The 'AbdoMAN': an artificial abdominal wall simulator for biomechanical studies on laparotomy closure techniques

Purpose

Incisional hernia remains a frequent complication after abdominal surgery associated with significant morbidity and high costs. Animal and clinical studies have exhibited some limitations. The purpose of this study was to develop an artificial human abdominal wall (AW) simulator in order to enable investigations on closure modalities. We hypothesized that a physical model of the human AW would give new insight into commonly used suture techniques representing a substantial complement or alternative to clinical and animal studies.

Methods

The ‘AbdoMAN’ was developed to simulate human AW biomechanics. The ‘AbdoMAN’ capacities include measurement and regulation of intra-abdominal pressure (IAP), generation of IAP peaks as a result of muscle contraction and measurements of AW strain patterns analyzed with 3D image stereo correlation software. Intact synthetic samples were used to test repeatability. A laparotomy closure was then performed on five samples to analyze strain patterns.

Results

The ‘AbdoMAN’ was capable of simulating physiological conditions. AbdoMAN lateral muscles contract at 660 N, leading the IAP to increase up to 74.9 mmHg (range 65.3–88.3). Two strain criteria were used to assess test repeatability. A test with laparotomy closure demonstrated closure testing repeatability.

Conclusions

The ‘AbdoMAN’ reveals as a promising enabling tool for investigating AW surgery-related biomechanics and could become an alternative to animal and clinical studies. 3D image correlation analysis should bring new insights on laparotomy closure research. The next step will consist in evaluating different closure modalities on synthetic, porcine and human AW.

Electronic supplementary material

The online version of this article (doi:10.1007/s10029-017-1615-x) contains supplementary material, which is available to authorized users.

Ergonomic factors on task performance in laparoscopic surgery training

This paper evaluates the effect of ergonomic factors on task performance and trainee posture during laparoscopic surgery training. Twenty subjects without laparoscopic experience were allotted into 2 groups. Group 1 was trained under the optimal ergonomic simulation setting according to current ergonomic guidelines (Condition A). Group 2 was trained under non-optimal ergonomic simulation setting that can often be observed during training in a skills lab (Condition B). Posture analysis showed that the subjects held a much more neutral posture under Condition A than under Condition B (p<0.001). The subjects had less joint excursion and experienced less discomfort in their neck, shoulders, and arms under Condition A. Significant difference in task performance between Conditions A and B (p<0.05) was found. This study shows that the optimal ergonomic simulation setting leads to better task performance. In addition, no significant differences of task performance, for Groups 1 and 2 using the same test setting were found. However, better performance was observed for Group 1. It can be concluded that the optimal and non-optimal training setting have different learning effects on trainees' skill learning.

The 'urge to move' on body supports

It is well known that people that sit or lie down for prolonged periods change their posture on a regular basis. Even when people are asleep on average 20-40 postural can be observed during an 8 hours period of night rest. One of the reasons that can be found in literature for this 'urge to move' is that these movements are necessary to persevere the blood flow in the tissue. The aim of this paper is to study the relation between tissue perfusion and pressure on the tissue and frequency of the load cycle. Each subject is subjected to a treatment scheme that varies in pressure and frequency of the load on the tissue. The pressure levels that are used are 2.7 kPa, 4.0 kPa and 5.3 kPa and the frequency levels that are used are loading/unloading at intervals of 5 min., 10 min., 15 min. Statistics shows that for 2.7 kPa there is a significant reduction of blood flow between time intervals of 5 min. and 10 min. (P=0.028), and 5 min. and 15 min. (p=0.009). Statistics also shows that there is no significant reduction in blood flow at the time interval of 10 minutes, for every level of pressure. This series of measurements seems to suggest that at the time interval of 10 minutes for every level of pressure the blood flow does not decrease compared to the start situation.

Grasping soft tissue by means of vacuum technique

INTRODUCTION

A notable characteristic of bariatric surgery is the frequent manipulation of the bowel. The bowel is large, delicate, flexible, and has a natural lubricant on the tissue surface. Therefore the bowel is difficult to grasp and manipulate. Vacuum technique is commonly used in industry for all types of grasping and manipulation. Two types of nozzles that differed slightly in geometry (NT1 and NT2), were reviewed in an experimental set up for pull tests on pig bowels.

MATERIALS AND METHODS

An experimental set-up was used to conduct a series of pull tests on pig bowel tissue. The basic principle of the measurements was a Newton's force balance; F(Pmax)=Δp×A. Student t-tests, two-way ANOVA and Wilcoxon signed rank tests were conducted for the statistical analysis of NT1 and NT2 with regard to the maximum pull force (F(Pmax)).

RESULTS

Concerning NT1 the Newton's force balance could not be confirmed. Concerning NT2 the Newton's force balance could partly be confirmed. For both nozzle types the effect of Δp on F(Pmax) was significant. F(Pmax) increases linear in proportion as Δp increases. This relation between F(Pmax) and Δp was confirmed by the Newton's force balance.

DISCUSSION

The results confirm that vacuum technique can be used as a grasp technique for soft organs, particularly the bowels. By means of a clever design of the nozzle a firm grip can be obtained on the bowel segments. Therefore vacuum technique should be studied for further development of instruments, graspers and retractors, to be used in the abdominal area.

Operative notes do not reflect reality in laparoscopic cholecystectomy

Background

Operative notes represent an essential element in safe patient care and should therefore be clear and accurate. This comparative study examined whether operative notes accurately represented the laparoscopic cholecystectomy (LC) as performed.

Methods

Nine Dutch teaching and non-teaching hospitals were invited to record 20 successive LCs each and to collect the corresponding operative notes. The main outcome measures were overall differences and correspondence between video recordings and notes based on the Dutch guideline for LC and the occurrence of iatrogenic gallbladder perforation. A comparison was made of the cumulative results of recordings and operative notes, and individual recordings were compared with the corresponding notes.

Results

Seven hospitals participated in the study; 125 video recordings and operative notes were fully analysed. Recordings showed more steps of the procedure than did notes. Individual comparisons showed significant differences (P≤0·001) between the recording and the corresponding note for the steps ‘Introducing trocars under vision’, ‘Condition of the gallbladder’, ‘Critical view of safety’ and ‘Removing first and second trocar under vision’. Iatrogenic gallbladder perforation with spilled bile occurred in 31 patients (24·8 per cent), and was both recorded and reported in 29 patients. Iatrogenic gallbladder perforation with spilled bile and spilled stones occurred in 15 patients (12·0 per cent), and was recorded and reported in 11 patients.

Conclusion

Operative notes do not adequately represent the actual LCs performed as they describe fewer important procedural steps. It is suggested that operative notes should include video recordings.

Discrepant perceptions of communication, teamwork and situation awareness among surgical team members

OBJECTIVE

To assess surgical team members' differences in perception of non-technical skills.

DESIGN

Questionnaire design.

SETTING

Operating theatres (OTs) at one university hospital, three teaching hospitals and one general hospital in the Netherlands.

PARTICIPANTS

Sixty-six surgeons, 97 OT nurses, 18 anaesthetists and 40 nurse anaesthetists.

METHODS

All surgical team members, of five hospitals, were asked to complete a questionnaire and state their opinion on the current state of communication, teamwork and situation awareness at the OT.

RESULTS

Ratings for 'communication' were significantly different, particularly between surgeons and all other team members (P ≤ 0.001). The ratings for 'teamwork' differed significantly between all team members (P ≤ 0.005). Within 'situation awareness' significant differences were mainly observed for 'gathering information' between surgeons and other team members (P < 0.001). Finally, 72-90% of anaesthetists, OT nurses and nurse anaesthetists rated routine team briefings and debriefings as inadequate.

CONCLUSIONS

This study shows discrepancies on many aspects in perception between surgeons and other surgical team members concerning communication, teamwork and situation awareness. Future research needs to ascertain whether these discrepancies are linked to greater risk of adverse events or to process as well as systems failures. Establishing this link would support implementation and use of complex team interventions that intervene at multiple levels of the healthcare system.

Vacuum grasping as a manipulation technique for minimally invasive surgery

Background

Laparoscopic surgery requires specially designed instruments. Bowel tissue damage is considered one of the most serious forms of lesion, specifically perforation of the bowel.

Methods

An experimental setting was used to manipulate healthy pig bowel tissue via two vacuum instruments. During the experiments, two simple manipulations were performed for both prototypes by two experienced surgeons. Each manipulation was repeated 20 times for each prototype at a vacuum level of 60 kPa and 20 times for each prototype at a vacuum level of 20 kPa. All the manipulations were macroscopically assessed by two experienced surgeons in terms of damage to the bowel.

Results

In 160 observations, 63 ecchymoses were observed. All 63 ecchymoses were classified as not relevant and negligible. No serosa or seromuscular damages and no perforations were observed.

Conclusion

Vacuum instruments such as the tested prototypes have the potential to be used as grasper instruments in minimally invasive surgery.

Tactile feedback exceeds visual feedback to display tissue slippage in a laparoscopic grasper

Virtual reality can help to learn basic laparoscopic tasks. However, no haptic feedback, which alerts for tissue slippage, is provided by most simulators, although, it might be of influence for the decrease of errors. This study explored whether visual or tactile feedback can be used to alert the surgeon of tissue slippage. Twenty-four participants performed a laparoscopic grasping task and where provided with either visual or tactile feedback about tissue slippage. The reaction time with the visual feedback was compared to the reaction time with tactile feedback signal. The results showed that when tissue slippage is simulated, tactile feedback shows significant faster reaction times (269ms) than visual feedback signals (398ms).

Non-invasive measurement of intra-abdominal pressure: a preliminary study

The importance of measuring intra-abdominal pressure (IAP) has increased since the negative effects of sustained increased IAP, also known as intra-abdominal hypertension (IAH), have become known. The relation between IAP and abdominal wall tension has been included in several reports. We have developed a device to measure abdominal wall tension by measuring force and distance. This device enables us to investigate the correlation between the abdominal wall tension and IAP. The abdomens of two corpses (one female, one male) were insufflated with air. IAP was increased and measured at intervals by means of a laparoscopic set-up. Abdominal tension was measured at seven points on the abdominal wall at each interval. Pearson's correlation coefficients were used to determine the relationship between IAP and tension for each point measured. ANOVA was used to assess relations between measured tensions versus applied pressure, locations and subjects. In both corpses, all points showed significant (p < 0.001) correlations between IAP and abdominal wall tension. The points along the mid transverse plane appear to be more similar compared to more cranial and caudal points. We have assessed the feasibility of a device that non-invasively can track changes in IAP. Measurements performed with the device are preliminary results, and further investigation is needed.

Haptics in minimally invasive surgery--a review

This article gives an overview of research performed in the field of haptic information feedback during minimally invasive surgery (MIS). Literature has been consulted from 1985 to present. The studies show that currently, haptic information feedback is rare, but promising, in MIS. Surgeons benefit from additional feedback about force information. When it comes to grasping forces and perceiving slip, little is known about the advantages additional haptic information can give to prevent tissue trauma during manipulation. Improvement of haptic perception through augmented haptic information feedback in MIS might be promising.

A short history of progression of research into seating and postural support

Numerous solutions for cushioning the contact area between product and user have been designed during the past centuries, but only in recent decades has systematic research been conducted on the underlying mechanical principles and the consequences of mechanical load imposed on the human skin and muscular skeletal system. In this paper a short history and future perspectives on the research in pressure ulcers is discussed and innovations in the field in the perspective of the history of the innovations are presented. Research in the past century on pressure ulcers has not (yet) led to the eradication of the problem. What can be observed is that the oxygen supply and blood flow to the cells has been studied in many different ways and reported throughout the last century. After the internal capillary pressure was measured in the famous study of Landis, external interface pressures on the tissue was the object of many studies. In these studies different devices that could measure interface pressure were used, but they mainly introduced more sophisticated and innovative means to measured blood flow and oxygenation. After decades of pressure measurements, devices were designed that could measure the missing component of the mechanical load, namely shear. Recently, commercially available shear sensors have been designed, and will, with no doubt, lead to many studies on the combined mechanical load on the tissue. However, although they are interrelated, still a large gap exists between measurements on external mechanical load and the study on the etiology of pressure ulcers.

Acquiring basic endoscopy skills by training on the GI Mentor II

BACKGROUND

Achieving proficiency in flexible endoscopy requires a great amount of practice. Virtual reality (VR) simulators could provide an effective alternative for clinical training. This study aimed to gain insight into the proficiency curve for basic endoscope navigation skills with training on the GI Mentor II.

METHODS

For this study, 30 novice endoscopists performed four preset training sessions. In each session, they performed one EndoBubble task and managed multiple VR colonoscopy cases (two in first session and three in subsequent sessions). Virtual reality colonoscopy I-3 was repeatedly performed as the last VR colonoscopy in each session. The assignment for the VR colonoscopies was to visualize the cecum as quickly as possible without causing patient discomfort. Five expert endoscopists also performed the training sessions. Additionally, the performance of the novices was compared with the performance of 20 experienced and 40 expert endoscopists.

RESULTS

The novices progressed significantly, particularly in the time required to accomplish the tasks (p < 0.05, Friedman's analysis of variance [ANOVA], p < 0.05, Wilcoxon signed ranks). The experts did not improve significantly, except in the percentage of time the patient was in excessive pain. For all the runs, the performance of the novices differed significantly from that of both the experienced and the expert endoscopists (p < 0.05, Mann-Whitney U). The performance of the novices in the latter runs differed less from those of both the experienced and the expert endoscopists.

CONCLUSIONS

The study findings demonstrate that training in both VR colonoscopy and EndoBubble tasks on the GI Mentor II improves the basic endoscope navigation skills of novice endoscopists significantly.

Stability of sitting postures: the influence of degrees of freedom

Observational studies of sitting have shown that, during spontaneous sitting, people adopt a variety of postures. Various researchers have formulated theories to explain why people adopt their sitting postures. Branton (1969) hypothesized that there is continual need for postural stability while sitting. Dempster (1955) stated that additional stability could be obtained through temporarily closing chains of body segments, or, in other words, through decreasing the number of degrees of freedom of the body. The present study elaborates on Dempster's theory. The aim of this study was to determine the influence of the degrees of freedom of the body on postural stability in sitting postures. For 21 different sitting postures, the total number of degrees of freedom was determined. Postural sway, a measure for postural stability, was determined using a 3D motion and position measurement system with ten healthy subjects. This study shows that the mean path length at the level of the second thoracic vertebra (PL0.05), a measure derived from postural sway, increases significantly (p < 0.0001) with an increase of the number of degrees of freedom of the body (DoFB). Closer examination of the data showed that a model taking into account only the degrees of freedom of the lumbar and thoracic spine and pelvis seems to be a better predictor of postural sway than the total number of degrees of freedom of the body.

Artificial midline-fascia of the human abdominal wall for testing suture strength

To reduce testing of human abdominal wall closure-modalities in test animals, a fibre reinforced rubber with identical mechanical properties compared to the human midline fascia (linea alba: LA) was developed. The microscopic structure of the human LA, stress-strain behaviour, maximum tensile force and macroscopic failure mechanism in tensile tests with human LA were defined as indicators for the required properties of the fibre reinforced rubber. A composite consisting of latex rubber and cotton fibres was developed that shows mechanical properties comparable to the human abdominal wall. The results of the tensile tests on sutured artificial LA were highly similar to those performed on sutured human LA. The material presented in this study is proposed as a substitute for human and animal tissues presently used to test suture techniques. A protocol for an approach to develop artificial fibrous soft tissue like fascie and tendon was drawn up.

Application of ergonomic guidelines during minimally invasive surgery: a questionnaire survey of 284 surgeons

BACKGROUND

This study aimed to obtain an answer for the question: Are ergonomic guidelines applied in the operating room and what are the consequences?

METHODS

A total of 1,292 questionnaires were sent by email or handed out to surgeons and residents. The subjects worked mainly in Europe, performing laparoscopic and/or thoracoscopic procedures within the digestive, thoracic, urologic, gynecologic, and pediatric disciplines.

RESULTS

In response, 22% of the questionnaires were returned. Overall, the respondents reported discomfort in the neck, shoulders, and back (almost 80%). There was not one specific cause for the physical discomfort. In addition, 89% of the 284 respondents were unaware of ergonomic guidelines, although 100% stated that they find ergonomics important.

CONCLUSIONS

The lack of ergonomic guidelines awareness is a major problem that poses a tough position for ergonomics in the operating room.

Sensitivity for pressure difference on the ischial tuberosity

Although research on sitting and sitting postures has been done for decades, the field of the subjective feeling of comfort or discomfort during sitting is still an unexplored field. On the basis of those studies some manufacturers claim enhanced subjective comfort because of pressure-relieving qualities of the seat cushions. The question is: does a relatively small pressure reduction enhance comfort? Before that question can be answered, the sensitivity for pressure differences applied to the skin must first be determined. The aim of this study was therefore, to determine the sensitivity of the ischial tuberosity for pressure difference in a healthy population. For this study five males and five females aged between 19 and 30 years with no exercise-induced muscle ache were selected. The (Deltaa) was determined for which stimulus (a + Deltaa) was judged as exceeding stimulus (a) in 50% of the trials. This value was called (Deltaa0.5) and was determined with an adapted simple up - down method with forced choice. Two different values for (a) were used: (a) = 13.3 kPa and (a) = 26.5 kPa and the pressure was applied with two different contact surface with diameters of 10 mm and 20 mm. For (a) = 26.5 kPa and d = 10 mm a Deltaa0.5 = 2.7 kPa was found. For (a) = 26.5 kPa and d = 20 mm a Deltaa0.5 = 3.5 kPa was found. For (a) = 13.3 kPa and d = 20 mm a Deltaa0.5 = 1.9 kPa was found.

Improvement of foot pedals used during surgery based on new ergonomic guidelines

BACKGROUND

This study aims to create new ergonomic guidelines for the design of foot pedals used during surgery.

METHODS

Observations in the operating room, a questionnaire among 45 laparoscopic surgeons/residents, an ergonomic literature study, and clog measurements were used to assess the problems occurring during use and to compile new guidelines for foot pedals. Based on these guidelines a new foot pedal was designed and a prototype was manufactured.

RESULTS

During the surgical procedure 91% of the subjects occasionally loses contact with the foot pedal, which 56% experience as very annoying. All subjects think that the current foot pedals obstruct their freedom of movement; 75% occasionally hit the wrong switch and 53% experience physical discomfort in their legs and/or feet. Therefore, 93% of the subjects would like to control the diathermy in a different way. The new prototype of a foot pedal was evaluated in a pilot test and proved to be ergonomically better than the currently used foot pedals.

CONCLUSION

The new guidelines for foot pedals result in an ergonomic improvement in their design.

Ergonomic problems encountered by the medical team related to products used for minimally invasive surgery

BACKGROUND

The aim of this study is to gain insight into the problems encountered by the medical team related to products used for minimally invasive surgery.

METHODS

An inventory was made of the problems encountered during 12 endoscopic operations performed in one city hospital (Eindhoven, the Netherlands). After the observation, a questionnaire was distributed to all medical staff involved.

RESULTS

All categories of personnel had physical, perceptional, and cognitive problems, especially surgeons, residents, and the sterile operation nurse. The main causes were the positioning of apparatus and staff, work clothing, and the limited reach of apparatus and/or instruments. Of the questionnaires, 80% were returned: 50% of the medical staff experienced perceptional problems and 63% had physical discomfort during the surgical procedure.

CONCLUSION

The diversity of problems observed and/or reported by the staff during minimally invasive surgery decrease the comfort, efficiency, and safety of the operating-room work environment. Therefore, a new design approach is needed for MIS products in order to address the problems that occur with the current equipment.

Improvement of the laparoscopic needle holder based on new ergonomic guidelines

BACKGROUND

The aim of this study is to create new ergonomic guidelines for the design of laparoscopic needle holders.

METHODS

An ergonomic literature study, observations in the operating room, handle-shaft angle measurements, and anthropometric data were used to compile new ergonomic criteria, specified to the function of a laparoscopic needle holder. Based on these guidelines a new needle holder was designed. The prototype and three currently available needle holders were evaluated according to the new guidelines. In addition, a pelvi-trainer test was done to measure the extreme wrist excursions.

RESULTS

The ergonomic evaluation of three commonly used handles and the new prototype indicate that the new handle is an ergonomic improvement in the field of laparoscopic needle holders: only the new handle satisfies all criteria. This is validated by the results of the pelvi-trainer test, which showed that the new prototype significantly (p <0.001) reduced the extreme wrist excursions.

CONCLUSION

The new design guidelines for a laparoscopic needle holder result in an ergonomic improvement of the instrument.

Free shoulder space requirements in the design of high backrests

The objective of this study was to determine the influence of scapular support on the effects of lumbar support and to prove that a high and straight backrest is inappropriate. In literature the importance of a lumbar support is noted, although data about optimal dimensions is an under-researched topic and in earlier studies on force distribution and muscle activity the backrest had a fixed form. The lumbar support is needed to maintain the lumbar lordosis but no studies deal with the question of the precise dimensions of the backrest at shoulder level. With a specially designed apparatus, forces on shoulder and seat were measured separately, and the force on the pelvis calculated, while varying seat and backrest inclination within the range from 0 degrees to 17 degrees. Seat-to-backrest angle (at the level of lumbar support) was kept constant at 90 degrees. The distance between the tangent to the lumbar support and the parallel tangent to the scapular support was varied from 0, 2, 4, 6 and 8 cm. This distance is called the free shoulder space. Electromyography was measured at the erector spinae at the levels of the L1, T8 and T5 vertebrae. For all seat angles, a free shoulder space of d=0 cm resulted in the highest back muscle activity. In agreement with the biomechanical model, EMG activity reduced with an increase of seat tilt and increase of free shoulder space. With increasing free shoulder space, a larger part of the total backrest force was carried by the lumbar support. This study shows that a high and straight backrest overrules lumbar support. Offering free shoulder space of at least 6 cm reduces back muscle activity and allows for lumbar support.

Evaluation of the usability of two types of image display systems, during laparoscopy

BACKGROUND

This study was performed to assess the optimal display location of a flat-screen monitor for laparoscopy. It was also performed to assess the posture (objective), opinion, and preference (subjective) of subjects using a flat-screen monitor positioned in the optimal display location and a cathode-ray tube monitor on a tower next to the operating table (current situation).

METHODS

Twelve surgeons performed cholecystectomies using the two display systems alternately. The postures of the operator and the assistant were assessed by an infrared video analysis system.

RESULTS

The posture of the assistant is significantly better when using a flat-screen monitor [more neutral head flexions (p = 0.036) and neutral neck torsions (p = 0.012)]. No significant differences were found for the posture of the operator. The operators and assistants felt more comfortable when using a flat-screen monitor (p = 0.008) and they preferred this display to the use of a monitor on a tower.

CONCLUSIONS

The use of flat-screen monitors is better for the physical and psychological comfort of the users, even though the technical performance is inferior in comparison with that of regular monitors.

Assessment of the ergonomically optimal operating surface height for laparoscopic surgery

PURPOSE

The aim of this study was to find the ergonomically optimal operating surface height for laparoscopic surgery in order to reduce discomfort in the upper extremities of the operators and the assistants. The operating surface height was defined as the level of the abdominal wall of a patient with pneumoperitoneum.

MATERIALS AND METHODS

Two pelvi-trainer tests were performed. One test was performed on six different operating surface heights. The (extreme) joint excursions of the shoulder, elbow, and wrist were measured by a video analysis method. Another test was performed by holding a laparoscope for 15 minutes while an electromyelograph of the biceps brachii was made. The results of both tests were evaluated subjectively by a questionnaire.

RESULTS

The ergonomically optimal operating surface height lies between a factor 0.7 and 0.8 of the elbow height of the operator/assistant. At this height, the joint excursions stay in the neutral zone for more than 90% of the total manipulation time, and the activity of the biceps brachii when holding the laparoscope stays within 15% of the maximum muscle activity.

CONCLUSIONS

The operating surface height influences the (extreme) upper joint excursions of the surgeon. The ergonomically optimal operating surface height reduces the discomfort in the shoulders, back, and wrists of the surgeon during laparoscopic surgery. This optimal table height range for laparoscopic surgery is lower than those currently available.

Improved usability of a new handle design for laparoscopic dissection forceps

BACKGROUND

Recent studies have shown that the shape of most instrument handles causes user discomfort and that none of the handles currently available on the market satisfies all ergonomic criteria. Therefore, we designed a handle with improved usability; i.e., it is easier to manipulate and its use entails less risk of injury for the operator. The aim of this study was to demonstrate that the intended improvements of the new design were successful.

METHODS

Six handles representative of the types that are currently available were compared with the new version. Eight surgeons used the seven handles during a precision task and a rough task in a pelvi-trainer. A questionnaire and video analyses were used to assess the usability of the handles.

RESULTS

Based on the responses to the questionnaire, we determined that there were significant differences between the new handle and the Aesculap handle (means of rotation and angle between handle and shaft). No significant differences were found between the new handle and the five other handles. The video analyses (documenting extreme vs neutral wrist excursions) showed significant differences between the new handle and the six other handles.

CONCLUSION

Compared to the six existing handles, the new handle has significantly improved usability; in particular, its hinged design obviates the need to make extreme wrist excursions.