Challenging The TKA Standard Of Care: Patient Specific Surgical Targets As Enabled By The Rosa

Total knee arthroplasty (TKA) is performed to treat end-stage arthropathy of the knee with substantial increases in surgical volumes projected from the existing 750,000 surgeries performed in North America annually. The current standard of care for a primary TKA is a medial parapatellar exposure with the surgical objective of a mechanically neutral limb alignment, with the tibial component perpendicular to the anatomic axis of the tibia. As patient dissatisfaction in their TKA is substantial, surgeons, allied health care workers and patients continue to work to optimize the outcomes by tailoring surgical approaches to patient specific characteristics, with a goal to diminish early and post-operative causes of dissatisfaction. As patient-reported functional outcomes scores are an important contributor of dissatisfaction, understanding how surgical objectives and technology affect measurable functional outcomes, patient-reported outcomes, health economic and inflammatory response is important.

One of the developing thoughts in TKA surgery has been the elucidation of the range of native alignment of patients' anatomy. As placing TKA components in positions dictated by the patient's unique anatomy has garnered greater attention, literature has suggested that respecting the patient's native anatomy of joint alignment may result in equivalent or possibly improved functional outcome scores compared to neutral mechanical alignment. Simultaneously, concerns have been raised that substantial varus alignment will inadvertently occur, with resultant negative impact on longevity. A more directive patient specific alignment (PSA) concept is the anatomic alignment approach that is built around the objective of achieving a 3 degree varus joint line with respect to the mechanical axis of the leg. It is thought that this may improve patient satisfaction and function as the anatomy of the joint is preserved, including improved soft tissue balance with less soft tissue releases required. However, as conventional instrumentation is imprecise and its use can result in a range of component alignments, a surgical objective of slight varus has a substantial risk of having the implants in too great of joint line angulation resulting in reduced longevity. Improved surgical instrumentation is required to enable PSA with the objective of precisely attaining anatomic alignment to avoid the negative effect of overly varus alignment.

Zimmer-Biomet has introduced the unique ROSA orthopaedic robot. This surgical instrument will enable the surgeon to easily achieve surgical objectives with greater precision than conventional techniques. In contrast with the market leader in orthopaedic robotic assistance, the ROSA also enables the surgeon to be flexible with surgical approach and potentiate intraoperative decision making by providing greater information intra-operatively. It also enables image or imageless care pathways to enable surgeons to do surgical planning themselves to create unique surgical objectives for each patient. These market differentiating features of this orthopaedic robot advance orthopaedic care and provide the basis of expanding the orthopaedic community's understanding of PSA. The robot will also enable further challenges to the current standard of care TKA. For example, quadriceps sparing approaches such as the subvastus approach have been demonstrated to improve early functional recovery but has also been suggested to have higher rates of implant malalignment. The flexibility of approach as well as the precision of the ROSA will potentiate this approach for enhanced recovery programs, which are important in this time of increased health care burdens with limited resources as well as demands for outpatient procedures. Finally, as the Persona ® MC potentiates physiologic function of the knee with a medial pivot point rather than non-physiologic kinematics of many other TKA designs, the knee potentially will feel more physiologic. As objective and subjective functional outcomes are substantial contributors to patient dissatisfaction, understanding how patient specific alignment and soft tissue sparing approaches might improve functional outcome is critical. Wearable technology, another recent advancement within orthopaedics, has demonstrable ability to measure innumerable functional variables, and will enable a greater understanding of how the ROSA in combination with the Persona MC will lead to improved outcomes and reduced resource use.

Current literature has used inflammatory response to assess the decreased amount of soft tissue disruption after robotic versus conventional TKA. Since objective and subjective joint stiffness and reduced range of motion are common complaints among patients with suboptimal outcomes after TKA, The investigators will examine knee inflammation and fibrosis as these likely contribute to stiffness. Understanding the effect of PSA ROSA TKA with the Persona MC on local and systemic inflammation both early post-operatively as well as at one year post-operatively will be achieved by advanced imaging as well as systemic markers in the context of each individual patient's unique cellular characteristics. Our proposal will also enable quantification of how soft tissue preserving approaches affect the local inflammatory response as well as muscle atrophy or edema.

Patient reported outcome measures (PROMs) are an important subjective metric to measure surgical success and traditionally have been the primary outcome measure for many studies. However, PROMs are limited by the multi-factorial nature of the measure as well as limited responsiveness and substantial ceiling effect. The improved data collection of wearable technology has enabled differentiation of factors influencing patient satisfaction with smaller numbers of patients. Because of this, wearable technology has several advantages as a primary outcome, including the fact that wearable technology directly measures functional outcomes: a primary source of dissatisfaction after a TKA. As restoration of the patient's anatomy within defined limits should enable the implant to function with greater harmony within the envelope of static and dynamic soft tissues, functional outcomes will be the primary outcome of this proposed randomized control trial (RCT).