**2. Design history**

Total knee arthroplasty has evolved significantly since its first inception in the late 19th and 20th centuries; implant designs have improved and advances in surgical tools have born less invasive techniques. Originally, the first arthroplasty was conceived as a simple resection arthroplasty in the 1860s. Excess bone was removed to improve motion, but this was limited by the recurrence of bone formation, at times, knee fusion and this arthroplasty often lead to instability if too much bone was removed [7]. This technique evolved to interposition arthroplasty, by which the insertion of soft tissue was used to reconstruct the joint surface and help prevent bone formation; this method was abandoned due to continued pain and failure of the interposition [8]. The hinged prosthesis of the 1950s was the first to replace the femoral and tibial surfaces, and patients experienced significant pain relief. Unfortunately, these linked prostheses were unable to replace complex knee kinematics and had high failure rates due to early loosening from stress shielding [9]. The 1970s saw the evolution of the condylar TKA prosthesis from Ranawat, Coventry, and Townley, which set the foundation of the less constrained and more anatomic modern implants of today [10–12].

Initially designed with a symmetrical femoral component, these condylar implant systems offered pain relief but featured a shallow, straight trochlear groove, and struggled to replicate natural patellar tracking. The 1980s brought a shift to an asymmetric, side-specific design [13] to better match the normal bony anatomy

#### **Figure 1.**

*Total Joint Orthopedics, Inc.'s (TJO) Klassic® Femur featuring a 9° double Q-angle to optimize patellofemoral tracking for both left and right-sided anatomy.*

*The Modern Universal Total Knee Arthroplasty: Maximized Value, Streamlined Efficiency DOI: http://dx.doi.org/10.5772/intechopen.101572*

of the distal femur of a patient and thus improve knee kinematics [13]. Multiple studies have failed to show any significant difference in knee clinical or functional scores in patients with a modern universal femoral component when compared to those with asymmetrical femoral design [14–17].

While the symmetrical femoral component fell out of favor due to patellofemoral complications that were encountered during the design evolution, such as poor tracking and dislocation, these issues have since been corrected with modern universal designs [13]. For example, one implant company, Total Joint Orthopedics, Inc.'s (TJO) patented Klassic Femur has a unique deepened anatomical trochlear groove, allowing for optimal patellar tracking along a 9° double Q-angle for both left and right-sided knees while still retaining a neutral outside profile of the anterior flange and restoring native kinematics (**Figure 1**) [18, 19].
