Ergonomics in the operating room: transition from open to image-based surgery

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ERGONOMICS IN THE OPERATING ROOM

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Cover design by Kirsten Bosscher

Printed by Print Partners Ipskamp, Enschede Published by Armaĝan Albayrak

All rights reserved. No part of this book may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage and retrieval system, without permission from the author.

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ERGONOMICS IN THE OPERATING ROOM

TRANSITION FROM OPEN TO IMAGE-BASED SURGERY

Proefschrift

ter verkrijging van de graad van doctor aan de Technische Universiteit Delft,

op gezag van de Rector Magnificus prof.dr.ir. J.T. Fokkema, voorzitter van het College van Promoties,

in het openbaar te verdedigen op dinsdag 16 december 2008 om 15.00 uur door

Armaĝan ALBAYRAK ingenieur Industrieel Ontwerpen

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Prof.dr. H. de Ridder Prof.dr. H.J. Bonjer

Copromotor:

Dr.ir. R.H.M. Goossens

Samenstelling promotiecommissie

Rector Magnificus, voorzitter

Prof.dr. H. de Ridder, Technische Universiteit Delft, promotor Prof.dr. H.J. Bonjer, Dalhousie University, Canada, promotor Dr.ir. R.H.M. Goossens, Technische Universiteit Delft, copromotor

Prof.dr.ir. C.J. Snijders, Technische Universiteit Delft, Erasmus Medisch Centrum Prof.dr. J. Lange, Erasmus Medisch Centrum

Prof. A. Melzer, University of Dundee, Scotland, UK Dr. med. U. Matern, University of Tubingen, Germany

Prof.ir. D.J. van Eijk, Technische Universiteit Delft, reservelid

Dr. G. Kazemier heeft als begeleider in belangrijke mate aan de totstandkoming van het proefschrift bijgedragen.

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CHAPTER 1 INTRODUCTION 9

1.1 LAPAROSCOPY 9

1.2 SURGICALTEAMANDWORKINGENVIRONMENT 11

1.3 ERGONOMICS 12

1.4 AIM 13

1.5 DESIGNFRAMEWORK 13

1.6 OUTLINEOFTHETHESIS 14

1.7 READINGGUIDE 15

CHAPTER 2 AN OVERVIEW OF ERGONOMIC PROBLEMS DURING SURGERY 17

2.1 PHYSICALERGONOMICS 18

2.2 SENSORIALERGONOMICS 24

2.3 COGNITIVEERGONOMICS 25

CHAPTER 3 ERGONOMICS IN THE OPERATING ROOMS OF DUTCH HOSPITALS 31

3.1 INTRODUCTION 32

3.2 MATERIALS AND METHODS 33

3.3 RESULTS 34

3.4 DISCUSSION 35

CHAPTER 4 DISCOMFORT DURING SURGERY: PRODUCT SOLUTION AND

EVALUATION 39

4.1 STUDY I:A NEWLY DESIGNED ERGONOMIC BODY SUPPORT FOR SURGEONS 41 4.2 STUDY II:IMPACT OF A CHEST SUPPORT ON LOWER BACK MUSCLES ACTIVITY DURING FORWARD

BENDING 55

CHAPTER 5 IMAGE QUALITY DURING LAPAROSCOPIC SURGERY 75

5.1 INTRODUCTION 76

5.2 MATERIALSANDMETHODS 79

5.3 RESULTS 86

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6.1 PHYSICALERGONOMICS 96

6.2 SENSORIALERGONOMICS 103

6.3 COGNITIVEERGONOMICS 104

CHAPTER 7 DESIGN FRAMEWORK FOR DESIGNERS: CASE STUDIES 111

7.1 INTRODUCTION 112

7.2 CASEI:SENSORIALERGONOMICS–ABDOMINAL WALL TENSION MEASUREMENT DEVICE 115 7.3 CASEII:COGNITIVEERGONOMICS-IMPROVING ERGONOMICS OF MINIMALLY INVASIVE SURGERY - GETTING THE MOST OUT OF AN INTEGRATED SUITE 122 7.4 CASEIII:PHYSICALERGONOMICS-DESIGN OF A HANDLE FOR CURVED INSTRUMENTS 130

7.5 CONCLUSION 136 CHAPTER 8 DISCUSSION 141 8.1 DESIGN FRAMEWORK 142 8.2 SURGICAL QUALITY 145 8.3 FUTURE RESEARCH 147 SUMMARY 149 SAMENVATTING 153 REFERENCES 157 ACKNOWLEDGEMENT 163 CURRICULUM VITEA 167 OVERVIEW PAPERS 169 GLOSSARY 171

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Minimally invasive surgery is practiced by a growing number of medical disciplines including general, orthopaedic, paediatric, thoracic and vascular surgery as well as in gynaecology and urology. Since the inception of minimally invasive surgery in general surgery, laparoscopic procedures have become a popular technique.

Laparoscopy refers to minimal invasive videoscopic procedures in the abdominal cavity. The first video-laparoscopic cholecystectomy (gallbladder removal) was performed in 1985 by the surgeon Erich Mühe in Germany (Jani et al., 2006). Already in 1999 in the United States, 47% of in total 2.,82,308 general surgical procedures were performed with laparoscopy (Jaspers, 2006). Over the past two decades, laparoscopic cholecystectomy has become the gold standard for surgical management of gallstone disease (Lichten et al., 2001). The growing interest for this method of gallbladder removal is driven by the advantages for the patient such as less pain after surgery, shorter recovery time, better cosmetic results and fewer infections complications (van Veelen, 2003).

Considering that laparoscopic cholecystectomy has become the gold standard, the basic steps of this procedure should be discussed to understand the many advantages for the patient. A standard laparoscopic procedure starts with a small incision in the abdominal wall, usually the umbilicus. Through a special hollow needle, the abdomen of the patient is inflated with gas (carbon dioxide, CO2), to create workspace for the surgeon. Through other small incisions, so-called trocars are placed which serve as ports to introduce laparoscopic instruments into the abdominal cavity (figure 1.1).

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Figure 1.1 During laparoscopic procedures several trocars are used which serve as entrance ports for

the laparoscopic instruments and endoscope into the abdominal cavity.

These instruments give the surgical team the ability to manipulate the organs. To observe the abdominal cavity, an endoscope equipped with a small video camera is inserted. The camera is attached to the camera controller (processor unit). During laparoscopy, the surgeon uses 5 or 10 mm instruments to perform the procedure successfully. Generally, the required equipment is placed on a laparoscopy trolley, which holds a monitor, a camera controller, an insufflator that is used for inflation of the abdomen and a light source to illuminate the dark abdominal cavity through a light guide cable connected to the endoscope (figure 1.2).

Figure 1.2 Laparoscopy trolley with the required equipment to perform a laparoscopic procedure.

Laparoscopy, like open surgery, requires general or regional anaesthesia and is therefore performed in the operating room (OR). The OR is a complex environment equipped with all the required equipment and instruments to perform all types of surgical procedures. The OR have a high-quality ventilation system to control and guarantee the quality of the airflow lowering infection risk. To provide a safe and clean environment, the OR’s are divided in areas. In the next paragraph, these different areas and the positioning of the surgical team will be introduced.

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The operating room is the working environment of the surgical team during surgical procedures and can be divided into three work areas (figure 1.3). The sterile area is around the operating table and in most of the OR’s positioned in the centre of the operating room underneath the clean airflow (laminar flow). The surgeon, the resident, and the scrub nurse are working in this sterile area on either side of the operating table. This environment is sterile from waist to breast height of the surgical team. The resident assists the surgeon during the procedure and the scrub nurse is responsible for passing the required instruments to the surgeon or to the resident. The anaesthesiology area is at the head of the patient. The anaesthesiologist is positioned in this area and is non-sterile. The anaesthesiologist is responsible for monitoring the patient and administering of drugs, fluid and blood.

The rest of the non-sterile work area in the operating room forms the third area; this area is the work environment of the circulating nurse. The task of the circulating nurse is to supply equipment and instruments from outside the sterile area to the surgical team and operate the equipment in non-sterile area. Dependent on the procedure, the radiology staff, other disciplines, or guests might also be present in this work area.

Figure 1.3 The three work areas in the operating room.

Although the principles are the same for open and laparoscopic procedures, laparoscopy has altered the way surgeons interact with the surgical field in many ways. Despite the changes in surgical practice due to the introduction of laparoscopic surgery, few changes have taken place in the operating room layout, the position, and posture of the members of the surgical team over the last 100 years. Contradictory, the operating rooms are becoming more and more technology driven. The increasing dependency on technology to perform surgical procedures has significant ergonomic implications for the surgical team. This introduces a multi-disciplinary approach to deal with, focusing on one side on the

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technology-driven trends and on the other side on the social-economic consequences in surgery. Regardless the kind of discipline, in surgery the human plays a central role. Surgery is practiced by humans to cure, care, and prevent the other humans from illness. Because care, cure, and prevention are human-centred, ergonomics plays an important role in the field of surgery.

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“Ergonomics discovers and applies information about human behaviour, abilities, limitations, and other characteristics to the design of tools, machines, systems, tasks, jobs, and environments for productive, safe, comfortable, and effective human use” (Sanders & McCormick, 1993).

Since ergonomics has become relevant for product development and product evaluation, the working principle is; “adapt the environment to the workers, instead of adapting the workers to their environment” (Goossens & Van Veelen, 2001). On this perspective, it is not surprising that knowledge in the field of ergonomics has significant contributions to offer improvement of surgical quality and optimisation of working conditions and performance of the surgical team. From ergonomic point of view the surgical quality can be defined as; “the level of efficiency, safety and comfort of a surgical procedures” (van Veelen, 2003). Efficiency is defined as the coefficient between effort and benefit. In this definition, effort also implies e.g. product life span and learning and understanding the use of the product (e.g. it can take several months to learn how to perform a task without errors). Safety deals with the wellbeing of the user (in the case of minimally invasive surgery also the wellbeing of the patient) and the prevention of injury. Comfort can be defined as a physical and mental state in which one is not aware of any discomfort. The surgical quality and the working condition can be influenced by a variety of organizational and economical aspect but also by human-error due to poor ergonomic conditions such as excessive workload, fatigue, poor human-product interaction, poor communication among staff, etc. (Gawande et al., 2003).

The field of ergonomics can be divided along the human functions: physical, sensorial, and cognitive ergonomics. All three types of ergonomics are relevant when discovering ways to improve surgical quality.

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Emphasis lies on the function of the human musculoskeletal system, which is used to adopt postures, move limbs, and conduct external forces through the body. On the product site, this covers products that support the body, tools and special outfits (Goossens & Van Veelen, 2001).

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In this area, the focus is on the human senses and human perception. On the product site this includes products that support the senses and perception, such as visual displays, but also tactile displays and auditory displays (Goossens & Van Veelen, 2001).

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Here the emphasis lies on remembering and processing information; on learning, decision making and judging a situation. It is based on knowledge of the psychology of thinking and remembering. The products that support this part of ergonomics can be schemes of structures, mnemonic devices, software to control a process and training devices (Goossens & Van Veelen, 2001).

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The aim of this thesis is to improve surgical quality through ergonomics in the operating room. The aim can be divided into the following categories:

Gain insight into the ergonomic problems in the operating room.

Gain insight into the current state of ergonomics in the operating room.

Gain insight into the body posture and physical discomfort that surgeons may experience during surgical procedures.

Gain insight into problems intrinsic to laparoscopic viewing regarding sensorial and cognitive ergonomics.

Development ergonomic solutions regarding the three domains of ergonomics. 1

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During this PhD-research the basic design cycle of Roozenburg and Eekels is used as a design framework (Roozenburg & Eekels, 1995). The most fundamental model of designing (basic design cycle) is supplemented with the Participatory Design (PD) approach.

The medical specialists are professional users with their specific needs, work conditions, working environment, (technical) jargon, work culture, etc. When designing products for professional users their involvement in the design process is crucial since designers can use their knowledge and experience to improve the quality of the design proposal.

A methodology, which can be used from this perspective, is Participatory Design (PD) that actively involves the user into the design process, leading to the designed product that meets the user’s specific needs. PD is an approach that is

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characterized by concern with a more human, creative, and effective relationship between those involved in technology’s design and its use (Namioka & Rao, 1996). PD has been started in Norway in the late 60s and early 70s with the development of the first object-oriented programming language SIMULA. Since its inception, more and more product designers are using this approach during their product development.

Participatory design assumes that:

Users are experts; PD acknowledges the importance of using the expertise of

users and treating them as equal partners on a development team.

Tools should be designed for the context in which they will be used;

participatory design realizes that an important step to designing new tools is to know where they will be used and in what context, which makes it difficult to design a tool away from the environment in which it will be used.

There should be methods for observing or interviewing end-users; to gain

an understanding of the environment in which the product will be placed and used, there are several techniques used to watch, observe and interview users in their workplace.

Recreating or play-acting a work situation will facilitate the design phase;

it mediates the expectations of the users by not providing a non-functional prototype at the very beginning of the design phase.

Iterative development is essential; the ideal participatory design project has

several iterations of a design-feedback loop, where the developers ask the user for their opinion (Namioka & Rao, 1996).

During this PhD project, the emphasise was on the user and their knowledge, the environment wherein this knowledge was created and collecting of data from this environment. Therefore, this PhD-research mainly consists of field studies and has therefore a high ecological validity. Some of these field studies are supplemented with experimental studies. During these field studies, it was difficult to control all the preconditions of testing. As a consequence of this, the results are exploratory and, where possible, it will be reflected on theoretical insights.

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This thesis is based on published or submitted articles. Some of the studies have the same starting point but a different focus. Each of the articles was introduced and discussed from the perspective of that particular focus. Inevitably, this has caused some overlap in the information provided in the different chapters. We have therefore included a reading guide for different reader groups (figure 1.5).

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The outline of this thesis is visualized in figure 1.4. Chapter 2 gives an overview of the ergonomic problems in surgery. In Chapter 3 the surgeons working area is highlighted regarding the current state of ergonomics in the operating rooms. Chapter 4 deals with the discomfort of surgeons during surgical procedures and evaluation of the developed product solution. In Chapter 5 the focus is on the quality of laparoscopic viewing wherein the quality measurements, the factors describing image quality, and surgeons’ perception of the image will discussed. Hereafter in Chapter 6, an overview of some practical ergonomic solutions will described. In Chapter 7 three cases will presented within the design framework as described in paragraph 1.5. Finally, in Chapter 8, the results of this thesis will discussed and recommendations for future research will described. The definitions of the terminology used in this thesis are described in the Glossary.

Figure 1.4 The outline of the thesis.

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Cooperation between two different disciplines “Industrial Design” and “Surgery” is the basis of this thesis and, therefore, two target groups were involved; medical specialist and designers. Hence, in some of the chapters, the focus is on the medical specialists and in others on the designers. The different studies discussed in the chapters of this thesis might also be interesting for policymakers. In figure 1.5 a reading guide for different reader groups is shown.

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This chapter is mainly based on the following book chapter and article:

Albayrak A and Snijders CJ. (2007). Basics of Surgery: Tools, techniques, attitude and expertise. Maarssen, Elsevier Gezondheidszorg. 151-169.

Bonjer HJ, Albayrak A, Stassen LPS, Casseres YA, Meijer DW. Improving the endoscopic image: tips and tricks. Submitted (2008).

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In the last 100 years little changes have take place in the operating room layout while the operating rooms are become more technology driven (Albayrak et al., 2004; Gallagher & Smith, 2003). The increasing dependency on technology to perform surgical procedures introduced ergonomic problems for the surgical team. In this chapter, an overview will be given of the ergonomic problems in surgery. These problems will be discussed along the three domains of ergonomics; physical, sensorial and cognitive. The physical ergonomics will be restricted to the strain of the musculoskeletal system, which is relevant for neck, shoulder, arm, hand problems, lower back, pelvis, and foot. As most of the sensorial and cognitive problems are seen during laparoscopy this two sections will be focused on the laparoscopic procedures.

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Open surgery employs large incisions, which allow direct access to tissues and organs. Through the incision, the surgeon can see, feel, and manipulate the organs in a natural way, which means that direct sensory perceptions and feedback are present. During open surgery, surgeons lean forward toward or across the surgical field to see and manipulate the organs. Consequently, during open surgery the posture of the surgeon is characterized by a head-bent and back-bent posture (figure 2.1). The surgeons’ freedom of movement during open surgery is less restricted allow for a more dynamic body posture than during minimally invasive surgery.

Figure 2.1 The surgeon’s head-bent and back-bent body posture is characteristic of open surgery.

Performing open surgical procedures has almost always required standing, uncomfortable body posture and the occasional need to exert substantial forces on tissues (Berguer, 1999). The body posture of the surgeons during open surgery was described as a head-bent and back-bent posture. Surgeons maintain this posture for long periods of time with the result that they experience physical discomfort during and after surgery. After open surgery, 36.5% of the surgeons report pain in the lower back, 20.6% stiffness of the shoulder and 17.5% pain in the neck (Mirbod et al., 1995). The lower back pain is caused by extending the upper body centre of mass forwards (figure 2.2). This leaning forwards results in increased muscle activity to balance the upper body. Finally, leading to neck and back pain, especially in the lower back. Previous studies showed that surgeons and scrub nurses experience substantial stress of the musculoskeletal system due to their frequent and prolonged static flexion of the neck and lower back (Kant et al., 1992). An OWAS-based (Ovako Working posture Analysis System) analysis of nurses working postures, shows that in both orthopaedic and urology wards, the working posture of the nurses was harmful to the musculoskeletal system (Engels et al., 1994).

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Figure 2.2 Displacement of the upper body centre of mass forward is accompanied with increased

muscle activity in the lower back to balance the upper body.

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During laparoscopic procedures, long instruments are used which give the surgeon the ability to manipulate the tissue, as they were replacing the hands of the surgeon with limited tactile feedback. In addition, the perception of the tissue is not direct on the tissue anymore but using a monitor. Consequently, during these kinds of procedures the posture of the surgeon is characterized by straight trunk, rotation and flexion of the neck. The upper limbs of the surgeon are usually in excursion for handling the long instruments (figure 2.3). During laparoscopic procedures, the body movement of the surgeon is very limited resulting in a more static upright body posture compared to open surgery.

Figure 2.3 During laparoscopy the straight trunk of the surgeon is often accompanied by rotation and

flexion of the neck. The upper limbs are usually in excursion for handling long instruments.

Although, during laparoscopy the posture of the surgeon is straight predominantly, due to wrong positioning of the monitors the neck is rotated. Furthermore, the operating table is originally designed for open surgery and is not optimal for minimally invasive procedures regarding the height adjustability. The limited adjustability of the operating tables causes excursion of the upper limbs for handling long instruments. Previous studies reported that approximately 10% of

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surgeons suffer from pain in the upper limbs and neck during and after minimally invasive surgery (Berguer et al., 1997). The characteristic working situation during laparoscopic procedures involves elongated instruments and limited mobility of the surgeon during the procedure (Schurr et al., 1999). Laparoscopy requires greater concentration and places greater mental stress on surgeons comparing to open surgery (Berguer et al., 2001).

The surgical team consists of people of different body stature. The operating table is adjusted in height according to the height of the surgeon. Frequently, however, this working height is not optimal for the remaining members of the team and leads to ergonomically poor conditions.

Laparoscopy is implemented in the operating rooms with limited adjustments. The current operating tables are originally designed for open surgery and they are not optimal for laparoscopic procedures regarding ergonomic guidelines (Berguer et al., 2002; van Veelen et al., 2002b). The current operating tables are adjustable in height between 725-1215 mm (Albayrak et al., 2004). A previous study showed that the discomfort and difficulty ratings were lowest when instruments handles were positioned at elbow height of the surgeon (Berguer et al., 2002). Regarding this guideline, the ergonomically operating surface height (defined as the navel height of the patient, lying on the operating table while the abdomen is filled with O2) lies between 0.7 and 0.8 of the elbow height (290-690 mm) of the surgeon (van Veelen et al., 2002b).

It should be clear that the current operating tables cannot be lowered enough to meet these ergonomic guidelines. This causes excursion/extension of the upper limbs for handling long instruments. Previous studies reported that approximately 10% of surgeons suffer from pain in the upper limbs and neck during and after laparoscopic procedures (Berguer et al., 1997). The characteristic work situation during laparoscopy involves elongated instruments and limited mobility of the surgeon during the procedure (Schurr et al., 1999). Even if, the posture of the surgeon is more upright during laparoscopy, however, it seems to be accompanied by substantially less body movement and weight shifting than during open surgery (Berguer, 1999). This situation could account for increased static postural fatigue. The configuration of the operating room regarding the ergonomics is restricted during laparoscopy. The percentage of total floor space occupied by personnel, furniture and equipment during laparoscopy is increased by 10% compared with open surgery (Alarcon & Berguer, 1996). Increasing OR crowding may present unnecessary hazards to traffic and adversely affect the performance of the surgical team.

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The surgical team also has to deal with problems related to non-optimal working height. The surgical team often consists of people with different body heights. Frequently, the height of the operating table is adjusted according to the height of the surgeon. However, this working height is not always optimal for the other members of the team and can lead to poor ergonomics conditions. The working surface height in relation to subject, performing manual work determines the upper extremity effort and the potential of musculoskeletal injury.

Even in the most modern and well-equipped operating rooms, surgeons often face ergonomic shortcomings. As a result, the surgeon is frequently forced to adopt uncomfortable body postures that contribute significantly to fatigue and discomfort, which may lead to musculoskeletal disorders.

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A working environment regarding ergonomics dictates unobstructed line of vision in neutral standing posture. However, in open surgery, the current position of the resident and scrub nurse mandates back and neck torsion and flexion to allow clear vision on the operating field (Gerbrands et al., 2004). To overcome this, most scrub nurses and residents rotate their body towards the operating field and use a footstool, particularly during deep intra-abdominal or intrathoracic procedures. The current height variation of the available footstools is not sufficient for the different body lengths in the surgical team.

Because of the position of the patient, surgeons tend to lean forward toward or across the surgical field to see and manipulate the tissue. This body posture resulting in physical complaints due to neck flexion (figure 2.4).

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Limited number and wrong positioning of the monitors in the operating room results in physical complaints in the neck (flexion, extension, and rotation).

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Due to the position and depth of the incision during open surgery, surgeons have fixed work posture, tending to work with arms abducted and unsupported. A high static load is imposed on the shoulder-neck region and shoulder joint by this posture.

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During laparoscopy, long instruments are used. Due to the fixed insertion point (position of the trocar) of these instruments, the surgical team has manipulating problems. Besides the manipulating problems, these instruments also cause discomfort in the shoulder if the operating table is not adjusted optimally. Since the operating tables are originally designed for open surgery they cannot adjust low enough which cause excursion of the upper extremities. Besides wearing heavy lead apron also caused physical discomfort in the shoulder-neck region (van Veelen et al., 2003b).

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The instruments that are used in open surgery are distinguished from instruments for laparoscopy with simplicity of their design and favourable mechanical characteristics. They allow the surgeons with short, solid, and direct contact with tissues and good tactile feedback.

There are three basic grip principles to handle instruments:

Force grip; grip with fingers and thumb around an object.

Force-precision grip; force grip that allows more precision: fingers and thumb are

in-line with the forearm.

Precision grip; grip that uses the thumb and distal joints of the fingers to grasp

an object.

A common grasping and manipulating problem is that instruments are being used differently than the way they are originally designed for. For instance, using a precision grip on a handle of an instrument that was designed for force grip. This unintended use of the instruments could result in physical discomfort like pressure on the fingers, elbow- and wrist pain.

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The complexity and inefficient mechanical properties of instruments for laparoscopy cause grasping and manipulating problems. The internal mechanical design of instruments results in substantially diminished tactile feedback and an unfavourable force transmission ratio from handle to tip (Berguer, 1999). In comparing with instruments for open surgery, 4 to 6 times more force is required to complete the same task with instruments for laparoscopy (Berguer, 1999). The most frequently used instruments for laparoscopy can be divided in 3 groups: dissector, grasper, and scissors. There is a variety of handle design inside this group like axial, angled shank, multifunctional pistol and ring handle. A previous study shows the results of an experimental comparison of various ergonomic handles and their design (Matern et al., 1999). The objective results of this study show that pressure areas caused by rings and pain caused by ulnar deviation occurred frequently when working with the ring handle.

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Bending forward of the body during open surgery to see, feel and manipulate the tissue better, results in increased muscle activity, especially in the lower back to balance the upper body. Maintaining this body posture for long periods of time has consequences for static strain and fatigue in the back muscles. The static strain results in muscle contraction.

The generalized excitation-contraction sequence of a nerve impulse travelling from the brain and causing a muscle contraction is as follows.

ATP (adenosine triphosphate) ADP (adenosine diphosphate) + CP (creatine phosphate) + energy

ATP is created by the metabolism of the basic foods we eat. This metabolism can occur in two different modes: aerobic, requiring oxygen, and anaerobic, not using oxygen. Aerobic metabolism uses a slow biomechanical pathway. On the other hand, anaerobic metabolism utilizes a fast glycolytic enzyme to break down the glucose molecule into two lactate molecules and produce two ATPs. The lactate molecule in the extracellular fluid of the body forms lactic acid, which is a direct correlate of fatigue. Thus, the trade-off aerobic metabolism is slow but very efficient, while anaerobic metabolism is very fast but inefficient and gives rise to fatigue.

During muscle contraction, less blood reaches the working muscle with a corresponding decrease in oxygen availability. This means that the muscle must

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rely on a smaller amount of aerobic metabolism and a greater amount of anaerobic metabolism with concurrent fatigue (Freivalds, 2004).

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During laparoscopy, the body movement of the surgeon is very limited as compared with open surgery and they have a more static upright posture. The static strain results in muscle contraction. Maintaining this position for long periods of time leads to fatigue in the muscles.

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During open surgery as well as laparoscopy, the surgical team tends to lean toward the rails of the operating table since this is the only supporting surface around the table. The solid and metal edge of this rail results in bruising in the soft tissue around the pelvis region.

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During open surgery, the diathermy equipment is handled by a knob, which is integrated in the instrument. Due to manual control of this equipment, a pedal is unnecessary.

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During laparoscopy, a pedal is used to handle the diathermy and ultra-scission equipment. The current pedals cause positioning problems due to loosing contact which contributes to a poor body posture of the surgeon. In addition, there is a risk of accidentally activating the wrong function (left or right) because of lack of vision. To hold the foot above the right side of the pedal the surgeon has to keep his/her foot generally in dorsal flexion. Due to the dorsal flexion of the foot, surgeon’s weight is not equally divided over both legs and finally results in an ergonomic poor and static body posture.

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The current ergonomic layout of operating rooms with crowding of free-standing equipment such as the laparoscopy tower, often precludes optimal placement of the monitor in front of the surgeon (Alarcon & Berguer, 1996). Accordingly, the visual axis between the surgeon’s eyes and the monitor is no longer aligned with the hands and instruments, Furthermore, the monitor is often far removed from the surgeon and thus the spatial location of the display system (sensory information) is

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remote from the manipulation area at the hand level of the surgeon (Hanna et al., 1998).

With the current monitors as the standard image display system for laparoscopic surgery, monocular depth cues within the image are further degraded by “anti-cues” arising from the monitor. These are caused by the monitor frame and the glare and reflection from the glass of the monitor. All these factors add to the degradation in task performance compared to open surgery with normal monocular vision.

Since the image display system during laparoscopic procedures replaces “the eye” of the surgeon, some factors influencing the image quality have to be mentioned. The three major components describing image quality are resolution, luminance and chroma (Hanna & Cuschieri, 2001). Image resolution determines the visibility of details in the image and refers to the sharpness and contrast of the picture; luminance refers to the amount of light available in the image (brightness), and chroma denotes the colour intensity or saturation. Several optical factors may degrade image quality (Eden et al., 1993). Resolution and contrast influence the ability to appreciate fine details of the image.

The resolution and contrast can also be reduced by glare. Glare can be caused either by internal reflections (on-axis glare) or by stray light entering the system from outside the field of view (off-axis glare)(Berber et al., 2002).

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(The theory explained in this section is adopted from Cuschieri, 2006a)

Humans perceive the three-dimensional world by a pair of two-dimensional retinas that react to visible light. The resulting image recognized by the subject in the cognitive process is known as a percept, which determines the interpretation of the visual information (Cuschieri, 2006a). Visual psychologists distinguish two kinds of perceptions: direct (perception of objects in 3D space) and indirect (perception of pictures/images of objects rather than the objects themselves) (Cuschieri, 2006a). During open surgical procedures, the surgeon can view the operating field directly. The theory of James Gibson can elucidate the cognitive stage of direct visual perception (Cuschieri, 2006a). This theory postulates a data-driven bottom-up process and implies direct perception (i.e. the visual data have sufficient information and are structured within the optical pathway before reaching conscious perception) (Cuschieri, 2006a). Conversely, during laparoscopic procedures surgeons must operate guided by images rather than reality (indirect perception).

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According to Gibson, pictures and images of objects have been shown to induce more perceptual errors than direct perception of objects because they are the result of viewing with inadequate information (Cuschieri, 2006a). This consideration is of paramount importance during laparoscopy since the surgical team is almost completely dependent on the indirect perception. The monitor is hereby the only interface between the surgical team and the surgical field and thus the main source yielding/displaying information about the progress of the procedure. A high quality of the image is therefore requisite to allow safe and efficient laparoscopic procedures.

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The image during laparoscopy, displayed on the monitor is a product of the so-called “imaging chain” consisting of light source, light guide cable, endoscope, camera, camera unit and monitor (Schwaitzberg, 2001). This results in several places where the image can be distorted. To be able to structure the complex relation between the quality of the displayed image, surgeons perception of this image, and the several components of the “imaging chain” as described above, the framework of the Engeldrum’s Image Quality Circle (Engeldrum, 2000) could serve as a framework. In figure 2.5 the topics, which are in the scope of this thesis, are shown in perspective of Engeldrum’s Image Quality Circle. The circle on the outside represents the original framework of Engeldrum (Engeldrum, 2000). The circle on the inside shows the topics, which are relevant for this thesis. The technology variables are not included in the research.

Figure 2.5 The circle on the outside represent the original framework of Engeldrum’s Image Quality

Circle (Engeldrum, 2000) and the circle on the inside represents the topics, which are in the scope of this thesis. The technology variables are not included in the research.

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The Image Quality Circle is a framework, which organizes the multiplicity of ideas that constitute image quality. The Image Quality process begins with determining Customer Quality Preference and in perspective of laparoscopic procedures represents the surgeon’s opinion of image quality. This judgment is connected to the third element Physical Image Parameters. These are objective measures of image quality such as the resolution of the endoscope and monitor and measurements of light transmission of the endoscope and light guide cables. The last part completing the circle is the Customer Perceptions – The “Nesses”. These are perceptual attributes mostly visual that form the basis of the judgment of the surgeon. (Since most visual perceptual attributes like, sharpness, brightness, etc. end with suffix “ness”, this term is used as a shorthand notation to emphasise the connection to human perception).

Laparoscopic surgery is introduced without much consideration for ergonomic limitations. The technology that surgeons use to perform laparoscopy caused a human-product miss-match. This has largely to do with shortcomings of the equipment and instrumentation that surgeons have to use or interact, unforeseen ergonomic issues (Gallagher & Smith, 2003).

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There are several factors intrinsic to laparoscopic viewing that degrade the surgical quality and enhance the probability of error during surgical procedures. Many of the related problems are due to the perceptual and spatial factors. One of the major perceptual problems is that the image on the flat monitor screen contains only monocular (pictorial) depth cues of the surgical field to the surgeon (Hanna & Cuschieri, 2001). This representation of the three-dimensional surgical field on a two-dimensional screen may reduce depth perception since retinal disparity, and therefore the resultant stereoscopic vision (i.e. integrated information from two viewpoints) providing the surgeon a strong sense of depth is missing (Shah et al., 2003).

A further perceptual problem in laparoscopy arises from scaling difficulties caused by the magnification and the severely degraded visual image of the anatomy in comparison to the experience of an open procedure (Gallagher & Smith, 2003). The various spatial difficulties encountered during laparoscopy result in problems with cognitive mapping and hand-eye coordination. The monitor presents vastly different images of anatomy due to the perspective and magnification of objects closest to the endoscope. Spatial discrepancies are also caused by a misinterpretation of angular relationships (the azimuth angle), because the entry

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points of instruments do not correspond with the optical axis of the endoscope camera (Gallagher & Smith, 2003).

Another problem with a spatial aspect involves camera etiquette. The surgeon has no direct control over the position or orientation of the endoscope. Instead, the surgeon must rely on the assistant to maintain an optimal position; however, frequently unintentional camera rotation occurs that can lead to disorientation and misinterpretation of position of the organs.

One of the problems limiting the surgeon’s acquisition of skill and degrading the surgical quality is due to the fulcrum effect. The fulcrum effect of the body wall causes an inversion of the perceived movements. An internal movement to the right is displayed as a movement to the left on the monitor. For an inexperienced surgeon this results in a significantly poorer performance (Gallagher & Smith, 2003).

Some of the problems are caused due to the limitations of the components of the “imaging chain”. Both light guide cables and endoscopes contain glass fibres to transmit light. These glass fibres have a high transmission coefficient. However, reduction of loss in light in light transmission occurs in the delivery system due to;

Differences of diameters on the connection of the light guide cable with the light source.

Differences of diameter between the light guide cable and the endoscope.

Surface losses and bulb absorption.

Because of these losses, the transmission coefficient of this part of the imaging channel is reduced to 20 percent in the best system. As a result of all the losses, a typical system will deliver considerably less then 1 W of visible light from a 250 W source lamp (Frank et al., 1997).

Additionally, loss in illumination is caused by ageing of the light source and mechanical damage due to repetitive use and sterilization of light guide cables and endoscopes resulting in breakage of fibres. Melted or broken fibres reduce the illuminance of the abdominal cavity. Optimal illumination of the dark abdominal cavity is indispensable for carrying out any minimally invasive procedure.

In an endoscope, the lenses are positioned in the centre surrounded by optical fibres that transmit light from the light source to the surgical field (Boppart et al., 1999). This configuration imposes certain problems. In the first place, the level of illumination across the surgical field is uneven, that is, the periphery of the endoscopic field is less well illuminated (Hanna & Cuschieri, 2001).

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The coaxial alignment of optical fibres and the optical lens system also results in a shadow less surgical field as both light directions and optical axis subtend the same angle to the target organ. Because shadows constitute very important pictorial depth cues, their absence detracts further from the visual information presented to the surgeon (Hanna & Cuschieri, 2001). In the second place, the viewing angle of the endoscope refers to the angle formed by the two outer visual limits and determines the diameter of the field of view and the magnification. Restricted field of endoscopic vision predispose to iatrogenic tissue injury when instruments move outside the field of view and account for the high percentage of bile duct and bowel injuries that are missed during laparoscopic surgery and declare themselves by virtue of major complications in the postoperative period (Fletcher et al., 1999; Russel et al., 1996).

The term distortion is applied to the image where lines at the edge of the image appear curved. Outward curved lines are termed “barrel distortion”, often encountered, in endoscopes. The distortion effect increases with wider field of view. Field curvature indicates that the centre and the edge of the image are not in focus at the same time. This is difficult to perceive during viewing by eye due to the constant refocusing of the human ocular lens.

The ergonomic problems discussed in this chapter show how divers the problems are that the surgical team has to deal with in their profession in daily life. The overview also shows the opportunities to improve the surgical quality and optimize the work conditions of the surgical team. In the next chapters, these problems will be analyzed from a certain perspective and the solutions will be discussed.

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This chapter is based on the following article:

Albayrak A, Kazemier G, Meijer DW, Bonjer HJ. (2004). Current state of ergonomics of operating rooms of Dutch hospitals in the endoscopic era. Minimal Invasive Therapy & Allied Technologies. 13(3); 156-160.

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Most of the laparoscopic procedures are performed in operating rooms, which originally have been designed for open surgery. The ergonomic layout of these operating rooms is often not suited for laparoscopic surgery. This study reports the current state of ergonomics of Dutch operating rooms for laparoscopic surgery. For this purpose, twenty-nine hospitals were visited and an inventory was made of the number of laparoscopy trolleys, presence of ceiling-mounted booms, and number, positioning and dimension of the monitors. Additionally, the number of operating rooms was recorded and the floor surface area of these operating rooms was measured. Positioning of the surgical team and monitors around the operating table were assessed and the range of height adjustment of the operating tables was documented. Results showed that the floor space of current operating rooms is too small to allow use of space occupying technological systems for laparoscopic surgery. Most of the monitors were positioned on a laparoscopy trolley with a fixed height and the operating tables cannot be lowered to a position, which allows an ergonomic posture of the surgical team. Implications of these findings toward positioning and posture of the surgical team are discussed.

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The majority of current operating rooms (OR’s) have been designed in the second half of the 20th century to allow performance of open surgery. Novel operating techniques, such as laparoscopic and robotic surgery, differ from open surgery in many ways. To perform these types of surgery successfully, trolleys for laparoscopic surgery, monitors, and robotic systems are required. Laparoscopic equipment such as camera, light source, and insufflator are usually placed on one or more laparoscopy trolleys. This trolley-based model restricts the ergonomic configuration of the operating room. Alarcon et al. showed that the percentage of total floor space occupied by personnel, furniture, and equipment during laparoscopic procedures increased by 10% over open procedures (Alarcon & Berguer, 1996). Increasing OR crowding may present unnecessary hazards to traffic and adversely affect the performance of the surgical team (Alarcon & Berguer, 1996). Most references of OR design state that the minimum dimensions for a modern OR should be 37 m2_{while specialized rooms require up to 55 m}2_of

floor space (Quebbeman, 1993).

A possibility for optimizing the workspace in the OR is placing laparoscopic equipment on a ceiling-mounted boom. This increases the working space around the operating table and will facilitate positioning of heavy trolleys, improving the ergonomic configuration of the OR.

During laparoscopic surgery, longer instruments are used compared to open surgery. Studies have shown that long laparoscopic instruments potentially cause excessive flexion and ulnar deviation of the surgeons wrist and abduction of the arms during manipulation, particularly if the operating table can not be lowered sufficiently (Berguer, 1998; Matern & Waller, 1999). It has been reported that the ergonomically optimal operating height is between 70 and 80 % of the height of the elbow of the surgeon (van Veelen et al., 2002b).

Menozzi et al. advised to position the monitors in front of the viewer with a downward gaze of approximately 100 to 250 below eye level (Menozzi et al., 1994). To allow these conditions, monitors should be mobile and in height adjustable. This study reports the current state of ergonomics of Dutch operating rooms for laparoscopic surgery.

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Twenty-nine Dutch hospitals have been visited. Two of the 29 visited hospitals were academic hospitals, 12 were teaching hospitals and 15 were community hospitals. The operating room departments of each hospital were visited and the following items were recorded:

Number of operating rooms per hospital type.

Number of available laparoscopy trolleys.

Mid monitor height (figure 3.1).

Monitor type and dimension.

Monitor placement (either on trolley or on ceiling-mounted boom).

Operating room floor surface area in m2.

Range of height adjustment of operating tables.

Positioning of the surgical team.

Figure 3.1 Mid monitor height.

The positioning of surgical teams was registered during 48 laparoscopic cholecystectomies and hernia repairs. To determine the optimum number and positioning of the monitor relative to the user’s eyes, each positioning was analysed.

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The average number of operating rooms per hospital type is presented in table 3.1.

Table 3.1 Average number of operating rooms per hospital type.

Hospital type Average number of operating rooms

University hospital 19.5

Teaching hospital 7.6

Community hospital 5.3

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In the 29 hospitals visited, 69 laparoscopy trolleys were present with a median of two and an average of 2.4 trolleys per hospital. The average number of trolleys at university hospitals was 2, at teaching hospitals 3.25 and at community hospitals 1.7.

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In total 65 monitors were available at the visited hospitals. The average mid monitor height was 163 cm (range 145-180 cm). All monitors were Cathode Ray Tube monitors (classic monitors) except for one monitor being a 13’ inch Liquid Crystal Display. All monitors were placed on trolleys except for two, which were attached on a ceiling-mounted boom. One of the 29 hospitals had ceiling-mounted booms for placement of two monitors. The dimension and the number of the monitors are shown in table 3.2. Fifty-one monitors (81%) were fixed on the top of the trolley. Twelve monitors (19%) were attached to the trolley by a swinging arm, allowing it to move towards or swing over the operating field.

Table 3.2 Dimension, number and mobility of monitors per hospital type.

Number of fixed monitors per hospital type

Number of swinging monitors per hospital type

Monitor dimension (inch)

Academic Teaching Community Academic Teaching Community

13 2 5 2 14 1 1 18 2 2 1 19 4 19 12 2 1 20 4 4 21 1

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The average operating room floor surface area was 37.45 m2_{(range 22.03 to 44.14}

m2_{). The average operating room floor surface area at academic hospitals was 32.1}

m2_{, at teaching hospitals 36.56 m}2_{and at community hospitals 38.05 m}2_.

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The average range of height adjustability of operating tables was from 725 mm to 1215 mm.

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Five different positions of surgical teams were registered (figure 3.2). Position 1 and 4 were encountered in 12% of procedures, position 3 and 5 in 21% of procedures, and position 2 in 67% of procedures. There was no difference in distribution of positioning of the surgical team over each type of hospitals.

Figure 3.2 Different positions of the surgical team during laparoscopic surgery.

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Laparoscopic surgery has changed the requirements of modern operating rooms greatly. To allow laparoscopic surgery, multiple monitors and a videoscopic working unit, which is usually assembled in a trolley, are necessary. In the early days of laparoscopic cholecystectomy, a monitor mounted on top of the videoscopic trolley was the only screen available to the surgical team. Positioning the screen in line of the surgeon’s eye and the target organ interfered with the operating table and the respirator, which is commonly standing at the right shoulder of the patient. A short swinging arm carrying the monitor mounted on the trolley can improve the degree of freedom to some extent. Attachment of the monitor on a ceiling-mounted boom allows a placement of the monitor without interference with operating table or respirator. The use of ceiling-mounted booms for supply of oxygen, anaesthetic

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gases, and electric outlets has become commonplace. Use of ceiling-mounted boom for monitors is, however, rare, given that only one of the visited had such a setup. The disadvantage of attaching a heavy monitor on a ceiling-mounted boom is the necessity to install heavy-duty booms. Moving the monitor and boom requires substantial physical strength. The latest high quality versions of flat screens, which are low in weight, are easy to position and take up less space.

In laparoscopic surgery, members of the surgical team stand on both sides of the table in the great majority of procedures. Assessing the position of the surgical team from an ergonomic point of view, position 1 and 4 require one monitor (12% of procedures), position 3 requires two monitors (11% of procedures), and position 2 and 5 require three monitors (77% of procedures) to allow unobstructed line of vision without neck torsion by each member of the surgical team (figure 3.3).

Figure 3.3 Ergonomically optimal positioning of the surgical team and number of monitors.

To allow the surgical team to watch the screen without cervical torsion, this study shows that employment of two or more monitors is mandatory in those instances. In this study, only seven of 29 (24%) hospitals used multiply monitors.

When the screen is attached on a ceiling-mounted boom that can be moved up and down, the optimal viewing angle of 10-25 degrees downward gaze can be realized (Menozzi et al., 1994). The optimal dimension of the monitor is determined by the distance between the surgeon’s eye and the screen. In the majority of the hospitals 19-inch screen were used. Considering this screen size, the average distance

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between the surgeon’s eyes and the screen should be between 70-95 cm (Menozzi et al., 1994).

The total length of the arm of the surgeon holding a laparoscopic instrument is approximately 30 cm greater than that of a surgeon’s arm holding an instrument for open surgery. Studies show that long laparoscopic instruments potentially cause excessive flexion and ulnar deviation of the surgeons wrist and abduction of the arms during manipulation (Berguer, 1998; Matern & Waller, 1999). The optimal height of the operating table in open surgery is three quarters of the height of the surgeon’s elbow (van Veelen et al., 2002b). Given that the average height of the elbow of the surgeon (± SD) is 110 cm (male and female) (www.dined.nl, 2004), the table should be positioned at a height of 82.5 cm for open surgery. Adding the length of laparoscopic instrument converts the optimal height of the operating table for laparoscopic surgery to 52.5 cm. To prevent undue strain of the surgeon’s upper limbs, operating tables should be lowered further than currently possible. Berguer et al. showed, using electromyography, that a mismatch between table height and body length of the surgeon increases muscular strain (Berguer et al., 2002).

The floor surface area of operating rooms in the first half of the 20th century tended to be greater than in the second half. In the early nineteen hundreds day light was a main source of lighting the surgical field. Therefore, large windows were necessary to provide sufficient exposure to day light. Furthermore, surgical instruments in large canisters were stored in the operating room instead of in a separate room. Due to the development of high power operating lamps and alternative design of the operating room complex, the floor surface area of operating rooms was reduced.

The introduction of laparoscopic surgery, image-guided surgery and other new technologies such as ultrasonic and radiofrequency surgery to ablate tissue has again increased the demand for space. The modern operating room should have a surface between 37 and 55 m2_{(Quebbeman, 1993). In this study, the average floor}

surface area of the operating rooms was 37 m2_{, which indicates that half the}

operating rooms are not fit for these novel technologies.

In conclusion, current operating rooms in The Netherlands are insufficient from an ergonomic point of view to perform laparoscopic surgery. Future designs of operating rooms and laparoscopic equipment should consider basic ergonomic principles to prevent work related injuries and to allow optimal performance of the entire surgical team.

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This chapter is based on the following articles:

Albayrak A, van Veelen MA, Prins JF, Snijders CJ, de Ridder H, Kazemier G. (2007). A newly designed ergonomic body support for surgeons. Surgical Endoscopy 21(10): 1835-1840.

Albayrak A, de Ridder H, Bonjer HJ, Goossens RHM, Snijders CJ, Kazemier G. (2006). Reducing muscle activity of the surgeon during surgical procedures. In Proceedings of the 16th World Congress on Ergonomics, Maastricht, The Netherlands: International Ergonomics Association.

Albayrak A, Goossens RHM, Snijders CJ, de Ridder H, Kazemier G. Impact of a chest support on lower back muscles activity during forward bending. Submitted (2008).

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One of the main physical ergonomic problems during surgical procedures is the surgeons’ uncomfortable body posture. Surgeons maintain this position for long periods often resulting in physical discomfort during and after surgery. Furthermore, people of different body height are often present within the surgical team. During both kinds of procedures, the operating table is adjusted in height best suiting the surgeon. Frequently, however, this working height is non-optimal for the other members of the team.

Study I is focusing on the design process of development of a product solution that supports surgeons during both open and minimally invasive procedures, reduces the surgeons muscle activity in the lower back and extremities, and solves problems related to non-optimal working height.

The aim of Study II is to investigate the impact of the developed product solution on lower back muscle activity during forward bending and to establish a possible relation between the supporting force and the kind of balancing strategy a person adopts.

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Increasingly, more general surgeons are performing minimally invasive procedures in addition to open surgery. Although the basics of laparoscopic and open procedures are similar, minimally invasive procedures have altered the way surgeons interact with the surgical field, which requires a change in the surgeon’s posture. A head- and back-bent posture and a twisted torso characterize the posture of the surgeon during open surgical procedures. Conversely, during laparoscopic procedures, the posture of the surgeon is characterized by a head- and back-straight posture. The poor ergonomic posture of surgeons during both kinds of procedures can result in physical discomfort.

Due to the position of the patient during open surgery, surgeons tend to lean forward toward or even over the surgical field to see and manipulate the tissue. This leaning forward results in increased muscle activity to balance the upper body. Kant et al. reported that surgeons and scrub nurses exhibited frequent static body postures that were ‘‘distinctly harmful’’ and contributed to physical fatigue during surgery (Kant et al., 1992). Maintaining the uncomfortable position of the body for longer periods results in musculoskeletal fatigue and physical complaints on the part of surgeons. After open surgery, 30% of surgeons report pain and stiffness of shoulders, neck, and lower back (Mirbod et al., 1995). These complaints are caused by extending the centre of gravity of the upper body forwards (figure 4.1).

Figure 4.1 Displacement centre of gravity of the upper body as a result of bending forward.

During laparoscopy, the upper extremities usually are in uncomfortable excursion for handling the long laparoscopic instruments (figure 4.2). The upright posture during these procedures, however, seems to be accompanied by substantially less body movement and weight shifting than during open surgery (Berguer et al.,