The Principles of Total Knee Arthroplasty Prevail with the Introduction of Innovative Technology

Total knee arthroplasty (TKA) has been a successful intervention to relieve pain and restore function in patients with end-stage knee arthritis. Over the years with experience, the principles and practices of this operation have evolved, but some fundamentals remain consistent. This includes the concepts of joint alignment and ligament balance that are important factors in the successful outcome of TKA, but some debate still exists concerning the optimal alignment and balance targets for each patient. While static bone resections in the coronal and sagittal planes position the components, soft-tissue management balances the knee joint. There is a close interplay with these two maneuvers, which require an understanding of the implications. While bone resection along the mechanical axis may necessitate soft-tissue releases to achieve appropriate alignment with fixed deformities, kinematic or anatomic alignment (there are several nomenclatures) adjusts the bone cuts with less need for soft-tissue releases to achieve a similar appropriate alignment. However, regardless of surgical plan for bone resection, it is important to understand the implications of fixed coronal and sagittal deformities, and how to achieve the ultimate correction and alignment. Fixed deformities are rarely limited to a single plane. Significant varus or valgus malalignment on the coronal plane is very often associated with sagittal plane and torsional deformities. Correction of the deformity should be done as completely as possible, because no residual degree of a fixed deformity will resolve successfully following surgery.

While conventional manual instrumentation has been traditionally used to determine intraoperative limb alignment, the introduction of innovative technologies, such as robotic TKA, offers promises of increased accuracy and efficiency in performing the surgery. The use of preoperative imaging or intraoperative bone mapping in robotic TKA creates a patient-specific 3D reconstruction of the knee with optimal bone resection and implant positioning. One of the intents of innovative technology is to quantify the qualitative feel of the ligament balance by way of numerical gap measurements. With 3D preoperative planning, projected numerical gap measurements demonstrate the virtual distances between the proposed bone resection in the medial and lateral compartments of the knee in flexion and extension. In contrast, an intraoperative kinetic balancing system has been introduced with a variety of TKA systems. This technology offers surgeons a quantitative assessment of load across the medial and lateral joint throughout the arc of motion and is used after bone resection with the trial components in place.

The new technologies in TKA are very attractive and are constantly evolving. Nevertheless, some limitations persist and could be improved by artificial intelligence and predictive modeling. At this time, the outcomes of robotic TKA have not translated to long-term functional outcomes compared with conventional TKA. Therefore, regardless of the technologies employed, the principles of manual TKA prevail.

Publication History

Article published online:
19 January 2024