Degradable, Absorbable Or Resorbable—What Is the Best Grammatical Modifier for an Implant That Is Eventually Absorbed by the Body?
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SCIENCE CHINA Materials REVIEW mater.scichina.com link.springer.com Published online 26 April 2017 | doi: 10.1007/s40843-017-9023-9 Sci China Mater 2017, 60(5): 377–391 Degradable, absorbable or resorbable—what is the best grammatical modifier for an implant that is eventually absorbed by the body? Yang Liu1, Yufeng Zheng1* and Byron Hayes2 ABSTRACT The adoption of grammatical modifier for im- INTRODUCTION plants or other kinds of biomaterials eventually absorbed by the body has been a long-standing confusing issue, and there Current situation are diverse terms in the large fields of research, which not Technologies labeled as absorbable, bioabsorbable, re- only causes the difficulties when searching on the Internet, sorbable, bioresorbable, degradable, biodegradable, or by but also blurs the meaning and boundaries for researchers. some other similar terms, all of which carry the inher- Prior unification attempts at laws/standards set the basis for such research fields towards researching, labeling, marketing ent underlying potential to allow treated tissue to return and instructions for use. Considering this, the typical gram- to its native state, have been developed for a long time. matical modifiers “biodegradable”,“resorbable”,“absorbable”, More specifically, it likely started with the use of sheep along with their noun forms used in the decades of scien- gut guitar strings (made of natural collagens, recognized tific research have been reviewed and explained, interdiscipli- as absorbable polymer today) to approximate wounds nary in chemistry, ecology, materials science, biology, micro- over 2,000 years ago in the Roman Empire [1]. As time biology, medicine, and based on usage customs, laws, stan- and technology progressed, the catgut suture technology dards and markets. The term “biodegradable” has been not became significantly refined and synthetic polymers were only used in biomaterials but also in ecology waste manage- ment, biomedicine and even natural environment. Mean- also developed, both of which led to the absorbable su- while, the term “resorbable” has long been used in biological tures we find in broad use today. Resorbable bioceramic reaction (osteoclast driven bone resorption), but is inappro- technologies also entered into use as bone fillers [2,3]. In priate for implants that do not carry the potential to grow addition, the newly evolving biodegradable metals (such back into their original form. The term “absorbable” focuses as Mg, Fe, and Zn and their alloys) are now making their more on the host metabolism to the foreign biodegradation way into the commercial marketplace [4,5]. All these products of the implanted material/device compared with the devices carry the promise of fulfilling their intended initial term “degradable/biodegradable”. Meanwhile the coherence physical/mechanical function and then undergoing com- and normalization of the term “absorbable” carried by its own positional conversion into components that are eventually in laws and standards contributes as well. In general, the au- thors consider the term “absorbable” to be the best grammat- absorbed by the body. ical modifier with respect to other adjectives which share the Meanwhile, numerous terms have been used to describe same inherence. A further internationally unified usage is the same general concept, with the diversity of terms pro- proposed by us. viding self-evidence of either the absence or non-adherence to standard terminology. Compounding this nomenclature dilemma, literature in the field of absorbable/biodegrad- Keywords: biodegradation, bioabsorption, bioresorption, able/resorbable implant materials has been increasing ex- biodegradable, absorbable, biomaterials ponentially since the mid-1980s when the synthetic alpha- 1 Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871, China 2 Biomaterials Research and Development, Medical Product Division, W.L. Gore & Associates, Inc, Flagstaff, Arizona 86003, USA * Corresponding author (email: [email protected]) May 2017 | Vol.60 No.5 377 © Science China Press and Springer-Verlag Berlin Heidelberg 2017 REVIEW SCIENCE CHINA Materials hydroxyester polymeric resins first became broadly avail- ignations of both ABSORBABLE and NONABSORBABLE able from commercial suppliers. To attain a preliminary sutures [15,16]. This same standardized language and clas- understanding of the scope of the confusion surrounding sifications remain in place today and have been for decades labeling of these implants, all any person has to do is to ini- embedded in both United States Federal laws and US-Food tiate an Internet search, which—in order to confidently ad- and Drug Administration (FDA) regulations [17–19] (to dress a single simple concept—begins as a convoluted as- be discussed in later section), as well as in the United States, terisk-filled multi-line query. British, and European Pharmacopeias [20–22]. Trying to Such problem not only causes the difficulties when change or reverse what has already been both functional searching on the Internet, but also blurs the meaning and and established in both regulations and law (now for boundaries for researchers. The absence of any universal decades) is both difficult and a questionable undertaking. term recognition unnecessarily complicates communica- Regardless of this historic and significant establishment of tion and confounds the selection of language for research ABSORBABLE as standardized terminology, it is possible papers, legal descriptions, international trade agreements, that a simple lack of awareness and/or rigorous review by as well as the language used in an implant’s labeling, those involved in the broader research and clinical fields marketing, and instructions for use. Regardless of its may have become the source for the plethora of similar and obviousness, the problem has been a present and fully analogously utilized terms we routinely encounter today. recognized problem that has persisted for decades. Some The advances in standard unification of the grammatical intermittent attempts have been made by researchers to modifier provide insights to the term usage in the research unify this disparate language into a single preferred term of such field. Due to the fact that many grammatical mod- [6,7]. As a result, multiple purportedly “definitive” papers ifiers have been used in this field for a long time, typical have been published through the years. However, many terms have been reviewed and explained, interdisciplinary of these papers reflect the perspective of a single author in chemistry, ecology, materials science, biology, microbi- or society, which often leads to conflicts between nomen- ology, medicine, and based on usage habits, laws, standards clature preferences [8–13] for even a single professional and markets. Furthermore, the international unification of society’s breadth of view can be similarly limited by its own the grammatical term usage is proposed. scope. Materials that are absorbed by the body do span many medical disciplines, and the breadth of the technol- TERMINOLOGY ogy’s applicability may contribute toward inhibiting any As stated in the opening sentence, multiple terms are be- one professional society from attempting a nomenclature ing utilized to describe the same general absorbable im- resolution—as can be evidenced at numerous conferences plant concept, which includes absorbable, bioabsorbable, where one can observe an internal array of presentations resorbable, bioresorbable, degradable, biodegradable, and and posters with titles and terminology spanning most (if potentially other similar themes. To provide an improved not all) the terms described in the 1st sentence. understanding of the scope of current language diversity, an overview of the usage of the aforementioned words was Standards development in advance undertaken to provide data that assisted in both confirming Typically absent from most of these historical nomencla- and clarifying the scope of the problem. The results are in- ture recommendations was any comprehensive consid- tended to provide a summary understanding of the scope eration of the truly broader medical context contained of confusion (i.e., how big the problem really is) so as to within medical dictionaries and the relevant pharma- better facilitate identification of an appropriate remedy. copeial and/or implantable device-related standards [14]. Early device and pharmaceutical companies, regulators, Overview of utilization of the terms “degrada- and any of the involved standards development organi- tion”/“biodegradation” and “degradable”/“biodegradable” zations all had to consciously think about and decide on “Degradation” and “biodegradation” are both used in the specific terms to include on their labels and in any polymers and ceramics for a period of time, and had been governing standard, regulation, and/or law. With implants noted by Prof. D. Williams as “the process as deleterious that are eventually absorbed by the body, the selection and change in the chemical structure, physical properties, standardization of terminology by the United States Phar- or appearance of a material” according to the American macopeia had already occurred and had fully focused on Society for Testing and Materials (ASTM) [23]. In the the term ABSORBABLE by 1939 through its official des- research of “biorelated” polymers, International Union 378 May 2017 | Vol.60 No.5 © Science China Press and Springer-Verlag Berlin Heidelberg 2017 SCIENCE CHINA