Robotic-assisted TKA with ligament tensioning may improve outcomes, decrease complications
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In total knee arthroplasty, unbalanced ligament tension is one of the primary reasons for complications and patient dissatisfaction.
Time has shown that not addressing the soft tissue envelope can result in pain, stiffness and laxity. Thus, obtaining exact measurements of a patient’s ligament balance is critical in developing a surgical plan and precise implant positioning. Preliminary studies reveal using a device to balance out ligament tension shows a decreased complication rate as compared to traditional, non-robotic knee replacement surgery. Presented herein is a robotic-assisted TKA technique that accurately predicts postoperative gaps before femoral resection. A stepwise presentation of the procedure is outlined in detail.
Source: Corin Group
Technology
While computer navigation has brought improved alignment accuracy to TKA, a recently published study indicated that ligament balance may have a greater impact on outcomes than alignment. The OMNIBotics BalanceBot (Corin Group) includes a robotic soft tissue tension device that can plan implant positioning with predictive balance tools.
Traditionally, surgeons put pressure on the knee to assess range of motion and ligament abnormalities. This can result in unpredictable and inconsistent ligament balancing. Rather than relying on subjective information, this robotic system provides objective data so that surgeons can intraoperatively plan implant placement to ensure alignment and balance, often eliminating the need for additional soft tissue releases.
Surgical technique
With this procedure, the surgeon can assess ligament abnormalities throughout the entire range of motion and before any femoral resections. First, sensors are applied to the knee (Figure 1) and a computer reads the incoming information about the condition of the knee and the tissues surrounding the knee. After femoral and tibial pin fixation, the hip is rotated circumferentially to calculate the center of the femoral head and the angle. The computer performs registration and creates a 3D map of the surface of the knee in real time with no MRIs or CTs required (Figure 2).
Patient kinematics, including the amount of laxity at a specific flexion angle and leg alignment, are tested (Figure 3). The tibial cutting guide is put in place and on-screen prompts assist in positioning the cutting slot. The tibial cut is made and validated.
The BalanceBot, which consists of two independently mobile robotic paddles, is inserted, allowing the surgeon to assess range of motion and ligament abnormalities and capture quantitative data that are used to preoperatively plan bone cuts and predict gap balance in real time. Specifically, force mode applies consistent tension to measure the soft tissue envelope, while gap mode sets the paddles to a fixed gap to provide force and stability data. The system then creates an initial balance assessment, which is a real-time graph of the medial and lateral gaps between the bones throughout the range of motion.
To position and cut the femur, the surgeon uses the system’s femoral planning module. This provides the ability to virtually position the femoral component and balance the extension, mid-flexion and flexion gaps (Figure 4). The extension gap is balanced by adjusting the varus/valgus angle and depth of the distal femoral resection. The flexion gap can be balanced to match the extension gap by modifying femoral internal/external rotation, anterior/posterior position and flexion/extension of the femoral component. Ligament tension is measured within 0.5 mm and rotational alignment is also measured within 0.5°.
To execute the planned femoral implant position, the robotic cutting arm and computer navigation are used to ensure proper positioning (Figure 5). The robotic arm is calibrated, and the surgeon begins with the distal resection. This resection is then validated by the surgeon to ensure the femoral extension gap has been achieved. Similarly, the anterior resection is performed by the surgeon and is validated to ensure rotational alignment and proper implant flexion and extension (Figure 6). The anterior and posterior condylar resections are made as performed in a traditional TKA, with the ability to recreate the predetermined plan. Throughout the procedure, the surgeon retains complete control of the saw, and the cutting guide does not allow for any motion other than what is in the operative plan.
For the final assessment, the femoral trial is positioned, and the ligament balancing device (with the articulating surface paddles attached) assesses the gaps. The surgeon takes the knee through the full range of motion using the same applied load that was used to plan the procedure. All gap measurements are visible on the computer screen as is alignment and laxity (Figure 7). Any necessary soft tissue corrections can be made.
Conclusion
Using this robotic system is akin to removing the knee and putting it on the computer screen with the ability to assess the pre-surgical ligament imbalance and knee malalignment. Ligament tension of the medial and lateral compartments throughout the full range of motion can be measured with objective data. This leads to heightened precision and results in significantly improved clinical outcomes and patient satisfaction (Figure 8).
Recent studies have found a 97.4% patient satisfaction rate, higher than previous studies investigating non-robotic knee replacement, which only had an 81.4% patient satisfaction rate. Other research has found improved pain scores when joint gap targets are achieved throughout flexion.
With studies indicating fewer soft tissue releases, less pain and predictable outcomes, computer navigation and robotic surgery with this new ligament balancing technology creates a powerful tool for the surgeon.
- References:
- Keggi JM, et al. Arch Orthop Trauma Surg. 2021;doi:10.1007/s00402-021-04043-3.
- Keggi JM, et al. EPiC Series in Health Sciences. 2020;4:160-164.
- Shalhoub S, et al. Arthroplast Today. 2019;doi:10.1016/j.artd.2019.07.003.
- Vigdorchik JM, et al. J Arthroplasty. 2022;doi:10.1016/j.arth.2022.04.042.
- Wakelin EA, et al. Impact of soft tissue balance on 2-year outcomes in TKA. Presented at: ISAKOS Biennial Congress; June 18-21, 2023; Boston.
- Wakelin EA, et al. Knee Surg Sports Traumatol Arthrosc. 2022;doi:10.1007/s00167-021-06482-2.
- For more information:
- Jeffrey H. DeClaire, MD, is an orthopedic knee specialist and founder of the Michigan Knee Institute. DeClaire’s email: jeffrey.declaire1@ascension.org.
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