# A Review Study on Total Ankle Replacement
## 3 Revision TAR
### Current Prostheses  
There are a number of prostheses that are currently used and available in the United States. The available implant systems include the STAR device, INBONE II TAR, INVISION TAR, INFINITY TAR, Salto Talaris TAR, Salta Talar XT Revision prosthesis, Zimmer trabecular Metal TAR, Vantage TAR and Cadence TAR [12]. The most commonly implemented TAR systems in the US are the INBONE, INFINITY, STAR and Vantage [65; 66; 67]. STAR is an original second-generation implant that has undergone several revisions. This implant was originally developed by Stryker and is now owned by DJO Global. This is an unconstrained mobile bearing implant, but was originally a two-component cemented system. Currently, it is the only mobile bearing, cementless system approved for use in the United States [33; 68]. Though studies have shown high patient satisfaction, there is concern for high rates of polyethylene failure and periprosthetic osteolysis with this prosthesis [45; 69; 70]. Figure 4 below shows the STAR ankle prosthesis. The INBONE II and INVISION total ankle replacement systems were both made by Wright Medical Technologies. Wright Medical was bought by Stryker, thus these implants are now owned by Stryker.. These are both two-component, fixed-bearing systems used for both primary and revision TAR. The INBONE II system evolved from the INBONE I system, which was a third-generation design cleared by the FDA in 2005. The INBONE II includes a change in talar design from flat to including a sulcus, in order to improve the stability between the polyethylene liner and talar component [71]. The INFINITY system is a fourth-generation design that is also a two-component, fixed bearing device. INFINITY design components can be used with the Prophecy, which is Infinity total ankle replacement with patient specific instrumentation. This implant uses preoperative ankle CT to develop patient specific cut guides. Patient specific instrumentation has been shown to decrease operative time with reproducible and accurate results [72; 73; 74]. Prophecy's prosthesis can also be used with the INBONE II, INFINITY and INVISION TAR [33; 75; 76; 77]. Figure 5 below shows the INBONE prostheses. Figure 4: STAR ankle prosthesis rendering in the foot. The Salto Talaris TAR is a third-generation implant that was originally designed as a mobile-bearing device. In 2006, the FDA approved a fixed-bearing, two-component version of the implant that is available in the US. The Salto Talaris XT Revision Ankle Prosthesis is a fixed-bearing, semi-constrained system that can be used for both primary and revision surgery. The implant is somewhat unique in that the tibial trial component is mobile, which uses the talar component to guide it to settle and self-align in the optimal position on the resected distal tibia surface [78]. The talar component uses the same general design as the primary implant [32]. Mid- and long term results of this implant have shown consistent positive results with significant increase in patient reported clinical outcomes [47; 79]. The Zimmer Trabecular Metal TAR is a third-generation, two-component, fixed-bearing system that uses a trans-fibular approach for implantation. This makes it the only laterally based TAR in the US, which avoids the anterior-based incision over the ankle joint to minimize wound healing issues. This approach also provides the ability to perform curved bone cuts which are more anatomic and biomechanically provide greater bony support [80]. The polyethylene spacer is made of highly cross-lined polyethylene (HXLPE) that has decreased wear and less debris when compared to standard spacers [33]. Figure 6 below shows the Zimmer TAR. Figure 5: INBONE prostheses and the labeled components. Finally, the Cadence and Vantage TARs are the newest systems. The Cadence is a fourth-generation, two-component, fixed-bearing implant that gained FDA clearance in 2016. The liner is made of HXLPE and the system reduces contact and frictional forces against the fibula with a recess in the tibia component.