Surg Endosc DOI 10.1007/s00464-014-4024-6
and Other Interventional Techniques
Ergon-trial: ergonomic evaluation of single-port access versus three-port access video-assisted thoracic surgery Luca Bertolaccini • Andrea Viti • Alberto Terzi
Received: 12 July 2014 / Accepted: 2 December 2014 Ó Springer Science+Business Media New York 2014
Abstract Background Single-port access video-assisted thoracic surgery (VATS), a technique progressively developed from the standard three-port approach in minimally invasive surgery, offers ergonomic advantages but also new challenges for the surgeon. We compared the ergonomics of three-port versus single-port VATS. Methods Posture analysis of surgeons was evaluated during 100 consecutive VATS wedge resections (50 triportal vs. 50 uniportal). Technically demanding procedures (major lung resection) were excluded. Operating table height, monitor height, distance and inclination were adjusted according to operator preference. Body posture was assessed by measuring head–trunk axial rotation and head flexion. Perceived physical strain was self-evaluated on the Borg Category Ratio (CR-10) scale. Mental workload was assessed with the National Aeronautics Space Administration– Task Load indeX (NASA–TLX), a multidimensional tool that rates workloads on six scales (mental, physical and temporal demand; effort; performance; frustration). Results All procedures were completed without complications. Head–trunk axial rotation was significantly reduced and neck flexion significantly improved in uniportal VATS. Viewing direction significantly declined (p = 0.01), body posture as measured on the Borg CR–10 scale was perceived as more stressful and the NASA–TLX score for overall
L. Bertolaccini (&) A. Terzi Thoracic Surgery Unit, Sacro Cuore Research Hospital, Via Don Angelo Sempreboni 5, 37024 Negrar, Verona, Italy e-mail: [email protected] A. Viti Thoracic Surgery Unit, S. Croce e Carle Hospital, Cuneo, Italy
workload was higher (p = 0.04) during triportal VATS. The NASA–TLX score for frustration was higher with uniportal VATS (p = 0.02), but the score for physical demand was higher in triportal VATS (p = 0.006). Conclusions The surgeon can maintain a more neutral body posture during uniportal VATS by standing straight and facing the monitor with only minimal neck extension/ rotation; however, frustration is greater than with triportal VATS. Keywords Ergonomics Physical workload Mental workload Video-assisted thoracic surgery
With advances in instruments, techniques and imaging, video-assisted thoracic surgery (VATS) has become the surgical approach of choice for a still growing number of procedures and plays a relevant part in minimally invasive thoracic surgery. There are several advantages for patients in undergoing VATS, including less postoperative pain, shorter hospital stay and quicker return to normal everyday activity [1]. Single-port access VATS, a technique progressively developed from the standard three-port approach, was initially described only for minor thoracic procedures [2] and then later applied in various other procedures including lobectomies [3]. VATS not only offers numerous benefits over conventional open surgery but also poses ergonomic challenges for surgeons [4]. The importance of ergonomics in VATS has been generally recognized and previous studies have shown that ergonomics and environmental factors can influence surgical performance in laparoscopy; for instance, correct ergonomic posture can reduce operating time [5]. Nevertheless, as VATS gains wider acceptance, ways to improve the ergonomics of the procedure will need to be found. To our
123
Surg Endosc
knowledge, few studies have addressed ergonomic concerns in VATS [4, 6, 7]. The aim of the Ergon-Trial was to compare the ergonomics of VATS wedge resection with the standard triportal and the uniportal access techniques performed by surgeons in a clinical setting. The two workloads commonly measured to assess the ergonomics associated with a specific surgical task are the physical and the cognitive. The physical workload measures the amount of physical demand on the body, while the mental workload assesses the amount of mental effort required to complete a surgical procedure. The overall workload level is derived from analysis of the physical and cognitive workloads.
Methods Three right-handed surgeons skilled in VATS approaches participated in the study. None reported physical complaints such as carpal tunnel syndrome or serious neck or back problems. Ergonomic analysis of the operating surgeon during 100 consecutive VATS wedge resections (50 triportal vs. 50 uniportal VATS) was performed. The operating surgeon selected the surgical approach based on the individual patient’s characteristics. Surgery for massive pleural adhesions and technically demanding procedures, such as major VATS lung resections, was excluded from the analysis. Each surgeon carried out at least 15 procedures with each approach, assisted by the same experienced assistants. The instruments were identical for each type of procedure. The operating table height and tilt and the monitor height were adjusted for each surgeon. Based on previous experience, the monitor was ideally placed in front of the surgeon to permit a moderate downward viewing angle of about 10°–30° without axial trunk rotation [8]. For the scrub nurse, the monitor was ideally placed just below eye level to allow a downward viewing direction of 0° to about 15°. Upward viewing angles, which may cause harmful neck extension, were avoided. For all participants, minimal neck torsion was aspired. An axial rotation less than *15° was considered ergonomically acceptable. During all interventions, the patient was positioned in lateral decubitus contralateral to the lesion, with the hip tilted backward approximately 5° and the shoulders backward approximately 10°; both arms were placed forward 90°, and the upside arm was bent at the elbow at 90° on the table for better lateral stability. Depending on which surgical technique is performed, two quite similar positions of the surgeon can be distinguished: in three-port access VATS (Fig. 1A), the surgeon stands in front of the patient at the level of the chest, the camera assistant stands on the same side and the scrub nurse stands in front of the patient at the level of the
123
patient’s leg. Two monitors are located at the level of the patient’s head, one in the surgeon’s line of vision and the other in the line of vision of the scrub nurse. The trocars are placed apart from the endoscope on both sides of the chest. To handle the instruments, the surgeon must rotate his upper body and lean over the patient. In the uniportal VATS set up (Fig. 1B), the surgeon and the assistant must be positioned in front of the patient in order to have the same thoracoscopic vision throughout the procedure and allow for more coordinated movements. The scrub nurse stands on the opposite side. The incision, about 4–5 cm long, is placed preferably in the fifth intercostal space in the anterior position just inferior to the breast and pectoralis major muscle [3]. Body posture was assessed with a video analysis system consisting of a digital camera positioned above the surgeon for observing the axial rotation of the head as compared with the trunk and of the head flexion in the sagittal plane. Measurements on the images were digitally performed with a line angle measuring tool in Adobe Photoshop CC for Linux (Adobe Systems Incorporated, San Jose, CA, USA). The workloads were evaluated by subjective and objective measures, in which the surgeon’s physical and mental exertion during the procedures was self-assessed during and after the operation and recorded. The eye height and the viewing distance (eye-to-monitor) and the monitor height in relation to the floor were measured to calculate the viewing direction (Fig. 2) according to the ergonomic equation [9]: eye height screen height viewing direction = sin : viewing distance The viewing direction is an ergonomic evaluation of the combined effort of neck flexion/extension and the angle of gaze performed by the extra ocular musculature [10]. For the measurements in the sagittal plane, we used the anatomic ear–eye line, running through the tragus of the ear and the canthus of the eye. In the neutral position of the head and neck, the ear–eye line has an inclined angle of *15° to the horizontal [11]. When the head is in *10° flexion, the anatomic ear–eye line is *5° above the horizontal [11]. Physical discomfort perceived during surgery was measured by means of the Borg Category Ratio (CR-10) scale, a widely accepted tool for evaluating physical workload [12]. The general perception of physical exertion comes from the integration of different symptoms arising from active muscles, joints, possible pain, and dizziness. The Borg CR-10 scale is a category scale with ratio properties consisting of numbers related to verbal expressions, which allows rate comparison between intensities as well as the determination of intensity levels. The scale is relatively simple to use; it is based on the surgeon’s
Surg Endosc Fig. 1 Operative setup in the Video-Assisted Thoracic Surgery (VATS) suite. A Operative setup in the triportal VATS technique. B Operative setup in the uniportal VATS approach. AC anaesthesia console, TC thoracoscopic console, FS flat screen, S surgeon, AS assisting surgeon, SN scrub nurse, IT instrument table
operator to achieve a particular level of performance. Because the definition of cognitive workload is human centred rather than task centred, the cognitive workload is defined uniquely by the demands of an objective task: as such, it reflects multiple attributes that may have different relevance for different individuals. The NASA–TLX rating scale is a multidimensional assessment tool that allows participants to rate their cognitive workloads on six scales (Table 1): mental demand, physical demand, temporal demand, effort, performance and frustration during task execution [14, 15]. Statistical analysis
Fig. 2 Parameters measured to calculate the ergonomic equation of viewing direction (an ergonomic evaluation of the combined effort of neck flexion/extension and angle of gaze performed by the extraocular musculature)
subjective estimation of physical strain experienced during tasks (score from 1 to 10, where 1 indicates no strain and 10 indicates extremely uncomfortable and painful strain). Seven areas of the surgeon’s body were evaluated: legs, back, neck, right and left shoulder, and right and left forearm. Perceived strain was scored every 10 min during each operation to record changes over time. On completing the operation, the surgeon evaluated the cognitive workload according to the National Aeronautics Space Administration–Task Load Index (NASA–TLX), a widely recognized tool for self-reporting workload perception [13]. The cognitive workload is a hypothetical construct that represents the cost incurred by a human
A power analysis was performed to calculate the sample size for unpaired analysis; a sample size of at least 63 procedures was needed, with a type 1 error rate set at 0.05 and power at 0.80. Continuous variables are presented as mean ± standard deviation. The two operational setups were compared using Student’s t test or Wilcoxon’s twosample test (discrete or continuous data) and Pearson’s v2 test or Fisher’s exact test when appropriate (dichotomous or categorical data). The NASA-TLX consists of two parts: ratings and weights.1 Ratings for each of the six subscales are obtained from the subjects following the completion of a task. A numerical rating ranging from 0 to 100 (from least to most taxing) is assigned to each scale. Weights are determined by the subjects’ choices of the subscale most relevant to 1
NASA–TLX software is available for free download at tlx.playgraph.com. Additional information can be found at humansystems.arc.nasa.gov/groups/TLX.
123
Surg Endosc Table 1 Subscales and items on the NASA-TLX rating scale
Table 2 Surgical indications for the 100 VATS wedge resections
Scale
Description
Mental demand
How much mental and perceptual activity was required (e.g. thinking, deciding, calculating, remembering, searching, etc.)?
Primary spontaneous pneumothorax
Was the surgical operation easy or demanding, simple or complex? How much physical activity was required (e.g. pushing, pulling, turning, controlling, activating, etc.)?
Physical demand
Was the surgical operation easy or demanding, slack or strenuous, restful or laborious? Temporal demand
How much time pressure did you feel due to the rate or pace at which the surgical operation elements occurred? Was the pace slow and leisurely or rapid and frantic?
Performance
How successful do you think you were in accomplishing the goals of the surgical operation? How satisfied were you with your performance in accomplishing these goals?
Effort
How hard did you have to work (mentally and physically) to accomplish your level of performance?
Frustration level
How insecure, discouraged, stressed, or secure, gratified, content did you feel during the surgical operation?
workload for them from a pair of choices. The weights are calculated from the tally of these choices from 15 combinatorial pairs created from the six subscales. The weights range from 0 to 5 (from least to most relevant). The ratings and weights are then combined to calculate a weighted average for an overall workload score. The significance level was set at 0.05 for all parameters. All statistical analyses were performed using R Software version 3.0.3.2
Results The data on 100 consecutive VATS wedge resections (50 triportal vs. 50 uniportal VATS) were collected and analysed. All 100 VATS procedures were completed without adverse events, major or minor complications. The average operating time was 54 ± 13 min, with no significant differences between the two techniques. Surgical indications are shown in Table 2. The target tissue sites were the same in all surgeries, which further minimized technical bias between the two approaches (metastases were localized in the upper lobes; wedge resection for interstitial lung 2
R is a free software environment for statistical computing and graphics. It compiles and runs on a wide variety of UNIX platforms, Windows and MacOS (www.r-project.org).
123
Triportal VATS (n = 50)
Uniportal VATS (n = 50)
p value
23
28
0.48
Upper lobe lung metastasis
6
4
0.53
Interstitial lung disease
21
18
0.63
disease was performed in the lingula or middle lobe, while pneumothorax was treated by wedge resection of the apex of the lung in all cases). For body posture assessment, the head–trunk axial rotation, head flexion in the sagittal plane, and viewing direction were successfully analysed for both techniques. Head–trunk axial rotation was significantly reduced during uniportal VATS (p = 0.03). The uniportal VATS settings were found to significantly prevent neck extension, and the viewing direction was significantly declined (p = 0.01). The angle of gaze was not influenced by the settings (p = 0.76) (Table 3). Evaluation of physical discomfort on the Borg CR-10 scale showed that the body posture during triportal access was perceived as significantly more stressful (p = 0.006), particularly in the right shoulder (p = 0.006) and the back (p = 0.02) (Table 4). Table 5 presents the results of the NASA–TLX cognitive workload assessment. The major difference was the physical component, which was rated higher in triportal than in uniportal VATS (47.47 ± 2.66 vs. 24.32 ± 5.53; p = 0.006). The NASA–TLX score was significantly higher for uniportal than triportal VATS, demonstrating that the overall workload the surgeons experienced during uniportal VATS was significantly greater than during triportal VATS (39.71 ± 3.54 vs. 23.46 ± 29.92; p = 0.041). The mental demand was rated higher for uniportal than triportal VATS (39.52 ± 3.21 vs. 28.94 ± 3.33; p = 0.20). Conversely, the physical demand was rated significantly lower during uniportal than triportal VATS (24.32 ± 3.53 vs. 47.47 ± 2.66; p = 0.0006). The ratings for the temporal demand were substantially similar for uniportal and triportal VATS (41.88 ± 3.63 vs. 40.67 ± 5.53; p = 0.89). The effort was rated significantly lower with the uniportal than with the triportal VATS settings (21.33 ± 4.52 vs. 48.72 ± 4.33; p = 0.001). There was no significantly difference in performance between uniportal and triportal VATS (37.13 ± 5.25 vs. 39.84 ± 4.94; p = 0.76). The NASA–TLX frustration scale scores showed that frustration was significantly greater with the uniportal than with the triportal VATS setting (45.68 ± 3.64 vs. 26.24 ± 3.31; p = 0.02).
Surg Endosc Table 3 Ergonomic parameters for rotation, flexion and viewing direction in 100 VATS wedge resections Triportal VATS (n = 50)
Uniportal VATS (n = 50)
p value
Head–trunk axial rotation (degree)
9.65 ± 5.45
2.13 ± 3.56
0.03
Head flexion in sagittal plane (degree)
4.32 ± 1.23
3.46 ± 2.23
0.76
-15.47 ± 4.69
-4.26 ± 3.32
0.01
Viewing direction
Table 4 Borg CR-10 scale scores for 100 VATS wedge resections
Neck
Triportal VATS (n = 50)
Uniportal VATS (n = 50)
p value
3.81 ± 1.03
3.45 ± 1.24
0.67
Shoulder Left
3.84 ± 0.47
3.27 ± 0.14
0.50
Right
6.87 ± 1.31
4.02 ± 1.12
0.006
Forearm Left
4.96 ± 1.31
5.24 ± 1.06
0.78
Right
5.12 ± 1.39
4.47 ± 1.64
0.51
Back
5.27 ± 0.89
4.51 ± 1.11
0.02
Legs
2.45 ± 0.44
2.34 ± 0.38
0.87
Overall
4.66 ± 0.94
3.86 ± 0.99
0.006
Table 5 Results of the NASA–TLX questionnaire in 100 VATS wedge resections Triportal VATS (n = 50)
Uniportal VATS (n = 50)
p value
Overall
23.46 ± 2.92
39.71 ± 3.54
0.04
Mental demand
28.94 ± 3.33
39.52 ± 3.21
0.20
Physical demand
47.47 ± 2.66
24.32 ± 3.53
0.006
Temporal demand
40.67 ± 5.53
41.88 ± 3.63
0.89
Effort
48.72 ± 4.33
21.33 ± 4.52
0.001
Performance
39.84 ± 4.94
37.13 ± 5.25
0.76
Frustration level
26.24 ± 3.31
45.68 ± 3.64
0.02
Discussion There is no uniform consensus on port placement for advanced VATS operations. The configuration is currently dictated by the surgeons’ preference based on individual experience. To facilitate instrument manipulation and adequate visualization during thoracoscopy, trocars are usually placed in a triangular fashion. This geometric
configuration allows the instruments to work at a 60°–90° angle with the target tissue, while trying to avoid the problems with long-handled tools (too far or too near port sites, chest wall interferences, etc.) [16]. In standard triportal VATS, the geometric configuration of a parallelogram meddling with the optical source creates a plane with a torsion angle that is ergonomically unfavourable. Likewise, the operating team derives the visual feedback of the surgical field from a monitor outside the operative field and away from the patient [17]. Due to this position, the line of vision is driven away from the line of action, creating a difficult posture that may cause musculoskeletal complaints [6]. On the other hand, one of the geometrical advantages of single-port access VATS is the translational alignment of instruments along the sagittal plane, bringing them to reach the target lesion from a caudo-cranial perspective. Therefore, by taking better advantage of these spatial and ergonomic features, surgeons can bring the operative fulcrum inside the chest to approach the target lesion in a fashion similar to open surgery [17]. The surgeon maintains a relatively static posture throughout most of VATS, which, from an ergonomic point of view, contributes to inefficiency [18]. Static postures have been demonstrated to be more stressful than dynamic positions, since muscles and tendons build up lactic acid and toxins when held for prolonged periods in the same position [18]. Moreover, the human body requires continuous active control to maintain proper balance. However, because two-thirds of the body mass are concentrated in the upper part, this creates an unstable balance system. Moreover, because the standing posture is similar to an inverted pendulum [19], the position during quiet standing actually relies on dynamic control even if the posture may seem static [20]. Indeed, the increased workload caused by poor ergonomics may substantially worsen the quality of surgical performance [9, 21]. Despite the notable technical advances in thoracoscopic surgery, little improvement in the surgeon’s working environment has been made to reduce the physical strains that this technique imposes [20]. Ergonomic studies have shown that thoracoscopy is more static than open thoracic surgery and recommended that postures during surgery should be as neutral as possible when a prolonged static posture is maintained throughout an intervention [7]. Our analysis suggests that the surgeon’s position during uniportal VATS reduces muscular effort and spares the involved joints (shoulder, forearm, etc.) from the excessive traction otherwise required in the triportal approach. Unfortunately, operating tables are not usually designed for performing VATS, and tall surgeons find it very difficult to lower the table to a height that would allow them to work comfortably with a natural, neutral ergonomic posture. This places an additional physical workload on the surgeon
123
Surg Endosc
who is much more sensitive to physical strain than to mental stress. While the burden of mental stress declines with experience acquired through repeating procedures, the strain perceived during the execution of physical tasks remains bothersome, with the ensuing toll on these surgeons’ health causing concern for long-term consequences unless preventive measures are taken. Furthermore, there is evidence that physical discomfort during VATS is very common [4, 7, 22, 23]. In the Ergon-Trial, we chose to observe only thoracoscopic wedge resection, since it is a frequently performed and relatively short procedure with technically standardized and clearly identifiable stages. For this surgical technique, we demonstrated that significant ergonomic benefits may be gained in the uniportal VATS suite. In uniportal VATS, the viewing direction is brought back to the path orientation and restores the natural eye-hand-target axis [10]. We also demonstrated that the physical workload is significantly less challenging with uniportal than with triportal VATS. The physical demand, self-reported after performing uniportal VATS, was rated significantly lower than after triportal VATS. The body posture during triportal VATS required more elbow flexion (causing prolonged activation of the biceps) and more wrist flexion (causing greater fatigue). In particular, due to instrument manipulation and interference from the surgical assistant (usually from his/ her arm supporting the camera), the surgeon has to raise and abduct his shoulders, thus overloading the trapezius muscle. In contrast, the more neutral ergonomic posture during uniportal VATS may have resulted from manipulation without influencing instrument movements [6, 7, 17, 24]. Cognitive workload assessment, as measured with the NASA–TLX, demonstrated that the global workload score was higher with uniportal VATS, primarily because of the greater mental demand involved. These contradictory evidences against uniportal VATS might have resulted from familiarity and pre-existing expertise with the three-port approach. Our performance analysis showed no statistically significant difference in task performance between uniportal and triportal VATS. Previous studies investigating laparoscopic surgical ergonomics were conducted with minimally invasive surgery novices [21]. In contrast, the Ergon-Trial involved only skilled surgeons to ensure that the subjects already possessed the basic surgical skills needed to perform the training tasks of varying difficulty levels. Novice surgeons, unfamiliar with basic surgical skills, would have experienced greater mental workloads and thus introduced a bias. The surgical results being equal, a surgeon skilled in both uniportal and triportal approaches will most likely prefer the one that provides better physical well being. There are several limitations of this study. First, because the trial was involved only three experienced surgeons at a
123
single centre, the results cannot be generalized to other clinical settings. Second, only thoracoscopic wedge resection VATS was observed. Nonetheless, since VATS is finding an ever-increasing role in the diagnosis and treatment of a wide range of thoracic disorders, larger-scale studies are desirable to better understand the ergonomics of other common VATS procedures. Future research should inform ergonomic guidelines for VATS and investigate the effect of ergonomic interventions on physical and mental workload. In conclusion, the uniportal VATS setting can significantly improve body posture during surgery: the surgeons can stand straight facing the monitor with minimal neck extension/rotation, thus benefitting from the ergonomic advantages this setting offers. However, uniportal VATS was associated with greater frustration. Acknowledgments The authors thank Mario Viti, a gifted multimedia artist, for his valuable help with the artwork. The authors thank Dr. Diego Gonzalez Rivas who kindly offered to review this paper. Disclosures Luca Bertolaccini, Andrea Viti, and Alberto Terzi declare no conflicts of interest or financial ties to disclose
References 1. Walker WS, Casali G (2008) The VATS lobectomist: analysis of costs and alterations in the traditional surgical working pattern in the modern surgical unit. Thorac Surg Clin 18:281–287 2. Rocco G (2012) One-port (uniportal) video-assisted thoracic surgical resections—a clear advance. J Thorac Cardiovasc Surg 144:S27–S31 3. Gonzalez Rivas D, Fernandez R, De La Torre M, Martin Ucar AE (2012) Thoracoscopic lobectomy through a single incision. MMCTS. doi:10.1093/mmcts/mms007 4. Welcker K, Kesieme EB, Internullo E, Kranenburg van Koppen LJC (2012) Ergonomics in thoracoscopic surgery: results of a survey among thoracic surgeons. Interact CardioVasc Thorac Surg 15:197–200 5. Joice P, Hanna GB, Cuschieri A (1998) Ergonomic evaluation of laparoscopic bowel suturing. Am J Surg 176:373–378 6. Wauben LSGL, Van Veelen MA, Gossot D, Goossens RHM (2006) Application of ergonomic guidelines during minimally invasive surgery: a questionnaire survey of 284 surgeons. Surg Endosc 20:1268–1274 7. Kranenburg L, Gossot D (2004) Ergonomic problems encountered during video-assisted thoracic surgery. Minim Invasive Ther Allied Technol 13:147–155 8. Hanna GB, Shimi SM, Cuschieri A (1998) Task performance in endoscopic surgery is influenced by location of the image display. Ann Surg 227:481–484 9. Van Det MJ, Meijerink WJHJ, Hoff C, Totte´ ER, Pierie JPEN (2009) Optimal ergonomics for laparoscopic surgery in minimally invasive surgery suites: a review and guidelines. Surg Endosc 23:1279–1285 10. Van Det MJ, Meijerink WJHJ, Hoff C, Van Veelen MA, Pierie JPEN (2008) Ergonomic assessment of neck posture in the minimally invasive surgery suite during laparoscopic cholecystectomy. Surg Endosc 22:2421–2427
Surg Endosc 11. Seghers J, Jochem A, Spaepen A (2003) Posture, muscle activity and muscle fatigue in prolonged VDT work at different screen height settings. Ergonomics 46:714–730 12. Borg G (2008) A general scale to rate symptoms and feelings related to problems of ergonomic and organizational importance. G Ital Med Lav Ergon 30:A8–A10 13. Cao A, Chintamani KK, Pandya AK, Ellis RD (2009) NASA TLX: software for assessing subjective mental workload. Behav Res Methods 41:113–117 14. Noyes JM, Bruneau DPJ (2007) A self-analysis of the NASA-TLX workload measure. Ergonomics 50:514–519 15. Hubert N, Gilles M, Desbrosses K, Meyer JP, Felblinger J, Hubert J (2013) Ergonomic assessment of the surgeon’s physical workload during standard and robotic assisted laparoscopic procedures. Int J Med Robot Comput Assist Surg 9:142–147 16. Trejo A, Jung MC, Oleynikov D, Hallbeck MS (2007) Effect of handle design and target location on insertion and aim with a laparoscopic surgical tool. Appl Ergon 38:745–753 17. Bertolaccini L, Rocco G, Viti A, Terzi A (2013) Geometrical characteristics of uniportal VATS. J Thorac Dis 5:S214–S216 18. Menozzi M, Von Buol A, Krueger H, Mie`ge C (1994) Direction of gaze and comfort: discovering the relation for the ergonomic optimization of visual tasks. Ophthalmic Physiol Opt 14:393–399
19. Gage WH, Winter DA, Frank JS, Adkin AL (2004) Kinematic and kinetic validity of the inverted pendulum model in quiet standing. Gait Posture 19:124–132 20. Lee G, Lee T, Dexter D, Godinez C, Meenaghan N, Catania R, Park A (2009) Ergonomic risk associated with assisting in minimally invasive surgery. Surg Endosc 23:182–188 21. Lee GI, Lee MR, Clanton T, Sutton E, Park AE, Marohn MR (2014) Comparative assessment of physical and cognitive ergonomics associated with robotic and traditional laparoscopic surgeries. Surg Endosc 28:456–465 22. Van Veelen MA, Nederlof EAL, Goossens RHM, Schot CJ, Jakimowicz JJ (2003) Ergonomic problems encountered by the medical team related to products used for minimally invasive surgery. Surg Endosc 17:1077–1081 23. Psihogios JP, Sommerich CM, Mirka GA, Moon SD (2001) A field evaluation of monitor placement effects in VDT users. Appl Ergon 32:313–325 24. Lee G, Kavic SM, George IM, Park AE (2007) Postural instability does not necessarily correlate to poor performance: case in point. Surg Endosc 21:471–474
123
and Other Interventional Techniques
Ergon-trial: ergonomic evaluation of single-port access versus three-port access video-assisted thoracic surgery Luca Bertolaccini • Andrea Viti • Alberto Terzi
Received: 12 July 2014 / Accepted: 2 December 2014 Ó Springer Science+Business Media New York 2014
Abstract Background Single-port access video-assisted thoracic surgery (VATS), a technique progressively developed from the standard three-port approach in minimally invasive surgery, offers ergonomic advantages but also new challenges for the surgeon. We compared the ergonomics of three-port versus single-port VATS. Methods Posture analysis of surgeons was evaluated during 100 consecutive VATS wedge resections (50 triportal vs. 50 uniportal). Technically demanding procedures (major lung resection) were excluded. Operating table height, monitor height, distance and inclination were adjusted according to operator preference. Body posture was assessed by measuring head–trunk axial rotation and head flexion. Perceived physical strain was self-evaluated on the Borg Category Ratio (CR-10) scale. Mental workload was assessed with the National Aeronautics Space Administration– Task Load indeX (NASA–TLX), a multidimensional tool that rates workloads on six scales (mental, physical and temporal demand; effort; performance; frustration). Results All procedures were completed without complications. Head–trunk axial rotation was significantly reduced and neck flexion significantly improved in uniportal VATS. Viewing direction significantly declined (p = 0.01), body posture as measured on the Borg CR–10 scale was perceived as more stressful and the NASA–TLX score for overall
L. Bertolaccini (&) A. Terzi Thoracic Surgery Unit, Sacro Cuore Research Hospital, Via Don Angelo Sempreboni 5, 37024 Negrar, Verona, Italy e-mail: [email protected] A. Viti Thoracic Surgery Unit, S. Croce e Carle Hospital, Cuneo, Italy
workload was higher (p = 0.04) during triportal VATS. The NASA–TLX score for frustration was higher with uniportal VATS (p = 0.02), but the score for physical demand was higher in triportal VATS (p = 0.006). Conclusions The surgeon can maintain a more neutral body posture during uniportal VATS by standing straight and facing the monitor with only minimal neck extension/ rotation; however, frustration is greater than with triportal VATS. Keywords Ergonomics Physical workload Mental workload Video-assisted thoracic surgery
With advances in instruments, techniques and imaging, video-assisted thoracic surgery (VATS) has become the surgical approach of choice for a still growing number of procedures and plays a relevant part in minimally invasive thoracic surgery. There are several advantages for patients in undergoing VATS, including less postoperative pain, shorter hospital stay and quicker return to normal everyday activity [1]. Single-port access VATS, a technique progressively developed from the standard three-port approach, was initially described only for minor thoracic procedures [2] and then later applied in various other procedures including lobectomies [3]. VATS not only offers numerous benefits over conventional open surgery but also poses ergonomic challenges for surgeons [4]. The importance of ergonomics in VATS has been generally recognized and previous studies have shown that ergonomics and environmental factors can influence surgical performance in laparoscopy; for instance, correct ergonomic posture can reduce operating time [5]. Nevertheless, as VATS gains wider acceptance, ways to improve the ergonomics of the procedure will need to be found. To our
123
Surg Endosc
knowledge, few studies have addressed ergonomic concerns in VATS [4, 6, 7]. The aim of the Ergon-Trial was to compare the ergonomics of VATS wedge resection with the standard triportal and the uniportal access techniques performed by surgeons in a clinical setting. The two workloads commonly measured to assess the ergonomics associated with a specific surgical task are the physical and the cognitive. The physical workload measures the amount of physical demand on the body, while the mental workload assesses the amount of mental effort required to complete a surgical procedure. The overall workload level is derived from analysis of the physical and cognitive workloads.
Methods Three right-handed surgeons skilled in VATS approaches participated in the study. None reported physical complaints such as carpal tunnel syndrome or serious neck or back problems. Ergonomic analysis of the operating surgeon during 100 consecutive VATS wedge resections (50 triportal vs. 50 uniportal VATS) was performed. The operating surgeon selected the surgical approach based on the individual patient’s characteristics. Surgery for massive pleural adhesions and technically demanding procedures, such as major VATS lung resections, was excluded from the analysis. Each surgeon carried out at least 15 procedures with each approach, assisted by the same experienced assistants. The instruments were identical for each type of procedure. The operating table height and tilt and the monitor height were adjusted for each surgeon. Based on previous experience, the monitor was ideally placed in front of the surgeon to permit a moderate downward viewing angle of about 10°–30° without axial trunk rotation [8]. For the scrub nurse, the monitor was ideally placed just below eye level to allow a downward viewing direction of 0° to about 15°. Upward viewing angles, which may cause harmful neck extension, were avoided. For all participants, minimal neck torsion was aspired. An axial rotation less than *15° was considered ergonomically acceptable. During all interventions, the patient was positioned in lateral decubitus contralateral to the lesion, with the hip tilted backward approximately 5° and the shoulders backward approximately 10°; both arms were placed forward 90°, and the upside arm was bent at the elbow at 90° on the table for better lateral stability. Depending on which surgical technique is performed, two quite similar positions of the surgeon can be distinguished: in three-port access VATS (Fig. 1A), the surgeon stands in front of the patient at the level of the chest, the camera assistant stands on the same side and the scrub nurse stands in front of the patient at the level of the
123
patient’s leg. Two monitors are located at the level of the patient’s head, one in the surgeon’s line of vision and the other in the line of vision of the scrub nurse. The trocars are placed apart from the endoscope on both sides of the chest. To handle the instruments, the surgeon must rotate his upper body and lean over the patient. In the uniportal VATS set up (Fig. 1B), the surgeon and the assistant must be positioned in front of the patient in order to have the same thoracoscopic vision throughout the procedure and allow for more coordinated movements. The scrub nurse stands on the opposite side. The incision, about 4–5 cm long, is placed preferably in the fifth intercostal space in the anterior position just inferior to the breast and pectoralis major muscle [3]. Body posture was assessed with a video analysis system consisting of a digital camera positioned above the surgeon for observing the axial rotation of the head as compared with the trunk and of the head flexion in the sagittal plane. Measurements on the images were digitally performed with a line angle measuring tool in Adobe Photoshop CC for Linux (Adobe Systems Incorporated, San Jose, CA, USA). The workloads were evaluated by subjective and objective measures, in which the surgeon’s physical and mental exertion during the procedures was self-assessed during and after the operation and recorded. The eye height and the viewing distance (eye-to-monitor) and the monitor height in relation to the floor were measured to calculate the viewing direction (Fig. 2) according to the ergonomic equation [9]: eye height screen height viewing direction = sin : viewing distance The viewing direction is an ergonomic evaluation of the combined effort of neck flexion/extension and the angle of gaze performed by the extra ocular musculature [10]. For the measurements in the sagittal plane, we used the anatomic ear–eye line, running through the tragus of the ear and the canthus of the eye. In the neutral position of the head and neck, the ear–eye line has an inclined angle of *15° to the horizontal [11]. When the head is in *10° flexion, the anatomic ear–eye line is *5° above the horizontal [11]. Physical discomfort perceived during surgery was measured by means of the Borg Category Ratio (CR-10) scale, a widely accepted tool for evaluating physical workload [12]. The general perception of physical exertion comes from the integration of different symptoms arising from active muscles, joints, possible pain, and dizziness. The Borg CR-10 scale is a category scale with ratio properties consisting of numbers related to verbal expressions, which allows rate comparison between intensities as well as the determination of intensity levels. The scale is relatively simple to use; it is based on the surgeon’s
Surg Endosc Fig. 1 Operative setup in the Video-Assisted Thoracic Surgery (VATS) suite. A Operative setup in the triportal VATS technique. B Operative setup in the uniportal VATS approach. AC anaesthesia console, TC thoracoscopic console, FS flat screen, S surgeon, AS assisting surgeon, SN scrub nurse, IT instrument table
operator to achieve a particular level of performance. Because the definition of cognitive workload is human centred rather than task centred, the cognitive workload is defined uniquely by the demands of an objective task: as such, it reflects multiple attributes that may have different relevance for different individuals. The NASA–TLX rating scale is a multidimensional assessment tool that allows participants to rate their cognitive workloads on six scales (Table 1): mental demand, physical demand, temporal demand, effort, performance and frustration during task execution [14, 15]. Statistical analysis
Fig. 2 Parameters measured to calculate the ergonomic equation of viewing direction (an ergonomic evaluation of the combined effort of neck flexion/extension and angle of gaze performed by the extraocular musculature)
subjective estimation of physical strain experienced during tasks (score from 1 to 10, where 1 indicates no strain and 10 indicates extremely uncomfortable and painful strain). Seven areas of the surgeon’s body were evaluated: legs, back, neck, right and left shoulder, and right and left forearm. Perceived strain was scored every 10 min during each operation to record changes over time. On completing the operation, the surgeon evaluated the cognitive workload according to the National Aeronautics Space Administration–Task Load Index (NASA–TLX), a widely recognized tool for self-reporting workload perception [13]. The cognitive workload is a hypothetical construct that represents the cost incurred by a human
A power analysis was performed to calculate the sample size for unpaired analysis; a sample size of at least 63 procedures was needed, with a type 1 error rate set at 0.05 and power at 0.80. Continuous variables are presented as mean ± standard deviation. The two operational setups were compared using Student’s t test or Wilcoxon’s twosample test (discrete or continuous data) and Pearson’s v2 test or Fisher’s exact test when appropriate (dichotomous or categorical data). The NASA-TLX consists of two parts: ratings and weights.1 Ratings for each of the six subscales are obtained from the subjects following the completion of a task. A numerical rating ranging from 0 to 100 (from least to most taxing) is assigned to each scale. Weights are determined by the subjects’ choices of the subscale most relevant to 1
NASA–TLX software is available for free download at tlx.playgraph.com. Additional information can be found at humansystems.arc.nasa.gov/groups/TLX.
123
Surg Endosc Table 1 Subscales and items on the NASA-TLX rating scale
Table 2 Surgical indications for the 100 VATS wedge resections
Scale
Description
Mental demand
How much mental and perceptual activity was required (e.g. thinking, deciding, calculating, remembering, searching, etc.)?
Primary spontaneous pneumothorax
Was the surgical operation easy or demanding, simple or complex? How much physical activity was required (e.g. pushing, pulling, turning, controlling, activating, etc.)?
Physical demand
Was the surgical operation easy or demanding, slack or strenuous, restful or laborious? Temporal demand
How much time pressure did you feel due to the rate or pace at which the surgical operation elements occurred? Was the pace slow and leisurely or rapid and frantic?
Performance
How successful do you think you were in accomplishing the goals of the surgical operation? How satisfied were you with your performance in accomplishing these goals?
Effort
How hard did you have to work (mentally and physically) to accomplish your level of performance?
Frustration level
How insecure, discouraged, stressed, or secure, gratified, content did you feel during the surgical operation?
workload for them from a pair of choices. The weights are calculated from the tally of these choices from 15 combinatorial pairs created from the six subscales. The weights range from 0 to 5 (from least to most relevant). The ratings and weights are then combined to calculate a weighted average for an overall workload score. The significance level was set at 0.05 for all parameters. All statistical analyses were performed using R Software version 3.0.3.2
Results The data on 100 consecutive VATS wedge resections (50 triportal vs. 50 uniportal VATS) were collected and analysed. All 100 VATS procedures were completed without adverse events, major or minor complications. The average operating time was 54 ± 13 min, with no significant differences between the two techniques. Surgical indications are shown in Table 2. The target tissue sites were the same in all surgeries, which further minimized technical bias between the two approaches (metastases were localized in the upper lobes; wedge resection for interstitial lung 2
R is a free software environment for statistical computing and graphics. It compiles and runs on a wide variety of UNIX platforms, Windows and MacOS (www.r-project.org).
123
Triportal VATS (n = 50)
Uniportal VATS (n = 50)
p value
23
28
0.48
Upper lobe lung metastasis
6
4
0.53
Interstitial lung disease
21
18
0.63
disease was performed in the lingula or middle lobe, while pneumothorax was treated by wedge resection of the apex of the lung in all cases). For body posture assessment, the head–trunk axial rotation, head flexion in the sagittal plane, and viewing direction were successfully analysed for both techniques. Head–trunk axial rotation was significantly reduced during uniportal VATS (p = 0.03). The uniportal VATS settings were found to significantly prevent neck extension, and the viewing direction was significantly declined (p = 0.01). The angle of gaze was not influenced by the settings (p = 0.76) (Table 3). Evaluation of physical discomfort on the Borg CR-10 scale showed that the body posture during triportal access was perceived as significantly more stressful (p = 0.006), particularly in the right shoulder (p = 0.006) and the back (p = 0.02) (Table 4). Table 5 presents the results of the NASA–TLX cognitive workload assessment. The major difference was the physical component, which was rated higher in triportal than in uniportal VATS (47.47 ± 2.66 vs. 24.32 ± 5.53; p = 0.006). The NASA–TLX score was significantly higher for uniportal than triportal VATS, demonstrating that the overall workload the surgeons experienced during uniportal VATS was significantly greater than during triportal VATS (39.71 ± 3.54 vs. 23.46 ± 29.92; p = 0.041). The mental demand was rated higher for uniportal than triportal VATS (39.52 ± 3.21 vs. 28.94 ± 3.33; p = 0.20). Conversely, the physical demand was rated significantly lower during uniportal than triportal VATS (24.32 ± 3.53 vs. 47.47 ± 2.66; p = 0.0006). The ratings for the temporal demand were substantially similar for uniportal and triportal VATS (41.88 ± 3.63 vs. 40.67 ± 5.53; p = 0.89). The effort was rated significantly lower with the uniportal than with the triportal VATS settings (21.33 ± 4.52 vs. 48.72 ± 4.33; p = 0.001). There was no significantly difference in performance between uniportal and triportal VATS (37.13 ± 5.25 vs. 39.84 ± 4.94; p = 0.76). The NASA–TLX frustration scale scores showed that frustration was significantly greater with the uniportal than with the triportal VATS setting (45.68 ± 3.64 vs. 26.24 ± 3.31; p = 0.02).
Surg Endosc Table 3 Ergonomic parameters for rotation, flexion and viewing direction in 100 VATS wedge resections Triportal VATS (n = 50)
Uniportal VATS (n = 50)
p value
Head–trunk axial rotation (degree)
9.65 ± 5.45
2.13 ± 3.56
0.03
Head flexion in sagittal plane (degree)
4.32 ± 1.23
3.46 ± 2.23
0.76
-15.47 ± 4.69
-4.26 ± 3.32
0.01
Viewing direction
Table 4 Borg CR-10 scale scores for 100 VATS wedge resections
Neck
Triportal VATS (n = 50)
Uniportal VATS (n = 50)
p value
3.81 ± 1.03
3.45 ± 1.24
0.67
Shoulder Left
3.84 ± 0.47
3.27 ± 0.14
0.50
Right
6.87 ± 1.31
4.02 ± 1.12
0.006
Forearm Left
4.96 ± 1.31
5.24 ± 1.06
0.78
Right
5.12 ± 1.39
4.47 ± 1.64
0.51
Back
5.27 ± 0.89
4.51 ± 1.11
0.02
Legs
2.45 ± 0.44
2.34 ± 0.38
0.87
Overall
4.66 ± 0.94
3.86 ± 0.99
0.006
Table 5 Results of the NASA–TLX questionnaire in 100 VATS wedge resections Triportal VATS (n = 50)
Uniportal VATS (n = 50)
p value
Overall
23.46 ± 2.92
39.71 ± 3.54
0.04
Mental demand
28.94 ± 3.33
39.52 ± 3.21
0.20
Physical demand
47.47 ± 2.66
24.32 ± 3.53
0.006
Temporal demand
40.67 ± 5.53
41.88 ± 3.63
0.89
Effort
48.72 ± 4.33
21.33 ± 4.52
0.001
Performance
39.84 ± 4.94
37.13 ± 5.25
0.76
Frustration level
26.24 ± 3.31
45.68 ± 3.64
0.02
Discussion There is no uniform consensus on port placement for advanced VATS operations. The configuration is currently dictated by the surgeons’ preference based on individual experience. To facilitate instrument manipulation and adequate visualization during thoracoscopy, trocars are usually placed in a triangular fashion. This geometric
configuration allows the instruments to work at a 60°–90° angle with the target tissue, while trying to avoid the problems with long-handled tools (too far or too near port sites, chest wall interferences, etc.) [16]. In standard triportal VATS, the geometric configuration of a parallelogram meddling with the optical source creates a plane with a torsion angle that is ergonomically unfavourable. Likewise, the operating team derives the visual feedback of the surgical field from a monitor outside the operative field and away from the patient [17]. Due to this position, the line of vision is driven away from the line of action, creating a difficult posture that may cause musculoskeletal complaints [6]. On the other hand, one of the geometrical advantages of single-port access VATS is the translational alignment of instruments along the sagittal plane, bringing them to reach the target lesion from a caudo-cranial perspective. Therefore, by taking better advantage of these spatial and ergonomic features, surgeons can bring the operative fulcrum inside the chest to approach the target lesion in a fashion similar to open surgery [17]. The surgeon maintains a relatively static posture throughout most of VATS, which, from an ergonomic point of view, contributes to inefficiency [18]. Static postures have been demonstrated to be more stressful than dynamic positions, since muscles and tendons build up lactic acid and toxins when held for prolonged periods in the same position [18]. Moreover, the human body requires continuous active control to maintain proper balance. However, because two-thirds of the body mass are concentrated in the upper part, this creates an unstable balance system. Moreover, because the standing posture is similar to an inverted pendulum [19], the position during quiet standing actually relies on dynamic control even if the posture may seem static [20]. Indeed, the increased workload caused by poor ergonomics may substantially worsen the quality of surgical performance [9, 21]. Despite the notable technical advances in thoracoscopic surgery, little improvement in the surgeon’s working environment has been made to reduce the physical strains that this technique imposes [20]. Ergonomic studies have shown that thoracoscopy is more static than open thoracic surgery and recommended that postures during surgery should be as neutral as possible when a prolonged static posture is maintained throughout an intervention [7]. Our analysis suggests that the surgeon’s position during uniportal VATS reduces muscular effort and spares the involved joints (shoulder, forearm, etc.) from the excessive traction otherwise required in the triportal approach. Unfortunately, operating tables are not usually designed for performing VATS, and tall surgeons find it very difficult to lower the table to a height that would allow them to work comfortably with a natural, neutral ergonomic posture. This places an additional physical workload on the surgeon
123
Surg Endosc
who is much more sensitive to physical strain than to mental stress. While the burden of mental stress declines with experience acquired through repeating procedures, the strain perceived during the execution of physical tasks remains bothersome, with the ensuing toll on these surgeons’ health causing concern for long-term consequences unless preventive measures are taken. Furthermore, there is evidence that physical discomfort during VATS is very common [4, 7, 22, 23]. In the Ergon-Trial, we chose to observe only thoracoscopic wedge resection, since it is a frequently performed and relatively short procedure with technically standardized and clearly identifiable stages. For this surgical technique, we demonstrated that significant ergonomic benefits may be gained in the uniportal VATS suite. In uniportal VATS, the viewing direction is brought back to the path orientation and restores the natural eye-hand-target axis [10]. We also demonstrated that the physical workload is significantly less challenging with uniportal than with triportal VATS. The physical demand, self-reported after performing uniportal VATS, was rated significantly lower than after triportal VATS. The body posture during triportal VATS required more elbow flexion (causing prolonged activation of the biceps) and more wrist flexion (causing greater fatigue). In particular, due to instrument manipulation and interference from the surgical assistant (usually from his/ her arm supporting the camera), the surgeon has to raise and abduct his shoulders, thus overloading the trapezius muscle. In contrast, the more neutral ergonomic posture during uniportal VATS may have resulted from manipulation without influencing instrument movements [6, 7, 17, 24]. Cognitive workload assessment, as measured with the NASA–TLX, demonstrated that the global workload score was higher with uniportal VATS, primarily because of the greater mental demand involved. These contradictory evidences against uniportal VATS might have resulted from familiarity and pre-existing expertise with the three-port approach. Our performance analysis showed no statistically significant difference in task performance between uniportal and triportal VATS. Previous studies investigating laparoscopic surgical ergonomics were conducted with minimally invasive surgery novices [21]. In contrast, the Ergon-Trial involved only skilled surgeons to ensure that the subjects already possessed the basic surgical skills needed to perform the training tasks of varying difficulty levels. Novice surgeons, unfamiliar with basic surgical skills, would have experienced greater mental workloads and thus introduced a bias. The surgical results being equal, a surgeon skilled in both uniportal and triportal approaches will most likely prefer the one that provides better physical well being. There are several limitations of this study. First, because the trial was involved only three experienced surgeons at a
123
single centre, the results cannot be generalized to other clinical settings. Second, only thoracoscopic wedge resection VATS was observed. Nonetheless, since VATS is finding an ever-increasing role in the diagnosis and treatment of a wide range of thoracic disorders, larger-scale studies are desirable to better understand the ergonomics of other common VATS procedures. Future research should inform ergonomic guidelines for VATS and investigate the effect of ergonomic interventions on physical and mental workload. In conclusion, the uniportal VATS setting can significantly improve body posture during surgery: the surgeons can stand straight facing the monitor with minimal neck extension/rotation, thus benefitting from the ergonomic advantages this setting offers. However, uniportal VATS was associated with greater frustration. Acknowledgments The authors thank Mario Viti, a gifted multimedia artist, for his valuable help with the artwork. The authors thank Dr. Diego Gonzalez Rivas who kindly offered to review this paper. Disclosures Luca Bertolaccini, Andrea Viti, and Alberto Terzi declare no conflicts of interest or financial ties to disclose
References 1. Walker WS, Casali G (2008) The VATS lobectomist: analysis of costs and alterations in the traditional surgical working pattern in the modern surgical unit. Thorac Surg Clin 18:281–287 2. Rocco G (2012) One-port (uniportal) video-assisted thoracic surgical resections—a clear advance. J Thorac Cardiovasc Surg 144:S27–S31 3. Gonzalez Rivas D, Fernandez R, De La Torre M, Martin Ucar AE (2012) Thoracoscopic lobectomy through a single incision. MMCTS. doi:10.1093/mmcts/mms007 4. Welcker K, Kesieme EB, Internullo E, Kranenburg van Koppen LJC (2012) Ergonomics in thoracoscopic surgery: results of a survey among thoracic surgeons. Interact CardioVasc Thorac Surg 15:197–200 5. Joice P, Hanna GB, Cuschieri A (1998) Ergonomic evaluation of laparoscopic bowel suturing. Am J Surg 176:373–378 6. Wauben LSGL, Van Veelen MA, Gossot D, Goossens RHM (2006) Application of ergonomic guidelines during minimally invasive surgery: a questionnaire survey of 284 surgeons. Surg Endosc 20:1268–1274 7. Kranenburg L, Gossot D (2004) Ergonomic problems encountered during video-assisted thoracic surgery. Minim Invasive Ther Allied Technol 13:147–155 8. Hanna GB, Shimi SM, Cuschieri A (1998) Task performance in endoscopic surgery is influenced by location of the image display. Ann Surg 227:481–484 9. Van Det MJ, Meijerink WJHJ, Hoff C, Totte´ ER, Pierie JPEN (2009) Optimal ergonomics for laparoscopic surgery in minimally invasive surgery suites: a review and guidelines. Surg Endosc 23:1279–1285 10. Van Det MJ, Meijerink WJHJ, Hoff C, Van Veelen MA, Pierie JPEN (2008) Ergonomic assessment of neck posture in the minimally invasive surgery suite during laparoscopic cholecystectomy. Surg Endosc 22:2421–2427
Surg Endosc 11. Seghers J, Jochem A, Spaepen A (2003) Posture, muscle activity and muscle fatigue in prolonged VDT work at different screen height settings. Ergonomics 46:714–730 12. Borg G (2008) A general scale to rate symptoms and feelings related to problems of ergonomic and organizational importance. G Ital Med Lav Ergon 30:A8–A10 13. Cao A, Chintamani KK, Pandya AK, Ellis RD (2009) NASA TLX: software for assessing subjective mental workload. Behav Res Methods 41:113–117 14. Noyes JM, Bruneau DPJ (2007) A self-analysis of the NASA-TLX workload measure. Ergonomics 50:514–519 15. Hubert N, Gilles M, Desbrosses K, Meyer JP, Felblinger J, Hubert J (2013) Ergonomic assessment of the surgeon’s physical workload during standard and robotic assisted laparoscopic procedures. Int J Med Robot Comput Assist Surg 9:142–147 16. Trejo A, Jung MC, Oleynikov D, Hallbeck MS (2007) Effect of handle design and target location on insertion and aim with a laparoscopic surgical tool. Appl Ergon 38:745–753 17. Bertolaccini L, Rocco G, Viti A, Terzi A (2013) Geometrical characteristics of uniportal VATS. J Thorac Dis 5:S214–S216 18. Menozzi M, Von Buol A, Krueger H, Mie`ge C (1994) Direction of gaze and comfort: discovering the relation for the ergonomic optimization of visual tasks. Ophthalmic Physiol Opt 14:393–399
19. Gage WH, Winter DA, Frank JS, Adkin AL (2004) Kinematic and kinetic validity of the inverted pendulum model in quiet standing. Gait Posture 19:124–132 20. Lee G, Lee T, Dexter D, Godinez C, Meenaghan N, Catania R, Park A (2009) Ergonomic risk associated with assisting in minimally invasive surgery. Surg Endosc 23:182–188 21. Lee GI, Lee MR, Clanton T, Sutton E, Park AE, Marohn MR (2014) Comparative assessment of physical and cognitive ergonomics associated with robotic and traditional laparoscopic surgeries. Surg Endosc 28:456–465 22. Van Veelen MA, Nederlof EAL, Goossens RHM, Schot CJ, Jakimowicz JJ (2003) Ergonomic problems encountered by the medical team related to products used for minimally invasive surgery. Surg Endosc 17:1077–1081 23. Psihogios JP, Sommerich CM, Mirka GA, Moon SD (2001) A field evaluation of monitor placement effects in VDT users. Appl Ergon 32:313–325 24. Lee G, Kavic SM, George IM, Park AE (2007) Postural instability does not necessarily correlate to poor performance: case in point. Surg Endosc 21:471–474
123
