and a more rapid recovery than with open surgery [8]. Whereas the patient benefits ... and an on-site ergonomics station to measure EMG data from surgeons at the .... SAGES Learning Center. The laptop computer contained the LabVIEW®.
Surg Endosc (1999) 13: 466–468
© Springer-Verlag New York Inc. 1999
Ergonomic problems associated with laparoscopic surgery R. Berguer,1 D. L. Forkey,2 W. D. Smith2 1 2
University of California Davis, School of Medicine, and VA Northern California Health Care System, 150 Muir Road (112), Martinez, CA 94553, USA Biomedical Engineering Program, California State University, Sacramento, 6000 J Street, Sacramento, CA 95819-6019, USA
Received: 17 March 1998/Accepted: 9 December 1998
Abstract Background: The Society of American Gastrointestinal Endoscopic Surgeons (SAGES) Task Force on Ergonomics conducted a subjective and objective assessment of ergonomic problems associated with laparoscopic instrument use. The goal was to assess the prevalence, causes, and consequences of operational difficulties associated with the use of laparoscopic instruments. Methods: A questionnaire was distributed asking respondents to rate the frequency with which they experienced pain, stiffness, or numbness in several body areas after laparoscopic operations. An ergonomics station was assembled to quantify forearm and thumb muscle workload. Processed electromyogram (EMG) signals were acquired from 27 volunteer surgeon subjects while they completed simulated surgical tasks using a hemostat and an Ethicon® laparoscopic grasper, with the aid of an endoscopic trainer and video monitoring system. Results: Of 149 surgeons responding to the questionnaire, 8% to 12% reported frequent pain in the neck and upper extremities associated with laparoscopic surgery. The ergonomics station demonstrated that the peak and total muscle effort of forearm and thumb muscles were significantly greater (p < 0.01) when the grasping task was performed using the laparoscopic instrument rather than the hemostat. Conclusion: These findings indicate that laparoscopic surgical technique is more taxing on the surgeon. Key words: Electromyography — Ergonomics — Laparoscopy
Patients experience less trauma during laparoscopic surgery and a more rapid recovery than with open surgery [8]. Whereas the patient benefits from laparoscopic techniques, the surgeon encounters difficulties that were not present during open surgical procedures. These difficulties include two-dimensional viewing of the three-dimensional surgical Correspondence to: R. Berguer
field and awkward instruments with force transmission properties inferior to their open surgical equivalents [10]. As a result, surgical tasks that take seconds during open surgery can take minutes during laparoscopic surgery. Surgeons report increased upper extremity fatigue [3] and occasional hand numbness [5–7, 9], after laparoscopic procedures. Laboratory studies employing a limited number of participants have demonstrated that surgeons’ forearm electromyogram (EMG) increases significantly when the laparoscopic grasper is used rather than a standard hemostat [2, 3]. The current study aimed to obtain both subjective and objective assessments of the physical workload of laparoscopic surgery in a larger sample of surgeons. We employed a questionnaire to collect body part discomfort information and an on-site ergonomics station to measure EMG data from surgeons at the Society of American Gastrointestinal Endoscopic Surgeons (SAGES) 1997 Annual Scientific Session in San Diego, California, USA. Methods The SAGES Task Force on Ergonomics developed and distributed a detailed questionnaire asking surgeons to report the frequency and degree of physical discomfort they recalled experiencing in various body parts associated with performing laparoscopic operations (Table 1). The questionnaire was given to approximately 800 conference attendees on registration, and the completed forms were collected at various sites at the Convention Center. A portable ergonomic measurement station (Fig. 1) was developed in conjunction with the Biomedical Engineering Program (BME) at California State University Sacramento (CSUS) to measure the physical workload of the thumb and forearm muscles by surface EMG during a simulated laparoscopic and open surgical task. Testing was performed at the conference learning center where surgeons learning other laparoscopic skills could participate if they wished. The ergonomic measurement station consisted of analog circuitry and a LabVIEW® program that ran on a Macintosh PowerBook 5300c with a National Instruments DAQCard-700. The EMG was processed electronically to digital conversion before the analog, thereby allowing a low sampling frequency of 9 samples/s. Each of the three channels of analog processing consisted of an instrumentation amplifier, an isolation amplifier, a band-pass filter (with a band pass between 20 and 180 Hz), a full-wave rectifier, and a smoothing filter (with a cutoff at 2 Hz). The overall gain per channel was 50,000. With the approval of the California State University Sacramento Committee for the Protection of Human Subjects, EMG data from 27 subjects
467 Table 1. SAGES 1997 questionnaire body part discomfort questions: have you experienced any of the following problems during or following laparoscopic surgery? Area/subject
Never
Occasionally
Frequently
Neck pain Neck stiffness Shoulder/arm pain Shoulder/arm stiffness Hand/wrist pain Hand/wrist stiffness Hand/wrist numbness Back pain Back stiffness Leg pain Leg stiffness
were collected. All but three subjects were practicing laparoscopic surgeons. A differential pair of Multi-Biosensors self-adhesive, pregelled, Ag/AgCl electrodes was placed on the participant’s skin over the thumb, common digital extensor, and superficial digital flexor muscles on the subject’s dominant hand and arm according to the established guidelines [4]. These muscles were selected because of their involvement in grasping motions common to laparoscopic and open surgery [2]. An additional electrode, used for a reference, was placed over the biceps muscle of the same arm. In preparation for electrode placement, the participant was asked to perform movements to identify the three muscles, and the skin above these muscles was wiped with an alcohol preparation pad. The participant’s maximum voluntary contraction (MVC) for each muscle was obtained before data collection by having the participant perform the same movements used to locate the muscles during electrode placement while opposing the maximal force by a passive resistance with the nondominant hand. The peak muscle activity for three iterations was averaged to obtain the MVC for each muscle. Once the MVC was obtained, the muscle activity (processed EMG) data was recorded while each subject opened and closed a modified springloaded alligator clip five times, using first a standard Crile hemostat and then a disposable curved laparoscopic grasper (Ethicon Endosurgery, Cincinnati, OH, USA). The laparoscopic maneuver involved the use of the laparoscopic grasper, a video monitoring system (Olympus Endoscopy, Japan), and an endoscopic trainer (Karl Storz, Germany) while the hemostat maneuver was performed openly in front of the subject. During each maneuver, the muscle activity was displayed graphically as a percentage of MVC versus time and saved to a disk (Fig. 2). After data collection, the peak processed EMG and integrated effort (the area under the processed EMG versus time graph) were calculated as indices of the physical workload placed on the surgeon. Paired two-tailed Student’s t tests were performed on the dependent variables to assess the effect of the type of instrument.
Results In all, 149 completed questionnaires were collected. The results are tabulated in Table 2. Most respondents reported performing laparoscopic gallbladder, hernia, and antireflux surgery, whereas half performed small bowel, colon, gastric, and splenic surgery, and one fourth performed adrenalectomy. Frequent pain or numbness in the neck, shoulder, arm, or wrist was reported by 8% to 12% of respondents, whereas stiffness in these areas was noted 9% to 18% of the time. The results of the other questions not directly related to laparoscopic instruments are not addressed in this article. The peak processed EMG, averaged for 27 subjects during use of the laparoscopic grasper, was higher than for the hemostat by a factor of 1.7, 2.1, and 4.0, respectively, for the thumb, extensor, and flexor muscles (Fig. 3a). The average integrated effort for the laparoscopic grasper in-
Fig. 1. Photograph of the ergonomic measurement station at the 1997 SAGES Learning Center. The laptop computer contained the LabVIEW® software program and displayed the EMG waveforms from the surgeon participants in real-time on the adjacent monitor.
creased by a factor of 2.4, 2.3, and 4.9 over that for the hemostat for the thumb, extensor, and flexor muscles, respectively (Fig. 3b). Statistical analysis of the EMG data demonstrated that the values obtained during the use of the laparoscopic grasper were significantly higher than the corresponding values for the use of the hemostat for all three muscles (p < 0.001). Discussion Every laparoscopic surgeon knows the relative awkwardness of video-endoscopic techniques and instruments in comparison to those used in open surgery. Recent case reports and laboratory studies have begun to highlight some of the ergonomic problems associated with laparoscopic surgery. The current report combines both subjective and objective assessments of the physical impact from use of laparoscopic instruments in a large sample of surgeons. Laparoscopic surgery has introduced many changes in the surgeon’s environment, but the most dramatic perhaps are the new configuration and methods of use of laparoscopic instruments. Tendick [11] first thoroughly discussed manipulation problems in laparoscopic surgery, highlighting the negative effects on the surgeon’s dexterity of the limited degrees of freedom during the use of laparoscopic instruments. Patkin [10] further reviewed human interface problems in endoscopic surgery, identifying the need for a human engineering (ergonomic) approach to the design of the laparoscopic operating environment. Several recent case reports have drawn attention to the potential for neurapraxia in the digital nerves of the thumb and fingers caused by pressure from the ringed grips of the laparoscopic instrument [5–7, 9]. We have reported that surgeons at the University of California Davis experienced significantly greater discomfort in their dominant arm after laparoscopic operations than after open operations [3]. The results of the current study support these previous findings by demonstrating a surprising 8% to 12% incidence of frequent pain or numbness in the neck or upper extremities after laparoscopic operations. This finding is particularly significant because the 149 respondents were experi-
468
Fig. 2. A typical graph of thumb-processed EMG (percentage of maximum voluntary contraction vs. time) showing a spring-loaded clip closed five times with both laparoscopic grasper and hemostat.
Table 2. Results of SAGES ergonomics questionnaire
Neck pain Neck stiffness Shoulder/arm pain Shoulder/arm stiffness Hand and wrist pain Hand and wrist stiffness Hand and wrist numbness
Never (%)
Occasionally (%)
Frequent (%)
41 33 39 40 45 43 59
43 44 43 39 36 40 26
9 18 12 11 11 9 8
upper extremity discomfort when using laparoscopic instruments? In a relatively large sample of surgeons, the results clearly demonstrate that the use of a laparoscopic instrument increases the muscular work of the forearm and thumb muscles by a multiple ranging from 2 to 5 compared with the use of a hemostat. Recent studies suggest two reasons for this finding: (a) Laparoscopic instruments are less efficient mechanically than open instruments (Gerber et al. master’s thesis CSUS 1998, unpublished data), and (b) the configuration of the handle in laparoscopic instruments results in poor ergonomic coupling of the surgeon’s hand to the instrument. Excessive flexion, ulnar deviation, and supination of the wrist causes a decreased transmission of muscular force across the wrist to the instrument handle [1–3, 11]. In conclusion, the current study strongly supports the hypothesis that there are significant ergonomic problems associated with the use of laparoscopic instruments that result in frequent physical discomfort for a substantial number of practicing surgeons. Further improvements in the mechanical and ergonomic components of laparoscopic instruments are needed to increase surgeons’ efficiency while decreasing their chance of work-related physical injuries.
References
Fig. 3. A Peak-processed EMG and B integrated EMG effort averaged for 27 surgeons grasping a spring-loaded clip with both a laparoscopic grasper and a standard hemostat. All differences between laparoscopic and open technique are statistically significant at p < 0.001.
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