Ahlberg 2007.

Methods	Randomised clinical trial.
Participants	Country: Sweden. Number randomised: 13. Postrandomisation drop‐outs: not stated. Revised sample size: 13. Average age: 32 years. Women: 7 (53.8%). Inclusion criteria: 1. Surgical residents from postgraduate year 1 or 2. 2. Experience in assisting with laparoscopic procedures. Exclusion criteria: 1. Previous experience of performing laparoscopic cholecystectomy.
Interventions	Participants were randomly assigned to two groups. Group 1: virtual reality training (n = 7). Group 2: no supplementary training (n = 6). Details of virtual reality training: 1. LapSim virtual reality simulator (version 2.0). 2. Basic skills (camera navigation, co‐ordination, clip application, lifting and grasping, cutting, and suturing) and dissection programmes (different anatomic variations of the hepatoduodenal ligament) with no haptic feedback. 3. The participants practised under supervision and received feedback given by the simulator as well as oral feedback given by the supervisor after each completed task until they showed proficiency on each of the 6 examination tasks at least twice.
Outcomes	The outcome reported was operating time.
Notes	Assessment: The participants performed 10 laparoscopic cholecystectomies each after the period of training and the outcomes of 10th surgery were considered except for 2 where the outcomes of the 5th surgery were considered. The operating time was 58% longer in the control group than the virtual reality group (P = 0.0586). We attempted to contact authors in October 2012. No replies were received.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Comment: This information was not available.
Allocation concealment (selection bias)	Unclear risk	Quote: "...sealed‐envelope method…." Comment: Further details were not available.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Comment: It is impossible to blind the participants to the groups.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Quote: "...Video assessments were performed by 2 observers...blinded concerning the subjects’ training status…" Comment: Although the video recording of the procedures was assessed by blinded observers, there is no information on whether any of the outcomes of interest for this review were assessed by observers blinded to the group of the participants.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Comment: This information was not available.
Selective reporting (reporting bias)	High risk	Comment: Some important outcomes which will generally be assessed were not reported.
Source of funding bias	Unclear risk	Comment: This information was not available.