time, number of movements and total path length [197]. Construct validity for MIS was shown in [198] using vascular anastomosis as a complex task. This study compares the ICSAD measures to subjective measures: size, angle, spacing between sutures, suture depth, damage to tissue, and leaks. The results showed that improvements in the measures were observable as the trainees gained experience and differences were found between novices and experts.
The ICSAD system was used in [199] to investigate whether there is a correlation between visual–spatial abilities, manual dexterity and surgical ability. Surgical performance was assessed with the ICSAD system and the OSATS method. Visual and manual dexterity were assessed using other validated methods (Mental Rotations Test, Surface Development Test, Gestalt Completion Test, Phase Discrimination Test, and Crawford Small Parts Dexterity Test). Some correlation was found with spatial ability and surgical ability in novices, while some correlations were found between manual dexterity and efficiency of hand motion.
The limitations of the ICSAD system are that it can only evaluate the performance that can be related to motion and time and that large external markers need to be worn by the trainee [200]. However, a significant advantage of ICSAD is that it can be used in any training environment, including in simulators, as presented in the following sections.
7.2
Simulator-based Training
A simulator entails some sort of model that allows a trainee to practice specific tasks related to the surgical procedures that are being learned. Simulator-based training has been proposed as a means of developing surgical skills in MIS, as the type of skills that need to be learned for MIS are easily trained with simulators [167]. The fidelity of the simulator model may vary significantly, as well as the tasks that are performed. Regardless of the complexity of the system, for a simulator to be effective, it needs to be part of a curriculum and follow a competency-based program, as opposed to just providing performance metrics [167]. Research that aims to evaluate the importance of high- versus low-fidelity simulators will be needed to fully exploit the potential of simulators as an educational tool [201].
There are three different types of simulators [176]: training boxes or physical simulators, virtual reality simulators and augmented reality or hybrid simulators. The following sections present the different types of simulators in more detail.
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7.2.1 Physical Simulators
Physical simulators are described as real objects that mimic to some extent the conditions present in surgery. For MIS, physical simulators often involve a training box that mimics the patient’s body, while the instruments enter through small openings. The MISTELS program described above is performed inside a physical simulator [193]. Other examples include the Simulab™ LapTrainer [170, 202], the LaproTrain™[203], and the i-Sim [204].
These simulators have the advantage of being low cost, portable, adaptable, and simple [170]. Their low cost means that they are more available to schools [165]. However, the most important advantage over virtual reality simulators is that, because real instruments are used in contact with real objects, realistic haptic feedback is provided to the trainee [205]. The main limitation of physical simulators is that they do not provide a measure of performance other than task completion time. Performance evaluation has to be done using GOALS, ICSAD or the FLS evaluation for the MISTELS tasks. Some researchers indicate that only those simulators that provide an objective measure of performance (other than time) can improve training and provide an adequate measure of skill [176].
7.2.2 Virtual Reality Simulators
VR simulators are those in which a computer program is used to create a model of the surgical environment and the instruments. These types of simulators address the problem of lack of feedback by computing performance metrics based on the movement of the instruments and/or of the trainee’s hands and their interactions with the virtual environment [191]. The interface usually allows a specific training schedule to be followed by the trainee and their progress over time can be measured and tracked. However, these simulators are usually costly and they lack realistic haptic feedback.
Although some studies indicate that a large number of injuries result from poor haptic feed- back [185], there is no consensus regarding the importance of haptics when performing surgery. Nevertheless, research has shown that haptics in VR training is important [176], especially during early basic skills training [5]. During MIS a distorted sense of haptic sensation is still present, as opposed to the complete loss of haptic feedback that results from robotic surgery; therefore VR trainers without haptics should only be used to learn hand–eye coordination [5].
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Significant research has been directed towards the development of VR simulators with haptic feedback. For example, a system developed at the University of Washington to simulate a suturing task uses the SensAble PHANToM® haptic interfaces with needle drivers attached to the end- effector [190]. However, VR simulators with some form of haptic feedback are not very realistic [167] and they are very costly [172].
7.2.3 Hybrid Simulators
In some applications, both physical and VR simulators have been shown to be equally effective for the development of basic MIS skills. VR trainers have the advantage of providing objective performance measures, while physical simulators provide accurate haptic feedback; however, nei- ther of them is ideal. Augmented Reality (AR) or hybrid simulators can provide the best of both worlds [167]. They combine real environments with realistic haptic feedback and software pro- grams that are able to enhance the surgical view, track instrument motion, provide performance metrics and track trainee progress. An example of an AR simulator is the ProMIS™ system, a hybrid simulator in which real instruments can be used, while the system tracks instrument tip motion to provide a measure of performance [206].
7.2.4 Robotic Surgery Simulators
As the skills required for laparoscopic surgery and robotic surgery are different, it is necessary to train and assess the skills in simulators that are appropriately designed for the type of procedure [161]. The dV-Trainer™ by Mimic Technologies [207] is a VR simulator that was designed for training in the use of the da Vinci surgical system. Ongoing work at CSTAR is currently focused on assessing the transferability of the skills learned on the Mimic system to the da Vinci using a Mastery Learning approach to training. Similarly, [177] presents the use of SimSurgery®, a 2D virtual reality simulator for the da Vinci with no haptic feedback.
AR simulators that allow the use of any real instrument can also serve as trainers for robotic surgical systems. For example, the da Vinci system was used with the ProMIS system mentioned above in [208]. The results showed construct validity for the use of the ProMIS measures as a means of measuring robotic performance.