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American, European views on using navigation for minimally invasive TKA diverge
While European surgeons integrate mini protocols and seek to limit tissue trauma, North American orthopedists continue with ‘mini-or-not’ comparisons.
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As interest in minimally invasive total knee arthroplasty grows, surgical communities on either side of the Atlantic have developed divergent views of the procedure, the impact of consumer advertising and the outlook for navigation.
In two presentations at the 6th International Congress of Expertise in Orthopaedic Navigation in Edinurgh, S. David Stulberg, MD, of Chicago and Alberto Gregori, FRCSEd, of Glasgow, offered differing North American and European perspectives on minimally invasive total knee arthroplasty (TKA) and the role navigation plays in the procedure.
But before any discussion begins regarding an American perspective, Stulberg suggests that surgeons note the difference between the “definition” and the “concept” of minimally invasive TKA. Many use the phrase “minimally invasive surgery” to describe procedures associated with decreased hospital stay, less pain and better outcomes. “However, whereas the term ‘minimally invasive’ is either clearly defined or understood in other medical applications, no such definition or understanding of the term currently exists when applied to TKA,” he wrote in a paper in the SLACK Incorporated journal Orthopedics.
Weak correlations, poor methodology and the impact of extraneous variables make it difficult to define such procedures. Most researchers associate mini procedures with incision length, but “the relationship of the length of the skin incision to any of the clinical outcomes associated with TKA is not established,” Stulberg wrote. Researchers have not even agreed on a method of measuring cuts and are only now determining objective measures for assessing procedures.
Less-invasive surgery
Advances in pain management also make it harder to determine the effect of surgical techniques on outcomes. “The introduction of various anesthetic and pain management therapy techniques designed to reduce perioperative morbidity and improve clinical outcomes makes assessing the role of less-invasive surgical techniques difficult,” he said.
Due to these complications, American surgeons use the term “less-invasive surgery” and focus on creating less tissue trauma. Yet, this phrase also proves problematic. Less-invasive techniques, such as quads sparing, tout soft tissue preservation but there remains no objective research backing this claim, Stulberg said. Furthermore, researchers lack a definition and measures for soft tissue trauma. “Thus, terms describing these approaches must be recognized by surgeons and patients as being descriptive rather than quantitative,” he wrote.
“The term ‘less-invasive’ TKA surgery implies the incorporation of a variety of anesthetic, pain management and perioperative management techniques designed to reduce morbidity and improve outcomes,” Stulberg wrote. “Although the importance of these approaches is not yet known, it is believed that they are as important as, and probably more important than, the surgical maneuvers currently called minimally invasive.”
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Courtesy of Alberto Gregori |
Direct-to-consumer issues, disclosure
The commercialization of these procedures creates ethical dilemmas in the American medical community, Stulberg said. Direct-to-consumer advertisements often publicize claims unfounded by substantial research, he said. Making matters worse in his view: more surgeons with corporate ties.
“The need for appropriate disclosure of these relationships is a topic of intense discussion within the orthopedic community,” he wrote. “Perhaps the biggest concern to the American orthopedic community is the potential that the promotion of less-invasive technology may result in false and inappropriate patient expectations about the outcomes of a TKA performed using less-invasive techniques.”
Yet, medical organizations strive to safeguard patients from exaggerated claims and prevent surgeons from overstepping ethical boundaries. He cites the American Association of Hip and Knee Surgeons’ guidelines on minimally invasive arthroplasty and stricter peer reviews as examples of ensuring ethical practices.
Need for computer-assisted surgery
Less-invasive procedures require less exposure and therefore minimize surgeons’ field of view. Surgeons employ miniaturized instruments, mobile windows or customized retractors to compensate for limited visualization, but they may inadvertently introduce more errors.
Smaller tools may decrease the accuracy of implant positioning and the location of cutting blocks. Similarly, smaller cutting blocks prove difficult to adhere to bone and may shift during resection. Procedures that call for removing blocks before finishing cuts can also alter the accuracy of the resection. “Finally, the use of ‘offset tools’ (eg, medially rotated total knee cutting blocks) may introduce alignment errors that are difficult to appreciate through the small minimally invasive incisions,” Stulberg wrote.
Computer-assisted surgery attempts to avoid these potential complications. Surgeons using this technology produce good or better average limb alignment than that achieved with manual surgery. In addition, computer-assisted surgery reduces the occurrence of misaligned limbs and ensures correct implant positioning. “These results have also emphasized the usefulness of computer-assisted techniques for measuring the accuracy of each step of the surgical procedure,” Stulberg wrote.
Using computers in these procedures remains essential, he said, but computer technology still must prove cost- and time-effective and keep pace with emerging mini techniques.
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Courtesy of S. David Stulberg |
A European viewpoint
Many of the differences between North American and European views regarding minimally invasive TKA stem from the acceptance of navigation, Gregori said. European surgeons readily embraced technology as a means of increasing visualization and reproducibility. Navigation allowed surgeons who were astute in traditional TKA to become secure in performing mini procedures.
European surgeons view mini approaches as a natural progression of navigation and do not conceptualize it as a “new development,” he said. Therefore, the ethical committees existing in North America prove unnecessary in Europe.
Industry push
Like Stulberg, Gregori said that commercialism helps drive the market for mini TKA procedures in North America. While this commercial pressure and subsequent consumer demand increased in the United States over the last four years, in Europe, “a more measured and investigative approach has been taken outside the private sector,” he said.
Industry claims of increased function and consumer interest add problems for average surgeons. Although experienced surgeons could manually achieve reproducible and accurate mini procedures, the average surgeon may not. “At best, however, average TKA surgeons (using mini procedures) achieve accuracy similar to the accuracy achieved with conventionally placed implants aligned in the accepted range of 3° valgus at 83%,” Gregori wrote. “These results are significantly inferior to the results achieved with navigation.”
Significant research on standard TKA shows more accurate alignment with navigation but, “no published evidence confirms that improved alignment with navigation exists in minimally invasive-navigated TKA apart from relatively small studies,” Gregori said.
Involvement in direct-to-consumer advertising can lead to deregistration in the United Kingdom. “Except for advertising on the Internet, advertising directly to patients is mainly a North American phenomenon,” Gregori said. Although media attention to minimally invasive total knee arthroplasty exists in Europe, consumer interest is not comparable to that in the United States. “However, European patients’ interest does not equal U.S. patients’ interest and has not generated the same demand for what can be deemed a ‘fashionable’ technique,” he wrote.
The lure of financial savings also strengthens the push for mini TKA in North America. “In Europe, little excess commercial pressure exists to provide a particular approach or surgery without patients leaving for competing private surgeons,” Gregori said. “However, this pressure exists in large North American urban areas.”
Because such procedures claim to decrease length of stay, medical centers may view the operations as a way to save money. North American patients receiving mini TKA prove to be highly motivated and often request the procedure. In addition, some North American patients would not be considered candidates for surgery in Europe, which may enhance the benefits of the operation.
The result of these accumulated differences: “It seems unlikely that outpatient minimally invasive TKA will progress in Europe as it did in North America,” Gregori said.
Is there a difference?
European surgeons often assess patient outcomes on perioperative factors — not surgical techniques. For example, they may evaluate flexion and extension on anesthetic use. In his survey of European surgeons, Gregori found that physicians using mini invasive navigation for TKA incorporate similar techniques into their traditional procedures. “Most surgeons surveyed have seen a remarkable change by using the rapid rehabilitation protocols of minimally invasive TKA for standard TKA,” he wrote.
Unlike American surgeons who compare quads-sparing and vastus medialis obliquus snip with subvastus approaches, European surgeons note minimal differences between these techniques. “This observation is supported by anatomical work by Holt et al that confirms that the anatomical relationship between the vastus medialis obliquus insertion and the patella follows a Gaussian curve with respect to the patellar height down to 93%,” Gregori wrote. “Similarly, fibers of the vastus medialis obliquus act as distal tensors of the medial retinaculum. Therefore, variable damage to this structure depends on an individual’s anatomy and not the approach.”
Similarly, European studies on mini procedures do not demonstrate the superior range of motion at six to 12 months postop as reported in North American research. “The European perspective of minimally invasive TKA seems to be echoed in Ranawat’s ethic of reduced tissue trauma surgery, rather than in the ‘minimally-invasive-surgery-or-not’ TKA of other proponents in North America,” Gregori wrote.
Benefit of mini protocols
Despite these differences, surgeons from both regions note the advantages of using the rehab protocols and analgesics of minimally invasive procedures with traditional arthroplasty. “Also, European and North American surgeons realized that reduced patellar eversion and resection of the suprapatellar pouch can minimize postoperative pain, improve mobilization and possibly improve proprioceptive function,” Gregori wrote.
For more information:
- Gregori A. Minimally invasive navigated knee surgery: a European perspective.
- Stulberg SD. Minimally invasive navigated knee surgery: an American perspective. Both presented in Orthopedics. 2005;28:S1235-1245.