Keywords

Introduction

Ergonomics literally stands for work rules. Ergonomics deals with the fit between people their work environment and tools. The international society of ergonomics defines ergonomics as: the scientific discipline concerned with the understanding of interactions among humans and other elements of a system and the profession that applies theory, principles, data and methods to design in order to optimize human well-being and overall system performance. Whereas ergonomic analyses have appraised its applications in other non-medical arenas, in the field of medical science it has been a largely neglected issue. A recent interest has blossomed with respect to ergonomics in the surgical field particularly after the advent of laparoscopic surgery. Ergonomic adjustments can help in decreasing fatigue and injuries to doctors making surgery safer besides improving efficiency and thus patient related outcome. This article reviews the available literature on ergonomical principles that are commonly encountered in the practice of laparoscopic surgery, the doctor and patient related consequences of working in ergonomically inefficient situations and critical ergonomic adjustments in instrument design and operation theatre methods recommended to correct these ergonomic inaccuracies.

Literature Related to Ergonomics

Literature pertaining to ergonomics in laparoscopic surgery is sparse. Evidence is based upon respondent surveys, comparative cohorts of ergonomically trained and not trained surgeons, experimental studies in skills laboratory or artificially simulated situations and is conspicuous by the absence of well-designed randomized clinical trials addressing the issue. The low interest in ergonomics in the medical field can be related to many factors, predominant of which might be a reluctance to analyse work- and work-related criticism and underestimation of the importance of the issue. Complaining of fatigue and stress related to surgical procedures were till lately considered an inelegant mannerism and attributed to surgeon inefficiency and thus such reports and analysis were criticized or discouraged. These issues are further compounded by the difficulty in assessing the outcome measures of assessment which are often inconsistent and ill-defined and are affected by a multiplicity of interactive phenomenon. An example is workload assessment, which can depend on multifarious components like physical, mental, temporal demands, task complexity, situational stress and distractions.

Doctor and Patient Related Consequences of Improper Ergonomics in Laparoscopic Surgery

Improper ergonomics in the operation theatre can lead to: unintentional injuries, increased operative time, errors and increased morbidity. It has been reported that poor design of surgical equipments lead to unintentional patient related injuries thus necessitating the need for standardization of instruments by regulatory authorities [1]. From the perspective of the surgeon posture related strains, nerve injuries, fatigue, decreased efficiency, increased psychological and mental stress can all result from incorrect ergonomics. In a survey of 260 respondents of gynaecological oncologist performing minimally invasive surgery, physical discomfort related to MIS was reported in 88% with complaints of persistent pain in 52%. To decrease pain, surgeons changed positions 78% of the times, limited the number of cases per day in 14%, spread cases throughout the week in 6%, limited the total number of cases in 3%. Of the group 29% had received treatment for pain symptoms in the form of physical therapy (59%), medical management (28%), surgery (13%), and time off from work (1%) [2]. The dominant upper extremity has been reported to be the primary site of discomfort in 73% of respondents in a survey on surgeons performing laparoscopic cholecystectomy [3]. In another respondent based study evaluating laparoscopic graspers, 98 completed the questionnaire (response rate 35%), 77% reported physical complaints directly attributable to the use of laparoscopic instruments [4]. Though the increased physical workload is eminent in laparoscopic surgery, studies have suggested an increased mental workload also reflected as increased number of errors in laparoscopic surgery [5]. Thus improper ergonomics can have important bearing on work efficiency and output with resultant economic implications. Poor table height adjustment, bad monitor positioning and suboptimal design of instrument handles were reported as important causes of complications [3].

Why and How Ergonomics of Laparoscopic Surgery is Different from that of Open Surgery

The issue of ergonomics has gained an interest lately after the advent of laparoscopic surgery. Whereas an increased awareness and a rational approach to address problems may be the reason for the upsurge in interest related to the subject, needless to say the effects have been multiplicated due to the decreased ergonomic ceiling, resultant to increased physical and mental demands as also task complexity. Performance of laparoscopic surgery is more stressful than open surgery [6]. The important arenas in laparoscopic surgery which differs from open surgery and needs consideration are: (1) Laparoscopic vision (2) Altered body postures (3) Longer operative times (4) Workplace layout i.e. table height, monitor and foot pedal directions (5) Design and function of laparoscopic surgical equipments (6) Mental workload due to requirement of enhanced skills [7, 8].

  1. (a)

    The Laparoscopic Vision and eye strain: The essential feature of laparoscopic vision is that it is an indirect view: (1) depends on image transmission, clarity, focussing, zooming, colour alteration and the efficient assistance of the camera holding person. (2) the field of view is restricted to the area under vision as degree of freedom of camera movement is limited (3) view is not under control of the surgeon (4) the vision is two dimensional posing difficulty in depth perception and spatial resolution. Resultant to these factors there is increased demand for visual workload and consequential fatigue [9, 10]. Eye strain was reported as a prominent ergonomic problem especially amongst junior surgeons involved in laparoscopic surgery [11]

  2. (b)

    Body Posture Related Problems: back pain, neck pain, shoulder/arm muscle strain and pains/paresthesia in hand and fingers: Uncommon body postures excessive muscular load due to fatigue and pressure points causing nerve injuries are the primary ergonomic concerns [9]. Back pain, neck pain fatigue irritability and hand discomfort are some of the commonly reported symptoms [12].

    Back pain and neck pain: Back pain is reported to be 15% more common in laparoscopy and has been attributed to be due to a number of factors: (a) awkward body posture due to far apart port positions, (b) need to look in one direction whereas instruments and foot pedals are often improperly positioned in a different direction (c) increased neck rotation duration due to incorrect alignment of monitor and work axis [13] Surgeons exhibit decreased mobility of the head and back and less anteroposterior weight shifting during laparoscopic manipulations despite a more upright posture. This more restricted posture during laparoscopic surgery may induce fatigue by limiting the natural changes in body posture that occur during open surgery having an important bearing on outcome [14]. Increased physical and mental workload both at baseline and thereafter in the operation theatre can lead to fatigue and facilitate error in surgical operations.

    Shoulder and arm muscle strains: The other posture related problems in laparoscopic surgery are shoulder strains and arm muscle strains due to high level of operating table compounded with pneumo-peritoneum and long working instruments. Higher upper extremity muscle strength is required in performing complex manipulative tasks of laparoscopic surgery [15]. Laparoscopic surgery requires more skills due to altered instrument designs and increased force due to use of small muscles. Additionally longer operating times especially initially in learning curve is needed as also increased concentration. Difference in loading between dominant and non dominant shoulders increased use of power morcellation repeated insertion and removals of laparoscopic instruments through trocars wherein strain occurs at the shoulder have been identified as predominant factors which pose risk to surgeons. An advantage of height of surgeon in this regard has been observed with increase in height resulting in decrease in time spent in extreme body posture [13]. Extreme displacements of the arm both vertical and horizontal due to insertion of instruments through fixed trocars resulted in increased workload especially on upper arm and foream muscles [16]. Thus mini breaks have been advised for posture readjustments [17].

    Wrist pain/hand pain/laparoscopic thumb/finger numbness: An extended wrist posture is often used for performing most laparoscopic tasks [18]. The “laparoscopic surgeons thumb” has been reported as a damage to the lateral digital nerve of the thumb which is a superficial branch of the radial nerve in the region [19, 20]. Increased paresthesia of fingers has been reported particularly more amongst junior surgeons in laparoscopic surgery [11]. The use of a ringed silicon rubber attachment has been proposed to prevent laparoscopic thumb [21] A questionnaire based survey with The SAGES Task Force on Ergonomics, respondents reported 8% to 12% frequent pain in the neck and upper extremities associated with laparoscopic surgery. The peak and total muscle effort of forearm and thumb muscles were significantly greater when the grasping task was performed using the laparoscopic instrument as compared with open hemostat [22].

Critical Adjustments for Improving Ergonomics in Laparoscopic Surgery

The critical adjustments to be made in laparoscopic surgery to improve the ergonomics of the procedure essentially comprise of modifications in the following aspects:

  1. 1.

    Work place lay out

  2. 2.

    Tool (instrument) design and use

  3. 3.

    Work environment modification

  4. 4.

    Training of staff.

1. Work Place Layout

In a transition from open to laparoscopic surgery the laparoscopic equipment and instrumentation have been adopted into an operation theatre suite ideally designed for open surgery. Operating room crowding is significantly more in laparoscopic surgery when compared with open surgery which calls for specially designed suite [23]. However there are a number of inherent differences between open and laparoscopic surgery and operation theatres exclusively designed for performance of laparoscopic surgery merit consideration. In a study evaluating the physical strain on surgeons performing laparoscopic cholecystectomy in modern as compared to standard OR (operating room) the former was found to be ergonomically beneficial [24]. In a prospective case-controlled study ten experienced surgeons performed surgery in two different ORs: a standard room and a modern room. The surgeons were asked to fill out questionnaires concerning physical and psychological wellbeing before and after surgery and had their heart rate variability registered during surgery. Physical strain experienced by the surgeon was less when performing laparoscopic cholecystectomy in a modern OR compared with a standard room [24].

A number of critical adjustments in work place layout need to be undertaken for improving the ergonomics of laparoscopic surgery (a) Operating table level (b) Monitor level (c) Foot Pedals (d) Positioning of operating surgeon and assistant.

OT Table Height: The height of the operating table has an important bearing on shoulder and hand muscle strain. Most operating tables are constructed keeping in view of open surgical procedures. The important difference between open and laparoscopic surgery is that the effective working height increases in laparoscopic surgery due to pneumo-peritoneum which distends the abdominal wall. Added to this issue is the long laparoscopic working instrument, wherein a considerable portion of the instrument protrudes out of the patients abdominal wall which necessitate increased shoulder elevation, shoulder abduction and elbow flexion thereby causing strain. In laparoscopic surgery task performance has been found to be best at the height of operating table wherein the abdominal wall of the patient corresponds to the thigh height of the operating surgeon which depends on the instrument handle type (shank, pistol axial and rod type) as also the angle of insertion of the instrument [25]. Thus substantial lowering of table, to a height of 30-60cmcm from the floor has been suggested to facilitate ergonomic working. A concern regarding efficient floor cleaning and hygiene issue has been raised as in open surgery the table height is usually at the level of belt height however no substantial evidence against it has been documented [25]. It has been said that the ideal operating table level should be such that: (1) the angle between lower & upper arm should be between 90° and 120°. (2) after the insertion of instruments they should be roughly at, or slightly below the level of the surgeon’s elbows (Fig. 1a, b) [17, 26, 27]. In a study on hand assisted laparoscopy the optimal table height proposed is such that the extracorporeal instrument handle is at elbow level or 5 cm above [28]. The use of arm support has been also been suggested [29]. Women surgeon experience greater difficulty in laparoscopic surgery and adjustment in OT table height is often required [30].

Fig. 1
figure 1

(a) Instrument handles at or below the level of elbow keeps the shoulder relaxed and indicates correct table height. (b) Incorrect table height and long external length of instruments leads to forearm being flexed

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Monitor Position: Eye-hand-target axis misalignment occurs because of limited freedom in monitor positioning and is an important ergonomic drawback during minimally invasive surgery [31]. A simulated laparoscopic suturing in which EMG data was compared in 18 surgeons performing the procedure with monitor positions at: eye level, at the height of the operating field and 45° to the right, the frontal eye level was found to be the most preferable. It has been suggested that two monitors should be placed to ease visualization of the operating surgeon and a contralateral positioned assistant [17, 25]. Ideally the monitor should be placed straight in front of each person, aligned with motor axis of forearm instruments in the horizontal plane and in the sagittal plane at 15–40° below eye level. An important limitation in minimally invasive surgery is misalignment in the eye-hand-target axis due to monitor positioning which can limit freedom of movement [31] (Fig. 2). The other advanced adjustments that can be implemented for ergonomic improvement are: mirror image correction for assistants in case of reverse alignment, head mounted camera, flat display screens and video display on flexible booms [17, 31, 32]. The important characteristics which influence the display characteristics are: contrast, detail, brightness, lighting uniformity, focussing uniformity, sharpness and colour. Rated scales are often implemented for assessing the perceptual quality for example: MVCS The Maryland Visual Comfort Scale [33].

Fig. 2
figure 2

Monitor position below eye level and in front

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Foot Pedals/Hand Control for Electrosurgical Equipment’s/Cordless Device: Laparoscopic surgery involves the application of various foot pedal controlled electrosurgical equipments. Attention should also be metted to the proper positioning of these foot pedals to avoid body rotation related strains. Foot pedals should be placed close to the foot, aligned in the same direction as the instruments i.e. towards the target quadrant of surgery as also the principal laparoscopic monitor.

A built-in foot rest can help provide the necessary foot support for prolonged usage. Often two pedals (for different devices) are used and the surgeon must be careful not to confuse them in the darkness [17].

Alternatively ESU operated by hand controls may be preferable to foot controls. Proximity of hand controls to the equipment handle is also important to ease its usage [34].The use of cordless laparoscopic ultrasonic device has been suggested by some authors [35].

Positioning of Assistants: The position of assistant varies according to individual operations, also the surgeon’s choice. Whereas surgeons often believe that the position of assistant does not have an important bearing some authors report observations to the contrary. In an analysis of hand technique and standing position during laparoscopic cholecystectomy it was observed that the position of assistants may have a detrimental effect on muscle work and pose physical injury to the surgeons. In the study virtual reality simulated generated performance was analysed. Physical ergonomics was assessed using “Rapid Upper Limb Assessment” (RULA), Mental workload was assessed with the National Aeronautics and Space Administration-Task Load Index (NASA-TLX).A high physical demand, effort, and frustration (p < 0.05) was recorded in the side standing as compared to the in between standing position of the operating surgeon. It was further noted that in the side standing position more effort was needed in the two handed as compared to one-handed manoeuvring (p < 0.05) [36]. However, another study using electromagnetic motion tracking sensor did not find any difference between the French and American position while performing laparoscopic cholecystectomy in modern minimal invasive surgical suite but noted a trend towards increased flexion of thoracolumbar spine in the French position [37].

Use of External Support System: Exosuits to help in external support has been shown to be decrease pain and fatigue without significant interference in dexterity of performance [38].

2. Tool (instrument) design and use: Ergonomic Deficiency in Design and Function of Laparoscopic Tools

With evolution of laparoscopic surgery a renaissance has been witnessed in the design of surgical equipments. Laparoscopic instruments suffer from ergonomically inadequate handle designs and inefficient handle to tip force transmission, which lead to surgeon fatigue, discomfort, and hand paresthesias [39, 40]. In a survey investigating the standard of laparoscopic instruments according to ergonomic design criteria it was observed that the handle of the instrument causing greatest discomfort met only few ergonomic criteria [40]. When compared to open surgery there are a number of drawbacks in laparoscopic instruments. The important issues being

  1. (a)

    Lack of haptic feedback: Laparoscopic surgery has the inherent disadvantage of lack of haptic feedback (tactile as well as force sensation) which necessitates more concentration and greater skill

  2. (b)

    Use of long instruments: the long instruments designed to be manoeuvrable into the depth of the abdominal cavity from exterior have an inefficient force transmission mechanism and form a large external arc thus more force is required which can result in fatigue of wrist and forearm muscle.

  3. (c)

    Limited degree of freedom of movement of laparoscopic instrument [9].

  4. (d)

    Inefficient instrument designs particularly handle designs [40].

(a) Laparoscopic Grasping and Lack of Haptic Feedback: Determinants of laparoscopic pinch force depends on surgeons experience, tissue type and visual feedback [41]. Visual feedback and haptic feedback are the two important sensory feedback mechanisms utilized by surgeons during performance of surgical operations. On comparing visual and tactile feed back in laparoscopic grasping, it was observed that the reaction time to tissue slippage was faster with tactile feedback thereby emphasizing the importance of tactile over visual feedback [42]. Novices generally tend to hold tissues with excessive grasp force and alterations in this regard have been suggested [43]. A relation with angle of the grasper with the tissue has been suggested and increasing grasp force observed with increase of angle [44]. Laparoscopic instruments have diminished haptic feedback which is an important drawback. The diminished haptic feedback and increased pinch force at the tip of the grasper leads to tissue damage in laparoscopic grasping due to use of excessive grasp force applied especially by novices which leads to tissue slippage as compared with barehanded grasping in open (safe grasp) [42]. Regardless of the level of experience, a need for augmented tactile feedback when learning laparoscopic grasp control has been envisaged [45].

(b) Laparoscopic Instruments and Inefficient Force Transmission: In an EMG study it was observed that a six-fold less efficient force transmission from handle to tip was noted with highest workload noted in forearm & thumb muscle during grasping, particularly prevalent in junior surgeons with <2 years experience in the technique [46]. In another study comparing pinch force required to grasp objects with laparoscopic instruments, tweezers used in open surgery and bare hand, it was observed that using a lap grasper, 14.5 times many practice trials were required, whereas with tweezers it was 4.5 times more as compared to bare hand. This difficulty was particularly evident in the grasping of stiff objects and in 84% times the laparoscopic instruments slipped while holding stiff objects [42].

(c) Limited Degree of Freedom in Laparoscopy: Laparoscopic instruments are manoeuvred through fixed ports, the movement is about a fulcrum in the body wall thus the degrees of freedom are limited and more dexterity of hand muscle will be required with resultant muscle fatigue.

(d) Inefficient Instrument Designs Particularly Handle Designs: The other limitations pertain to the design of laparoscopic instruments precisely the handle designs and sizes which can lead to need for excessive grasp force with odd flexion or hyperextension deformities and resultant nerve injuries and paraesthesias.

The Critical Adjustments in Tool Design and Use

The critical adjustments in laparoscopic instrumentation include:

  1. i)

    Design of laparoscopic instruments: precisely innovations in the handle designs, haptic enhancement, hand size considerations

  2. ii)

    Instrument use: port positioning and instrument angulation.

  3. iii)

    Camera ergonomics

i) Design of Laparoscopic Instruments: Precisely Innovations in the Handle Designs, Haptic enhancement, Hand size considerations:

Handles of Laparoscopic Instruments:The common handle designs of instruments can be classified based upon the grip position and angulation or alignment of the shaft of the instrument with grasping unit or handle. Depending upon the type of grip or handle, the instruments can be classified as (1) Ring and Shank handles or finger grip type (2) Palm grip handles often synonymous addressed as pistol grip handles (3) Wire bend handles (4) Rod Handle (Figs. 3, 4, and 5).

Fig. 3
figure 3

Ring Shank Handle at angle with shaft

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Fig. 4
figure 4

Palm grip handle partly Inline with shaft useful where rotatory movements at wrist is needed like suturing

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Fig. 5
figure 5

Rod Handle as seen in hook

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The handles can be held with finger grip or palm grip. The ring and shank handles and the pistol handle are the two common types of handles seen in most laparoscopic instruments. The typical example of a rod handle is the laparoscopic hook. The ring shank handles have the advantages of facilitating one handed manipulation during dissection and cutting, directing, they are often reusable, sterilizable, interchangeable and can be used by both right and left hands. The pistol handles on the other hand are usually disposable and allow the integration of several functions [47]. The instruments can have a locking rachet or maybe of the non-locking type. (Fig. 6).

Fig. 6
figure 6

Instruments with a rachet or locking mechanism

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Additionally, the angle of handle with shaft can be inline or angulated configuration. In contrast with open surgery where most instruments are designed primarily in an in-line configuration, laparoscopic instruments are generally angulated at shaft and handle junction as the direction of insertion into the abdominal cavity and direction of target in abdominal cavity differs.

The ring and shank are usually placed in at an angulation to the shaft whereas the pistol grip handle can be in both co axial or angulated configurations. A point to be noted here is that the use of term pistol grip has been varyingly used to denote a palm grip as well as an angulated handle shaft configuration and similarly ring handle is often used to imply an angulated handle shaft configuration. The ideal laparoscopic instrument should enable the surgeon to keep both wrists in a neutral (unbent) position, permit the surgeon to keep both arms at the sides of their body, avoid pressure points on the hands, allow the surgeon to apply force with a power grip (hammer or gunstyle) hand position and facilitate fine manipulation with a precision grip (pencil or forceps style) hand position [17].

Handle Shaft Configuration Inline Versus Angulated Configurations: The in-line handle configuration has been proposed to be advantageous over the pistol (angulated) configuration when grasping at 90° to the surgeon [39]. In a study on the optimal handle shaft angle for laparoscopic bowel suturing a 40° angle was found to be optimal as opposed to zero and 80° configuration [48]. Contrarily studies have suggested the axial handle to be equal or superior to the ring handle in most laparoscopic tasks [49]. A survey on comfort intuitiveness precision and stability of seven types of instrument handles which included those designed for laparoscopic as well as robotic surgery, three handles—the laparosopic needle holder, da Vinci wrist and joy stick like handle scored the most for all the above criteria [50].

Laparoscopic Grasping: Choosing the Right Type of Handle—Precision Grasping Versus Power Grasping: Data recommending the use of one handle over the other type is lacking nevertheless some recommendations have been made. While choosing an instrument the important factors to be considered are: (1) the type of surgical procedure (2) the time duration.

Human grasping activities has been classified broadly into two types (1) precision grip (2) power grip [51]. In precision grip the position of thumb is abducted while in power grip the position of the thumb is adducted. In power grip the force is generated between the thumb along with thenar eminence against the rest of the fingers (Fig. 7) whereas in precision grip it is between thumb and fingers.

Fig. 7
figure 7

Power grip with smooth handles for heavy instruments like stapling, note here grip is between thenar eminence and rest of the fingers

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The precision grip is interchangeably referred to as pinch grip or finger grip in studies, on the other hand the power grip is often mentioned as pistol grip or palm grip.

Precision Grasping for Fine Dissection (Fig.  8 ): The precision grip handles and finger grip and are advantageous when work with precision like fine grasping or dissecting is intended [29, 52].

Fig. 8
figure 8

Precision grip/finger grip/pinch grip where meticulous work is needed like dissection, note here force is exerted between thumb and other fingers

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Grasping Tissues for Prolonged Period: While grasping tissue for prolonged time periods an instrument with a palm grip and locking mechanism is to be preferred Instrument that incorporates a locking or ratchet mechanism will maintain the force. “Palming” an instrument (removing the thumb from the ring and placing the palm against the handle) can reduce the amount of wrist flexion and increase the surgeon’s power (Fig. 9) [17].

Fig. 9
figure 9

Palming a ringed instrument when prolonged grasping is required note here the thumb is released from the ring and the ringed instrument is held with the palm

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In a study evaluating pistol grip with pinch grip survey feedback indicated that a significantly greater number of participants felt that using the pistol grip they experienced a greater degree of freedom and lesser discomfort nevertheless the authors refrained from making any substantial conclusions based upon the study [53].

Heavy Grasping as in Stapling/Power Grip: In a study using muscle EMG analysis comparing palm and finger grips it was observed that palm grip is more powerful than the finger grip when grasping with laparoscopic instruments, particularly at angles perpendicular to the surgeon’s sagittal plane [54]. Thus power grip handles with large smooth surface and pistol type handle shaft alignment should be preferred while using heavy instruments like staplers [17]. Further the necessity for an optimal diameter of the instrument handle dependent on hand size is emphasized for best result a detrimental effect is observed in both extremes viz: small hand size as well as long fingers [55, 56].

Innovations in Laparoscopic Graspers: The proposed ergonomic considerations for laparoscopic instrument handles are: Thumb use for rotation of the knob, increasing the contact area, littleforce for opening/closing of the instrument, easy clamping with one hand use, moulded rubber grips [47]. Recent innovations include, adjustable handle shaft angles, rotatory handles, self-righting instruments and provision of power grasping in procedures that require heavy sustained grasp like stapling.

Use of a Rotational Handle Piece: The earliest report of the ergonomic benefits of a rotational handle was reported way back in 1993 when a more relaxed hand position and smooth manipulations were observed [57]. In explorative and experimental studies using a rotational handle piece for precision movements it was observed that rotational hand piece had a better ergonomic position for the wrist and was best suited for low table heights [29, 58]. A number of ergonomic handles have been studied to improve efficiency reduce rotational stress and pressure points in the hands and wrist.

Other innovations: Lately the incorporation of a hand held robotic device is being studied for ergonomic benefits and a relative advantage over conventional laparoscopic instruments has been noted especially in performing complex task like suturing by the novice surgeons [59]. The use of rounded jaws of laparoscopic grasper has been proposed to diminish grasp force [60]. An added haptic feedback method incorporated in graspers has been related to be useful especially in feeling for tissue consistencies pressure of grasping and arterial pulsation in a study [4]. Innovations incorporating use of tactile sensing function display in grasping instruments has been suggested [61, 62].

Laparoscopic Suturing Choosing the Right Type of Instrument: Laparoscopic suturing has a number of ergonomic disadvantages as compared to open suturing due to two dimensional vision, working through long instruments in limited space, lack of touch and need for good coordination between right and left hands. Moreover the formation of loops for knotting and preventing its escape from the instrument is challenging [63]. Laparoscopic suturing is generally best performed with an instrument having the following characteristics: Coaxial in-line alignment which facilitates rotation of the instrument with simple wrist motions. Precision grasp and locking mechanism to hold the needle, thus obviating the need for the constant application of force by the surgeon [17]. The ideal ergonomic characteristics of needle holders suggested is: Grip opening 65–90 mm, Ring Dimension: length 30 mm, width 24 mm, Angle between grip and tube 14° to 24°, Presence of spring, Opening and closure by flexors and extensors of the fingers The two innovative ergonomic handles and needle holders described are the Cuschieri Ball Handle and the Cuschieri Pencil Handle [47]. In a crossover trial using laparoscopic simulator studying laparoscopic suturing, the authors found that the pistol grip handle led to more tissue damage and non goal directed actions as compared with in line needle holder [64]. The pistol type alignment causes lesser ulnar deviation as compared to co axial alignment however the former alignment may be disadvantageous in many surgical attributes precisely in laparoscopic suturing where an unrestricted rotation at the wrist is desirable but restricted with the sharply angulated pistol type alignment due to limitations caused by hyperextension at the wrist [17]. However other authors have found pistol grip needle drivers to be beneficial [52]. The other point of consideration for an efficient laparoscopic suturing is needle insertion angle best within a range of 80° to 100° and grip placed at proximal and middle third shaft of needle [65].

Hand Size: Most laparoscopic instruments are designed for a hand size of 6.5 or more therefore surgeons with smaller hand sizes are at an inherent ergonomical disadvantage in use of laparoscopic ring instruments as also in the use of staplers. Contrarily in larger hand sizes also there is difficulty in handling smaller instruments where power grip is desirable [55, 56, 66]. Designing equipment with provision for varying hand sizes is thus desirable. In another anonymous survey a similar observation was noted. In the survey women reported the following devices more awkward than their male counterparts: laparoscopic stapler, laparoscopic Harmonic scalpel, and the laparoscopic LigaSure [67].

Need for Standardization: In order to standardize designing of laparoscopic instruments some authors have proposed a framework for research on laparoscopic instrument handles [68].

ii) Instrument Use Port Positioning and Instrument Angulation:

The important ergonomic considerations in port positioning and instrument use are principles incorporating: triangulation, avoiding reverse alignment, avoiding crossing of equipment and limiting scissoring effect.

The Ratio Between Internal and External Length of the Instrument and Haptic Perception: The ideal length of the instrument that has to be inserted into the abdominal cavity has an important bearing on haptic perception. In a study evaluating the impact of differential length ratios (intraabdominal/external length) of laparoscopic instrument on haptic functions, it was observed that a non symmetrical bias in tissue stiffness was observed in tangential probing as opposed to radial probing especially in novices due to the fulcrum effect but the same was not observed in experts handling [69]. The best ergonomics are thus achieved when ratio of intrabdominal length equals external length and is 1 [70].

Insertion Angles: Insertion angles of laparoscopic instruments have important bearing on the ergonomics. The important angles which need attention are: (a) Manipulation angle (b) Elevation angle (c) Optical Axis target view angle (d) Azimuth angle.

Manipulation angle: angle between two working instruments (Fig. 10).

Azimuth angle: angle between one side instrument & telescope considered as a horizontal projection (Fig. 11).

Elevation angle: angle between the instrument and patients body (Fig. 12).

There is a direct correlation between manipulation & elevation angles. If manipulation angle is of 60°, optimal elevation angle which yields the shortest execution time and optimal quality performance is 60°. Wide manipulation angles leads to higher elevation angles for optimal performance and task efficiency. Manipulation angle should range between 45° and 75°. The ideal angle should be 60°. Manipulation angles <45° or >75°—increased difficulty and degraded performance.

Fig. 10
figure 10

Manipulation angle: angle between two working instruments, ideal 45–75 degree

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Fig. 11
figure 11

Azimuth angle

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Equal azimuth angles improve task efficiency. The secondary or operating ports for assisting instruments should be placed after the insertion of the telescope.

Shaft sign: When the Azimuth angle is small the axis of the scope is circumjacent to the axis of the instrument and can lead to obstructed visualization due to the intervening shaft of the instrument known as the shaft sign.

Fig. 12
figure 12

Elevation angle: angle between the instrument and patients body

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Optical Axis Target View Angle and Optical Axis and Instrument Axis Alignment: The optical axis target view angle is the angle formed between the scope axis and target operation area for example the inferior liver surface in cholecystectomy. It varies with the degree of the scope viz 0 degree scope/30 degree scope and angulation of insertion. The 90° optical axis target view angle is said to have the best accuracy i.e. optical axis is at 90° to surface of the target to be viewed [71].

The various types of optical axis alignment with instrument manipulation are broadly:

  1. (1)

    In-optical axis manipulation (one instrument on either side of the laparoscope) (Fig. 13).

  2. (2)

    Off-optical axis manipulation-dominant type i.e. both instruments on one side of the laparoscope to the dominant hand of the surgeon,

  3. (3)

    Off-optical axis manipulation—non dominant type i.e. both instruments on one side of the laparoscope on the nondominant side) (Fig. 14).

    Fig. 13
    figure 13

    Concepts demonstrated are: triangulation of instruments/in optical axis alignment (camera between two working ports)

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    Fig. 14
    figure 14

    Off optical axis parallel instrumentation (instruments on one side of telescope) helpful in certain surgeries example hernia repair

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The ideal position is an in optical alignment or coaxial alignment between of the visual axis and instrument axis. Off-optical axis non dominant placement is a reasonably good alternative in certain surgeries like hernia repair. As the optical axis and instrument axis increases from 0° to 180° there is marked degradation in performance. Reverse alignment should be avoided as far as possible for the operating surgeon: this occurs due to camera direction in opposition to working ports—leads to task performance degradation [72]. In summary extreme horizontal or vertical displacement of instrument insertion should be avoided [6].

Use of articulating instruments: Laparoscopic instruments with articulating endpieces compromises of a new generation of instruments which improve the degree of freedom due to their flexibility but the complexity of the instrument may cause difficulty in handling especially in novices [73].

iii) Camera Ergonomics

The laparoscopic vision is essentially a 2D vision so depth perception and spatial orientation is altered. Often hand-eye coordination is disrupted by the incongruent mapping between the orientation of the endoscopic view and the actual operative field thereby resulting in higher mental and physical load. Any alteration in camera axis i.e.rotational distortion can significantly decrease performance. Performance is best when the endoscopic image is perfectly aligned with the actual task space (0° image rotation), but degraded progressively as a function of deviation from perfect alignment [74].The distance of the camera from the target also affects performance, the greater the distance worse the performance. The recent innovations that are being investigated to overcome these draw backs are: multiple 2D cameras, shadow introduction, use of a 3D camera, automatic image realignment system, left to right mirror image correction, inverted mirror image projection head mounted cameras and autostereoscopic monitors [75,76,77,78]. The 3D stereoscopic vision has been noted to produce less visual fatigue and cognitive workload in training curriculum of novices [79]. However though some benefit is seen in novices but no difference was noted in experts using 3D vs 2D vision [59]. The 2D laparoscopic image is noted to produce more eye strains however refocussing problems is also an observed drawback of the 3D vision in laparoscopy [80]. The direction of view of the endoscope describes the angle between the centre of the visual field (optical axis) and the physical axis of the endoscope. Optical axis to target view angle is the angle between the optical axis of the endoscope and the plane of the target. The best task performance during endoscopic work is obtained with an optical axis to target view angle of 90° [81].

3. Work Environment Modification

Environment chaos and auditory chaos and distractions affects surgical motor performance and learning and increase surgeons psychological burden in simulated laparoscopic tasks [82]. Decreasing mental distractions by work environment modification can improve mental performance. Classical music has been shown to consolidate memory [83].A systematic review of music on simulated surgery performance has failed to demonstrate significant benefit, however in laparoscopic surgery it has been suggested to improve performance related to efficient transferring of instrument and decreased mental workload [84, 85].

4. Training of Staff

Trunk Muscle Training, Posture Fatigue, and Performance in Laparoscopic Surgery

In comparison of thirty-one participants in training group, (6-week, 18-session trunk i.e. abdominal and back muscle endurance training program) versus control group (no increased endurance training session), the training group had decreased errors in performing laparoscopic surgery [86].

Importance of training OT personnel (nursing staff and surgeon): Some studies have suggested that the use of video game training can improve skill performance of laparoscopic tasks, however a systematic review has failed to find any significant difference [87].

Ergonomics: Laparoscopy Versus NOTES/SILS/Robotics

Higher ergonomic risks and muscular exertion was noted in a NOTES as compared with conventional laparoscopy [88, 89]. SILS also requires greater skills and has more ergonomic constraints. The difference in ergonomics between conventional laparoscopic surgery, NOTES, robotic and SILS is beyond the scope of discussion in the current topic.

Conclusion

Laparoscopic surgery inadvertently leads to certain ergonomic constraints related to body posture, prolonged time duration, limited vision, lack of haptic feedback and inconvenience caused by long instruments with limited freedom of movement and ineffective force transmission. If ergonomic problems are not corrected laparoscopic surgery can lead to fatigue, muscle strains, paresthesias, visual strains and fatigue in the surgeon and assistants and thus hamper performance. Certain critical adjustments in work place layout related to OT table height, monitor position, correct placement of foot pedals and efficient design and choice of instruments and equipments as also insertion angles can significantly decrease the physical and mental strain of the operating team. With increasing experience, proper training and right choice of equipments one can circumvent the ergonomic constraints of laparoscopic surgery.

Key Clinical Points

  1. 1.

    Improper ergonomics in the operation theatre can lead to unintentional injuries, increased operative time, errors and increased morbidity

  2. 2.

    The important arenas in laparoscopic surgery which differs from open surgery and needs consideration are: (1) Laparoscopic vision (2) Altered body postures (3) Longer operative times (4) Workplace layout (5) Design and function of laparoscopic surgical equipments (6) Mental workload due to requirement of enhanced skills.

  3. 3.

    A number of critical adjustments in work place layout need to be undertaken for improving the ergonomics of laparoscopic surgery (1) Operating table level (2) Monitor level (3) Foot Pedals (4) Positioning of operating surgeon and assistant.

  4. 4.

    It has been said that the ideal operating table level should be such that: (1) the angle between lower & upper arm should be between 90° and 120°. (2) after the insertion of instruments they should be roughly at, or slightly below the level of the surgeon’s elbows.

  5. 5.

    Ideally the monitor should be placed straight in front of each person, aligned with motor axis of forearm instruments in the horizontal plane and in the sagittal plane at 15–40 degree below eye level.

  6. 6.

    The other advanced adjustments that can be implemented for ergonomic improvement are: dual display, mirror image correction for assistants in case of reverse alignment, head mounted camera, flat display screens and video display on flexible booms.

  7. 7.

    Foot pedals should be placed close to the foot, aligned in the same direction as the instruments i.e. towards the target quadrant of surgery as also the principal laparoscopic monitor.

  8. 8.

    Laparoscopic instruments suffer from ergonomically inadequate handle designs and inefficient handle to tip force transmission, which lead to surgeon fatigue, discomfort, and hand paresthesias.

  9. 9.

    When compared to open surgery there are a number of drawbacks in laparoscopic instruments. The important issues being (1) Lack of haptic feedback (2) Use of long instruments which result in an inefficient force transmission mechanism and form a large external arc thus more force is required which can result in fatigue of wrist and forearm muscles (3) Limited degree of freedom of movement of laparoscopic instrument and fulcrum effect (4) Inefficient instrument designs particularly handle designs.

  10. 10.

    The critical adjustments in laparoscopic instrumentation include: (1) design of laparoscopic instruments precisely innovations in the handle designs, haptic enhancement, hand size considerations (2) instrument use: port positioning and instrument angulation. (3) camera ergonomics.

  11. 11.

    Insertion angles of laparoscopic instruments have important bearing on the ergonomics. The important angles which need attention are: (1) Manipulation angle (2) Elevation angle (3) Optical Axis target view angle (4) Azimuth angle.

  12. 12.

    The various types of optical axis alignment with instrument manipulation are broadly: (1) In-optical axis manipulation (one instrument on either side of the laparoscope) (2) Off-optical axis manipulation-dominant type i.e. both instruments on one side of the laparoscope to the dominant hand of the surgeon, (3) Off-optical axis manipulation—non dominant type i.e. both instruments on one side of the laparoscope on the nondominant side.