Can Armrests Improve Comfort and Task Performance in Laparoscopic Surgery?

Abstract

Objective:

The study sought to determine whether the support provided by armrests influenced task quality, task efficiency, and surgeon comfort during laparoscopic surgery.

Summary Background Data:

Complex laparoscopic surgery requires precise movements, and usually long execution times and an uncomfortable stance. Discomfort in the shoulders, back, and neck is an established complaint among laparoscopic surgeons and is related to the unnatural postures adopted during laparoscopic interventions. Discomfort, and the associated fatigue, is a contributory factor in the execution of errors.

Methods:

Nineteen subjects completed a bimanual simulated laparoscopic task both with and without the aid of bilateral armrests. The task was completed in both an ideal unstressed posture and an uncomfortable, stressed elevated posture that more closely represents real laparoscopic operating conditions. Task duration was prolonged sufficiently to precipitate muscular fatigue. The participants also completed a visual analogue scale instrument on level of discomfort symptoms experienced in every part of the upper limbs and vertebral spine. Execution errors (task quality) and completion times (task efficiency) were recorded automatically by the laparoscopic simulator.

Results:

Error rates and discomfort measures were significantly improved when the armrests were used, but there was no significant change in task completion time.

Conclusions:

The use of armrests in simulated laparoscopic surgery brings measurable comfort and task performance benefits, which could transfer to actual surgical procedures.

Nineteen subjects performed prolonged simulated laparoscopic tasks, both with and without surgical armrests. Task performance data were obtained from a laparoscopic simulator and the subjects completed questionnaires regarding comfort. The armrests significantly reduced task execution errors and improved comfort, although task completion time was unaltered.

Compared with open surgery, laparoscopic surgery presents manipulation difficulties because the instruments are less effective, uncomfortable, and offer reduced freedom of movement.^1–4 The largely static posture required during minimal access surgery, which is dictated by port placement and the site of the monitor, is known to cause eye strain and arm, shoulder, and spine discomfort.^9,10 In addition, maneuvering instruments, which pass through access ports into the abdomen, increase muscle activity and require adoption of awkward positions of the upper limbs.^11,12 As a result of these constraints, the physical workload in laparoscopic surgery is significantly increased over that required for an equivalent open procedure.^9,13

Research comparing tonic skin conductance level and electro-oculograms in both conventional and endoscopic tasks has demonstrated that most surgeons experience greater mental effort, frustration, and tension during laparoscopy than during open surgery.⁵ Indeed, a “surgical fatigue syndrome,” which occurs on average after 4 hours of laparoscopic surgery, has been described.¹⁴ Its symptoms include mental exhaustion, increased irritability, impaired surgical judgment, and reduced dexterity.

Efforts to improve the ergonomics of laparoscopic surgery, and consequently reduce the error rate, have enabled the ideal position of the laparoscopic surgeon to be defined: the arms should be slightly abducted, pronated, and rotated inward at shoulder level; the elbows should be bent at 90° to 120° and the instruments should be grasped while maintaining the natural position of an inactive hand.¹⁵ Unfortunately, this position is frequently in conflict with constraints imposed by the operating environment, and the surgeon is often obliged to maintain an awkward stance with both arms abducted.

The use of an arm support has been investigated in other fields of manual manipulation requiring prolonged and constrained posture, unsupported arms, direction-fixed gaze, and the need for execution of precise movements. In video display terminal workers, muscular fatigue and discomfort were increased when an arm support was not used.^16–18 Conversely, the use of an armrest has been shown to reduce the load on the shoulder muscles.¹⁹ In the medical field, armrests have been designed for ocular microsurgery and neurosurgery.^20,21

Previous basic ergonomic studies²² indicated that support of the shoulder, elbow, and wrist significantly improves the accuracy of laparoscopic manipulations by the endoscopic surgeon, demonstrating the need for intuitive forearm/hand rests in laparoscopic surgery. The aim of the present study was to evaluate the effect of an armrest on laparoscopic task performance and surgeons' comfort. For precise quantification, the experiments were carried out using a virtual reality laparoscopic surgical simulator.

The experiments were designed to test the hypothesis that the provision of an ergonomic armrest facilitates greater manipulative control and accuracy, hence reducing error rate and discomfort level experienced by the surgeon during simulated laparoscopic surgery.

MATERIALS AND METHODS

The study design is shown in Figure 1. Nineteen subjects with no prior experience of laparoscopy (16 males and 3 females; mean age, 31.8 years; range, 24–44 years) were recruited as participants to the study, which involved performance of a standardized task on a virtual reality surgical simulator. The subjects had normal (or corrected) vision and had either no experience or very limited experience of video-based games. Seventeen subjects had less than 3 hours of experience with surgical simulators. Two subjects (nonsurgeons) had used the laparoscopic simulator previously for a total of 10 to 15 hours each.

FIGURE 1. Experimental design of the study.

The simulated surgical task was selected on the basis that it required bimanual activity and induced fatigue after prolonged performance. The task involved lifting a box with one instrument to enable the other instrument to pick up an underlying needle, transfer it to a target, and then release it. The lifting and grasping roles were alternated between hands on successive executions of the task. The task was executed on the LapSim Basic Skills Laparoscopic Simulator (Surgical Science, Gothenburg, Sweden).

The entire exercise was completed in 2 separate days with a rest period of 24 hours. In accordance with random allocation, 9 participants performed the exercise using armrests on day 1 and without the armrest on day 2 at the same time (morning or afternoon), whereas 10 performed the exercise without the armrests on day one and used the armrest on day 2, again at the same time (morning or afternoon).

Subjects had to execute the task 50 times in an ideal unstressed position (ie, with the handles of the LapSim set at the appropriate height for each individual to allow an elbow flexion angle of 90°) and immediately afterward to execute the task 200 times in an elevated stressed position (ie, with the handles at shoulder height).

The monitor was placed 140 cm from the eyes of the subject (4 times the screen diagonal) and the center of the screen was adjusted to the eye level of each subject.

The elevated stressed posture was chosen as a fatigue-inducing stance encountered during some laparoscopic procedures. In the ideal unstressed posture, 50 repetitions of the task were considered sufficient to detect any significant performance differences with and without the armrest. For the elevated stressed posture, 200 task repetitions were chosen to ensure occurrence of fatigue and discomfort symptoms. Prior to undertaking the experiment, subjects completed a short set of familiarization tasks consisting of 6 repetitions, with and without armrests, in both the ideal and the elevated postures.

At the end of each set of tasks, the subjects completed a questionnaire, based on a visual analogue scale (VAS), designed to assess discomfort symptoms in every segment of the upper limb and back. The subjective opinions of the subjects were also obtained.

The armrest used in the experiment consisted of a horizontal tube, 1000 mm in length and 25 mm in diameter, lying in front of the subject and articulated at each end to provide unrestricted movement in the horizontal plane. Each subject chose the appropriate height of the armrests for both the ideal and elevated posture. Adjustments in the experiment were provided by independent alteration of the armrest height, the operating table height, the instrument handle height, and the video screen height, and were fixed at the beginning for each subject. Figure 2 illustrates the experimental setup.

FIGURE 2. A subject executing the task on the LapSim trainer: (A) with arms in the ideal posture; (B) with arms in the elevated posture.

During each section of the experiment, an observer recorded the time spent by the subject with the forearms resting on the armrest and the particular segment of the forearm that was in contact with the armrest.

The endpoints of the experiment were as follows:

• Error rate: the number of occasions recorded by the simulator on which the subject applied unacceptable pressure to the tissue with the tip of the instrument;

• Maximum tissue damage: the extent, in millimeters, of deformation of the tissue plane caused by unacceptable instrument pressure, measured by the simulator;

• Task efficiency: time to execute the task, recorded by the simulator;

• Participant's comfort level: Subjective discomfort measures obtained from the VAS questionnaire;

• Subjective opinions of the armrest;

• Observed armrest use.

• Statistical analysis was carried out using SPSS for Windows v11.5 (SPSS Chicago, IL). The significance level was set at 5% and all statistical tests were 2-tailed.

RESULTS

The data on error rates and tissue damage are shown in Table 1. The number of errors, maximum tissue damage, and execution time were not normally distributed. The differences of the paired variables were not symmetrically distributed so the data were analyzed with the nonparametric sign test. Discomfort VAS scores, also not normally distributed, were analyzed with the Wilcoxon test. The subjective armrest data were analyzed with the binomial test for 2 alternative nominal categories.

TABLE 1. Comparison of Number of Errors, Depth of Tissue Damage, and Time to Perform Tasks, With and Without Armrest for Both Experimental Conditions

The median time (and interquartile range) for the 200 repetitions in elevated stressed posture with armrests and without armrests were 2028 (508) seconds and 1954 (610) seconds respectively (Table 1). Such a long period (>30 minutes) operating with arms at shoulder height, was observed (as predicted) to induce fatigue in the subjects. This was an essential component part of the experimental design in the evaluation of the postulated beneficial effect of armrests use. The study was not intended to compare performance in the ideal unstressed versus the elevated stressed arm postures.

The data demonstrate that participating subjects executed significantly fewer errors when using the armrest in both the ergonomically ideal unstressed and elevated stressed hand-arm postures (P = 0.019 and P = 0.004, respectively). Equally, subjects obtained significantly improved “maximum tissue damage” scores when using the armrest in both ideal unstressed and elevated stressed postures (P = 0.001 and P = 0.019, respectively). There was no significant difference in execution times attributable to the presence or absence of the armrest.

The subjects' evaluation of the discomfort level at the end of the tasks revealed a statistically significant reduction of the VAS discomfort score in every part of the upper limbs and the vertebral spine with the use of the armrest (Table 2). Moreover, the participants' opinion was that it was easier to perform the tasks using the armrest. When asked what configuration they would prefer if they had to repeat the task, all indicated a preference for the use of the armrest (Table 3).

TABLE 2. Subjective Evaluation of Discomfort Using a Visual Analogue Scale Questionnaire

TABLE 3. Outcomes of Questionnaire on Subjective Preference for Use of the Armrest

Observation of the participants during execution of the tasks revealed that 12 (63%) subjects rested the middle third and 7 (37%) the proximal third of their forearms on the armrest. During the execution of the task in the ideal position, 17 (89%) subjects kept their forearms continuously on the armrest and 2 (11%) kept the forearms on the armrest for most of the time. During the execution of the task in the elevated position, 18 (95%) subjects kept their forearms on the armrest continuously and 1 (5%) for most of the time.

DISCUSSION

In this study, all objective and subjective comparisons, with the exception of execution time, significantly favored the use of armrest support. However, unlike actual surgery, the virtual reality task does not require the subjects to correct errors that have been executed and as a result, error execution does not translate in a corresponding time penalty. This is at variance with surgical reality, in which the execution of errors may result in significant delays in task completion. It is reasonable to expect that armrest support will result in reduced execution of laparoscopic operations directly as a result of the reduced error rate demonstrated in the experiment. In this respect, the present study probably underestimated the potential benefits of armrests in advanced laparoscopic surgery.

The device employed for this experiment, with a tube crossing in front surgeon, is obviously not suitable for clinical operative use, as it would present an unacceptable impediment between the surgeon and patient. In addition, the height of the experimental device could not be easily adjusted; in actual surgery, this would be required to meet changing operating conditions. Following the positive results of this study, a system suitable for clinical use has been developed and is undergoing pilot evaluation. Although the present study has been conducted in the context of laparoscopic surgery, armrests of this type could be adopted for open procedures and other endoscopic procedures.

Undoubtedly, discomfort consequent on arms elevation in the abducted position during laparoscopic surgery can be minimized by tipping the table, elevation of the surgeon on a stable platform or adjusting the position of the ports. However, these facilitatory measures are by no means always possible especially during precise and exacting laparoscopic tasks, eg, intracorporeal suturing, when the surgeon has to maintain accurate control of the long needle drivers with both upper limbs totally unsupported. Frequently, these tasks entail long periods of execution such that surgeon experiences the inevitable discomfort brought on by fatigue and strain. In the present study, the elevated stressed posture was adopted to mirror the surgical stance often imposed on the surgeon during advanced laparoscopic operations as a consequence of the kinematic restrictions of the endoscopic approach. Furthermore, we chose to deliberately precipitate discomfort and fatigue in this stressed elevated position within the time constraints of the experiment (median execution time of more than 30 minutes).

Previous ergonomic studies have shown that hand movements do not correlate with movement of the laparoscopic instrument tips when the upper limb is unsupported. However, when the shoulder and elbow joints are held in support fixation, hand movement correlate well with movements of the instrument tip in terms of both velocity and angular velocity.²² The findings of the present study confirm that the precision of laparoscopic surgical manipulations can be increased if the upper limbs are supported by armrests. This result was evident both in the ergonomically ideal unstressed posture and in the stress elevated stance. This observation can be explained by a double beneficial action of the armrests. First, armrests offer a support on which the forearms of the operator can be fixed enabling improved control the movements of the hands and consequently laparoscopic instruments by reducing physiological tremor. Second, the armrests prevent or delay the occurrence of fatigue and discomfort in the muscles of arm, shoulder, and upper spine muscles during the execution of long procedures. These considerations are supported by the results of questionnaires completed by participants after execution of the experiments. Indeed, all the participants in the study found it significantly easier to execute the task using the armrests both in the ideal unstressed and elevated stressed positions. They also indicated a distinct preference for the use of the armrests.