Published 12/1/2013

Face Off: Robotic Knee Surgery

Robotic knee surgery is the wave of the future.

William M. Mihalko, MD, PhD

The use of robotic technology is increasing in many aspects of manufacturing and in our everyday lives. We now have robotic technology to clean our floors and aid in the construction of many everyday devices—from smartphones to automobiles. However, like many other technological advances, robotic technology is infiltrating the field of medicine, particularly orthopaedic surgery, at a slower rate.

Robotic systems in orthopaedic surgery can be described in the following three ways:

  • Active systems, such as the ROBODOC® (Curexo Technology Corp.) and CASPAR (computer-assisted surgical planning and robotics) technologies, are capable of performing individual tasks autonomously.
  • Passive systems provide additional information during a procedure but do not perform an action and require constant surgeon control.
  • Semiactive systems, such as computer-aided saw guides, constrain or adjust surgical actions, but the final control still depends on the surgeon.

One of the most frequently used robotic surgical systems is the da Vinci Surgical System, which mimics and refines a surgeon’s hand movement. This technology has been applied to procedures such as prostatectomy, but its use in orthopaedics is limited.

The main robotic system in knee surgery is the RIO (MAKO Surgical, now owned by Stryker Corp.) system for unicompartmental knee arthroplasty (UKA). This semiactive system uses a computed tomography-based preoperative plan with intraoperative registration. The technology uses haptic (tactile feedback) constraints to convey a more precise method of preparing the bone for implant placement to the surgeon.

Overall, the use of robotics for total knee arthroplasties (TKAs)and UKAs has demonstrated an ability to improve component positioning, but no study has demonstrated improved functional outcomes at near-term or medium-term follow-up. This may be due to limited sensitivity of clinical outcome measures or to the limited follow-up. Longer-term follow-up is needed to demonstrate whether improved positioning results in clinically significant improvements in patient outcomes.

A newer technology—navigated freehand bone cutting (NFC)—has what this author believes is the most potential to be useful in knee arthroplasty surgery. This technology can use either preoperative three-dimensional imaging or computer navigation registration landmarks to aid surgeons in aligning implants. It has the added advantage of ridding the operating room of manufacturer-specific instrumentation and the potential to eliminate bulky, heavy pans and instruments as well as the central supply sterilization nightmares.

With NFC, the surgeon selects the implant manufacturer, and the technology provides the cutting parameters. The surgical saw displays the cutting plane on the bone and real-time haptic technology turns the saw off if the surgeon directs it out of the plane of the planned implant position. Although evidence is lacking to support the use of these technologies in a widespread routine fashion, the evidence available indicates that this will be the wave of the future.

A substantial amount of personnel time and manufacturer overhead is involved in creating and sterilizing the instruments to implant arthroplasty components during knee surgery. When these costs are negated, the cost basis for the robotic technology becomes apparent. Stryker’s recent acquisition of MAKO Surgical—for more than $1 billion—is evidence that this implant manufacturer believes robotics has a promising future in knee arthroplasty surgery.

The use of robotic technology also will enable a patient-specific approach to implant design and surgery in the future. Just as dental robotic milling technology can create custom ceramic crowns for implantation in minutes, so could robotic technology someday enable the creation of custom orthopaedic implants.

The use of robotics in our lives will continue to increase, and its applications in knee arthroplasty are just being realized. These examples are merely the tip of the iceberg; robotic technology is the best current option we have to advance our surgical knee procedures from the subjective to the objective realm.

William M. Mihalko, MD, PhD, chairs the AAOS Biomedical Engineering Committee.

Disclosure information: Dr. Mihalko reports ties to the following: Aesculap/B. Braun; Medtronic; Smith & Nephew; Stryker; Saunders/Mosby-Elsevier; Springer; Journal of Arthroplasty; Reconstructive Review; American Orthopaedic Association; ASTM International.

Despite the claims, robotic surgery hasn’t improved outcomes yet.

Lucas Armstrong, MD, and William A. Jiranek, MD

Robotic-assisted orthopaedic surgery has been used in the United States for more than 20 years, ever since the introduction of the ROBODOC® system to assist in total hip arthroplasty in 1991. Currently, more than 25 robotic systems are in clinical use in Europe, with varying amounts of surgeon control and technology.

The theoretical advantages of robotic systems for TKA are quite appealing and include the following: improved accuracy of bony cuts, more reliable and reproducible outcomes, and improved precision in component placement. However, adoption of this technology has been slow for several different reasons.

The disadvantages to utilizing robotic-assisted surgery include the following:

  • a steep learning curve and significant up-front costs
  • the need for additional personnel in the operating room
  • increased operative time due to other invasive procedures required to place the referencing fiducials (markers)
  • the need for significant forces to cut eburnated, arthritic, subchondral bone, which can deflect cutting instruments
  • the possibility of increased surgical exposure and soft-tissue disruption to allow for use of this technology

Many studies have shown that using robotic techology results in improved mechanical alignment and component positioning for knee arthroplasty, particularly for medial UKA. Unfortunately, no long-term studies correlate these improvements with better clinical outcomes or increased implant longevity.

One randomized, controlled study on robotic-assisted TKA showed improved radiographic outcomes in some measured parameters but no improvement in others. Nor did it show any improvement in the clinical outcomes of postoperative range of motion, Knee Society Score (KSS), or knee functional score. The improvement of radiographic outcomes came at a cost of increased operative time and an increased rate of complications, including a tendon rupture and peroneal nerve injury.

Another prospective, randomized, controlled study compared conventional medial UKA with robot-assisted surgery. The robotic group had better radiographic outcomes and alignment as well as a short-term trend toward clinical improvement based on the Western Ontario and McMaster Universities Osteoarthritis Index and KSS scores at 6 and 12 weeks, but this did not meet statistical significance. However, operative time increased by 16 minutes for the robotic group.

Other studies have shown no short-term improvement in mean KSS, and no change in KSS score, Marmor rating, or significant differences in the individual measures of these scores with robotic-assisted surgery.

One problem inherent with technology is that it can fail. One study reported a 23 percent failure rate, while another reported only a 3 percent technology failure rate.

New technology also raises the issue of increased cost. All robotic-assisted knee arthroplasty requires preoperative planning with a computed-tomography scan. Along with the monetary cost of the scan comes the increased exposure to radiation for the patient.

The initial capital equipment cost of robotic technologies can exceed $800,000—exclusive of mechanical maintenance, calibration, and software updates. One review paper suggested that this cost could be recouped in approximately 2 years with increasing utilization of the technology, but this analysis is predicated on the assumption that payers will continue to reimburse for this technology, which has yet to show improved clinical outcomes.

Much like computer navigation-assisted knee arthroplasty, robotic-assisted knee arthroplasty leads to improved accuracy and consistency in placement of both TKA and medial UKA components, with fewer outliers. It allows a direct transfer of preoperative plan to the operating room environment, but cannot correct a flawed preoperative plan. Robotic-assisted surgery increases operative time, requires a learning curve (with the potential for increased complications), and increases cost without any improvements in clinical outcomes or implant longevity.

For more information on robotic surgery, see “Robotic Surgery in Arthroplasty.”

Lucas Armstrong, MD, specializes in adult reconstruction; William A. Jiranek, MD, is the section editor for adult reconstruction for the AAOS Orthopaedic Knowledge Online Journal.

Disclosure information: Dr. Jiranek reports ties to the following: DePuy, a Johnson & Johnson Company; Orthopaedic Knowledge Online Journal; American Association of Hip & Knee Surgeons; Orthopaedic Learning Center. No information is available for Dr. Armstrong.


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