Ergonomic assessment of a new hand tool design for laparoscopic surgery based on surgeons’ muscular activity

Highlights

• An approach to assess laparoscopic handle tools is presented.

• time–frequency analysis of the dynamic EMG signals is used.

• The ergonomic design is assessed based on surgeon’s prolonged activities.

• The proposed design outperforms one of the most used tools in the market.

• This method can be used to in the selection of surgical tools when programming extended procedures.

Abstract

Laparoscopic surgery techniques are customarily used in non-invasive procedures. That said traditional surgical instruments and devices used by surgeons suffer from certain ergonomic deficiencies that may lead to physical complaints in upper limbs and back and general discomfort that may, in turn, affect the surgeon’s skills during surgery. A novel design of the laparoscopic gripper handle is presented and compared with one of the most used instruments in this field in an attempt to overcome this problem. The assessment of the ergonomic feature of the novel design was performed by using time–frequency analysis of the surface electromyography (sEMG) signal during dynamic activities. Singular Spectrum Analysis (SSA) was used to decompose the sEMG signal and extract the median frequency of each muscle to assess muscle fatigue. The results reveal that using the proposed ergonomic grip reduces the mean values of the muscle activity during each of the proposed tasks. The novel design also improves the ease of use in laparoscopic surgery as it minimises high-pressure contact areas, reduces large amplitude movements and promotes a neutral position of the hand, wrist and forearm. Furthermore, the SSA method for time–frequency analysis provides a powerful tool to analyse a prescribed activity in ergonomic terms. The proposed methodology to assess muscle activity during surgery activities may be useful in the selection of surgical instruments when programming extended procedures, as it provides an additional selection criterion based on the surgeon’s biomechanics and the proposed activity.

Introduction

Laparoscopic surgery techniques (LST) are widely used in numerous types of surgeries nowadays due to the proven benefits for the patients and the cost savings for health centres. However, the surgeons’ surgical instruments and devices suffer from certain ergonomic deficiencies that often produce physical complaints in the upper limbs and general discomfort that may adversely affect the surgeon’s skills during surgery (Alleblas et al., 2017). Two general factors contribute to these problems: the prolonged static postures and a higher activity with upper limb muscles in uncomfortable postures (McDonald et al., 2014, Dalager et al., 2017, Lowndes and Hallbeck, 2014, Tsafrir et al., 2015), leading to numbness or tingling in the arms or hands. These prolonged static postures are strongly related to musculoskeletal disorders and, therefore, special attention must be paid to ensure occupational health and safety for the surgeon.

Adequate instruments must be used to achieve a comfortable working position for the upper limbs and to reduce the muscle activity and fatigue related to the prolonged postures adopted by the surgeon. In this sense, surgeons, designers and engineers have been working together to obtain standard anthropometric measurements to improve the designs of laparoscopic instrumental for LST (Yu et al., 2016b, Sun et al., 2014, Hallbeck et al., 2017). New instrument designs must consider ergonomic aspects during surgery, as widely proven in the literature (Choi, 2012, Alleblas et al., 2016, Tung et al., 2015). However, conventional devices and surgical instruments used in LST lack ergonomic criteria to reduce muscle fatigue in surgeons. Among the documented ergonomic limitations affecting the minimally invasive approach are operational issues with instrument design (González et al., 2015), force feedback (Smit et al., 2017), stresses caused by monitor placement (Berguer et al., 2003, Yu et al., 2016a, Harada et al., 2018), and perceptual challenges. Van Veelen and Meijer (1999) reported MIS-related surgeon discomfort rates of 40% to 60%; larger survey studies on the subject haven reported symptoms (often persistent) related to MIS in the 12% to 18% range. They also revealed that poor design of laparoscopic surgery instruments lead to work-related diseases among surgeons relating to hand and upper limb discomfort, hand paraesthesia and temporary compression neuropathies of the fingers. More recently, several studies conducted by Yu et al., 2016b, Yu et al., 2016a show that modern instruments have unnatural handling characteristics as a result of poor ergonomic design. These studies found that inadequate adjustment of the handle to the ergonomics of the human hand result, for example, in too higher forces and too smaller movements of the fingers to move the grip. This leads to fatigue or cramping in the surgeon’s hands. Studies such as Sutton et al.’s 2014 highlight this by exposing how surgeons with a smaller hand size had to treat their hands more often and experienced more musculoskeletal complaints compared to surgeons with larger hands. As Trejo et al. (2007) point out in their study, one of the leading causes of surgeon post-surgery pain or numbness is the non-neutral postures adopted during the MIS procedure caused by poor ergonomic design. Cuschieri (1995) set the basis and described how surgical fatigue resulting from poor design could lead to mental exhaustion, increased irritability, impaired surgical judgement and reduced dexterity. Studies such as that of Van der Peijl and Herder (2001) found that an inadequate adjustment of the handle to the ergonomics of the human hand leads to uncomfortable positions of the arm and small finger movements with excessive manipulation forces. Another reason for discomfort, according to the study by Aitchison et al. (2016) is neck and shoulder stress from looking at the monitor. The surgeon has no direct control over his direction of vision when an assistant holds the endoscope, which can lead to communication problems and disturb the surgeon’s eye–hand coordination. Besides, the laparoscopic image is often unstable due to tremors and sudden movements of the surgical assistant, as the task is often a time-consuming and tiring one performed in a confined space, which leads to non-ergonomic circumstances. Other studies confirm this by pointing out that sustained postures without sufficient recovery time are risk factors for fatigue and musculoskeletal injuries during surgery (Szeto et al., 2012).

Several studies have superficially investigated the opening and closing of the surgical instruments in quasi-static conditions (Maithel et al., 2005), the force and motion in instrument handling (Horeman et al., 2014), the hand and finger kinematics (Pérez-Duarte et al., 2014, Loukas and Georgiou, 2011) and the surface Electromyography (sEMG) activity during different laparoscopic procedures and with different laparoscopic graspers (Berguer et al., 2003, Judkins et al., 2006, Szeto et al., 2013, Dufaug et al., 2016, Zhang et al., 2017). Some studies such as that of Berguer et al., 1998, Berguer et al., 1999, Emam et al., 2001, Emam et al., 2002, Quick et al. (2003), applied surface electromyography (sEMG) analysis to demonstrate that different handle designs transmitted various stresses to the forearm muscles. However, in the studies mentioned above, the sEMG data processing was performed under the supposition of isometric contractions and, therefore, considering the sEMG signal as a stationary signal. Muscle contractions performed by surgeons during their activity are dynamical, and therefore, non-stationarity must be considered to assess the functionality of the hand tool properly. There is a gap in the literature concerning time–frequency analysis in the assessment of muscle fatigue during laparoscopic surgery and also, in the comparison of different dynamic tasks and instruments. The objective of this work is to compare a novel design of the handle of the laparoscopic gripper with one of the most used instruments in this field by using time–frequency analysis techniques to evaluate ergonomics during dynamic activities. Singular Spectrum Analysis (SSA) was used to quantify time–frequency parameters to assess the performance of the novel design. SSA is a non-parametric technique that decomposes an original time series into a set of additive components. The grouping of these components allows not only to separate the interest signal from noise but to group the different components according to several criteria based on the information given by them. The use of SSA techniques enables isolating noise and retrieving time–frequency parameters to perform an ergonomic assessment of the tool based on physiological criteria.