Due to financial constraints, the study could not be continuedout as planned. Enrolled participants will finish treatment per study protocol.

The current proposal aims to investigate the patellar tracking in adult patients receiving Journey II Bi-Cruciate Stabilized (BCS) total knee arthroplasty (TKA) before and one year after surgery, positioned with the CORI Robotics System instrumentation. The hypothesis is that less change in patella tracking before and after surgery will lead to less anterior knee pain complaints. Patella tracking is investigated using 4Dimensional Computer Tomography (4D CT) imaging.

Researchers will compare the group of participants that will receive a patella onlay button with the group that will not receive a patella onlay button with their TKA to see if there is a difference in motion and pain experienced by the participants.

Rationale: Pain at the anterior side of the knee after total knee arthroplasty is still a common phenomenon with an incidence reported to be as high as 49 percent. The aetiology is poorly understood and several mechanisms have been postulated. Next to the influence of alignment on retinacular stresses, overstuffing of the patellofemoral joint and instability also lead to higher retinacular stresses and are shown to lead to anterior knee pain. These mechanisms are all related to surgical technique and implant positioning. There are also mechanisms related to prosthesis design, like the sagittal curve, trochlear depth and trochlea shape.

New implant designs like the Journey II prothesis are designed to replicate optimal geometry and optimal tibiofemoral and patellofemoral kinematics. Therefore, the Journey II Bi-Cruciate Stabilized (BCS) seems the optimal implant to reduce anterior knee pain. However, large registry studies show that a higher revision rate is seen when no patellar button is used in case of the Journey II BCS. The use of a patellar button is still under debate, but using an onlay patella button has clear influence on the patella tracking. Therefore, there might be a relation between the use of an onlay patella button and the retinacular balance and thus clinical results.

With current surgical instrumentation the positioning of the prosthesis based on the kinematics of the natural knee is challenging, and a small error can completely counteract the normal motion defined by the implant design/geometry. Therefore, comparative studies are only leading to new evidence when the surgical technique is including objective and accurate tools, like the CORI robotic platform. With the CORI, component positioning can be set based on constitutional alignment and ligament functioning. Furthermore, the patellofemoral compartment can be taken into account during the surgery to enable optimal geometry replication of the trochlea in the sagittal plane. This enables the surgeon to position the components accurately within the envelop of motion of a specific joint.

With new emerging imaging techniques, the investigators are able to investigate in vivo patella tracking. One of these promising techniques is the 4D CT imaging. This technique is proven to be accurate within 1 mm and 1° and therefore useful to investigate the patellofemoral compartment.

The current proposal aims to investigate the patellar tracking in patients receiving Journey II BCS total knee arthroplasty (TKA) before and one year after surgery, positioned with the CORI Robotics System instrumentation. The hypothesis is that less change in patella tracking before and after surgery will lead to less anterior knee pain complaints. Patella tracking is investigated using 4Dimensional Computer Tomography (4D CT) imaging.

Research participants/locations:

A total of 100 participants will be included in the study from two sites in the Netherlands (Radboudumc and Treant medical centers). Half of the participants will undergo TKA placed with the CORI Robotics and a patella onlay button and the other half (50 participants) will undergo a TKA placed with the CORI Robotics System and without a patella onlay button.

Inclusion Criteria:

• Non-inflammatory knee osteoarthritis, which is confirmed by radiology.

• Osteoarthritis is unilateral or bilateral with the contralateral knee functioning properly, not operated on in the last 6 months.

• Set to receive a primary cemented total knee arthroplasty.

• Aged between 50 and 80 years, inclusive, on the day of the operation.

  • This age limit of 50 is based on the desire to include exclusively patients with primary osteoarthritis. As osteoarthritis is an age-related disorder, it generally involves adults over the age of 50 years. Patients under the age of 50 years who present with osteoarthritis usually have osteoarthritis due to a secondary cause (e.g. post-traumatic osteoarthritis).
  • A maximum age of 80 years will be employed. This age limit will be adopted because patients should be well able to perform an extension-flexion movement while a dynamic CT scan is made.

• In stable health (American Society of Anesthesiology (ASA)-score ≤ 3) and is free of or treated for cardiac, pulmonary, haematological, or other conditions that would pose excessive operative risk.

• Patient has a correctable or <10° rigid (non-correctable) varus deformity of the knee.

• Participants must be able to give informed consent.

• Patient plans to be available for follow-up until two years post-operative.

• Ability to walk for 2 minutes without walking aid

Exclusion Criteria:

• Valgus deformity
• Body MAss Index (BMI) > 35.
• Previous hip /knee/ankle replacement surgery in the last 12 months, or is planned to have a hip replacement in the next 6-12 months.
• Patient has had major, non-arthroscopic surgery to the study knee, including High Tibial Osteotomy (HTO).
• Patient has an active, local infection or systemic infection
• Incomplete or insufficient tissue surrounding the knee.
• Severe damage to the medial or collateral knee ligaments and popliteal tendon
• Documented osteoporosis with patient in active medical treatment.
• Patient has physical, emotional or neurological conditions that impacts gait or balance, or would compromise compliance with post-operative rehabilitation and follow-up.
• Bone quality compromised by disease or infection which cannot provide adequate support and/or fixation to the prosthesis
• Knee flexion < 90 degrees
• > 30 degrees extension deficit (active restraint to extension)
• Patient does not have a proper functioning patella tendon on the affected side; measured as inability of active extension of the knee
• Patient has active rheumatoid arthritis, any auto-immune disorder, immunosuppressive disorder or a terminal illness.