Review Question - QID 219252

This patient has a distal periprosthetic distal femur fracture around a well-fixed, stemmed total knee arthroplasty (TKA) femoral component. Given that the implant is well-fixed, and the patient has adequate bone stock, they would be best managed with open reduction internal fixation via locked-plating techniques (Answer 4).

Distal femur periprosthetic fractures can be managed similarly to native knee distal femur fractures. Most importantly, loose implants (i.e. implants that are no longer fixed at the implant-bone interface) or implants lacking adequate remaining bone stock must be revised. On the other hand, well-fixed implants with adequate bone stock (as in this case) may be retained and the fracture may undergo reduction and fixation through a variety of techniques. In such cases, surgeons must be conscious of the underlying TKA implant design, as this dictates fixation construct compatibility. While all modern CR total knee implants can accommodate a retrograde nail (Illustration A), some posterior stabilized (PS) implants cannot (Illustration B). Of note, this patient has an intramedullary stem on the distal femur prosthesis, which precludes the ability to perform intramedullary nailing for fixation. Given their adequate remaining bone stock, this patient should undergo open reduction internal fixation utilizing locked plating techniques (Illustration C).

Meneghini and colleagues performed a retrospective review of their institutional supracondylar femur periprosthetic fractures treated with retrograde intramedullary nailing (rIMN; with locked screws) versus periarticular locked plating. They reported 29 patients in the rIMN group and 66 patients periarticular fracture group with a nonunion rate of 9% and 19%, respectively, at a mean 32-month follow-up. The authors concluded that despite additional screw fixation, periarticular plating resulted in a higher rate of nonunion compared to rIMN. Of note, they acknowledge that many fractures are not amenable to rIMN fixation and periarticular locked plating remains a viable treatment option.

Ruchholtz and colleagues provided a comprehensive review of the management of periprosthetic fractures around the knee with clinical pearls to clinical decision-making. They emphasize that implant stability and remaining bone stock serve as the cornerstones to determine the most appropriate treatment modality. They discuss their techniques for fixing these fractures with intramedullary nailing, periarticular locked plating, and revision arthroplasty using hinged prostheses as indicated. The authors emphasize always having revision TKA components available should there be unexpectedly loose implants when attempting to perform operative fixation. They conclude that early mobilization is the goal in aged patients to prevent complications associated with being bed-bound.

Figures A and B demonstrate a distal femur periprosthetic fracture with well-fixed, stemmed implants and adequate proximal bone stock. Illustration A displays CR implant design with a femoral notch recess which can accommodate a retrograde intramedullary nail. Illustration B displays PS implant designs and delineates the difference between open and closed-box designs. Only open-box PS TKA implants can accommodate a retrograde intramedullary nail. Illustration C shows this patient’s post-operative imaging in which dual plating was utilized to safely facilitate immediate weight bearing.

Incorrect Answers:
Answer 1: Uniplanar external fixator placement would not be appropriate as it would not facilitate early weight bearing. Further, prolonged use would result in excessive knee stiffness and inferior functional outcomes.
Answers 2&3: As discussed, stemmed implants preclude retrograde intramedullary nailing. Extramedullary fixation techniques or revision arthroplasty are required in these unique situations.
Answer 5: Distal femur replacement is generally reserved for cases in which (1) the underlying implants are loose and/or (2) the remaining bone stock is inadequate to facilitate non-hinged revision components.