or a metal plate which is fixed with screws.

A loose femoral component is managed with a revision involving a femoral component with a long stem. Rarely, an extensive fracture in the elderly may require the replacement of the entire lower end of the femur (distal femoral replacement).

Tibial periprosthetic fractures

Tibial fractures occur most commonly due to mal-aligned components or in patients with a prior history of tibial surgery. Nonsurgical treatment in the form of bracing/casting may be done for nondisplaced stable fracture. Unstable fractures with a stable prosthesis may be managed with plates, cables, wires, etc. Fractures with an unstable prosthesis are revised usually with a long stem prosthesis.

Patellar periprosthetic fractures

Kneecap (patella) fractures are common in cases where the patella is resurfaced with a plastic prosthetic component. Fractures of the patella occur commonly due to intraoperative surgical techniques. Damage to the blood supply of the patella may lead to patellar bone death and subsequent fracture.

Irregular resurfacing of the patella, inappropriate thickness of the residual patella, and the use of single peg implants have been associated with patellar periprosthetic fractures.

Patellar fractures leading to disruption of the extensor mechanism (the ability to raise a straight leg), or with an unstable prosthesis are managed with surgical treatment. The surgical treatment may consist of removal of the patella, wire fixation, partial removal of the patella, revision of prosthesis, etc.

Stable fractures may be fixed with nonsurgical methods such as casting/bracing. Patients with periprosthetic patella fractures may complain of only minor pain in front of the knee as compared to tibial or femoral periprosthetic fractures where the pain is severe prompting a visit to the ER.

Summary

Knee replacement surgeries are some of the most successful surgeries in modern medicine. Complications are rare and patient satisfaction rates are very high. Periprosthetic knee replacement fractures are rare with the use of modern implants and techniques.

Surgeon experience in knee surgeries is an important fracture that may determine the outcome of the surgery. Periprosthetic fractures usually require operative treatment and a surgeon well trained in revision surgeries may offer the best management of the fractures.