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Periprosthetic fractures after TKA entail three treatment options
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 Mark W. Pagnano |
There are three chief treatment modalities for periprosthetic fractures after total knee arthroplasty: an intramedullary nail through the knee joint, a locked periarticular plate, and replacement of the old prosthesis and all broken bone with a distal femoral replacement device, according to an orthopedic investigator.
“These fractures have been difficult to address for years and years, but now there is more of a streamlined approach to the thought process and the surgical techniques,” said Mark W. Pagnano, MD, a professor of orthopedic surgery at Mayo Clinic.
Fortunately, the prevalence of this condition is low, “ultimately affecting slightly less than 1% of all total knee replacements,” said Pagnano, noting that older patients with poor quality bone are at highest risk. The area most commonly affected is the high stress bone, just proximal to the femoral component.
Retrograde nailing
The typical cause is low-energy trauma among elderly patients with relatively poor bone quality. Rarely do these fractures arise from the implant itself having loosened or worn out over time.
A major goal of treatment is a fracture union that allows for maintaining alignment of the leg, through the length of the bone and rotation of the entire leg, which can be partially achieved by attaining maximal distal fixation and minimizing stripping/devascularization of comminuted zones. “You also want to avoid stiffness of the knee and infection,” Pagnano told Orthopedics Today.
Using a retrograde nail is best suited for patients with a high metadiaphyseal fracture. Besides being tissue-friendly, this technique is “mechanically advantageous in face of medial comminution,” Pagnano said. “But you need to obtain good fixation in that distal segment of bone. That is why a retrograde nail is really only applicable to a small subgroup of patients — 5% to 10%. It is also probably the least invasive of the three options.”
The second option, locked periarticular plating, is the treatment of choice for the vast majority of these injuries, according to Pagnano, who spoke at the 2010 Annual Current Concepts in Joint Replacement Spring Meeting in Las Vegas. “These specific plates provide you with improved distal fixation,” he said. Because these patients have a small amount of bone around the femoral component, “there are more choices on where to put screws to fix it in place.”
Not only can distal fixation be maximized with this technique, but there is less risk for malalignment. “Once the plate is fixed to the distal fragments, then attached to the proximal fragments, there is often improved aligning of the entire leg,” Pagnano said. “Locked plates also provide good coronal plan stability, so that limits the chance of a rotational malalignment.”
The benefit of the second-generation locked plates is that screws can be inserted at multiple angles as opposed to a fixed angle. “This allows you to use more screws in good bone, and thereby improve the fixation of the overall construct,” Pagnano said.
Revision arthroplasty
The third treatment option is revision total knee arthroplasty (TKA) with a hinged implant. Like an intramedullary nail, it is reserved for a small portion of patients — those with either a loose implant against the bone or with badly comminuted bone.
“This technique, particularly in an elderly patient, is often the most reliable way to deal with severe comminuted bone,” Pagnano said. “However, it does have the downside of eliminating the patient’s own bone.”
Because periprosthetic fractures after TKA mostly occur in the elderly with numerous medical issues, “these patients are at substantial risk of developing perioperative complications, such as wound healing problems, infection or delayed healing of the bone,” Pagnano said. However, by selecting the appropriate treatment based on bone quality, “you will maximize the chance of success and minimize the risk of perioperative complications.” – by Bob Kronemyer
Reference:
- Pagnano MW. Periprosthetic fractures after TKA: hold’em or fold’em. Paper 53. Presented at the 2010 Annual Current Concepts in Joint Replacement Spring Meeting. May 23-26. Las Vegas.
- Mark W. Pagnano, MD, can be reached at the Mayo Clinic, 200 First St. SW, Rochester, MN 55944; 507-284-5276; e-mail: pagnano.mark@mayo.edu.
