The incidence of periprosthetic fracutres (PPF) of the femur is ~ 1.3%, increasing as patients live longer and stay active with their TKA. There is a close association with osteoporosis, with 4 of 5 occurring in elderly women, and the vast majority occurring after low-energy fall in patients over 60 years old .
The algorithm to evaluate the PPF begins with determining the implant stability (as noted in the Rorabeck classification system) [2-4].
If the implant is stable, then the fracture should be addressed with ORIF using either the submuscular bridge plating via a minimally invasive plate osteosynthesis, MIPO, technique or a retrograde intramedullary nail.
The submuscular plates offer a minimally invasive approach with locking screws to improve fixation in bone that is virtually always osteoporotic. Advantages of a plate includes reliability in cases of significant comminution and distal extension due to the ability to achieve distal fixation with many screw options. The plate contour further facilitates fracture reduction and maintenance of reduction. However, studies suggest there is a risk of varus collapse when the fracture involves the medial femoral condyle. Furthermore, patients are unable to weight bear following fixation, and similar to patients with hip fractures, delayed mobilization can lead to significant complications such as pneumonia and DVT.
Retrograde nails similarly offer a minimally invasive approach, but can only be used in implants that have an open notch to allow nail insertion, and no stem. The notch size determined by the knee implant, which can be quite variable, and surgical planning to identify the implant is necessary to avoid surprises during the case. In CR-TKA, the notch diameter is between 11 – 20 mm, in PS-TKA, the notch is narrower. The space should be at least 1 mm larger than the planned IMN. Some common implant notch sizes: S&N Genesis II: 16.5, Zimmer NexGen 14.1 – 21.6, Omnifit – closed box, DePuy TC3 – closed box, DePuy Sigma CR and PS (17.4 vs. 11.9).
If the implant is unstable, then the fracture and the loose component must be addressed. Depending on the remaining bone stock, this requires a stemmed femoral implant vs. a hinge or a distal femoral replacement. The fracture is also addressed with cables.
Meta-analysis of locking plate and retrograde IMN union rates is around 90% [5,6].
However, meta-analysis suggests locking plate complication rates (35%) were lower than IMN (53%), albeit rates were not statistically different, and appear high in both groups, highlighting the severity of this complication (and the underlying morbidity of the patients that suffer this complication). This complication is most common in the frail elderly population, and therefore, it remains unclear whether one fixation type has a significant impact on the risk for complications. The most common complications were nonunion and malunion (6% each, yet these rates were 2x higher in patients treated nonoperatively).
1. Berry, D.J., Epidemiology: hip and knee. Orthop Clin North Am, 1999. 30(2): p. 183-90.
2. Rorabeck, C.H. and J.W. Taylor, Classification of periprosthetic fractures complicating total knee arthroplasty. Orthop Clin North Am, 1999. 30(2): p. 209-14.
3. Rorabeck, C.H. and J.W. Taylor, Periprosthetic fractures of the femur complicating total knee arthroplasty. Orthop Clin North Am, 1999. 30(2): p. 265-77.
4. Su, E.T., H. DeWal, and P.E. Di Cesare, Periprosthetic femoral fractures above total knee replacements. J Am Acad Orthop Surg, 2004. 12(1): p. 12-20.
5. Shin, Y.S., H.J. Kim, and D.H. Lee, Similar outcomes of locking compression plating and retrograde intramedullary nailing for periprosthetic supracondylar femoral fractures following total knee arthroplasty: a meta-analysis. Knee Surg Sports Traumatol Arthrosc, 2016.
6. Ebraheim, N.A., et al., Periprosthetic Distal Femur Fracture after Total Knee Arthroplasty: A Systematic Review. Orthop Surg, 2015. 7(4): p. 297-305.