This is a pilot randomized trial to assess the feasibility of a definitive trial to determine the effect of robot-assisted partial knee replacements versus standard total knee replacements.

Knee osteoarthritis (OA) pain is an important source of morbidity and cost to the health care system. Over 60,000 knee replacement surgeries are performed in Canada every year, making it the second most common surgery. Our institution (St. Joseph's Healthcare Hamilton) is the first hospital in Canada to purchase a Mako RIO orthopaedic robot to assist with performing knee replacements. The knee is divided into three compartments, and one, two, or all three compartments can become arthritic. Over 90% of patients with end-stage knee OA receive a total knee replacement (also known as total knee arthroplasty or TKA) even if they have one or two healthy knee compartments. Partial knee replacements are an option for these patients but these procedures are very technically demanding and associated with a higher risk of implant failure. For this reason, few surgeons are experts at partial knee replacements. We believe that we can use robotic technology to make it easier for surgeons to perform partial replacements more accurately, thereby increasing the quality and survivorship of partial knee replacements. This may lead to better patient-important outcomes like return to activity, pain, and satisfaction, and eventually better access to high-quality partial knee replacements for Canadians. This will be the first study to evaluate total knee replacements (standard care) versus robot-assisted partial knee replacements, and could lead to greater uptake of robotic technology in orthopaedics and a shift toward anatomy-sparing partial knee replacements.

Inclusion criteria

• Adult (18+)
• Unicompartmental knee OA with or without concomitant patellofemoral OA, requiring surgical treatment
• Two study surgeons independently agree that the patient is eligible for either treatment group

Exclusion criteria

• Inability to provide informed consent (e.g. cognitive disability, language barrier)
• Revision knee surgery
• Simultaneous bilateral knee surgery
• Previous major knee surgery or trauma
• The robot or required components are unavailable (e.g. technical difficulties, robot-specific disposables out of stock)
• A CT scan cannot be obtained prior to surgery
• Patient does not wish to participate

We will share data upon reasonable request for non-commercial purposes. This may require an institutional data-sharing agreement.

Upon study completion.

Surgeons cannot be blinded to treatment group. It would not be feasible to blind the health care team and patients because the incisions and imaging are visually distinguishable. We will attempt to minimize bias in subjective measures by presenting patients with balanced information on each treatment group prior to the trial. All participants will receive a computed tomography (CT) scan prior to surgery to maintain blinding and to give surgeons additional information about 3 dimensional modelling for implant placement. Data analysts will be blinded to treatment allocation. An independent outcomes assessor will independently review radiographic alignment for each patient and review relatedness of adverse events and re-operations. The independent assessor cannot be blinded because imaging is visually distinguishable.