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Can only be used with specific total knee revision implants
9%
67/714
Exhibit highly ductile material properties to engage to host bone via Morse-taper design
17%
122/714
Exhibit poor cement interdigitation and therefore cannot be cemented to the host bone
6%
46/714
Higher long-term survival rates compared to cortical allografts for metaphyseal defects
64%
459/714
Primarily utilized in Anderson Orthopedic Research Institute type 1 defects
2%
14/714
Select Answer to see Preferred Response
Highly porous metaphyseal cones (i.e. tantalum) have been shown to have significantly improved long-term survival rates compared to cortical allografts in revision total knee replacement (TKA) with significant metaphyseal defects. The improved survival is attributed to improved biocompatibility and osseointegration rates of highly porous metal cones compared to cortical allografts. In the setting of revision total knee arthroplasty (TKA), removal of prior implants often results in a metaphyseal void in the tibia, femur, or both. These voids can be classified based on the Anderson Orthopedic Research Institute (AORI) classification. While some, smaller voids have appropriate cancellous bony support (AORI Type 1), larger voids may require some form of augmentation in order to appropriately place and align revision implants (AORI Type 2 and 3). Metaphyseal voids were historically filled or replaced with cortical allografts to provide structural support. Unfortunately, graft resorption or graft fractures led to high rates of failure. As an innovative solution, metaphyseal cones and sleeves were developed as alternative options to address metaphyseal voids. In the setting of revision TKA, surgeons should always be prepared for possible metaphyseal defects, especially when removing prior cemented implants or spacers. Haidukewych et al. reviewed the different forms of metaphyseal fixation in the setting of revision TKA. They discuss the dramatic increase of expected revision TKA procedures over the next decade and the importance of effective management. They conclude that familiarity with different surgical options and implants is needed to address each patient’s specific needs. Beckman and colleagues performed a systematic review comparing structural allografts to porous metal cones for the treatment of severe bone defects during revision TKA. They found that porous metal cones showed a significantly lower loosening rate in AORI 2 and 3 defects than cortical allografts. They concluded the increased use of porous metals will continue to improve outcomes utilizing these newer implants. Figure A shows this patient’s revision construct that utilized a metaphyseal cone and diaphyseal-engaging tibia components. Incorrect Answers: Answers 1&2: Metaphyseal cones are highly porous metaphyseal void fillers that exhibit brittle properties. The cones only engage to tibial trays through direct contact as a non-modular implant, independent from the tibial tray and stem modular system. This makes them highly versatile and can be utilized with any company’s revision TKA system. Metaphyseal sleeves, on the other hand, are modular constructs that directly attach to a stem through a threaded interface and to the tibial tray through a Morse-taper junction. Answer 3: Highly porous cones (i.e. tantalum) can be cemented into host bone and is encouraged if their intended scratch fit to host bone interface is lacking when placing the final implant. This often occurs in the setting of osteoporotic host bone. Answer 5: The Anderson Orthopedic Research Institute Type 1 defects have intact metaphyseal bone with good cancellous bone at or near the normal joint line. These types of defects do not require metaphyseal augmentation.
2.5
(4)
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