Letters to the Editor / The Journal of Arthroplasty 29 (2014) 648–649
noble one that may lead to this goal. Many of the problems that Dr. Harris alludes to such as metal-on-metal interface adverse reactions, were first noted by the various international registries. It is imperative that we reach the AJRR's goal of 90% of hospital enrollment and to that extent, these efforts are moving in the right direction which is certainly quite exciting for our field. The registry needs to eventually provide level IV data that include information that may be relevant, including comorbidities, surgeon experience, and other patient factors, as well as details concerning each specific prosthesis being evaluated. I really would like to mention that these are not the only potential answers to our problems. Many of the failures that Dr. Harris alludes to would not have been picked up by a limited introduction because they were only detected at 1 to 2 years or later mean follow-up times. Larger numbers reveal problems through registries or from adverse case reports, however, many of these failures will only be picked up at longer-term follow-up. In addition, one must realize that a limited introduction might not pick up certain serious problems. For example, in the pharmacology industry, if a drug led to a mortality in 5 (0.5%) of 1000 cases, if 100 patients were treated, there would be a 50–50 chance that this would not even be picked up. It is only after thousands of drugs are taken that problems are found. This might be analogous to our field where thousands of prostheses might need to be implanted before we see an increasing failure rate. I would also like to think that we should not completely discourage innovation of new prostheses or devices. An alternate device approval mechanism includes the pre-market approval pathway supplemented by an investigational device exemption (IDE) study. Unfortunately, few devices are approved under this pathway [3]. In addition, another way to ensure safety is through post-market surveillance of medical devices as mandated by the FDA in which serious adverse events are supposed to be reported. However, a recent study by Mahomed et al [4] found that as few as 6% of serious adverse events are captured. We need to combine all of these methods that include in vitro testing, as well as pre-market and post-market clinical outcome evaluations for any new devices. I agree with Dr. Harris that this past decade has been unsettling and disappointing. However, one must realize that this last decade has encompassed an expansion in the indications for our prostheses. The mean age for patients receiving total hip arthroplasties is going down and patients want to be much more active. In addition, we are performing these procedures in patients with more comorbidities. This expansion of the indications may partially account for the disappointing results. We must also realize that there have been problems in every decade since the inception of this procedure, from using Teflon materials in the 1970s, to poor cementing techniques in the 1980s, to poor fixation surfaces for cementless designs in the 1990s, and we have evolved just as described by Green [1]; progress in medical technology will parallel the mechanisms of evolutionary biology with the release of some new devices eventually proven to be inferior or ineffective. We learned from many of our failures which ultimately led to timely successes and improvements. For example, even Dr. Harris' work and present success of highly cross-linked polyethylene was built on the multiple prior attempts and failures to try to improve on polyethylene wear. Once again, I commend Dr. Harris for bringing up this topic for discussion. The exact mechanisms by which we combine registries with graduated introduction, as well as other mechanisms need to be further defined. Michael A. Mont MD Rubin Institute for Advanced Orthopedics Center for Joint Preservation & Replacement Sinai Hospital of Baltimore Baltimore, Maryland
649
William J. Hozack MD Rothman Institute Thomas Jefferson University Philadelphia, Pennsylvania John J. Callaghan, MD Department of Orthopaedics University of Iowa Iowa City, Iowa http://dx.doi.org.10.1016/j.arth.2013.10.012
References 1. Green SA. The evolution of medical technology: lessons from the Burgess Shale. Clin Orthop Relat Res 2001;385:260. 2. Zywiel MG, Johnson AJ, Mont MA. The Orthopaedic Forum. Graduated introduction of orthopaedic implants: encouraging innovation and minimizing harm. J Bone Joint Surg Am. 2012;94:e158(1-5). 3. Pietzsch JB, Aquino LM, Yock PG, et al. Review of U.S. medical device regulation. J Med Device 2007;1:283. 4. Mahomed NN, Syed K, Sledge CB, et al. Improving the post-market surveillance of total joint arthroplasty devices. Open Rheumatol J 2008;2:7.
Response to Dr. Mont Dear Michael, I value your response to my Letter to the Editor and espouse the similarities between your thoughts and mine. While I agree that “the devil is in the details,” I also feel that the thrust of the major concept of stepwise introduction is very important and will determine how progress will take place. Look how parallel your suggestion of “graduated introduction” is to Malchau's stepwise concept. Both you and he restrict the general release of innovation until after the results are available from those selected centers which study the innovation for a substantial period of time before a general release. The monitoring needs to be by institutions or nations with a level 4 registries because only level 4 registries have the serial radiographic analysis, which is essential. We also agree that the duration of time of study and analysis may well need to be 5 years or so in order to be representative of the true risk. It might be less for especially selected innovations of unique types. But it is essential that large numbers of cases—those from the graduated or stepwise introduction study and many after the general release would continue to be followed by registry surveillance (local, regional, or national), no longer as a specific project but rather the increasingly routine data collection by registries as is being done now many places in the world. Only this wide inclusion in routine registry post-marking surveillance will address the less common complications (for example 1 of 5000). But in reality total hip surgery today is not being challenged by complications at that rare level, namely 1 of 5000. Today we are talking about complications at the 10%, 20%, 30% and even higher rates. I do disagree with Green's advice that we do Darwinian natural selection as the approach to innovation. Surely we can do better than that in the 21st century—as both your editorial and my letter describe. Sincerely, Bill Harris William H. Harris MD, DSc
http://dx.doi.org.10.1016/j.arth.2013.10.013
The Conflict of Interest statement associated with this article can be found at http://dx.doi.org/10.1016/j.arth.2013.10.013.
noble one that may lead to this goal. Many of the problems that Dr. Harris alludes to such as metal-on-metal interface adverse reactions, were first noted by the various international registries. It is imperative that we reach the AJRR's goal of 90% of hospital enrollment and to that extent, these efforts are moving in the right direction which is certainly quite exciting for our field. The registry needs to eventually provide level IV data that include information that may be relevant, including comorbidities, surgeon experience, and other patient factors, as well as details concerning each specific prosthesis being evaluated. I really would like to mention that these are not the only potential answers to our problems. Many of the failures that Dr. Harris alludes to would not have been picked up by a limited introduction because they were only detected at 1 to 2 years or later mean follow-up times. Larger numbers reveal problems through registries or from adverse case reports, however, many of these failures will only be picked up at longer-term follow-up. In addition, one must realize that a limited introduction might not pick up certain serious problems. For example, in the pharmacology industry, if a drug led to a mortality in 5 (0.5%) of 1000 cases, if 100 patients were treated, there would be a 50–50 chance that this would not even be picked up. It is only after thousands of drugs are taken that problems are found. This might be analogous to our field where thousands of prostheses might need to be implanted before we see an increasing failure rate. I would also like to think that we should not completely discourage innovation of new prostheses or devices. An alternate device approval mechanism includes the pre-market approval pathway supplemented by an investigational device exemption (IDE) study. Unfortunately, few devices are approved under this pathway [3]. In addition, another way to ensure safety is through post-market surveillance of medical devices as mandated by the FDA in which serious adverse events are supposed to be reported. However, a recent study by Mahomed et al [4] found that as few as 6% of serious adverse events are captured. We need to combine all of these methods that include in vitro testing, as well as pre-market and post-market clinical outcome evaluations for any new devices. I agree with Dr. Harris that this past decade has been unsettling and disappointing. However, one must realize that this last decade has encompassed an expansion in the indications for our prostheses. The mean age for patients receiving total hip arthroplasties is going down and patients want to be much more active. In addition, we are performing these procedures in patients with more comorbidities. This expansion of the indications may partially account for the disappointing results. We must also realize that there have been problems in every decade since the inception of this procedure, from using Teflon materials in the 1970s, to poor cementing techniques in the 1980s, to poor fixation surfaces for cementless designs in the 1990s, and we have evolved just as described by Green [1]; progress in medical technology will parallel the mechanisms of evolutionary biology with the release of some new devices eventually proven to be inferior or ineffective. We learned from many of our failures which ultimately led to timely successes and improvements. For example, even Dr. Harris' work and present success of highly cross-linked polyethylene was built on the multiple prior attempts and failures to try to improve on polyethylene wear. Once again, I commend Dr. Harris for bringing up this topic for discussion. The exact mechanisms by which we combine registries with graduated introduction, as well as other mechanisms need to be further defined. Michael A. Mont MD Rubin Institute for Advanced Orthopedics Center for Joint Preservation & Replacement Sinai Hospital of Baltimore Baltimore, Maryland
649
William J. Hozack MD Rothman Institute Thomas Jefferson University Philadelphia, Pennsylvania John J. Callaghan, MD Department of Orthopaedics University of Iowa Iowa City, Iowa http://dx.doi.org.10.1016/j.arth.2013.10.012
References 1. Green SA. The evolution of medical technology: lessons from the Burgess Shale. Clin Orthop Relat Res 2001;385:260. 2. Zywiel MG, Johnson AJ, Mont MA. The Orthopaedic Forum. Graduated introduction of orthopaedic implants: encouraging innovation and minimizing harm. J Bone Joint Surg Am. 2012;94:e158(1-5). 3. Pietzsch JB, Aquino LM, Yock PG, et al. Review of U.S. medical device regulation. J Med Device 2007;1:283. 4. Mahomed NN, Syed K, Sledge CB, et al. Improving the post-market surveillance of total joint arthroplasty devices. Open Rheumatol J 2008;2:7.
Response to Dr. Mont Dear Michael, I value your response to my Letter to the Editor and espouse the similarities between your thoughts and mine. While I agree that “the devil is in the details,” I also feel that the thrust of the major concept of stepwise introduction is very important and will determine how progress will take place. Look how parallel your suggestion of “graduated introduction” is to Malchau's stepwise concept. Both you and he restrict the general release of innovation until after the results are available from those selected centers which study the innovation for a substantial period of time before a general release. The monitoring needs to be by institutions or nations with a level 4 registries because only level 4 registries have the serial radiographic analysis, which is essential. We also agree that the duration of time of study and analysis may well need to be 5 years or so in order to be representative of the true risk. It might be less for especially selected innovations of unique types. But it is essential that large numbers of cases—those from the graduated or stepwise introduction study and many after the general release would continue to be followed by registry surveillance (local, regional, or national), no longer as a specific project but rather the increasingly routine data collection by registries as is being done now many places in the world. Only this wide inclusion in routine registry post-marking surveillance will address the less common complications (for example 1 of 5000). But in reality total hip surgery today is not being challenged by complications at that rare level, namely 1 of 5000. Today we are talking about complications at the 10%, 20%, 30% and even higher rates. I do disagree with Green's advice that we do Darwinian natural selection as the approach to innovation. Surely we can do better than that in the 21st century—as both your editorial and my letter describe. Sincerely, Bill Harris William H. Harris MD, DSc
http://dx.doi.org.10.1016/j.arth.2013.10.013
The Conflict of Interest statement associated with this article can be found at http://dx.doi.org/10.1016/j.arth.2013.10.013.
