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We have read with interest “The Ethical Implications Of Recent Innovations In Knee Arthroplasty”, by Holt et al. (1). In it, the authors appear to imply that minimally invasive knee surgery is an “unethical procedure”, especially in comparison to computer-assisted surgery. In our review and experience with both of these new technologies, we cannot draw the same conclusions.

The authors have implied that computer-assisted surgery (CAS) has been completely scientifically validated. In fact, to date it has never been shown that computer-assisted surgery applied to knee or hip replacements has made any clinical differences. We personally utilize CAS often, have published on its use (1,2,3) and are advocates of this new technology. We believe that the field of joint arthroplasty will evolve into using CAS commonly over the next few years. However, we acknowledge that there are only a few published studies that can show any possible advantages for using this technology which has only sometimes described better radiographic alignment when compared to conventional techniques (4-8). No studies have described improved patient outcomes or provided mid- or long-term follow-up. In addition, there are other reports that show only similar radiographic results to standard techniques or even inferior radiographic results with more outliers and increased complications with CAS (9,10). Also, there can be problems with rotational alignment where there may be a false view with CAS which can compound errors. The procedure takes longer than standard techniques in all studies and this is not just a learning curve. There is an increased risk of infection, nerve injury, and fracture after insertion and removal of the tracking pins. Also important is the increased cost because of the increased time to perform as well as the expensive technology which exceeds $200,000.00 for the hardware. The software required for use can add between $30,000.00 and $40,000.00 per year. These increased overall costs are not paid for by the hospital or insurance companies and therefore must be borne in some cases by the patient. Is it not unethical to introduce a technique that has only theoretical radiographic benefit and no demonstrated proven clinical utility that is so expensive? Is the surgeon using CAS without validating the cost:benefit ratio? Holt et al. even agree (page 228, column 2, lines 21-24) that “the utility of computer-navigated arthroplasty will remain unknown until long-term follow-up data are available.” However, their statement that “… the likelihood of implant failure and the need for expensive revision surgery may be reduced (page 228, column 2, lines 18-21),” still remains unproven for CAS.

Do we believe that computer-assisted devices can help an experienced surgeon? Not really. They already have a 95%+ success rate and failures attribuatable to malalignment make up a small percentage of the remaining 5%. So the question is, "will CAS help the great majority of surgeons who perform more than 90% of the cases? We can’t be sure because this group is not the one publishing their experience with CAS. In summary, we do believe that CAS will be the wave of the future, but at present it has demonstrated only theoretical advantages and it adds increased time, complications, and costs for the procedures.

As for minimally invasive surgery (MIS), some studies have shown beneficial or at least equivalent effects when compared to conventional techniques(2,3) Some advocates of MIS have reported less post-operative pain, reduced hospital stays, and an earlier return to function when compared to standard approach for total knee arthroplasty. Other articles have shown increased early complications using this technique (skin necrosis, malposition) which might be expected with any new procedure(2,3). Most MIS advicates have urged that work be done at study centers and these techniques have generally not been released to the public unless surgeons are adequately trained. Two of us were involved in a study concerning one minimally invasive surgical technique (2,9,18). This technique was not released for general use until it satisfied at least three criteria: 1) there was at least two to four year minimum follow-up by using the technique; 2) a prospective study with multiple centers showed no increased complication rates; and 3) multiple authors and multiple institutions were able to at least equal the results when comparing this technique to standard techniques for total knee arthroplasty. Although we have used the technique since 1999, only after a randomized study was presented at the annual meeting of the American Academy of Orthopaedic Surgeons and accepted for publication, was general use expanded. It is true that some companies have released techniques or instrumentation for MIS techniques before they have been studied or deemed as “safe”, but the same can be said for CAS, as well as many other new technologies being introduced into orthopaedics. We recommend an evolutionary approach to using these techniques(9). Multiple other surgeons and centers have described slightly different MIS approaches that appear safe at short-term follow-up(11-18).

This article reminds us of one written by Charles Rockwood in 1988 who asked whether “operative arthroscopy is an appropriate method of treatment of patients who have a problem about the shoulder” … “it should be considered a research tool”(19). Eighteen years later this is a generally accepted technique with low risk for complications and the preferred technique for most shoulder procedures.

Holt et al imply that certain new procedures are unethical to use until they are 100% proven. They state that known results are needed before one can obtain informed consent; however, this is not true. Informed consent implies that the surgeon has adequately described the risks/benefits and given patients other possible options.

One of the co-authors of this Ethics in Medicine article has published his results on “Minimally Invasive Navigated Knee Surgery: A European Perspective”(20). In that article it was stated that “most surgeons who use minimally invasive TKA have consistently reported early improved range of motion, rapid mobilization, and reduced analgesic requirements. Furthermore, little difference exists between minimally invasive TKA with navigation and minimally invasive TKA without navigation. Similarly, in both North America and Europe, patients who have minimally invasive TKA achieve discharge criteria earlier than patients who have standard TKA. The improvement is independent of patient demographics.” This article extolling the virtues of MIS is in contradistinction to their comments about MIS in the Ethics in Medicine article.

The minimally invasive approaches have led some prosthetic manufacturing companies to develop better instrumentation and many surgeons have been able to downsize their incisions while maintaining or improving their surgical techniques. This is all the more important in light of the results of Sharkey et al., who won the Insall Award in 2002 and found that over 50% of knee revisions occur within two years of surgery and can be considered technique-related(21). Any improvements in technique can reduce revision rates and lead to better patient outcomes, which has been a direct result of this new MIS technology.

Is it unethical for companies to introduce new products and new instrumentation systems? These are changed every few years by the companies, especially by offering different bearing surfaces such as different iterations of polyethylene. Is this all unethical human experimentation? We agree that some companies promote products and techniques without performing appropriate due diligence; perhaps in some cases this is unethical, especially, direct to patient marketing without validation. However, this should not be a general condemnation of the entire field of MIS surgery or joint replacement surgery in general.

In summary, a major problem with the treatise is that the authors have not used the same criteria for the two procedures. They have not objectively critiqued both CAS and MIS. Both are surgical procedures and only if the MIS actually uses a differently designed prosthesis (which it does not to date), would it be reviewed by the FDA. Both procedures have had articles published on the experiences (both positive and negative). Both are limited by lack of long term follow-up. Does alignment that is closer to what you set out to accomplish result in better long-term results? Do MIS knees last longer? Having a smaller scar is not enough; is the reason they have shorter stays because someone is paying better attention to post-op care? What other factors contribute? Both procedures are limited by realistically evaluating them in the context of different experienced surgeons and different surgical values. The authors believe that new techniques should not be introduced for general use until they fulfill at least three criteria: 1) a minimum two to four year mean follow-up with at least a limited number of surgeons that have extensively studied the technique; 2) prospective randomized studies that at least show no harm with the new technique; and 3) reproducibility among multiple institutions and surgeons with the new technique. We agree with Holt et al. that there are issues with direct to consumer (patient) marketing of new, unproven approaches, but this should not be a general condemnation of the entire field. We appreciate the authors bringing this topic to the forefront for debate as it is important for these kind of discussions about new technologies to occur.

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