**7. Emerging technologies**

Contained defects occur from a cyst or a cavity and are treated by filling off the defect or bone cut. One must remember that there is a limit for moving the bone cut level. Augmentation

Peripheral defects typically occur in varus knees in the posteromedial plateau and in valgus knees in the distal lateral femur. These kinds of defects are also managed with cement, bone graft, and metal augments. When they occur in tibia, the translation of the tibial tray away from the location of the defect could be sufficient. If not deeper than 10 mm, the defect can be eliminated by resecting the tibia at a lower level until, at a maximum of, 20 mm, but these authors recommend using metal augmentation and intramedullary stems to protect the

There are theoretical concerns when choosing the right implant. For those who choose anatomical and kinematic alignment, the implant tends to reproduce the knee's anatomy and the surgeon should preserve at the most ligaments and the natural inclination of the native's articular line. In such cases, the PCL should be preserved whenever it's possible, since it is a

Anterior cruciate ligament (ACL) plays a role with PCL during knee flexion and extension. As the knee flexes, the femur slides back in tibia (rollback) until a point where the ACL is completely strengthened. As the knee extends, the femur slides forward until a point that the PCL resists this movement. For arthrosis of one compartment, when ALC and PCL are intact, a meniscal-bearing design could be used (e.g., Oxford® unicompartmental prosthesis). As arthrosis progresses, ACL becomes insufficient. When PCL is not sacrificed, the movement of rollback occurs and theoretically, the tibial baseplate should be flat. When PCL is sacrificed, the tibial baseplate should be concave, containing forward and backward motion. However, some of the newer implants now allow PCL sacrifice or retention, regardless the shape of

Mobile-bearing designs have increased the sagittal plane conformity which helps to control anteroposterior translation. The increased coronal plane conformity typically presented in mobile-bearing TKA also increases the contact area and lessens contact stresses. These advantages tend to reduce the rate of polyethylene wear. Polyethylene is self-aligned with the femoral component. It reduces the cross-shear stresses and facilitates central patellar tracking. In a fixed-bearing TKA, if the tibial component is left in internal rotation, it moves tibial tuberosity laterally, enhancing the risk of patellar subluxation. Besides, mobile-bearing designs also contribute to diminish the incidence of lateral releasing. Clinically, the fixed-bearing and mobile-bearing TKA systems have performed similarly in outcome studies. These authors favor the use of mobile-bearing designs, especially for younger and higher-demand patients

with cement, bone, or metal wedges or blocks should be considered in these cases.

implant from interface shear forces (**Figure 15**).

varus/valgus stabilizer, and it can absorb stress.

**6. Choice of implant**

18 Primary Total Knee Arthroplasty

tibial baseplate.

with longer life expectancies.

Patient-specific instruments could be made from preoperative imaging (MRI or CT scans of specific sequences). It could allow the production of manufactured specific cutting guides. These guides are made in respect of the individual anatomy, including osteophytes and bone defects in the correct orientation. It would direct the bone resection before the preplanned knee, avoiding using standard intraoperative cutting guides. Specific guides should require fewer trays of kit, leading to greater operative efficiency, and are expected to reduce operative time and produce more accurate bone cuts. At this point, there are a lot of studies that suggest the use of specific guides with good functional outcomes. Nevertheless, cost-effectiveness still needs to be proven.

Robotic surgery combines navigation with a robot that performs the bony resection, controlled by the surgeon. A preoperative CT scan is used to template the knee. It has a theoretical advantage of not deviating from the defined cutting plane or axes of resection. Despite the appeal that it would reproduce better mechanical axis, additional studies are necessary to justify its use outside the experimental environment before it gets universally used.
