Original article
Quantitative analysis of technological innovation in minimally invasive surgery A. Hughes-Hallett1 , E. K. Mayer1 , P. J. Pratt2 , J. A. Vale1 and A. W. Darzi1,2,3 1 Department of Surgery and Cancer, 2 The Hamlyn Centre, Institute of Global Health Innovation, and 3 Centre for Health Policy, Institute of Global Health Innovation, Imperial College London, London, UK Correspondence to: Dr E. K. Mayer, Department of Surgery and Cancer, St Mary’s Campus, Imperial College London, London W2 1NY, UK (e-mail: [email protected])
Background: In the past 30 years surgical practice has changed considerably owing to the advent of
minimally invasive surgery (MIS). This paper investigates the changing surgical landscape chronologically and quantitatively, examining the technologies that have played, and are forecast to play, the largest part in this shift in surgical practice. Methods: Electronic patent and publication databases were searched over the interval 1980–2011 for (‘minimally invasive’ OR laparoscopic OR laparoscopy OR ‘minimal access’ OR ‘key hole’) AND (surgery OR surgical OR surgeon). The resulting patent codes were allocated into technology clusters. Technology clusters referred to repeatedly in the contemporary surgical literature were also included in the analysis. Growth curves of patents and publications for the resulting technology clusters were then plotted. Results: The initial search revealed 27 920 patents and 95 420 publications meeting the search criteria. The clusters meeting the criteria for in-depth analysis were: instruments, image guidance, surgical robotics, sutures, single-incision laparoscopic surgery (SILS) and natural-orifice transluminal endoscopic surgery (NOTES). Three patterns of growth were observed among these technology clusters: an S-shape (instruments and sutures), a gradual exponential rise (surgical robotics and image guidance), and a rapid contemporaneous exponential rise (NOTES and SILS). Conclusion: Technological innovation in MIS has been largely stagnant since its initial inception nearly 30 years ago, with few novel technologies emerging. The present study adds objective data to the previous claims that SILS, a surgical technique currently adopted by very few, represents an important part of the future of MIS. Click here to listen to the author discuss the contents of this article. Paper accepted 16 October 2014 Published online in Wiley Online Library (www.bjs.co.uk). DOI: 10.1002/bjs.9706
Introduction
Healthcare innovation can be defined as ‘a dynamic and continuous process involving the introduction of a new technology or technique that initiates a change in practice’1 – 3 . In the past three decades, surgical practice has undergone radical change with the move from conventional surgery to minimally invasive surgery (MIS). This change has been driven, at least in part, by technological innovation. Since the mid-1990s innovation in MIS has been gradual, driven by the refinement of existing surgical tools. This gradual refinement has been interrupted occasionally by the advent of a novel surgical approach or tool, for example the introduction of surgical robotics, single-incision laparoscopic surgery (SILS) or natural-orifice transluminal endoscopic surgery (NOTES)4 – 8 . © 2015 BJS Society Ltd Published by John Wiley & Sons Ltd
Patents are the initial step in the commercialization of a concept or technology, and as such patent counts probably represent a good metric with which to measure technological innovation3 . In addition to being reliable and relevant measures of innovation, patents are readily available on publicly accessible databases. As measures of innovation diffusion9,10 , patent and publication activities have been examined widely in the social science literature9 – 13 but have only recently been applied and validated for the assessment of healthcare technologies1 . The aim of this analysis was to use patent and publication data to address two broad aims: first, to establish objectively the major areas of technological innovation within MIS since 1980 and, second, to assess the innovations that have been proposed, within the surgical literature, as BJS 2015; 102: e151–e157
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the major emerging technologies in MIS (robot-assisted laparoscopic surgery, SILS and NOTES). Methods
The methodology used in this paper is based on previously published work proposing and validating patents and publications as metrics for innovation in healthcare technology. The following formula was used to correct for the exponential increase in publication and patenting over time1 : original
IIinormalized = ci =
IIi
ci
ti t2011
where IIi is the innovation index, i the year in question, ti the total number of patents granted by the US patent office and ci the innovation constant (modified from Hughes-Hallett et al.1 ). Once the corrected year-on-year counts for publications and patents (the innovation indices) had been collated, growth curves for each of the technology clusters were plotted. In addition to individual growth curves, composite charts displaying the patent and publication activity of all the investigated technologies were generated to illustrate the chronicity of technology development in MIS.
database was also undertaken using the same search strategies to generate a measure of year-on-year publication activity. In addition to the technologies identified in this step, clusters that have been referred to repeatedly in the contemporary surgical literature as areas of potential growth (SILS, NOTES and robot-assisted laparoscopic surgery) were added to the growth analysis.
Data analysis Patent and publication data were plotted against each other to determine the nature of their relationship. Depending on whether the relationship was linear or non-linear Pearson’s (r) or Spearman’s rank (r S ) correlation coefficients respectively were used to determine the degree of correlation between patent and publication numbers. When examining the chronology of patent and publication activity in the patent clusters identified, a 4-year moving average (the data point for a specific year calculated as an average of the year in question and the preceding 3 years) was used to make the data easier to interpret. Data analysis was undertaken in GraphPad Prism® (GraphPad Software, La Jolla, California, USA). Results
Overall trends in patenting and publication Establishing top performing technology clusters by patent filings Initially, a search was performed of the European patent office master documentation database, DOCDB14 , using the proprietary software package PatentInspiration (AULIVE, Ypres, Belgium). A Boolean search strategy specific to MIS (Table S1, supporting information) was used to establish patenting and publication activity within the time intervals 1980–2011 and 2000–2011. The result of the patent search was then used to create lists of the top 30 performing patent codes for the two intervals. These two time intervals were compared to highlight areas of contemporaneous innovation. Once generated, these top 30 codes were sorted into related surgical technologies by two authors, with differences in opinion arbitrated by a third. Only well defined technology clusters, not pertaining to specific surgical subspecialties, were selected for in-depth analysis. To identify any patents within these technology clusters not captured within the top 30 patent codes, a Boolean search of the DOCDB was undertaken specific to each cluster (Table S1, supporting information). A further search of the PubMed © 2015 BJS Society Ltd Published by John Wiley & Sons Ltd
The initial search of patenting and publication databases revealed 27 920 patents and 95 420 publications pertaining to MIS since 1980. After correcting for the exponential rise in patent and publication activity over time, using the formula above, the growth in both patents and publications was found to be highly correlated (r S = 0⋅949) and both followed an S-shaped pattern of growth (Fig. 1).
Top performing technology clusters The top 30 performing patent codes for the interval 1980–2011 are summarized in Table S2 (supporting information). The area in which the greatest number of patent codes have been filed was minimally invasive surgical instruments, comprising 52⋅6 per cent of patents falling in the top 30 (Table 1). The other areas fulfilling the criteria for growth analysis were: sutures, image guidance and surgical robotics (Table S2, supporting information). When the search was restricted to the time frame of 2000–2011, no new technology clusters emerged. Among the clusters analysed, the dominance of instrument innovation appeared to have waned somewhat, whereas www.bjs.co.uk
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drop off in patenting, starting in 2009, was seen for both NOTES and image guidance. Assessment of the correlation between patent and publication activity within these clusters demonstrated a strong correlation for instruments, sutures, surgical robotics and image guidance (r S = 1⋅929, 1⋅855, 1⋅937, 1⋅945 respectively; all P < 1⋅001). NOTES and SILS demonstrated lower correlation, with r S = 1⋅609 (P < 1⋅001) and r S = 1⋅532 (P = 1⋅002) respectively.
Patents Publications
No. of patents/publications
8000
6000
4000
Chronology of minimally invasive surgery
2000
0 1980
1985
1990
1995
2000
2005
2010
Patent and publication growth in minimally invasive surgery, 1980–2011
Fig. 1
Table 1
Top performing technology clusters
MIS instruments* Sutures Image guidance Surgical robotics Not included in analysis
1980–2011
2000–2011
498 (52⋅6) 65 (6⋅9) 37 (6⋅1) 60 (3⋅9) 287 (30⋅3)
157 (45⋅1) 11 (3⋅2) 26 (7⋅5) 26 (7⋅5) 128 (36⋅8)
Values in parentheses are percentages. *Including laparoscopic ports and trocars.
surgical robotics and image guidance showed increases in their patent share among the top performing codes.
Growth in the top performing and literature-derived technology clusters Corrected patent and publication counts were plotted against time for the six technology clusters identified within MIS (minimally invasive surgical instruments, sutures, surgical robotics, image guidance, NOTES and SILS) in order to establish their individual growth curves (Fig. 2). Across the six technology clusters, three different patterns of growth were observed. Instruments and sutures showed an S-shaped growth curve. For the instrument cluster this initial sigmoid curve was followed by a period of new growth, starting in 2000 (Fig. 2). Surgical robotics and image guidance demonstrated exponential growth, both starting in the early 1990s. The growth curves for SILS and NOTES both demonstrated rapid contemporaneous growth. On examination of the curves in more detail, a © 2015 BJS Society Ltd Published by John Wiley & Sons Ltd
In addition to plotting the growth curves for specific technology clusters, individual clusters were plotted alongside one another to gain an understanding of the chronology of technology development in MIS (Fig. 3); 4-year moving averages were used to allow a better understanding of trends. This demonstrated that image guidance, sutures, instruments and surgical robotics all had exponential phases of growth beginning in the late 1980s. Both sutures and instruments reached a plateau in growth by the mid-1990s (Fig. 2). A similar pattern of growth was seen in publication and patenting activity for MIS overall (Fig. 1). From their take-off in the late 1980s, image guidance and surgical robotics showed a sustained, albeit shallower, exponential rise in activity. From 1990 until the arrival of NOTES and SILS in 2005, no rapid increase was seen in any of the technologies examined. In 2005, both NOTES and SILS showed the beginning of a rapid increase in patent and publication activity. This activity was sustained for SILS, but for NOTES plateaued in 2009 (Fig. 2). Discussion
This paper examined innovation in MIS chronologically and quantitatively, scrutinizing technologies identified using a published methodology1 in addition to those that have recurred in the recent literature4 – 8 . Three patterns of growth in innovation were identified, each of which contained technologies exhibiting unique characteristics. After an initial burst of innovation corresponding to the adoption of laparoscopic techniques, innovation within MIS globally was seen to plateau until the early 2000s, when a second phase of innovation growth occurred. Within the social science literature, the concept of quantitative analysis of innovation using patent and publication-based metrics has been investigated extensively11,15 . However, quantitative research in the medical literature is limited to two papers1,3 . These two papers approached the problem of quantifying innovation differently. Trajtenberg3 examined the value of www.bjs.co.uk
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d
Image guidance 50
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40 200
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Sutures
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c
b
Instruments
200 30
20
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0 1980 1985 1990 1995 2000 2005 2010
100 10
0 1980 1985 1990 1995 2000 2005 2010
e
NOTES
0 1980
f
1985
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0
SILS
Growth curves for chosen technology clusters: a instruments and b sutures, demonstrating a classical S-shaped growth curve; c surgical robotics and d image guidance, showing a gradual but exponential pattern of growth; and e natural-orifice transluminal endoscopic surgery (NOTES) and f single-incision laparoscopic surgery (SILS), expert-identified areas of growth demonstrating steep and contemporary exponential growth
Fig. 2
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Instruments Sutures Surgical robotics Image guidance NOTES SILS
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150 No. of patents (instruments category)
No. of patents∗
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50
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0 1980
a
1985
1990
1995
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0
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b
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0
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Fig. 3 Growth curves for a patents and b publications displayed to highlight the chronology of technological innovation in laparoscopic surgery. Values are 4-year moving averages. *All technologies except instruments; †all technologies except robotic surgery and sutures. NOTES, natural-orifice transluminal endoscopic surgery; SILS, single-incision laparoscopic surgery (SILS)
patent data within a single specific technology3 , whereas Hughes-Hallett and colleagues’ work1 offered a mechanism with which to identify and predict emerging technology clusters, and to quantify an innovation’s current and potential clinical impact. Within MIS there seem to have been three distinct patterns of growth since its initial inception in the 1980s. The genesis of MIS was associated with the most visible innovation spike. In this phase, rapid exponential growth in publication and patenting activity surrounding the development of novel surgical instruments and consumables was seen (represented by the instrument and suture categories). This spike represents the development of the basic minimally invasive surgical tools, and correlates closely with the overall growth curve for MIS. Generally speaking, these technologies are simple and of low cost, accounting for the rapid growth in patent and publication activity as industry and surgeons respectively designed and validated novel and essential tools. Subsequent to this highly correlated, exponential phase of growth, these technology clusters plateaued, reaching a point of diffusion saturation in the mid-1990s, as the laparoscopic surgeon’s ‘tool box’
became saturated. At this point new patents or research tended to pertain to refinement of existing technology rather than inception of new devices12 . In the mid-2000s a new growth spike was seen in MIS overall and within the instrument cluster, probably pertaining to the adoption of new approaches to MIS (robotics, SILS and NOTES). Interesting trends were also found in the remaining technology clusters examined, with robotics and image guidance exhibiting a different pattern of growth. These technology clusters began their exponential phases of growth at a similar time to the instruments and sutures. However, in contrast to a rapid exponential growth, they experienced a prolonged exponential growth phase, and appeared not to have yet reached the point of diffusion saturation after more than 15 years. The reasons for this are probably multifactorial, but two factors in particular seem worth discussion. First, the nature of these two technology clusters means that they pose numerous and complex engineering challenges compared with the other technology clusters examined, perhaps resulting in a slower rate of development. In addition, they serve to expand the practice of MIS rather than providing the tools necessary to
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undertake it, and as such might be viewed as ‘non-essential’; as a consequence they might garner less resource from industry than the comparator and more fundamental technologies. Interestingly, although robotic surgery appears to be on a continued trajectory of exponential growth, image guidance has seen a drop off in patenting activity, perhaps corresponding to a saturation point. The final growth pattern was one of contemporary rapid exponential growth, and was seen within the literature-derived technology clusters of NOTES and SILS. Examining the growths of the technology clusters individually, it appears that SILS is undergoing a sustained and rapid exponential growth, implying innovation growth, whereas the growth of NOTES seemed to plateau after 2009. This plateau in patent and publication number within NOTES would suggest a dwindling of innovation and interest in the subject, and may reflect a failure of this approach to cross the ‘chasm’ that exists between the innovators and the early adopters (Fig. 4). The concept of a diffusion chasm was first proposed by Rogers9 and represents the point where a technology must translate from a research environment to a normal clinical setting.
Exponential growth
Saturation
Penetration of target adopters
Incubation
This chasm may also be responsible for the recent downturn in patenting surrounding image guidance in MIS, which has failed to translate into widespread operative practice despite prolonged and sustained innovation and investment. Interestingly, no novel clusters of technological innovation emerged in the more contemporary period examined. All of the innovation clusters unveiled by the systematic search of the patenting database saw the beginning of their growth curves in the late 1980s and early 1990s (Fig. 3), with no new technology clusters being identified in the period 2000–2011. This failure to identify any new clusters may be in part down to the failure of the methodology to identify potentially important innovation in its nascence1 . Equally, however, and perhaps more likely, this may suggest a stagnation in innovation, with few, if any, novel technologies having had a significant impact on minimally invasive surgical practice. Although the methodology proposed here offers a quantitative approach to defining past innovations, and assisting in assessing future technologies of influence in MIS, it is not without limitations. The first is the surrogacy
Innovators (2·5%)
Early adopters (13·5%)
Early majority (34%)
Late majority (34%)
Laggards (16%)
The chasm
S-shaped diffusion curve demonstrating the three phases of growth in any technological innovation (incubation, exponential growth and diffusion saturation) matched to the characteristics of the individual members of the adopting population9
Fig. 4
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of the measures used. To establish the diffusion, and as such the success, of a given innovation, the proportion of patients in which that innovation has been used must be measured. Although this represents the standard approach when looking at innovation within MIS, it is impractical owing to the huge number of innovations to be examined. Looking to the future of MIS, the present study adds objective data to the previous subjective claims that SILS, a surgical technique that has currently been adopted by very few, represents an important part of the future of MIS. This transition from specialist to mainstream practice may be facilitated by improvements in tools to perform the technique, with a likely role for robotic surgery. Disclosure
The authors declare no conflict of interest. References 1 Hughes-Hallett A, Mayer EK, Marcus HJ, Cundy TP, Pratt PJ, Parston G et al. Quantifying innovation in surgery. Ann Surg 2014; 260: 205–211. 2 Rogers W, Lotz M, Hutchison K, Pourmoslemi A, Eyers A. Identifying surgical innovation: a qualitative study of surgeons’ views. Ann Surg 2014; 259: 273–278. 3 Trajtenberg M. A penny for your quotes: patent citations and the value of innovations. RAND J Econ 1990; 21: 172–187. 4 Rivas H, Díaz-Calderón D. Present and future advanced laparoscopic surgery. Asian J Endosc Surg 2013; 6: 59–67.
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5 Aurora A, Ponsky J. Future perspectives on scarless surgery: where we have been and where we are going. In Scar-Less Surgery (1st edn), Desai M, Gill I (eds). Springer: London, 2013; 341–351. 6 Hafron J, Kaouk JH. Technical advances in urological laparoscopic surgery. Expert Rev Med Devices 2008; 5: 145–151. 7 Ficarra V, Ploumidis A, Lumen N. The infancy of robotic laparoendoscopic single-site renal surgery: waiting for needed technological improvements. Eur Urol 2013; 63: 281–282. 8 Lee WJ, Chan CP, Wang BY. Recent advances in laparoscopic surgery. Asian J Endosc Surg 2013; 6: 1–8. 9 Rogers E. Diffusion of Innovations (5th edn). Free Press: New York, 1962. 10 Ryan B, Gross N. The diffusion of hybrid seed corn in two Iowa communities. Rural Sociol 1943; 8: 15–24. 11 Daim TU, Rueda G, Martin H, Gerdsri P. Forecasting emerging technologies: use of bibliometrics and patent analysis. Technol Forecast Soc Chang 2006; 73: 981–1012. 12 Bengisu M, Nekhili R. Forecasting emerging technologies with the aid of science and technology databases. Technol Forecast Soc Chang 2006; 73: 835–844. 13 Nelson AJ. Measuring knowledge spillovers: what patents, licenses and publications reveal about innovation diffusion. Res Policy 2009; 38: 994–1005. 14 European Patent Office. EPO Patent Information Resource ‘DOCDB’; 2008. http://www.epo.org/searching/ subscription/raw/product-14-7.html [accessed 23 September 2013]. 15 Hagedoorn J, Cloodt M. Measuring innovative performance: is there an advantage in using multiple indicators? Res Policy 2003; 32: 1365–1379.
Supporting information
Additional supporting information may be found in the online version of this article: Table S1 PubMed and PatentInspiration search strategies (Word document) Table S2 Summary of top 30 patent codes for the intervals 1980–2011 and 2000–2011 (Word document)
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Quantitative analysis of technological innovation in minimally invasive surgery A. Hughes-Hallett1 , E. K. Mayer1 , P. J. Pratt2 , J. A. Vale1 and A. W. Darzi1,2,3 1 Department of Surgery and Cancer, 2 The Hamlyn Centre, Institute of Global Health Innovation, and 3 Centre for Health Policy, Institute of Global Health Innovation, Imperial College London, London, UK Correspondence to: Dr E. K. Mayer, Department of Surgery and Cancer, St Mary’s Campus, Imperial College London, London W2 1NY, UK (e-mail: [email protected])
Background: In the past 30 years surgical practice has changed considerably owing to the advent of
minimally invasive surgery (MIS). This paper investigates the changing surgical landscape chronologically and quantitatively, examining the technologies that have played, and are forecast to play, the largest part in this shift in surgical practice. Methods: Electronic patent and publication databases were searched over the interval 1980–2011 for (‘minimally invasive’ OR laparoscopic OR laparoscopy OR ‘minimal access’ OR ‘key hole’) AND (surgery OR surgical OR surgeon). The resulting patent codes were allocated into technology clusters. Technology clusters referred to repeatedly in the contemporary surgical literature were also included in the analysis. Growth curves of patents and publications for the resulting technology clusters were then plotted. Results: The initial search revealed 27 920 patents and 95 420 publications meeting the search criteria. The clusters meeting the criteria for in-depth analysis were: instruments, image guidance, surgical robotics, sutures, single-incision laparoscopic surgery (SILS) and natural-orifice transluminal endoscopic surgery (NOTES). Three patterns of growth were observed among these technology clusters: an S-shape (instruments and sutures), a gradual exponential rise (surgical robotics and image guidance), and a rapid contemporaneous exponential rise (NOTES and SILS). Conclusion: Technological innovation in MIS has been largely stagnant since its initial inception nearly 30 years ago, with few novel technologies emerging. The present study adds objective data to the previous claims that SILS, a surgical technique currently adopted by very few, represents an important part of the future of MIS. Click here to listen to the author discuss the contents of this article. Paper accepted 16 October 2014 Published online in Wiley Online Library (www.bjs.co.uk). DOI: 10.1002/bjs.9706
Introduction
Healthcare innovation can be defined as ‘a dynamic and continuous process involving the introduction of a new technology or technique that initiates a change in practice’1 – 3 . In the past three decades, surgical practice has undergone radical change with the move from conventional surgery to minimally invasive surgery (MIS). This change has been driven, at least in part, by technological innovation. Since the mid-1990s innovation in MIS has been gradual, driven by the refinement of existing surgical tools. This gradual refinement has been interrupted occasionally by the advent of a novel surgical approach or tool, for example the introduction of surgical robotics, single-incision laparoscopic surgery (SILS) or natural-orifice transluminal endoscopic surgery (NOTES)4 – 8 . © 2015 BJS Society Ltd Published by John Wiley & Sons Ltd
Patents are the initial step in the commercialization of a concept or technology, and as such patent counts probably represent a good metric with which to measure technological innovation3 . In addition to being reliable and relevant measures of innovation, patents are readily available on publicly accessible databases. As measures of innovation diffusion9,10 , patent and publication activities have been examined widely in the social science literature9 – 13 but have only recently been applied and validated for the assessment of healthcare technologies1 . The aim of this analysis was to use patent and publication data to address two broad aims: first, to establish objectively the major areas of technological innovation within MIS since 1980 and, second, to assess the innovations that have been proposed, within the surgical literature, as BJS 2015; 102: e151–e157
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A. Hughes-Hallett, E. K. Mayer, P. J. Pratt, J. A. Vale and A. W. Darzi
the major emerging technologies in MIS (robot-assisted laparoscopic surgery, SILS and NOTES). Methods
The methodology used in this paper is based on previously published work proposing and validating patents and publications as metrics for innovation in healthcare technology. The following formula was used to correct for the exponential increase in publication and patenting over time1 : original
IIinormalized = ci =
IIi
ci
ti t2011
where IIi is the innovation index, i the year in question, ti the total number of patents granted by the US patent office and ci the innovation constant (modified from Hughes-Hallett et al.1 ). Once the corrected year-on-year counts for publications and patents (the innovation indices) had been collated, growth curves for each of the technology clusters were plotted. In addition to individual growth curves, composite charts displaying the patent and publication activity of all the investigated technologies were generated to illustrate the chronicity of technology development in MIS.
database was also undertaken using the same search strategies to generate a measure of year-on-year publication activity. In addition to the technologies identified in this step, clusters that have been referred to repeatedly in the contemporary surgical literature as areas of potential growth (SILS, NOTES and robot-assisted laparoscopic surgery) were added to the growth analysis.
Data analysis Patent and publication data were plotted against each other to determine the nature of their relationship. Depending on whether the relationship was linear or non-linear Pearson’s (r) or Spearman’s rank (r S ) correlation coefficients respectively were used to determine the degree of correlation between patent and publication numbers. When examining the chronology of patent and publication activity in the patent clusters identified, a 4-year moving average (the data point for a specific year calculated as an average of the year in question and the preceding 3 years) was used to make the data easier to interpret. Data analysis was undertaken in GraphPad Prism® (GraphPad Software, La Jolla, California, USA). Results
Overall trends in patenting and publication Establishing top performing technology clusters by patent filings Initially, a search was performed of the European patent office master documentation database, DOCDB14 , using the proprietary software package PatentInspiration (AULIVE, Ypres, Belgium). A Boolean search strategy specific to MIS (Table S1, supporting information) was used to establish patenting and publication activity within the time intervals 1980–2011 and 2000–2011. The result of the patent search was then used to create lists of the top 30 performing patent codes for the two intervals. These two time intervals were compared to highlight areas of contemporaneous innovation. Once generated, these top 30 codes were sorted into related surgical technologies by two authors, with differences in opinion arbitrated by a third. Only well defined technology clusters, not pertaining to specific surgical subspecialties, were selected for in-depth analysis. To identify any patents within these technology clusters not captured within the top 30 patent codes, a Boolean search of the DOCDB was undertaken specific to each cluster (Table S1, supporting information). A further search of the PubMed © 2015 BJS Society Ltd Published by John Wiley & Sons Ltd
The initial search of patenting and publication databases revealed 27 920 patents and 95 420 publications pertaining to MIS since 1980. After correcting for the exponential rise in patent and publication activity over time, using the formula above, the growth in both patents and publications was found to be highly correlated (r S = 0⋅949) and both followed an S-shaped pattern of growth (Fig. 1).
Top performing technology clusters The top 30 performing patent codes for the interval 1980–2011 are summarized in Table S2 (supporting information). The area in which the greatest number of patent codes have been filed was minimally invasive surgical instruments, comprising 52⋅6 per cent of patents falling in the top 30 (Table 1). The other areas fulfilling the criteria for growth analysis were: sutures, image guidance and surgical robotics (Table S2, supporting information). When the search was restricted to the time frame of 2000–2011, no new technology clusters emerged. Among the clusters analysed, the dominance of instrument innovation appeared to have waned somewhat, whereas www.bjs.co.uk
BJS 2015; 102: e151–e157
Technological innovation in minimally invasive surgery
10 000
e153
drop off in patenting, starting in 2009, was seen for both NOTES and image guidance. Assessment of the correlation between patent and publication activity within these clusters demonstrated a strong correlation for instruments, sutures, surgical robotics and image guidance (r S = 1⋅929, 1⋅855, 1⋅937, 1⋅945 respectively; all P < 1⋅001). NOTES and SILS demonstrated lower correlation, with r S = 1⋅609 (P < 1⋅001) and r S = 1⋅532 (P = 1⋅002) respectively.
Patents Publications
No. of patents/publications
8000
6000
4000
Chronology of minimally invasive surgery
2000
0 1980
1985
1990
1995
2000
2005
2010
Patent and publication growth in minimally invasive surgery, 1980–2011
Fig. 1
Table 1
Top performing technology clusters
MIS instruments* Sutures Image guidance Surgical robotics Not included in analysis
1980–2011
2000–2011
498 (52⋅6) 65 (6⋅9) 37 (6⋅1) 60 (3⋅9) 287 (30⋅3)
157 (45⋅1) 11 (3⋅2) 26 (7⋅5) 26 (7⋅5) 128 (36⋅8)
Values in parentheses are percentages. *Including laparoscopic ports and trocars.
surgical robotics and image guidance showed increases in their patent share among the top performing codes.
Growth in the top performing and literature-derived technology clusters Corrected patent and publication counts were plotted against time for the six technology clusters identified within MIS (minimally invasive surgical instruments, sutures, surgical robotics, image guidance, NOTES and SILS) in order to establish their individual growth curves (Fig. 2). Across the six technology clusters, three different patterns of growth were observed. Instruments and sutures showed an S-shaped growth curve. For the instrument cluster this initial sigmoid curve was followed by a period of new growth, starting in 2000 (Fig. 2). Surgical robotics and image guidance demonstrated exponential growth, both starting in the early 1990s. The growth curves for SILS and NOTES both demonstrated rapid contemporaneous growth. On examination of the curves in more detail, a © 2015 BJS Society Ltd Published by John Wiley & Sons Ltd
In addition to plotting the growth curves for specific technology clusters, individual clusters were plotted alongside one another to gain an understanding of the chronology of technology development in MIS (Fig. 3); 4-year moving averages were used to allow a better understanding of trends. This demonstrated that image guidance, sutures, instruments and surgical robotics all had exponential phases of growth beginning in the late 1980s. Both sutures and instruments reached a plateau in growth by the mid-1990s (Fig. 2). A similar pattern of growth was seen in publication and patenting activity for MIS overall (Fig. 1). From their take-off in the late 1980s, image guidance and surgical robotics showed a sustained, albeit shallower, exponential rise in activity. From 1990 until the arrival of NOTES and SILS in 2005, no rapid increase was seen in any of the technologies examined. In 2005, both NOTES and SILS showed the beginning of a rapid increase in patent and publication activity. This activity was sustained for SILS, but for NOTES plateaued in 2009 (Fig. 2). Discussion
This paper examined innovation in MIS chronologically and quantitatively, scrutinizing technologies identified using a published methodology1 in addition to those that have recurred in the recent literature4 – 8 . Three patterns of growth in innovation were identified, each of which contained technologies exhibiting unique characteristics. After an initial burst of innovation corresponding to the adoption of laparoscopic techniques, innovation within MIS globally was seen to plateau until the early 2000s, when a second phase of innovation growth occurred. Within the social science literature, the concept of quantitative analysis of innovation using patent and publication-based metrics has been investigated extensively11,15 . However, quantitative research in the medical literature is limited to two papers1,3 . These two papers approached the problem of quantifying innovation differently. Trajtenberg3 examined the value of www.bjs.co.uk
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Growth curves for chosen technology clusters: a instruments and b sutures, demonstrating a classical S-shaped growth curve; c surgical robotics and d image guidance, showing a gradual but exponential pattern of growth; and e natural-orifice transluminal endoscopic surgery (NOTES) and f single-incision laparoscopic surgery (SILS), expert-identified areas of growth demonstrating steep and contemporary exponential growth
Fig. 2
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Fig. 3 Growth curves for a patents and b publications displayed to highlight the chronology of technological innovation in laparoscopic surgery. Values are 4-year moving averages. *All technologies except instruments; †all technologies except robotic surgery and sutures. NOTES, natural-orifice transluminal endoscopic surgery; SILS, single-incision laparoscopic surgery (SILS)
patent data within a single specific technology3 , whereas Hughes-Hallett and colleagues’ work1 offered a mechanism with which to identify and predict emerging technology clusters, and to quantify an innovation’s current and potential clinical impact. Within MIS there seem to have been three distinct patterns of growth since its initial inception in the 1980s. The genesis of MIS was associated with the most visible innovation spike. In this phase, rapid exponential growth in publication and patenting activity surrounding the development of novel surgical instruments and consumables was seen (represented by the instrument and suture categories). This spike represents the development of the basic minimally invasive surgical tools, and correlates closely with the overall growth curve for MIS. Generally speaking, these technologies are simple and of low cost, accounting for the rapid growth in patent and publication activity as industry and surgeons respectively designed and validated novel and essential tools. Subsequent to this highly correlated, exponential phase of growth, these technology clusters plateaued, reaching a point of diffusion saturation in the mid-1990s, as the laparoscopic surgeon’s ‘tool box’
became saturated. At this point new patents or research tended to pertain to refinement of existing technology rather than inception of new devices12 . In the mid-2000s a new growth spike was seen in MIS overall and within the instrument cluster, probably pertaining to the adoption of new approaches to MIS (robotics, SILS and NOTES). Interesting trends were also found in the remaining technology clusters examined, with robotics and image guidance exhibiting a different pattern of growth. These technology clusters began their exponential phases of growth at a similar time to the instruments and sutures. However, in contrast to a rapid exponential growth, they experienced a prolonged exponential growth phase, and appeared not to have yet reached the point of diffusion saturation after more than 15 years. The reasons for this are probably multifactorial, but two factors in particular seem worth discussion. First, the nature of these two technology clusters means that they pose numerous and complex engineering challenges compared with the other technology clusters examined, perhaps resulting in a slower rate of development. In addition, they serve to expand the practice of MIS rather than providing the tools necessary to
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undertake it, and as such might be viewed as ‘non-essential’; as a consequence they might garner less resource from industry than the comparator and more fundamental technologies. Interestingly, although robotic surgery appears to be on a continued trajectory of exponential growth, image guidance has seen a drop off in patenting activity, perhaps corresponding to a saturation point. The final growth pattern was one of contemporary rapid exponential growth, and was seen within the literature-derived technology clusters of NOTES and SILS. Examining the growths of the technology clusters individually, it appears that SILS is undergoing a sustained and rapid exponential growth, implying innovation growth, whereas the growth of NOTES seemed to plateau after 2009. This plateau in patent and publication number within NOTES would suggest a dwindling of innovation and interest in the subject, and may reflect a failure of this approach to cross the ‘chasm’ that exists between the innovators and the early adopters (Fig. 4). The concept of a diffusion chasm was first proposed by Rogers9 and represents the point where a technology must translate from a research environment to a normal clinical setting.
Exponential growth
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This chasm may also be responsible for the recent downturn in patenting surrounding image guidance in MIS, which has failed to translate into widespread operative practice despite prolonged and sustained innovation and investment. Interestingly, no novel clusters of technological innovation emerged in the more contemporary period examined. All of the innovation clusters unveiled by the systematic search of the patenting database saw the beginning of their growth curves in the late 1980s and early 1990s (Fig. 3), with no new technology clusters being identified in the period 2000–2011. This failure to identify any new clusters may be in part down to the failure of the methodology to identify potentially important innovation in its nascence1 . Equally, however, and perhaps more likely, this may suggest a stagnation in innovation, with few, if any, novel technologies having had a significant impact on minimally invasive surgical practice. Although the methodology proposed here offers a quantitative approach to defining past innovations, and assisting in assessing future technologies of influence in MIS, it is not without limitations. The first is the surrogacy
Innovators (2·5%)
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S-shaped diffusion curve demonstrating the three phases of growth in any technological innovation (incubation, exponential growth and diffusion saturation) matched to the characteristics of the individual members of the adopting population9
Fig. 4
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of the measures used. To establish the diffusion, and as such the success, of a given innovation, the proportion of patients in which that innovation has been used must be measured. Although this represents the standard approach when looking at innovation within MIS, it is impractical owing to the huge number of innovations to be examined. Looking to the future of MIS, the present study adds objective data to the previous subjective claims that SILS, a surgical technique that has currently been adopted by very few, represents an important part of the future of MIS. This transition from specialist to mainstream practice may be facilitated by improvements in tools to perform the technique, with a likely role for robotic surgery. Disclosure
The authors declare no conflict of interest. References 1 Hughes-Hallett A, Mayer EK, Marcus HJ, Cundy TP, Pratt PJ, Parston G et al. Quantifying innovation in surgery. Ann Surg 2014; 260: 205–211. 2 Rogers W, Lotz M, Hutchison K, Pourmoslemi A, Eyers A. Identifying surgical innovation: a qualitative study of surgeons’ views. Ann Surg 2014; 259: 273–278. 3 Trajtenberg M. A penny for your quotes: patent citations and the value of innovations. RAND J Econ 1990; 21: 172–187. 4 Rivas H, Díaz-Calderón D. Present and future advanced laparoscopic surgery. Asian J Endosc Surg 2013; 6: 59–67.
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5 Aurora A, Ponsky J. Future perspectives on scarless surgery: where we have been and where we are going. In Scar-Less Surgery (1st edn), Desai M, Gill I (eds). Springer: London, 2013; 341–351. 6 Hafron J, Kaouk JH. Technical advances in urological laparoscopic surgery. Expert Rev Med Devices 2008; 5: 145–151. 7 Ficarra V, Ploumidis A, Lumen N. The infancy of robotic laparoendoscopic single-site renal surgery: waiting for needed technological improvements. Eur Urol 2013; 63: 281–282. 8 Lee WJ, Chan CP, Wang BY. Recent advances in laparoscopic surgery. Asian J Endosc Surg 2013; 6: 1–8. 9 Rogers E. Diffusion of Innovations (5th edn). Free Press: New York, 1962. 10 Ryan B, Gross N. The diffusion of hybrid seed corn in two Iowa communities. Rural Sociol 1943; 8: 15–24. 11 Daim TU, Rueda G, Martin H, Gerdsri P. Forecasting emerging technologies: use of bibliometrics and patent analysis. Technol Forecast Soc Chang 2006; 73: 981–1012. 12 Bengisu M, Nekhili R. Forecasting emerging technologies with the aid of science and technology databases. Technol Forecast Soc Chang 2006; 73: 835–844. 13 Nelson AJ. Measuring knowledge spillovers: what patents, licenses and publications reveal about innovation diffusion. Res Policy 2009; 38: 994–1005. 14 European Patent Office. EPO Patent Information Resource ‘DOCDB’; 2008. http://www.epo.org/searching/ subscription/raw/product-14-7.html [accessed 23 September 2013]. 15 Hagedoorn J, Cloodt M. Measuring innovative performance: is there an advantage in using multiple indicators? Res Policy 2003; 32: 1365–1379.
Supporting information
Additional supporting information may be found in the online version of this article: Table S1 PubMed and PatentInspiration search strategies (Word document) Table S2 Summary of top 30 patent codes for the intervals 1980–2011 and 2000–2011 (Word document)
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