Participants are medical students recruited through advertisements on websites at three student associations (Young Surgeons, Young Anesthesiologist, and the General Student newspaper) at the Copenhagen University Medical School, Copenhagen, Denmark. All volunteers are then invited to an obligatory introduction meeting in order to qualify for the trial.Inclusion criteria are: 1) Medical bachelor degree (completion of the first 3 years out of six at University of Copenhagen Medical School). 2) Informed consent before enrollment. Exclusion criteria are: 1) having conducted more than 3 independent laparoscopic procedures. 2) Prior experience with VR simulation. 3) Not fluent in the Danish language.
The VR simulator task and equipment
The VR simulator used is a LapSim®, version 2010, produced by Surgical Science, Sweden. Monitor: Dell 22", Simball™ 4D Joystick by G-coder Systems AB with a double footswitch.
All participants will be instructed in the operational technique and use of the VR simulator. The procedure specific VR task is a right-side laparoscopic salpingectomy due to an ectopic pregnancy. At the end of each completed task, the VR simulator sums up a weighted total score based on the values of 11 variables, which reflect time spent and quality of performance and presents an automated feedback on each variable, Table . This is available for all participants.
The 11 variables that generate the automated feedback on the VR simulator
The training sessions are repeated until the predefined proficiency level, referred to as the 'expert level', has been reached twice within five consecutive repetitions. The instructor observes correct use of instruments and operation technique. The predefined proficiency level was set and validated in a previous study by the same research group [15
], and it has shown to improve surgical skills, such as time and precision, in the operation room [4
The experimental intervention group and the control group
The experimental intervention group has the option of receiving three feedback sessions from an instructor. The instructor feedback consists of 10 to 12 min of standardized assessment of an operation on the VR simulator and assessment of the automated feedback produced by the VR simulator. The first feedback is given following the first operation on the VR simulator. The participants decide when they want the optional second and third feedback session. One instructor (the main author) provides the feedback in order to ensure consistency and uses the same template for every participant.
The control group only receives the automated feedback produced by the VR simulator.
Both groups are asked to complete a questionnaire before and after the trial pertaining to perception of own surgical skills, satisfaction with VR training, and carrier choice.
Primary outcome measures are number of repetitions to reach 'expert level' and total time (min) used to reach 'expert level'.
The secondary outcome measure is the weighted total score obtained when 'expert level' is reached which is based on the above mentioned 11 variables, Table .
Post hoc analyses will focus on results from the questionnaire reflecting the student's self-perception and the effect of sex and computer gaming skills.
The trial fully complies with the Helsinki Declaration on biomedical research. The Danish National Committee on Biomedical Research Ethics evaluated and approved the trial (journal number: H-3-2010-082). The Danish Data Protection Agency approved collection, analysis and storage of data, approval code 2007-58-0015/30-0996.
All participants are provided with written information on the trial. Participation is voluntary; no material goods are given to participants. The trial is registered at clinicaltrials.gov with trial registration number: NCT01497782.
Randomization and participation
The central computerized randomization is performed by the Copenhagen Trial Unit. The randomization procedure is concealed and executed by using the participants' unique Central Personal Register number. The trial follows the CONSORT Statement for randomized trials, Figure . Stratification variables are sex and computer gaming experience (less than or equal to or more than 20 h annually).
Enrollment of participants according to the COSORT Statement.
Once the participants are randomized, they can book a VR training time in an online schedule created for the purpose. All participants are given instructions on how to use the VR simulator, e.g., how to enter and exit the task, instrument use, and diathermy use. This is ensured by one of the main investigators (JO and FB). Only these two persons will be in contact with the participants.
Each training session lasts approximately 3 h, and only one training session per day is allowed. The participants have to complete the trial within an 8-week period.
Every time the participants work with the VR simulator, the details and scores for each repetition are electronically recorded. The data will be entered in a secure database by an independent observer. One of the two main investigators is present at all training sessions in the skills laboratory at Rigshospitalet, University Hospital of Copenhagen where the simulator is located.
Sample size calculation and statistical analysis
Based on data in a previous study [15
], we assume that participants in the intervention group and in the control group on the average will use 25 and 40 repetitions, respectively, to reach 'expert level'. With alpha set at 0.05 and beta set at 0.80, the sample size adds up to 98 participants in the trial.
The data will be analyzed using SPSS (Chicago, IL) version 15.0 and the SAS version 9.1. Two sided significance tests will be used.
Analysis of the first experiment, i.e. instructor feedback approach vs. an independent approach: The distributions of each outcome measure will be compared between the intervention group and the control group using the general linear uni-variate model and the analyses repeated with the co-variate semester number and the two protocol specified co-factors (indicator of sex, and indicator of computer game experience) included. A post hoc analysis including sex, the intervention indicator(I) and the interaction between I and sex will be conducted to explore the role of the sex.
If the assumptions of the general linear model (normally distributed residuals and variance homogenecity of the groups compared) cannot be fulfilled using simple transformations of the data, the distributions of the intervention group and the control group will be compared using a non-parametric test (Mann-Whitney) as will the two distributions of the results of the questionnaire reflecting the students self-perception at the end of the trial.
To adjust the P values for multiplicity Holm's procedure will be used [16
All of the above analyses will be complete case analyses. If a significant effect of the intervention after adjustment for multiplicity is noted three sensitivity analyses will be carried out where increasing degree of bias will be artificially induced by replacing missing values by constructed ones reflecting the degree of scepticism of the observed effect as follows.
Worst case scenario
Missing values will be replaced by the most pessimistic value in the opposite group. For time spent e.g. missing values in the group where the best effect was found will be imputed by the maximum value found in the other group and missing values in that group will be imputed by the minimum value found in the first group.
Missing values will be imputed by most pessimistic value in the group to which it belongs.
Missing values will be imputed by mean value found during the complete case analysis of the group to which the missing value did not belong.
Analysis of the second experiment, i.e. the retention of skills
To analyze the data collected during the second experiment comprising time spent and number of repetitions used to reach the expert level by those persons who completed the first experiment the mixed model with repeated measures will be used. An unstructured co-variance matrix will be used. If convergence fails, a choice will be made between the compound symmetric (cs) and the cs plus a random intercept using Akaike's criterion. The basic model will be as follows:
Where I is the indicator of intervention, t is time (time1 and time2 corresponding to experiments 1 and 2 respectively) and a through d are coefficients of the regression equation.
A significant main effect of time indicates that in general retention is present and a significant interaction between I and t indicates that the magnitude of the retention depends on the intervention. The analysis will be repeated with the semester # and the protocol specified stratification variables included as co-variates.
If a significant result is obtained it will be tested in a post hoc analysis if the retention depended on the students' sex or computer game experience (one factor at a time will be included in the model and the possible interactions involving the intervention and time analyzed).
Missing values Using the mixed model with repeated measures secures that all observed values are used and that no bias will be present as long as values are missing at random.
To examine the potential effect of bias resulting from values missing not at random a worst case but still not completely implausible scenario is defined as one where each value missing in the second experiment is identical with the corresponding value obtained during the first experiment. The missing values will be imputed accordingly and the analysis then repeated.