Tim Drew

Computer-controlled endoscopic performance assessment system

Abstract We have devised an advanced computer-controlled system (ADEPT) for the objective evaluation of endoscopic task performance. The system’s hardware consists of a dual gimbal mechanism that accepts a variety of 5.0-mm standard endoscopic instruments for manipulation in a precisely mapped and enclosed work space. The target object consists of a sprung base plate incorporating various tasks. It is covered by a sprung perforated transparent top plate that has to be moved and held in the correct position by the operator to gain access to the various tasks. Standard video endoscope equipment provides the visual interface between the operator and the target-instrument field. Different target modules can be used, and the level of task difficulty can be adjusted by varying the manipulation, elevation, and azimuth angles. The system’s software is designed to (a) prompt the surgeon with the information necessary to perform the task, (b) collect and collate data on performance during execution of specified tasks, and (c) save the data for future analysis. The system was alpha and beta tested to ensure that all functions operated correctly.

Psychomotor skills for endoscopic manipulations: differing abilities between right and left-handed individuals.

OBJECTIVE The objective of this study was to compare the psychomotor aptitudes relevant to endoscopic manipulations between right-handed and left-handed subjects. SUMMARY BACKGROUND DATA There has been little research on the psychomotor performance in relation to minimal access surgery and there are no psychomotor tests to evaluate aspects of psychomotor abilities relevant to endoscopic manipulations. METHODS A microprocessor-controlled psychomotor tester was developed for objective evaluation of endoscopic performance. The task involved negotiating ten target holes with a probe under videoscopic imaging. Subjects consisted of two groups of 10 medical students: right- and left-handed. After a prestudy familiarization session, each subject performed two test runs with one hand, followed by two runs with the other hand. These test runs were repeated 1 week later. The outcome measures were the total execution time, force on backplate, angular deviations, error rate, and first-time accuracy. RESULTS A significant difference in the error rate and first time accuracy was observed between subjects (p < 0.001 and p < 0.001, respectively) and between the dominant and nondominant hands (p < 0.001 and p < 0.025, respectively), with no significant change with practice. Right-handed subjects performed better with either hand in terms of error rate (p < 0.001) and first time accuracy (p < 0.001). Practice improved the execution time (p < 0.001) and the degree of angular deviations (p < 0.02). CONCLUSIONS Right-handed subjects perform less errors and exhibit better first time accuracy. The parameters that improve with practice reflect the positive effect of training, whereas others, such as errors rate and first time accuracy which do not, reflect innate abilities.

Mechanisms of cervical spine injury in Rugby Union: a systematic review of the literature

Background Severe cervical spine injury in rugby union (rugby) exerts a major impact on the individual who sustains the injury and on the broader society. Since the late 1970s, authors of rugby case report studies have postulated that the underlying mechanism of cervical spine injury is hyperflexion of the neck. However, this is in conflict with findings from more recent experimental studies. These have shown that it is more likely that the majority of cervical spine injuries occur due to buckling of the cervical spinal column. Objective To investigate the primary mechanism of cervical spine injury in rugby. Methods A comprehensive and systematic review of the literature was undertaken. Six key factors were identified and subsequently used to investigate the two principally postulated mechanisms of cervical spine injury: hyperflexion and buckling. Results Facet dislocations, in particular bilateral facet dislocations, were identified as the most common types of cervical spine injury in rugby. Trauma occurred most often at lower cervical spinal levels, notably the C4/5 and C5/6 motion segments. Experimental studies demonstrate that bilateral facet dislocations occurring at the lower cervical spinal levels are primarily produced via buckling. Conclusion Our analysis of key factors for cervical spine injury in rugby shows that it is unlikely that the majority of injuries occur after hyperflexion of the neck. It appears more likely that they are the result of buckling of the cervical spinal column.

Do you get value for money when you buy an expensive pair of running shoes

Objective: This investigation aims to determine if more expensive running shoes provide better cushioning of plantar pressure and are more comfortable than low-cost alternatives from the same brand. Methods: Three pairs of running shoes were purchased from three different manufacturers at three different price ranges: low (£40–45), medium (£60–65) and high (£70–75). Plantar pressure was recorded with the Pedar® in-shoe pressure measurement system. Comfort was assessed with a 100 mm visual analogue scale. A follow-on study was conducted to ascertain if shoe cushioning and comfort were comparable to walking while running on a treadmill. Forty-three and 9 male subjects participated in the main and follow-on studies, respectively. The main outcome measure was the evaluation of plantar pressure and comfort. Results: Plantar pressure measurements were recorded from under the heel, across the forefoot and under the great toe. Differences in plantar pressure were recorded between models and between brands in relation to cost. Shoe performance was comparable between walking and running trials on a treadmill. No significant difference was observed between shoes and test occasions in terms of comfort. Conclusions: Low- and medium-cost running shoes in each of the three brands tested provided the same (if not better) cushioning of plantar pressure as high-cost running shoes. Cushioning was comparable when walking and running on a treadmill. Comfort is a subjective sensation based on individual preferences and was not related to either the distribution of plantar pressure or cost.

A microprocessor-controlled psychomotor tester for minimal access surgery

AbstractBackground: There is little reported information on psychomotor performance in relation to minimal access surgery (MAS). Methods: A microprocessor-controlled endoscopic psychomotor tester (the Dundee Endoscopic Psychomotor Tester—DEPT) has been developed to evaluate psychomotor aspects of MAS. Experiments were conducted on 20 medical undergraduates to evaluate accuracy and reliability of the tester. Results: The study demonstrated a significant difference between subjects (p < 0.01). It also identified three individuals who enacted 16, 22, and 40 errors while the majority (85%) sustained less errors with a median of 4.5. Conclusions: DEPT provides a standard, reproducible, objective real-time scoring system. It identifies individuals who cannot adjust to endoscopic viewing and therefore manipulate from endoscopic images.

Shoes influence lower limb muscle activity and may predispose the wearer to lateral ankle ligament injury

Lateral ankle ligaments are injured by hyperinversion of the foot. Foot position is controlled by the lower limb muscles. Awareness of foot position is impaired by wearing shoes. We aimed to determine the influence of wearing shoes upon muscle activity. Sixty‐two healthy subjects underwent the same measurements, barefoot and with standardized shoes in a random order. Electromyography (EMG) was recorded from the peroneus longus muscle in response to sudden and unanticipated inversion of the ipsilateral foot. Following foot inversion, the EMG signal showed an initial peak muscle contraction followed by a sustained smaller contraction. Both changes were significantly greater in shoes compared to the barefoot condition for all tested degrees of inversion. Muscle contraction following sudden inversion of the foot was significantly greater when wearing shoes. This greater muscular contraction may be an intrinsic mechanism to oppose the increased moment created by the inverted foot/shoe condition, and hence, may counter balance the increased tendency to injure the lateral ankle ligaments created by wearing shoes.

Total radiated power, infrared output, and heat generation by cold light sources at the distal end of endoscopes and fiber optic bundle of light cables.

AbstractBackground: Skin burns and ignition of drapes have been reported with the use of cold light sources. The aim of the study was to document the temperature generated by cold light sources and to correlate this with the total radiated power and infrared output. Methods: The temperature, total radiated power, and infrared output were measured as a function of time at the end of the endoscope (which is inserted into the operative field) and the end of the fiber optic bundle of the light cable (which connects the cable to the light port of the endoscope) using halogen and xenon light sources. Results: The highest temperature recorded at the end of the endoscope was 95°C. The temperature measured at the optical fiber location of the endoscope was higher than at its lens surface (p < 0.0001). At the end of the fiber optic bundle of light cables, the temperature reached 225°C within 15 s. The temperature recorded at the optical fiber location of all endoscopes and light cables studied rose significantly over a period of 10 min to reach its maximum (p < 0.0001) and then leveled off for the duration of the study (30 min). The infrared output accounted only for 10% of the total radiated power. Conclusions: High temperatures are reached by 10 min at the end of fiber optic bundle of light cables and endoscopes with both halogen and xenon light sources. This heat generation is largely due to the radiated power in the visible light spectrum.

Development of force measurement system for clinical use in minimal access surgery

BackgroundAnalysis of force in minimal access surgery (MAS) is important for instrument design, surgical simulators, and in the understanding of tissue trauma incurred during surgery. The aim of this study is to develop a force measuring system for use with different instruments in clinical practice.MethodsStrain gauges were connected to both arms of a standard -5 mm interchangeable forceps handle. A rotational sensor was used to indicate the relative position of the handle arms, and consequently the jaws’ position. A generic force-direction assembly was manufactured to determine the force direction at the port site. Interface electronics included signal conditioning and patient isolation circuits. Dedicated software was used for data acquisition, display, and analysis. To test their performance after sterilization, repeated force measures were obtained with the instruments after 10 cycles of autoclaving. Graduated weights were used to calibrate the strain gauges and a spring balance was employed to calibrate the force applied at the instrument tip. Calibration tests were also carried out to determine the effect of mounting the force direction assembly onto the access port.ResultsGripping, dissecting, pushing, and pulling forces, along with the vector sum of forces acting at the port site, were synchronously displayed with the operative video record. Repeated autoclaving caused no deterioration in force sensing or signal transmission. The accuracy of the strain gauge readings was ±0.05 V for the jaw force and ±0.1 V for the force at the access port. The additional force created by the force direction assembly force was 7% of the port force alone.ConclusionForce measurement system has been developed for clinical use. The system measures the gripping, dissecting, pulling and pushing forces as well as the force vector at port site. It also determines the position of instrument’s jaws.

A new method of fixation in osteoporotic bone: A preliminary report

Over-tightening of cortical bone screws in osteoporotic bone results in weak fixation. Once a screw is over-tightened and the bone thread form is stripped, there are limited means at the surgeons disposal to rescue the situation, none of them entirely satisfactory. We describe a simple device that is specifically designed to resolve this problem. It consists of a nylon cavity plug and applicator. The plug is inserted into the stripped hole and the screw re-applied and tightened in the normal manner. The plug expands and forms a load-bearing region on the inner face of the bone. Tests on osteoporotic cadavaric bone have shown that the plug effectively re-establishes screw fixation. When compared to an over-tightened screw, the plug is at least twice as resistant to loads acting to pull the screw out of the surrounding bone.

Trampoline-related injuries in children: a preliminary biomechanical model of multiple users

Background The recent popularity of domestic trampolines has seen a corresponding increase in injured children. Most injuries happen on the trampoline mat when there are multiple users present. This study sought to examine and simulate the forces and energy transferred to a childs limbs when trampolining with another person of greater mass. Methods The study used a computational biomechanical model. Results The simulation demonstrated that when two masses bounce out of phase on a trampoline, a transfer of kinetic energy from the larger mass to the smaller mass is likely to occur. It predicted that when an 80 kg adult is on a trampoline with a 25 kg child, the energy transfer is equivalent to the child falling 2.8 m onto a solid surface. Additionally, the rate of loading on the childs bones and ligaments is greater than that on the accompanying adult. Conclusions Current guidelines are clear that more than one user on a trampoline at a time is a risk factor for serious injury; however, the majority of injuries happen in this scenario. The model predicted that there are high energy transfers resulting in serious fracture and ligamentous injuries to children and that this could be equated to equivalent fall heights. This provides a clear take-home message, which can be conveyed to parents to reduce the incidence of trampoline-related injuries.