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History of Ergonomy in Surgery
Publication history, Reflections & comments
Ergonomics, the scientific study of people at work, has been applied to surgery for only three decades in a formal way. Pre-modern surgery required only simple tools for a few simple tasks though a few important ergonomic principles emerged. Real pressure to apply ergonomics has only come with increasingly complex technology for surgery. In microsurgery this challenge during the 1970s was met successfully by individual research. In the 1990s laparoscopic surgery brought more difficult ergonomic problems to a wider audience. Current challenges make it important to try and learn lessons from the past. These include robotic and computer technology, cognitive ergonomics (e.g. decision-making and error) and team work.
Ergonomics is the scientific study of people at work with the aims of improving accuracy, productivity, training, satisfaction, and safety. Its relevance to surgery seems obvious, though it has been applied less often here in a formal way than to other forms of work. In its first fifty years ergonomics has progressed to encompass three main divisions - physical ergonomics (tools and work-space), cognitive ergonomics, and organizational ("macro-") ergonomics. In surgery the latter two are emerging only recently as part of "error in medicine" and work teams in the operating room.
Throughout history the best surgeons, like the best engineers and managers, were generally good intuitive ergonomists before terms like ergonomics came into use. They seemed to know the importance of designing equipment and information to suit their workers and how to organize systems of work in the best way. Because ergonomics aims to improve productivity and the satisfaction of workers, it becomes the norm in a civil society, provided there is the necessary awareness and knowledge, and the time and the means to apply it. A successful industrialist of the early nineteenth century, Robert Owen, recognized the commercial importance of looking after his workpeople at least as well as his machines, though his motivation was as much humane as commercial.
Animals are now recognized as tool-users and they even apply ergonomics. A bird poking at termites in a hole for food picks a twig of convenient thickness for its beak as well as long enough to reach down the termite hole. When humans have the awareness and the opportunity, they choose tools for themselves that are well-designed, both for carrying out the intended task ("functionality") and for their own comfort. The handle of an axe for chopping wood has a complex series of curves suited to a grip by one hand near the butt, and a sliding grip by the other as it applies continues forward force during a swing of the axe-head. The handle of a scythe developed over many centuries has been a similar example of rational and complex design, its wide curves in three dimensions designed so that when positioned for use the centre of gravity is directly under the point of grip. For the last two decades this effect has been mimicked in motorized cutters for the edges of grass lawns.
The development of such good designs begins as a process of trial and error in the physical world, and then in the mind. Later rules and general principles develop, to short-cut the time and effort of error. Some of these become part of safety codes and good industrial practice. The quickening rate of design improvement is mirrored by claims of "ergonomics" in advertising for products as diverse as motor cars and laparoscopic needleholders.
Sometimes good design fails to evolve. Typically this happens when technology for a particular purpose develops so quickly that the human needs for the design of a tool or system were left behind, for example the early years of the Industrial Revolution. It is up to ergonomics to close the feed-back loop.
Ergonomics in early modern surgery
In the era of pre-modern surgery, there were glimmerings of good ergonomic practice. In about the year 1000 the Arab physician Albucasis (quoted in Spink 1973) said "let your surgery for cataract be done by the light of the sun at noon". He was speaking of a lighting level of about 100 000 lux, compared with 60 000 lux for a standard modern operating room light. Research confirms the everyday observation that within wide limits there is a direct correlation between the level of lighting intensity and the ability to see fine detail (Lythgoe 1933).
Up until Morton's landmark use of ether anesthesia for a leg amputation in 1846, most surgical operations were brutal, brief, and simple. Surgeons needed little more than knives for amputation and forceps and probes for foreign bodies. William of Clowes, surgeon to the first Queen Elizabeth said that for amputation "he needed only three instruments- a specially sharpened saw, a double-edged knife, and a scalpel" (Bennion 1979).
Handles for surgical knives did not change in shape for a long time time. A few had hilts and pommels to avoid slip of the grip of the hand. "Only by about 1770 did handles that had been turned and were circular in section become hexagonal for easier grasp" (Bennion 1979). However there were occasional examples of inspired ergonomic thinking. The operation of perineal lithotomy (cutting for bladder stone from below) required an L-shaped incision, with a quarter turn of the knife in the fingertips to avoid awkward hand movement in the limited space between the thighs. To achieve this, tarry string was wrapped around the base of the blade to give a circular cross-section that could be twisted within the tips of the thumb, index, and middle finger. This principle was to be re-stated formally two centuries later, as one of the design criteria for handles of microsurgical instruments in the 1970s (Patkin 1978b). This allowed the operator to keep the hand steady by saving having to supinate the forearm under high magnification during dissection or suturing.
Surgery in the early nineteenth century saw the development of several different types of forceps in which the handles and jaws could be locked in position by a single gripping movement within one hand. This saved using a screwing movements requiring both hands and then freed up a hand. Locking mechanisms culminated in the ratchet-based forceps designed by Spencer Wells and its thousands of later variations in different fields of surgery, liberating the hand of the surgeon or assistant from having to apply force to an instrument or tissue.
Scissors of the ancient Romans all had the two handles joined by a spring hinge at one end. The modern type, with a hinge at the screw joint, dating back about a thousand years. Their use in surgery for delicate dissection evolved especially in late nineteenth century centres in the United States (Bennion 1979). A description of such delicate use was given by Australian surgeon Sir Hugh Devine, who wrote:
"After prolonged use of these scissors - always of exactly the same weight - I have been able to develop with them a sense of touch that enables me to recognize with the tips of the scissors the slightest difference of tissue density, and therefore to identify blood vessels and other structures by the feel of them".
This was an early statement on the mechanics of tissue dissection, an area which even today remains hardly researched at all. Indeed one of the great needs in surgery is research into theorems of dissection. Good surgeons have long recognized intuitively that division of soft tissue with a single blade is best carried out at right angles to lines of tension. Effective dissection therefore requires setting up such lines of adequate tension to as many points as there are tongues of tissue extending outwards. Today one may often see a surgical videotape where the operator is trying to tear elastic tissue with two pairs of forceps that are placed too far apart. A useful extra rule of dissection would state "if you want to tear elastic tissue using two pairs of forceps, put them close together so you are able to exceed the elastic limits of the particular tissue by moving them apart".
The decade leading up to 1900 was a time of certainty among humans that they had reached the pinnacles of knowledge. But at this time there was also a tiny hint of the huge changes to come in technology, driven by discoveries well away from the field of surgery. In urology, miniature versions of the electric light globes developed by Thomas Edison made cystoscopy possible, where previously the only way of illuminating the inside of the bladder had been the light of a candle reflected along a thin straight tube in the urethra serving also for vision. This lighting was quickly augmented by lens systems similar to those in telescopes, then by the Hopkins solid-rod lens systems in the 1960s, and next by the use of fibre-optics. After this came video display on a monitor to replace squinting down an eyepiece with their head squeezed close to the patient's thighs, thanks to the "camera on a chip" made especially popular in the 1980s as the "sports-cam".
However in the year 2000 video displays in operating theatres still have poor ergonomics. Most monitor screens used in endosurgery of the prostate are too bulky for the urologist to place conveniently. In other areas of lap surgery it is common to see laparoscopic surgeons gazing upwards at a monitor and cricking their neck backwards instead of gently flexing it so their angle of gaze is at 15 to 45 degrees below the horizontal as is standard in business offices. The technology had outrun the ergonomics for the moment.
The advances that led to such human problems were based on discoveries in physics and innovations in technology that had nothing inherently human in their size or time-related properties. They had to be scaled, up or down, to suit human requirements for vision within dimensions and distances and lighting levels, dictated not just by the dimensions of the human subject but also by those of the human operator and his or her capacities of perception and skill.
Interlude - A Surgical Area Not Investigated
It has always been obvious that wide differences in skill, safety and speed existed between individual surgeons though the detailed reasons for them have rarely been studied formally. Why the differences?
In the early twentieth century, following a tonsillectomy on one of his twelve children, one of the pioneers of Time and Motion Study, Frank B. Gilbreth had noted in 1916 that "...surgeons could learn more about motion study, time study, waste elimination, and scientific management from the industries than the industries could learn from the hospitals" (Gilbreth 1916). He was the first person to apply motion-picture photography to the study of surgical operations, but others did not continue or extend this research at the time. In the 1930's there was again interest in the analysis of the movements of the surgical team (4) but a widespread application of work analysis to surgical procedures did not occur (5). Much later a study examined the relation between hand-grips and dexterity in surgery (Patkin 1965), the term "ergonomics" was used for the first time in a surgical context (Patkin 1967). An eminent authority commented on the desirability of continuing this work (Dudley 1976) but the literature in this field remained sparse apart from microsurgical applications discussed below.
Some attempts were made to design instrument handles in a systematic way, based on analysis of hand grip, mechanical and physiological factors, and properties of needles and tissues (Patkin 1969, 1971). In the 1990s other surgeons began to take an interest in an ergonomic basis for surgery, stimulated by the problems of laparoscopic surgery (Cuschieri 1993, Patkin 1995, Berguer 1996, 1999).
The Two Recent Challenges—Micro And Lap Surgery
The two areas in the latter half of the twentieth century where technology ran ahead of the initial abilities of surgeons to cope with them were microsurgery and laparoscopic surgery. They were literally difficult to handle from the start. Problems of handle design, as well as other ergonomic problems, were solved in the 1970s for microsurgery (as is described a little later) while those of laparoscopic surgery are still being solved, as will also be discussed.
Microsurgery, in particular microvascular and microneurosurgery, began their modern phase (beyond eye and ear surgery) in the late 1960s and early 1970s. Much of the early work was replantation of amputated fingers and hands, repair of small blood vessels, nerves and lymphatics, and then transplantation of free composite tissue grafts for repair of major injuries and anatomical defects.
The pioneers in this field were exceptionally talented and driven. However even they realized that practising this small-scale surgery, as well as teaching it to others less gifted, required ergonomic insights and application to solve challenges to normal human capacity. These challenges were how to see more accurately the fine detail available under magnification, how to control fine movements of the hand and tremor, and how to design seating and workplace layout for such critical work (Patkin 1978a).
Practical solutions to the problems of microsurgery emerged (Patkin 1978b). The dozen different factors which aggravated normal hand tremor were classified (long-term, intermediate, short-term) and defined. Applying this information helped improve the fine control necessary for small-scale dissection and reconstruction.
As an example, the most important factor is point of support of the limb or instrument. A ruler for drawing a straight line is a simple example of an anti-tremor device. Analysis of hand and finger posture was critical for this and for the design of suitable instruments. One of the design criteria to emerge for the "external precision grip" of the hand was hemi-cylindrical handles which when closed gave a circular cross-section 8 or 9 mm in diameter. Another was prescribing the stiffness of fine instruments in the range of 50 to 80 grams weight (0.5-0.8 Newton), instead of haphazard levels found in commercial products, in which stiffness ranged up to a kilogram or slightly beyond.
Visual factors beyond magnification were likewise defined. These included glare, colour contrast, and the moulding effect of directional lighting. These and other factors were taken straight from the literature on ergonomic factors in industrial processes. Seating was investigated, and in time there were chairs developed specifically for microsurgery. Improvements in microscope design included the adding of 15 or 20 cm extensions to the oculars to save the surgeon from having to hunch forwards. Elements of skill acquisition were analysed based on industrial models.
The success of these measures is now evident. Little or nothing seems to have changed in applying ergonomics to microsurgery in the two decades since the end of the 1980s, measured either by publications, advertising of new equipment designs, or discussions of ergonomic problems in microsurgery since then. By contrast there is a continuing stream of publications dealing with ergonomic aspects of laparoscopic surgery.
Laparoscopic surgery and its offshoots
At the start of the era of laparoscopic surgery in the 1990s, surgeons were confronted by a series of problems closely comparable to those of microsurgery. These were eye-hand co-ordination, design of long thin instruments with jaws or blades to be opened and shut and shafts to be rotated and angulated, the interpretation of a three-dimensional space from a two-dimensional display, and the process of skill acquisition. There were also new problems of integrating increasingly complex optical and mechanical systems to which were also added video and pneumatic systems, x-ray and other imaging devices, and the many additional people to manage these in crowded operating rooms.
The pressures to solve these problems were far greater than was the case with microsurgery. There were increased financial and professional pressures on surgeons to learn the new techniques of "key-hole" surgery in a short time and heavier financial commitments of surgical equipment companies to meet this market. The solutions have also been more elusive. They will be even more difficult in dealing with robotics and with computer-based surgery using "intelligent agents".
Cognitive and Macro-Ergonomics
Space does not allow a discussion of these two newest areas of application of ergonomics to surgical practice. Suffice it to say that there is a large and rapidly growing literature in both. Cognitive ergonomics is about how humans handle information and the basis for human error, and the process of acquiring skills, whether they are mental ones like judgement and diagnosis or physical ones like dissecting tissues.
Macro-ergonomics or organizational ergonomics deals with how people work togther (or not) in a group or organization, and the various cultural and psychological factors that determine their success or failure. The size of group studies varies from the two or three people on the flight deck of a commercial aircraft to the interactions within a large corporation. No longer is the operating room just one or two nurses and an anaesthetist with a surgeon in charge, but a team of various specialists and support staff working closely together.
The integral role of ergonomics in surgery is now entrenched and can only grow. Recent history shows that surgeons will need ergonomics in the design of their work and equipment, and as part of their skills, whether manual, cognitive, or as managers. Ergonomics will be needed in detail by those who work with wurgeons - equipment designers, designers and managers of OR facilities, and architects and managers of surgical facilities.
Berguer R. Ergonomics in the operating room. Am J Surg;171(4):385-6. 1996
Berguer, R., D.L. Forkey, and W.D. Smith, Ergonomic problems associated with laparoscopic surgery. Surg Endosc, 13(5): p. 466-8. 1999 Berguer, R., Surgery and ergonomics. Arch Surg, 1999. 134(9): p. 1011-6.
Cuschieri, A., et al., Coaxial curved instrumentation for minimal access surgery. Endosc Surg Allied Technol, 1(5-6): p. 303-5. 1993.
Devine, H. Surgery of the alimentary tract. Wright, Bristol. 1941
Dudley HA. Operative ergonomics. Nurs Mirror Midwives J 143(18):53-4 1976.
Gilbreth FB. Motion study in surgery. Canadian Journal of Medicine and Surgery 40:22-31. 1916
Lythgoe RJ. The measurement of visual acuity. MRC Special Report Series No. 173. London HMSO 1932
Patkin M The hand has two grips: an aspect of surgical dexterity, Lancet, 1, 1384-5. 1965
Patkin M. Ergonomic aspects of surgical dexterity. Med J Aust 2(17):775-7. 1967
Patkin M Surgical instruments and effort, referring especially to ratchets and needle sharpness, ibid., 1, 225-6. 1970
Patkin M. Ergonomics and the operating microscope. Adv Ophthalmol;37:53-63. 1978a
Patkin M Selection and care of microsurgical instruments, ibid., 37, 23-33. 1978b
Patkin M, Isabel L. Ergonomics, engineering and surgery of endosurgical dis-section. Journal of the Royal College of Surgeons Edinburgh 40:120-132. 1995.
Spink MS, Lewis G. Albucasis on surgery and instruments / a definitive edition of the Arabic text with English translation and commentary Berkeley : University of California Press, 1973
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Contents
Summary
INTRODUCTION
Ergonomics under older labels
Ergonomics in early modern surgery
The End of Simplicity
Interlude - A Surgical Area Not Investigated
The Two Recent Challenges—Micro And Lap Surgery
Cognitive and Macro-Ergonomics
CONCLUSION
HISTORY OF ERGONOMY IN SURGERY
M.PATKIN
Department of Surgery, Flinders University, Adelaide, Australia
This paper was presented at a conference at Hanover on the future of surgical technology. The invitation had come about through firm friendship established with Ulrich Matner, a coming young leader in applying ergonomics to surgery in Germany.
I had met him at the ?Texas meeting of the Human Factors Society where a group of about 20 people had come together to discuss ergonomics in surgery. This in turn had resulted from an internet meeting with Beurger, a young Californian surgery, whose interest in ergonomics had begun soon after the start of the era of laparoscopic surgery.
At Hanover I again met Sir Alfred Cuschieri. whose surgical department at Dundee had led developments in the same area. You can see his many contributions on Medline or by visiting his departmental website.
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