Correspondence *Division of Urology, Department of Surgery, McMaster Institute of Urology at St Joseph's Hospital, 50 Charlton Avenue East G343, Hamilton, ON L8N 4A6, Canada

Email matsumo@mcmaster.ca

Introduction

Traditionally, surgeons have been trained through apprenticeship,¹ with the majority of cognitive motor learning initiated and practiced within the clinical setting. Owing to several factors, including time and financial constraints, societal issues and the exponential growth of medical knowledge, this is no longer the ideal environment in which to acquire surgical skills. Many surgical educators have begun to include surgical models within the curriculum. Current research indicates that training on simulators is transferable and might prove to be a crucial supplement to the traditional curriculum. Using models that are reliable and valid, coupled with objective instruments that measure technical skill, these simulators might prove to be useful for training and also evaluation.

Theories of skills acquisition

Competency in surgery requires proficiency in many domains. Technical skill is of paramount importance to surgical competence. Society considers technical proficiency as the most important quality in a surgeon.² Theories of cognitive motor learning include Kopta's theory, Schmidt's schema theory, the traditional apprenticeship model, the cognitive apprenticeship model and Ericsson's rationale for the acquisition of expertise.¹ These five theories of cognitive motor learning are summarized in Box 1.

Kopta's theory involves three phases of acquisition of motor skills.^{1, 3} The cognitive phase involves the student observing new procedures, in addition to reading, listening and asking questions to acquire the intellectual knowledge of the procedure.^{1, 3} Performance of procedures is erratic, because the student must deconstruct a procedure into its component steps. During the integrative phase, the trainee receives feedback while practicing and learns to integrate this knowledge with the appropriate motor responses, resulting in more fluid and graceful movements that are less erratic. In the autonomous phase, continued practice results in efficient performance of the task, without cognitive input.^{1, 3} At this point, the task is performed automatically. The Kopta theory emphasizes the importance of observation followed by practice.

Schmidt's theory involves the acquisition of new motor skills on the basis of previous experiences.^{1, 4} Before the initiation of movement, the student plans the movement by determining the relevant conditions relating to their present environment. The second phase involves the generation of specific muscle commands required to perform the movement. Feedback (including tactile, visual and auditory components) following the movement is the third phase. The final phase is the acquisition of knowledge of the outcome (i.e. success or failure of the movement). The knowledge acquired during the four phases is stored after the task has been performed.^{1, 4} With practice, the relationship between the four constructs strengthens; therefore, both practice and feedback are necessary for the development of a new motor skill according to Schmidt's schema theory.¹

The traditional apprenticeship model is composed of three constructs: observation, coaching and practice.¹ The student observes the mentor repeatedly perform a task and then begins to practice it under the tutelage of the mentor. Once the student becomes comfortable with the procedure, the mentor's role is gradually reduced, providing only hints or feedback.¹ The traditional apprenticeship model demonstrates the importance of the gradual attainment of skills by the student until he or she can perform the entire procedure unaided.

The cognitive apprenticeship model is derived from the traditional apprenticeship model; however, the traditional model teaches skills in the context of their use, whereas the cognitive apprenticeship model decontextualizes the knowledge so that a student can apply their new skills in different settings.^{1, 5} The cognitive apprenticeship model has three components performed by the mentor (modeling, coaching and scaffolding) and three components performed by the student (articulating, reflecting and exploring).^{1, 5} Modeling involves the mentor explaining the process so that the knowledge is externalized and stated explicitly. The trainee begins performing the task with the mentor coaching by providing feedback and suggestions to improve the student's performance. The student's goal is to approximate the performance of the expert. Thus, the mentor provides scaffolding or support for the gradual acquisition of independent performance. As the trainee's performance improves, the mentor's role is gradually withdrawn. Eventually, the student's knowledge increases to a point at which they can synthesize the information and articulate it or problem-solve.

Reflection involves the student comparing their own problem-solving ability with an expert's or another student's. This process is improved by reproduction of the performance; for example, by video recording the student carrying out a procedure so that they can review their performance to see what they did well and what mistakes they made. Exploration occurs when the trainee formulates and tests new hypotheses and eventually advances the overall body of knowledge.^{1, 5}

These models of cognitive motor learning emphasize the early stages of learning. Ericsson's model of the acquisition of expertise emphasizes the importance of focused attention and deliberate practice in acquiring expert skill.^{1, 6} Ericsson found that time of day was an important factor in success, with the morning being the best time to practice because this was when the ability to perform complex cognitive activities was the highest.^{1, 6} Furthermore, Ericsson identified the importance of rest. It seems that more than 4 hours of practice per day causes fatigue, with a resultant decrease in the quality of the student's performance.^{1, 6} These two points could prove to be important for planning a surgical trainee's practice regimen.

Changing paradigms

Since Sir William Halsted introduced the German residency training system to North America in the late 1800s, it has been the basis of most surgical training programs, with an emphasis on graded responsibility.^{1, 7} This philosophy of education, however, might no longer be optimal. Educators are re-evaluating the methods of training surgeons because of several factors, including time and financial constraints owing to the increasing demands on health systems, societal issues and the exponential growth of medical knowledge that is bringing about the development of more complex procedures and the introduction of new technologies.⁸

The additional time required to train a student in the operating room creates additional demands on a health care system that has significant pre-existing fiscal and resource constraints. There is less time for the surgeon to teach and, thus, less opportunity for the student to learn and practice. One study estimated the cost of lost time during operations in which a surgical resident assisted amounted to US$47,970 over the 4 years of a surgical residency.⁹

Patients who require more complex surgery are increasingly being referred to academic hospitals, requiring the medical staff's full attention.^{2, 10} Clinical care is becoming increasingly outcome-based and patients are better informed with regard to their medical conditions because of wider access to information. Medical errors are highly scrutinized and often reported in both the medical literature and the general media.^{8, 11, 12} Society no longer accepts morbidity that is associated with trainee error. It sometimes seems that there is a developing culture of blame, with increasing numbers of legal claims being made by patients dissatisfied with their treatment.

The exponential growth of medical knowledge has also affected surgical training. Advancement of medical knowledge includes the development of new surgical techniques. Many procedures are becoming less invasive but are difficult to learn, requiring more experience to master them. Specific to such minimally invasive techniques as laparoscopy, surgical trainees must learn new procedures without the added advantage of three-dimensional vision or tactile feedback. These two senses are heavily relied on in the acquisition of new motor skills. In addition, the recent reduction of the working week to 80 h for surgical residents in the US might result in insufficient time to provide adequate exposure to certain procedures. In response, educators have increased the length of certain residency programs and developed a number of subspecialties that require further fellowship training.

Simulators and model fidelity

Many educators have incorporated the use of simulators to combat some of the issues associated with surgical training. Although many believe surgical expertise is a reflection of an individual's intrinsic ability, empiric research has confirmed the importance of repeating tasks so that they become familiar and, once proficient in a particular technique, enable an individual to maintain a high level of skill.^{13, 14} Simulators are instruments that reproduce, under artificial conditions, components of surgical tasks that are likely to occur under normal circumstances.¹⁵ Airline pilots have been trained by simulation for years.¹⁶

The types of models include cadaver, animal, bench and computer software-based simulators. Each modality of a simulator has its advantages and limitations. Cadaver models provide a true anatomic representation, but the tissue quality might not be as realistic as living tissue. In addition, cadaver training is expensive and provides only a one-time use for a specific surgical procedure, and there is a limited supply of cadavers for a growing number of medical students. Live animals provide a model with appropriate tissue texture; however, housing and care costs are significant and animals provide only a one-time use, with anatomy that is not entirely representative of their human counterparts. Such procedures are also governed by various animal welfare laws, depending on the country the procedures are taking place in, which can add to costs. Additionally, the use of both human cadavers and live animals raises ethical issues. More recently, the possibility of contamination by bovine encephalopathy (so called 'mad cow' disease) has become a concern.¹⁷ Subsequently, many educators are beginning to rely more heavily on bench or dry laboratory models and computer software-based simulators.

Bench models sacrifice fidelity for safety, availability, portability and reduced cost, overall.^{1, 18} With the advances in material technology and computer hardware and software, simulators have become more advanced, with higher fidelity and more capacity for assessment and feedback. Examples of commercially available surgical simulators are summarized in Table 1. Many of these simulators have yet to undergo vigorous validity testing. Fidelity of a model refers to how realistic it is.⁸ A simulator does not need to look realistic as long as the pertinent steps of the procedures are performed.⁸ That is, a low-fidelity simulator can provide the same benefit as a high-fidelity model. The three factors that are important in the fidelity of bench models are visual representation, tissue texture and 'surgical task constructs'.⁸ Surgical task constructs are the crucial steps of the procedure that must be represented in the model. Matsumoto et al.¹⁹ randomized 40 senior medical students to a low-fidelity bench model, high-fidelity model or didactic training group to assess midureteral stone extraction. The low-fidelity model consisted of a polystyrene cup, plastic straws and a Penrose drain to represent the bladder, ureters and urethra, respectively. The high-fidelity model consisted of a video endoscopy-based system. Final evaluation was performed on the high-fidelity model and assessed by checklist, global rating score, pass rating and time. Both groups who received training on a model performed better than students who only received didactic lessons; however, there was no difference between the low- and high-fidelity model groups. The effectiveness of a model is, therefore, not necessarily dependent on its fidelity.

Table 1 Commercially available surgical models.

Full tableFigures & Tables indexDownload Power Point slide (259K)

Despite low-fidelity models having similar usefulness to high-fidelity models, many students are skeptical of their value and have considerably less enthusiasm for training on a low-fidelity than a high-fidelity model.¹⁸ A model of surgical skills is of limited use if the intended users do not accept it. In a study performed by Grober et al.¹⁸ using models of varying fidelity, the students preferred the educational merits of the high-fidelity model. The researchers speculated that the junior residents had a strong desire to participate in live surgery in which they could manipulate functioning tissues, and did not completely appreciate the simpler models. Despite many trainees preferring models of higher fidelity, however, these simulators are often more expensive than low-fidelity models and, therefore, not necessarily affordable for many institutions. Further research is needed to determine the optimal roles that both low- and high-fidelity models should have in a surgical curriculum in general, in addition to the most cost-efficient models for institutions that have tight financial constraints.

The uses of these different models should complement each other. One possible solution would require junior residents to use low-fidelity models to gain exposure to the crucial steps of the procedure until they achieve a certain level of proficiency. The student would then graduate to training on the high-fidelity model.¹⁸ Surgical educators at McGill University, Montréal, Canada have adopted such a strategy, whereby residents must demonstrate competency on low-fidelity models before advancing to high-fidelity models.^{13, 20} For centers that do not have access to high-fidelity simulators, the trainee would advance directly to patient care after attaining the required level of proficiency on low-fidelity models.

Transferability of skills from models

Transferability involves knowledge and skills learned in one context being applied effectively in another setting.¹³ The most important outcome of simulators is the ability for skills learned on a model to be translated into improved performance in the clinical setting. Transferability of skill sets learned on low-fidelity models to both high-fidelity models and use in real patients has been evaluated by various authors.

Anastakis et al.¹⁰ demonstrated that surgical skills learned on bench models were transferred appropriately to human cadavers. Junior residents were divided into three groups. One group received a text on the steps of the procedure, the second group received instruction on a bench model and the third group received training on cadavers. Following training, all subjects were evaluated for their performance of the procedure on a cadaver. The residents in the bench model and cadaver groups did better than those who learned from a text; however, there was no difference between the bench model and the cadaver groups.

Grober et al.¹⁸ examined the effect of different instructional modalities in urologic microsurgery and transferability to an animal model for performance of a vasovasostomy. The authors randomly allocated junior surgical residents into three training groups: high-fidelity, low-fidelity and didactic. The high-fidelity model was an in vivo rat vas deferens and the low-fidelity model consisted of silicon tubing.¹⁸ The subjects were evaluated using checklists, expert ratings, procedure time, hand-motion analysis, patency of the anastomosis and presence of sperm on microscopy. The groups who received training on a model had improved delayed anastomotic patency rates compared with those who only received didactic instruction. At 1 month after the procedures, there were higher rates of sperm on microscopy in the high-fidelity model group compared with the didactic group. There was no difference between the high- and low-fidelity groups with respect to sperm on microscopy.¹⁸

Fried et al.²¹ randomly allocated general surgery residents into either a group that received laparoscopic simulator training or the control group. Assessment of improvement was made using both a simulator and a porcine model. It was reported that those who received laparoscopic simulator training had improved performance from baseline in five of the seven basic laparoscopic skills tested compared with improvement in only one of the tasks in the control group.

Few studies have assessed the direct transferability of skills learned on a model to the clinical setting. Naik et al.²² demonstrated that a simple wooden model was useful for learning and practicing fiberoptic orotracheal intubation, and that these skills were transferable to the operating theatre environment. Twenty-four residents in internal medicine and anesthesia who had not performed fiberoptic intubation were randomly allocated to use either the bench model or didactic instruction for learning. Residents were evaluated performing the procedure on a live patient and measured by a number of parameters, including the global rating scale. The global rating scale was the score given by the anesthesiologist on a text-anchored scale of 1–5 for the participant's ability to handle the instrument.²² Success was defined as the ability of the participant to properly place an endotracheal tube in a live, anesthetized human patient with fiberoptic assistance in the allotted time of 210 seconds.²² The bench model group did better than the control group during the final assessment, as measured by the time required to complete the task, checklists, global rating scale and overall success.

Scott et al.²³ found that laparoscopic simulator training improved performance on laparoscopic maneuvers during laparoscopic cholecystectomy. Seymour et al.²⁴ studied learning transfer from a high-fidelity simulator to the clinical setting. The authors reported that residents who trained with a laparoscopic virtual reality simulator, in addition to the standard programmatic training, were quicker and less likely to injure the gallbladder, burn nontarget tissue and fail to progress during laparoscopic cholecystectomy compared with controls who had only received the standard programmatic training.

Surgical models are becoming an important component of a surgical trainee's curriculum; however, simulators, regardless of the degree of fidelity, will only function as an adjunct to, not a replacement for, traditional teaching in the clinical setting. There is no substitute for the skills and experience gained by a trainee while under the close supervision of a mentor.

Assessment of surgical skills

Assessment of a surgical trainee throughout their training is important. Identifying a student's strengths and weaknesses enables specific remediation, if necessary, at appropriate points in the training. There are several components to a good assessment instrument.

Reliability measures the reproducibility or precision of the test or testing device.¹⁷ The reliability of a test can be assessed in different manners, including the test–retest method, the split-half reliability of a test and determination of the internal consistency of the test using Cronbach's coefficient.^{1, 17} The test–retest method requires the test to be administered on two separate occasions.¹ The split-half reliability method compares the performance of a participant on half of the examination with their performance on the other half.¹ Cronbach's coefficient is a more sophisticated statistical method of determining internal consistency that is similar to correlating all possible 'split-halves'.¹ Validity assesses whether the model truly teaches what it is intended to teach.¹⁷ A model can be assessed for validity in many ways, including content, face, criterion and construct validities. A model with high predictive validity can also be used as an assessment tool for determining whether the trainee is ready to perform such a task in the operating room.¹⁷ In addition to reliability and validity, the ideal assessment instrument should possess feasibility, comprehensiveness, flexibility, timeliness, accountability and relevance to the examiner and candidate.¹

The performance of a task can be assessed in many ways. Time to complete a procedure is one potential end point; however, many important elements of a good surgeon would not be fully evaluated and incorporated into a time score. Perhaps more importantly, students might not perform or be aware of all the necessary steps, which would lead to a better time score but an incorrectly performed procedure.⁸ Two other forms of assessment are checklists and global ratings. Checklists itemize the important steps of a procedure, whereas global ratings evaluate the overall process of the surgical task; both checklists and global rating scales correlate with potential outcomes of the procedure.⁸ With the combined use of checklists and global ratings, it is possible to assess the acquisition of new surgical skills adequately.^{8, 25, 26}

Instruments, including logbooks and observation with and without criteria, have been used to evaluate surgical proficiency.^{2, 27} The recording of procedures in a logbook does not ensure that the tasks were performed well and, therefore, lacks validity.² Observation without criteria has low interobserver and intraobserver reliability;² however, it does represent a better method of evaluation than logbooks.¹ Observation with criteria has the best validity of these three modalities and high interobserver reliability.^{2, 10, 25, 27} Various studies have demonstrated that direct observation with criteria has validity and reliability similar to an objective structured clinical examination (OSCE).¹ An OSCE is a multi-station clinical examination that is used by many medical schools and board certification authorities as an assessment of knowledge and performance.¹

In the future, a simulator might potentially be used as an assessment tool in a high-stakes examination. Although practicing as a surgeon requires knowledge, decision-making and technical skill, formal evaluations for licensure only assess the cognitive aspects of surgery. Most licensing authorities have implemented an OSCE as a mandatory component of evaluation, to demonstrate fitness to practice independently. It is possible that a high-fidelity simulator might become a component of a high-stakes assessment, requiring the implementation of an objective structured assessment of technical standard examination. This examination measures operative performance. It is derived from the OSCE format and utilizes both checklist and global rating scores to measure performance.^{10, 17, 25, 26, 28} It is a reliable and valid measure of technical skill.^{1, 25, 28}

Guillonneau²⁹ does not support tests that assess surgical skills. He states that "surgical skill tests are problematic because they open the door to a use that will escape us, sooner or later." His concern is that if such an 'objective' evaluation is implemented, other institutions and authorities will eventually evaluate surgeons, rather than their peers (i.e. experienced surgeons). He also states that technical skill is not the goal in surgery but the minimum requirement. This is true; however, the current examinations that a trainee must successfully complete to demonstrate fitness for independent practice are not measures of excellence but measures of competence. It seems appropriate to include a measure of technical skill because this, in addition to knowledge and decision-making, is required to function as a urologist.

Another issue with the inclusion of technical skills assessment in a high-stakes examination, such as a licensing or board certification examination, is the type of skill that is to be assessed. Should a high-stakes assessment evaluate basic skills, such as laparoscopic suturing, or the ability to perform a complete procedure, such as a laparoscopic nephrectomy? At present, there is no model available that can simulate an entire complex urologic procedure, such as laparoscopic pyeloplasty, and many simulators for a variety of 'mini-procedures' would be necessary to simulate different components of a complete surgery. For a specific model to be implemented in the licensing process, validation studies are required to confirm the appropriateness of a model for testing and certifying. Currently, the use of simulators as tools for the assessment of competence in a high-stakes evaluation is controversial.¹⁷

Conclusions

It is crucial that as the practice of surgery evolves, the modalities by which future surgeons are trained also develop. The era of training by apprenticeship only is over. During this period of limited time and resources, a multimodality philosophy towards surgical education should be embraced; however, simulators should function as an adjunct to, and not a replacement for, traditional teaching in the operating room. Haluck and Krummel³⁰ state that simulators improve surgical education by providing efficient training outside the operating room, in addition to increasing the efficiency of training within the operating room. The process of cognitive motor learning for surgical skill might be not only enhanced by simulation, but also evaluated by a simulator. Future use of simulators could include their incorporation into a high-stakes assessment, but this is controversial.

At present, there is no model available to simulate an entire complex urologic procedure that is appropriate for inclusion in a licensing examination. As material and software technology advances, this issue will probably be addressed. It seems appropriate to include a measure of technical skill because this, in addition to knowledge and decision-making, is required to function as a urologist. It is probable that this will be implemented in the future. More research is needed regarding the validity and transferability of various training models, particularly if they are to become a form of assessment for certification or licensure.

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