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Healing rate 90% when using structural allografts for periprosthetic fractures
Plating, nailing, stemmed TKR components are options for managing supracondylar fractures.
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Fractures that occur around total knee replacement prostheses can be prevented. But when faced with such a fracture, Allan E. Gross, MD, FRCS, has relied on some key factors to help him select the most appropriate treatment for his patients.
At a recent Current Concepts in Joint Replacement meeting he presented options for preventing and treating a variety of supracondylar fractures.
Surgeons must first assess whether the fracture is amenable to stabilization with a conventional or supplemented total knee replacement (TKR) implant, Gross said in his presentation. They should consider implant stability, fracture stability and the site where the fracture occurred.
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Images: Gross AE |
For the more common metaphyseal femur fractures, he suggested using a locking periarticular buttress plate or supracondylar intramedullary locking nail.
Displaced fractures with unstable implants should get the straight forward treatment: “You have to do a revision and you have to use stemmed components,” he said.
One option to consider in some periprosthetic fracture cases is a structural allograft into which a press-fit TKR prosthesis has been cemented. “This is a technique that can be used when you have loss of the distal femur and it’s impossible to instrument it,” Gross said.
Structural allografts
Using that technique, he reported a 90% success rate treating distal femoral periprosthetic fractures in 10 patients at about 6 years follow-up, average. The results were published in The Journal of Arthroplasty in 2004. Gross has since treated about 10 more patients with these types of periprosthetic fractures.
Gross prepares the allograft/prosthesis construction on the back table, fitting it to the proximal femur.
He then inserts the allograft construct with a step or oblique cut, which provides good primary stability and creates enough surface area for maximum healing at the graft-host junction.
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“The advantages of structural allografts are you can attach the soft tissue. You have early stability in fracture union, no violation of the host canal, and re-revision is facilitated by restoration of bone stock and available healthy host canal,” Gross said.
Managing bone loss
Patients with many of these difficult, displaced fractures often present with an unstable implant and loss of bone stock. Gross said addressing that bone loss is just as critical as fixing the fracture.
The bone loss usually occurs secondary to osteolysis and often is so extensive in the knee area that augments are not indicated. Gross has successfully used local autograft in conjunction with a structural allograft to enhance the fracture union. Ways to prevent such devastating fractures include removing any hardware about 3 months prior to TKR surgery.
“If the hardware needs to be removed at the time of primary replacement, protect stress risers using stems or restrict weight-bearing for about 6 weeks,” Gross said.
Another prevention technique: Avoid placing the box cut in an eccentric position.
It could lead to an intraoperative fracture, particularly with a posterior stabilized femoral component.
For more information:
- Allan E. Gross, MD, FRCS, can be reached at Mt. Sinai Hospital, 600 University Ave., Suite 476A, Toronto, Ontario M5G 1X5; 416-586-4611; e-mail: allan.gross@utoronto.ca. He is a consultant to Zimmer Inc.
References:
- Gross AE. Supracondylar fractures: Two sides of the coin. #90. Presented at the 23rd Annual Current Concepts in Joint Replacement Winter 2006 Meeting. Dec. 13-16, 2006. Orlando, Fla.
- Gross AE. Periprosthetic fractures of the knee. J Arthroplasty. 2004;19(4):47-50.