Basic principles apply to treating periprosthetic tibia fractures

Treatment for periprosthetic tibia fractures should be based on the type of fracture and how it relates to the component, according to information presented at the 2010 Annual Meeting of the Orthopaedic Trauma Association.

“Is the component loose or failing, or is the component intact?” said Richard J. Jenkinson, MD, FRCSC, a lecturer in orthopedic surgery at the University of Toronto. “In general, if the implant is stable, you should try to fix the fracture independent of the implant. But if the implant is unstable and/or failing, the patient will likely require revision arthroplasty, as well as fixation of the fracture.”

Fracture classification

The Mayo classification system subdivides injuries into four types, predicated on anatomic location, plateau, adjacent to stem, distal to stem, or tibial tubercle, and whether the prosthesis is well fixed or loose.

Type 1, medial or lateral plateau fractures, “tend to occur with a failing prosthesis with osteolysis,” Jenkinson told Orthopedics Today. Patients often need revision arthroplasty. “You should plan on using a stemmed prosthesis [normally a longer stem] that will dissipate the force past the fracture and allow it to heal.”

To address the loss of bone from osteolysis, defects can be managed with cement, bone graft, metal augments or custom prostheses. “I tend to use metal augments for the smaller defects, and a structural bone graft for a very large defect,” Jenkinson said.

Type 2 are metadiaphyseal tibial fractures, and in these cases, Jenkinson said he assesses the stability of the if a knee replacement and whether there is sufficient bone to fix the fracture.

“Sometimes, these fractures are very proximal, so there will not be much bone attached to the prosthesis,” Jenkinson said. “Locking plates allow you to achieve better fixation in a smaller amount of bone.” More than one plate, even if it is locking, may be required.

Revision arthroplasty

It is also important to “respect soft tissues when applying hardware,” said Jenkinson, who spoke during a symposium on periprosthetic fractures at the 2010 Annual Meeting of the Orthopaedic Trauma Association. “If you make your incisions too large and unnecessarily strip too much soft tissue off the bone, you increase the chance of complications like nonunion and infection from damaging the soft tissue.”

If the implant is unstable, then revision arthroplasty is warranted. “Because of the fracturing and the loss of stable proximal tibia, this is a challenging revision,” Jenkinson said. Therefore, “a tumor prosthesis or a large allograft or a more extensive prosthetic solution, such as trabecular metal cones, may be required for a stable knee revision.”

Mayo types 3 and 4

Type 3, diaphyseal tibial fractures, are usually treated independent of the knee replacement because there is generally sufficient bone for treatment with standard open reduction internal fixation (ORIF) techniques.

“The main difference between this type of fracture and a regular tibial fracture is that because of the knee replacement you cannot treat with an intramedullary nail,” Jenkinson said, noting that ORIF with plating is often the best option. Furthermore, to avoid soft tissue complications, such as infection, minimally invasive techniques can be employed.

For a simple type 3 fracture, “it is preferable to obtain an anatomic reduction with absolute stability using lag screws and compression plates, whereas if the fracture is comminuted it is probably better to achieve a functional reduction and rely on relative stability and callus formation,” he said.

Tibial tubercle fractures, Mayo type 4, represent failure of the extensor mechanism of the knee. “This is a challenging problem in knee arthroplasty to restore functionality,” Jenkinson said. In general, a large bone piece should be treated with fixation and a smaller piece treated more like a patellar tendon rupture. Repair of a small bony piece may also require augmentation with a semitendinosus graft or even an extensor mechanism allograft.

“Although these four types of fractures are rare injuries, you can definitely have successful outcomes if you apply appropriate treatment principles,” Jenkinson said. – by Bob Kronemyer

References:

• Hanssen AD, Stuart MJ. Treatment of Periprosthetic Tibia Fractures. Clinical Orthop Relat Res. 2000;(380): 91-98.
• Jenkinson RJ. Periprosthetic tibia fractures. Presented at the 2010 Annual Meeting of the Orthopaedic Trauma Association. Oct. 13-16, 2010. Baltimore.

• Richard J. Jenkinson, MD, FRCS(C), can be reached at the University of Toronto, MG361, 2075 Bayview Ave., Toronto, Ontario, Canada M4N 3M5; 416-480-6160; e-mail: richard.jenkinson@sunnybrook.ca. He has no direct financial interest in any products or companies mentioned in this article.

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