Robotic-Assisted Total Knee Arthroplasty

Anatomy and Physiology

Robotic TKR uses a preoperative CT scan to create a 3D reconstruction of the original knee. This patient model is then used to calculate the measurement of the femoral and tibial bone resection and select the exact size of the implant.[7]

The aim of TKA is to restore the mechanical axis, restore the joint line, restore balance in flexion and extension gaps, and restore the Q angle for perfect patella tracking. To reach these goals, the preservation of the surrounding soft-tissue is crucial. Destruction of the collateral ligaments, PCL, or extensor mechanism may lead to delay in the recovery, decrease joint stability, and decrease prosthesis life. Robotic TKA limits saw action, which reduces iatrogenic bone and soft-tissue damage.[8][9]

There are multiple factors that affect the successful outcome of total knee arthroplasties, such as the perfect position of the prosthesis, accurate balance of flexion-extension gaps, perfect tensioning of the ligament, and soft-tissue preservation. Most of these factors are surgeon-related, which varies based on the skills and experience of the performing surgeon. Thus, in conventional total knee arthroplasty, techniques involving bone resection and soft tissue balancing are associated with poor reproducibility and the lack of the advantage of finetuning implant positioning along with the risk of iatrogenic soft tissue injuries. Inaccurate prosthesis positioning or gap balancing may lead to reduced patient recovery and prolonged rehabilitation, less satisfactory outcomes, increased instability with the reduction in the implant lifespan.[10][11]

Robotic total knee arthroplasty uses certain software to convert anatomical images into a virtual three-dimension reconstruction of joints. The anatomy is usually obtained by requesting pre-operative CT or intraoperative tibia and femur mapping. The surgeons use this model to plan the perfect bone cut, implant positioning, limb alignment, and bone coverage based on the patient’s anatomy. The intraoperative robotic device helps to minimize iatrogenic soft-tissue and bony injury.[1][12][13]

Indications

Robotic TKR was developed to improve bone preparation accuracy and decrease the possibility of outliers to guarantee a longer prosthesis lifespan. Adequate restoration of the mechanical axis in TKA is associated with a decrease in polyethylene wear and a lower revision arthroplasty rate.[14][15][16]

Some literature demonstrated accepted flexion and extension gaps in 94% of the robotic TKR patients however in the conventional TKR patients this figure was 80%. The system allows the surgeon to adjust soft tissue balance using gap measurements provided by the robotic software. This can be done before any bone cuts or after cuts are made.[17]

Contraindications

Increased surgical time is a risk factor for surgical site infection. So in any patient who has an increased risk of infection for any reason, it is preferable to do the quicker conventional arthroplasty operation to avoid infection.

Equipment

 There are different types of robotic knee arthroplasty. Certain types actively do all steps of tibial and femoral bone resections, known as “fully active.” Other types enable the surgeons to do the surgery while giving feedback intraoperatively to assist in control resection of the tibia and femur to the pre-operative surgical plan, and this group is known as “semi-active.” The surgeon makes the approach, puts the retractors to protect the soft tissues. The robotic TKR then performs the bone resections according to the previous preoperative plan. This robotic TKR system has visual, audio, and tactile feedback that assists the surgeon in controlling his force and the direction of movement of the saw during the femoral and tibial bone resection.

Some robotic TKR provides software to convert two-dimension knee X-rays into a three-dimension bone model, and the role of the robotic device is to assist in applying the cutting blocks and perform the bone resections with better accuracy.[1]

Technique or Treatment

Robotic  TKA is a technology that uses dynamic referencing to assess knee stability, alignment, and knee range of movement intraoperatively, enabling intraoperative adjustments of bone resection and positioning of the prosthesis. Reduced soft-tissue dissection and muscle injury help reduce the inflammatory response and improve the achievement of physiotherapy goals quickly, such as straight leg raise restoration.[7]

Examples of the Available Robotic-Assisted TKA Systems

There are several types of robotic TKR with different brand names. One of these types consists of a robotic arm designed to assist in TKA through a haptic interface. This semiactive robotic system stops the saw when bone resection begins to go outside predetermined parameters set in the preoperative plan. It improves the surgeon's ability to perform the knee alignment and protect the soft tissue components like the MCL, PCL, and the popliteal artery. It creates a three-dimensional model of the patient's knee from CT images to exactly calculate bone resection, prosthesis size, and position.[18]

Another type of semiactive robotic system is a handheld robotic burr manually controlled by the surgeon. It is used for partial knee arthroplasty (unicondylar TKR and patellofemoral knee arthroplasties); it is also now available for TKA. Instead of working through a haptic interface, it is a semiactive system that follows the navigation field's burring tool trajectory. It controls the exposure and speed of the burr to protect against undesired resection of tibia or femur. This system does not need preoperative CT. It also can be used with different prosthetic implants and different brands.[14][19][20]

Some other types were developed to obtain adequate implant fit and positioning; it is a CT based autonomous active system and is suitable for any prosthesis. The CT scan is uploaded to software to create a three-dimensional image, then the surgeon plant the surgery preoperatively and decide the exact resection size of the bone, prosthesis sizing, and positioning. The surgeon confirms the restoration of the mechanical axis. After the usual surgical approach, positioning, and validation of the device with pins followed by navigation markers, then the robotic tools do both femoral and tibial cuts.[14][21]

The last type of robotic TKR is a motor-powered robotic TKR that helps the surgeon to do precise tibial and femoral cuts. It needs a preoperative plan to avoid mistakes while using a conventional saw, oscillating to ensure accurate alignment and positioning of the prosthesis. This type of robotic TKR does not use a preoperative CT scan. One of its disadvantages is that it is only suitable for one type of knee prosthesis.[14][19][22]

Complications

The robotic TKR is expensive and needs software applications to be installed. The preoperative CT adds a cost to the total cost of the procedure and increased radiation exposure. Also, there is an increase in the time of operation, especially during the learning phase. In addition, the surgical team's continuous training and software updates are needed. Additional time is required for preoperative planning, and a technical engineer is usually needed in the operating room to facilitate the robotic procedure. If any unresolved difficulties happen, it will require intraoperative conversion to conventional TKA.[1]

Clinical Significance

The robotic TKR  has increased significantly over the last years. Robotic TKR improves surgeons' ability to control implant positioning, ligament balance, and limb alignment, leading to increased prosthesis survivorship. As this technology continues to increase, more long-term studies are required to check how robotic surgery will affect implant survivorship. There are promising mechanical, radiographic, and clinical results of robotic TKR. Hence, most arthroplasty surgeons support the continued usage of this robotic technology to improve surgical accuracy and patient outcomes in knee arthroplasty.[23] 

Revision knee surgery is indicated for postoperative complications with the main focus on implant loosening, whether septic or aseptic. Kaplan-Meier survival analysis of a 10-year follow-up study showed a higher survival rate for the robotic-assisted total knee arthroplasties.[24]

Enhancing Healthcare Team Outcomes

Robotic TKA is characterized by decreased postoperative pain and requirement of analgesia, better HB levels, quicker restoration of the straight leg raise test, a short stay in the hospital, and better knee flexion on discharge in comparison with a conventional TKA.[7] However, there were some reports showed that there is no significant improvement of long-term clinical outcomes of robot TKA in comparison with conventional TKA, which included evaluating the long term postoperative range of motion and incidence of complications. The short term results showed that robotic TKR is better than conventional TKR in these aspects.[25]