A Quantitative Analysis of Technological Innovation in Minimally Invasive Surgery

1

A quantitative analysis of technological innovation in minimally invasive surgery

Archie Hughes-Hallett, MRCS1, Erik K Mayer, PhD1, Philip J Pratt, PhD2, Justin A Vale, MS1, Ara W Darzi, FRS1,2,3

1. Department of Surgery and Cancer, Imperial College London
2. The Hamlyn Centre, Institute of Global Health Innovation, Imperial College London
3. Centre for Health Policy, Institute of Global Health Innovation, Imperial College London

Corresponding author

Erik Mayer,

Department of Surgery and Cancer,

St Marys Campus,

Imperial College London,

W2 1NY

Submitted as original research

Abstract

Background

In the last 30 years surgical practice has undergone dramatic changed due to the advent of minimally invasive surgery (MIS).This paper chronologically, and quantitatively, examines the changing surgical landscape, 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 period 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.In addition technology clusters having been repeatedly referred to in the contemporary surgical literature were also included in analysis.Growth curves of publications and patents 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, SILS and NOTES. When examining the respective technology clusters,three patterns of growth were observed: a classical S-shape (instruments and sutures); a gradual exponential rise (image guidance and surgical robotics); and a rapid contemporaneous exponential rise (SILS and NOTES).

Conclusion

This paper has revealed technological innovation in MIS has been largely stagnant since its initial inception nearly 30 years ago, with few novel technologies emerging. This said, there has been a recent and sustained spike in innovation surrounding SILS giving weight to the claim that it represents an important part of the future landscape of MIS.

Introduction

HealthcareInnovation can be defined as ‘a dynamic and continuous process involving the introduction of a new technology or technique that initiates a change in practice’.1–3In the last three decades, surgical practice has undergone radical change with the move from conventional to minimally invasive surgery (MIS).This transition has brought with it a change in the way in which surgeons undertake their operating practice.This change has beendriven, at least in part, by technological innovation. Since the mid 1990s,thisinnovation in MIS has been largely incremental punctuated by disruptive changes in approach, an example of a disruptive change being the advent of robot assisted laparoscopic surgery.4More recently, two novel approaches to minimally invasive surgery have been proposed in the literature but have not yet been widely adopted into surgical practice: single incision laparoscopic surgery (SILS) and natural orifice transluminal endoscopic surgery (NOTES).5–9

Patents are the initial step in the commercialisation of a concept or technology and as such patent counts represent a good metric with which to measure technological innovation.3 In addition to being both reliable and relevant measures of innovation, patents are readily available on publiclyaccessible databases. As measures of innovation diffusion,10,11 patent and publication activity have been widely examined in the social science literature10–14 but have only recently been applied and validated for the assessment of healthcare technologies.1

The aim of this analysis was to utilisepatent and publication data to address two broad aims.Firstly, to objectively establish the major areas of technological innovation within MISsince 1980 and, secondly, to assess the innovations that have been postulated,within the surgical literature,as the major emerging technologies in MIS (robot assisted laparoscopic surgery, SILS and NOTES).

Methods

The methodology utilised in this paper is based on previously published work proposing and validating patents and publications as metrics for innovation in healthcare technology.When correcting for the previously demonstrated, exponential rise in patents and publications, the formula below was used.The formula below was used to correct for the exponential increase in publication and patenting over time.1

IIi = innovation index i = year in questionti = total number of patents granted by US patent office

ci = innovation constant (modified from Hughes-Hallett et al.1)

Once the corrected year-on-year counts for publications and patents (i.e. the innovation indices) had been collated, growth curves for each of the respective 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.

Establishing top performing technology clustersby patent filings

Initially, a search was performed of the DOCDB (Europeanpatent office master documentation database) patent database15 using the proprietary software packagePatentInspiration (AULIVE, Ypres, Belgium).A Boolean search strategy specific to MIS (Appendix 1) was used to establish patentingand publication activity within the time periods 1980 to 2011, and 2000 to 2011.The result of the patent search was then used to create lists of the top 30 performing patent codes for the two time periods. These two time periods were compared to highlight areas of contemporaneous innovation.

Once generated, these top 30 codes were sorted into related surgical technologies by two authors (AHH and EKM) with any difference in opinion arbitrated by a third (JV). Only well definedtechnology 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 (Appendix 1).Using the same search strategies a further search of the PubMed database was also undertaken to generate a measure of year-on-year publication activity.

In addition to the technologies identified in this step, clusters that have been repeatedly referred to in the contemporary surgical literature as areas of potential growth (SILS, NOTES and robot assisted laparoscopic surgery) were addedtothe growth analysis.

Data Analysis

Patent and publication data were plotted against each other in order to determine the nature of their relationship.Depending on whether the relationship was linear or non-linear Pearson’s (r) or Spearman’s rank (rs) correlation coefficients, respectively, were used to determine the degree of correlation between patent and publication numbers.Data analysis was undertaken in GraphPad Prism (GraphPad Software Inc, CA, USA).

Results

Overall trends in patenting and publication

The initial search of patenting and publication databases revealed 27,920 patents and 95,420 publications pertaining to MIS since 1980. When corrected, the growth in both patents and publications were found to be highly correlated (rs = 0.949) following an S-Shaped pattern of growth (Figure 1).

Top performing technology clusters

The top 30 performing patent codes for the period 1980 to 2011, are summarised in Appendix 2.The area in which the greatest number of patent codes has been citied was, perhaps unsurprisingly, minimally invasive surgical instruments, making up 53.0% of patents falling with the top 30 (Table 1).The other areas fulfilling the criteria for growth analysis were: sutures, image guidance and surgical robotics (Appendix 2).

When the search was restricted to the more contemporary time frameof 2000 to 2011 no new technology clusters emerged. Despite thisAmong the clusters analysed, the dominance of instrument innovation appeared to have waned somewhat withsurgical robotics and image guidance seeing increases in their patent share amongst 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 (Figure 2).

Across the six technology clusters,threediffering patterns of growth were observed.Within instruments and sutures, an S-shaped growth curve was observed.For the instrument cluster this initial sigmoid curve was followed by a period of new growth.while Surgical robotics and SILS both demonstrated exponential growth, starting in the early 1990s and 2005 respectively.starting in the mid 1990s and continuing up until 2011.While the growth curves for SILS and NOTES both demonstrated contemporary and rapid exponential growth.image guidance and NOTES both demonstrated a period of exponential growth followed by a drop off in the number of patents filed.

When assessing the correlation between patent and publication activity within these groups, instruments, sutures, surgical robotics and image guidance all demonstrated strong correlation (rs = 0.929, 0.855, 0.937, 0.945 respectively).All were statistically significant with p0.001.NOTES and SILS demonstrated lower correlation with rs = 0.609 (p < 0.001) and 0.532 (p = 0.002) respectively.

The chronicity of minimally invasive surgery

In addition to plotting the growth curves for specific technology clusters, individual clusters were plotted alongside one another to garner an understanding of the chronicity of technology development in MIS (Figure 3), four year moving averages were used to allow for 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, corresponding to the rise in publication and patenting activity in MIS overall (Figure 1).As previously mentioned, from their take off in the late 1980s, image guidance and surgical robotics have seen a sustained, albeit shallower exponential rise in activity. From 1990 until the arrival of NOTES and SILS in 2005, no rapid take off is seen in any of the technologies examined.In 2005, both NOTES and SILS see the beginning of a rapid increase in patent and publication activity.This activity is sustained for SILS, but for NOTES plateaus in 2009.

Discussion

This paper haschronologically and quantitatively examined innovation in MIS, scrutinising technologies identified usinga previously published methodology1 in addition to those that have recurred in the recent literature.5–9 Three patterns of growth (rapid exponential growth followed by a plateau, prolonged exponential growthand finally rapid contemporary exponential growth) were identified, each of which contained technologies exhibiting uniquecharacteristics.When examining the chronicity of technological innovation in MIS it was found to be polarised with the technologies experiencing rapid exponential growth found at opposite ends of the time period examined, with a period of innovation stagnation apparent in between these two poles.

Within the social science literature, the concept of quantitative analysis of innovation utilising patent and publication-based metrics has been extensively investigated.12,16 However, quantitative research in the medical literature is limited to two papers: Trajtenberg’s3paper examining the value of patents as measures of healthcare innovation and Hughes-Hallett et al.’s recent publication ‘Quantifying innovation in surgery’.1 These two papers approach the problem of quantifying innovation quite differently.Trajtenberg’s work examined the value of patent data within a single specific technology;3 whileHughes-Hallett et al.’s work offered a mechanism with which to identify and predict emerging technology clusters, in addition to offering a process allowing quantification of an innovation’s current and potential clinical impact potential.1

Within MIS there seem to have been three distinct patterns of growth since its initial inception in the 1980s. The genesis of MIS is associated with the most visible innovation spike.In this phase we see a rapid exponential growth in publication and patenting activity surrounding the development of novel surgical instruments and consumables (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, design and validate novel and essential tools.Subsequent to this highly correlated, exponential phase of growth, these technology clusters remain areas of significant innovation,but reachplateau reaching the point ofdiffusion saturationin the mid 1990s, as the laparoscopic surgeon’s ‘tool-box’ becomes saturated.At this point any new patents or research tend to pertain to the refinement of existing technology rather than inception of new devices.13This point of diffusion saturation is represented by the plateau of a classical S-shape growth curve (Figure 4).10In the mid 2000s a new phase of growth is seen in both MIS overall and within the instrument cluster, this spike probably pertains to the adoption of new approaches to MIS (robotics, SILS and NOTES) and the novel instrumentation they require.

Perhaps more interesting were the trends seen in the remaining technology clusters examined, with robotics and image guidance exhibitinga differentpattern of growth.These technology clustersbegin their exponential phases of growth at a similar time to the previously discussed group but, in contrast torapid exponential growth they have experienced a prolonged exponential growth phase, and in fact appear not to have yet reached the point of diffusion saturation after more than 15 years.The reasons for this are almost certainly multifactorial, but two factors in particular are worth discussion.First, the nature of these two technology clusters means they pose numerous and complex engineering challengeswhen compared to the other clusters of technology examined, perhaps resulting in a slower rate of development.In addition to this they also represent ‘non-essential’ technologies they serve only to augment the practice of MIS rather than providing the tools necessary to undertake it,and as such can be viewed as ‘non-essential’,thereby garnering less resource from industrythan the comparator and more fundamentaltechnologies.

The final growth pattern was one ofcontemporary rapid exponential growth, and was seen within the literature-derived technology clusters of NOTES and SILS.These technologies had a relatively low number of overall patents, and correspondingly lower correlation coefficients. When examining the growths of the technology clusters individually it appears that SILS is undergoing a sustained and rapid exponential growth, implying innovation growth, while the growth of NOTES is stalling with the number of patents and publications surrounding the technology beginning 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 ofNOTES’s to cross ‘the chasm’ that exists between the innovators and the early adopters (Figure 4).The concept of a diffusion ‘chasm’ was first proposed by Everett Rogers and represents the point a technology must translate from a research to normal clinical environment.10 This chasm may also be responsible for the recent downturn in patenting surrounding image guidance in MIS, which despite prolonged and sustained innovation and investment has failed to translate into widespread operative practice.

When examining the chronicity of technology,an observation has been the apparent failure of any novel clusters of technological innovation to emerge in the more contemporary period examined. All of the innovation clustersunveiled by the systematic search of the patenting databasesaw the beginning of their growth curves in the late 1980s and early 1990s (Figure 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 nascence,1 but equally, 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. This would fit with the hypothesis put forward by Riskin et al. which proposed that enabling technology shifts such as MIS are rare occurrences with the remainder of innovation being incremental in nature.4Another potential explanation for this stagnation is increasing medical device regulation.The regulatory process for novel devices is, both in Europe and the United States, significantly more arduous than for those that are similar to pre existing technologies.This approach to medical device regulation has the potential to stifle innovation with device manufacturers likely to shy away fromnovel technologies due to the increased financial risk associated with the regulatory process.

Although the methodology proposed here offers a quantitative approach to defining past, and assisting in assessing future technologies of influence in MIS, it is not without its limitations.First amongst these is the surrogacy of the measures used.To truly establish the diffusion, and as such the success, of a given innovation or cluster of innovation an assessment of the proportion of patients in which that innovation has been used must be measured.Although this represents the gold standard approach when looking macroscopically at innovation within MIS it is impractical due to the huge number of innovations to be examined.In addition, the way in which the data is constrained by the search terms used, relying on terms being both specific and sensitive enough to generate meaningful results.In this respect the methodology is imperfect in a similar fashion to that of systematic reviews, which are an accepted and valued part of evidence synthesis.

Looking to the future of MIS the data presented herein adds objective data to the previous subjective claims that SILS, a surgical technique that has as yet only been adopted by very few, represents a significant part of the future of MIS.This transition from specialist to mainstream practice will most likely be facilitated by improvements in the tools used to perform the technique, with robotic assistance perhaps the most likely to provide this technological segway.