Periprosthetic Fracture

Broken bones around a joint replacement are called periprosthetic fractures. MedicalRF.com / Getty Images

A periprosthetic fracture occurs when a bone that surrounds an orthopedic implant is broken.  Most common after hip or knee replacement, periprosthetic fractures can be serious complications of joint replacement that often requires additional surgery.

As prosthesis is another word used to describe orthopedic implants, and the most common fractures around implants occur after joint replacement.  Therefore, the term periprosthetic fracture is used to describe a broken bone that occurs in the bone surrounding a joint replacement implant.

Why Bones Break Around Implants

  • Stress Riser: A stress riser is an area where stress on the bone is focused as a result of a nearby implant.  For example, patients who have orthopedic implants in both the hip and knee, may have an area between the implants where forces on the bone are concentrated creating a stress riser.  This area of the bone may be more prone to injury because or the concentrated forces.
  • Stress Shielding: Metal implants can alter forces that stimulate bone growth.  Normal bone responds to stress by thickening and becoming stronger.  In patients with implants supporting the bone, it is possible that bone surrounding the implant weakens and becomes more susceptible to fracture.
  • Loose Implants: Loose implants can cause the bone around the implant to break.  As the implant moves once it becomes loose, the bone can weaken and eventually lose the ability to support the implant.

    All of these factors can lead to weakening of the bone surrounding the prosthesis and susceptibility to fracture.  As more and more replacements are being surgically implanted, especially with growth in the number of hip and knee replacements being performed, the numbers of periprosthetic fractures are rising.

      More active patients are having joint replacements, and more young patients are having joint replacement; factors that are leading to a rising number of periprosthetic fractures occurring.

    Other factors should also be considered as possible reasons the bone fractured, including pathologic fractures, infections of the implant, and osteoporosis.

    Treatment of Periprosthetic Fractures

    Treatment of a fracture around a joint replacement is difficult and must be managed on a case by case basis.  There is no single method used to treat all fractures, but here are some of the possibilities:

    • Non-Surgical Treatment: Nonsurgical treatment may be appropriate for a small number of periprosthetic fractures.  However, in most periprosthetic fractures, particularly in the lower extremity, surgery is the recommended treatment.
    • Repair The Broken Bone: If the joint replacement is held solidly in the bone (i.e. not loose), then the bone is typically repaired.  It can be a challenge repairing the bone because the usual hardware may not be able to be used because the joint replacement may be in the way.  Orthopedic companies make a variety of specialty plates, screws, and rods that can be used in these circumstances to repair the fracture.
    • Revision Joint Replacement:  If the joint replacement is loose, the fracture repair is typically accomplished with the placement of a new joint replacement, called a revision joint replacement.  Revision replacement is often complex surgery that requires specialized implants and significant rehabilitation after surgery.

    Rehab After Surgery

    Rehabilitation after surgical treatment of a periprosthetic fracture can be more complicated and prolonged when compared to typical knee replacement rehab and hip replacement rehab.  Often patients need to limit weight-bearing on the extremity, and the rehabilitation typically takes longer to resume normal activities.

    Sources:

    Shah RP, et al. "Periprosthetic Fractures Around Loose Femoral Components" J Am Acad Orthop Surg August 2014 ; 22:482-490.

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