Figure 1. Anteroposterior radiograph of the left knee.
Figure 2. Lateral radiograph of the left knee.
A 79-year-old woman presents with severe pain in the left knee after she fell at home. The patient underwent a total knee replacement on her injured knee 10 years ago without complications. Prior to the fall, her knee was asymptomatic. Anteroposterior and lateral radiographs (Figures 1 and 2) show an impacted periprosthetic distal femur fracture.
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Elderly patients with osteoporosis are at particularly high risk of sustaining periprosthetic fractures due to their poor bone quality and increased risk of unintentional falls. Fractures that occur proximal to the supracondylar line of the distal femur can usually be treated with open reduction and internal fixation. Adequate bone stock around the femoral prosthesis is required in order for the fixation to hold. If the distal femur fracture extends to the metal prosthesis, fixation with a lateral plate and screws is often no longer an option.1,2
Distal femoral replacement is indicated in patients with a distal periprosthetic fracture and who have significant bone loss and comminution. The advantage of a distal femoral replacement is that it provides immediate fixation with weight-bearing as tolerated. Distal femoral replacement is also widely used for oncologic reconstruction of the knee.
During distal femoral replacement the femur is cut proximal to the supracondylar line. The tibial component is removed and prepared for a revision stemmed tibial baseplate. Careful attention is made to ensure the length of the legs remain equal, the patella tracks well, and the rotation of the components is accurate. The tibial and femoral components are usually hinged together for varus and valgus stability of the knee.
Survivorship of distal femoral replacement is much lower than that seen with a traditional total knee replacement because of the nature of the salvage procedure. Survivorship of a distal femoral replacement at 4 years is just over 80% and 73% at 10 years.2 In elderly patients with limited mobility, distal femoral replacement functions very well; however, younger, more active patients are likely to experience early implant failure.
Dagan Cloutier, MPAS, PA-C, practices in a multispecialty orthopedic group in the southern New Hampshire region and is editor-in-chief of the Journal of Orthopedics for Physician Assistants.
1. Jassim SS, McNamara I, Hopgood P. Distal femoral replacement in periprosthetic fracture around total knee arthroplasty. Injury. 2014;45(3):550-553.
2. Appleton P, Moran M, Houshian S, Robinson CM. Distal femoral fractures treated by hinged total knee replacement in elderly patients. J Bone Joint Surg Br. 2006;88(8):1065-1070.