Supplementary Material 2. Assessment of Risk of Bias

Supplementary material 2. Assessment of risk of bias

A. Linear instruments

Abd Ellatif 2013

Bias / Authors' judgement / Support for judgement
Random sequence generation (selection bias) / Low risk / "Patients were randomized to receive SALC or CLC using sealed envelopes. Randomization was achieved using a computer-generated schedule."
Allocation concealment (selection bias) / Low risk / "...the results were sealed into envelopes (either SALC or CLC groups). An envelope was fetched and opened in the operating room by an operating room nurse not otherwise engaged in the study."
Blinding of participants and personnel (performance bias) / Low risk / "Patients and the surgical and nursing team that provided postoperative care were blinded as to the type of procedure a patient underwent by placing four strips at the umbilicus, subxiphoid, right hypochondrial, and right lumber areas, whether it was SALC or CLC, and they were kept in place till the first visit."
Blinding of outcome assessment (detection bias) / Low risk / "Patients and the surgical and nursing team that provided postoperative care were blinded as to the type of procedure a patient underwent by placing four strips at the umbilicus, subxiphoid, right hypochondrial, and right lumber areas, whether it was SALC or CLC, and they were kept in place till the first visit."
Incomplete outcome data (attrition bias) / Low risk / No such evidence.
Selective reporting (reporting bias) / Low risk / No such evidence.
Other bias / Unclear risk / Source of funding was not reported.

Borle 2014

Brown 2013

Bias / Authors' judgement / Support for judgement
Random sequence generation (selection bias) / Unclear risk / Insufficient information to permit judgement.
Allocation concealment (selection bias) / Low risk / "Patients were randomized after induction of anesthesia."
Blinding of participants and personnel (performance bias) / Low risk / "Steri-strips and bandages were placed on all patients at the umbilicus, epigastrium, and right upper quadrant at the usual trocar sites of traditional four-port laparoscopic cholecystectomy. Patients were instructed to remove their bandages after 48 h, at which point they were unblinded to which procedure they had."
Blinding of outcome assessment (detection bias) / Unclear risk / Insufficient information to permit judgement.
Incomplete outcome data (attrition bias) / Low risk / No such evidence.
Selective reporting (reporting bias) / Low risk / No such evidence.
Other bias / High risk / Industry-funded trial and present conflicts of interest.

Justo-Janeiro 2014

Bias / Authors' judgement / Support for judgement
Random sequence generation (selection bias) / Low risk / "Patients were prospectively randomized to each group by simple card draw from a box with sealed envelopes at the moment the surgical procedure was scheduled."
Allocation concealment (selection bias) / Low risk / "Patients were prospectively randomized to each group by simple card draw from a box with sealed envelopes at the moment the surgical procedure was scheduled."
Blinding of participants and personnel (performance bias) / Unclear risk / Insufficient information to permit judgement.
Blinding of outcome assessment (detection bias) / Low risk / "…the observer was blinded to the LC type."
Incomplete outcome data (attrition bias) / High risk / Three enrolled patients were excluded from the analysis.
Selective reporting (reporting bias) / Low risk / No such evidence.
Other bias / Unclear risk / Source of funding was not reported.

Khorgami 2013

Bias / Authors' judgement / Support for judgement
Random sequence generation (selection bias) / Low risk / "...were equally randomized ... by using a central randomization process based on a computer-generated list coordinated by an independent statistician who was not otherwise involved in the study."
Allocation concealment (selection bias) / Unclear risk / Insufficient information to permit judgement.
Blinding of participants and personnel (performance bias) / Low risk / "In all groups, four dressings were placed over the usual sites for 4PLC to blind both the patients and nurses responsible for the pain score evaluation and the data gathering to the type of procedure used until the postoperative visit during the first week."
Blinding of outcome assessment (detection bias) / Low risk / "In all groups, four dressings were placed over the usual sites for 4PLC to blind both the patients and nurses responsible for the pain score evaluation and the data gathering to the type of procedure used until the postoperative visit during the first week."
Incomplete outcome data (attrition bias) / Low risk / No such evidence.
Selective reporting (reporting bias) / Low risk / No such evidence.
Other bias / Unclear risk / Source of funding was not reported.

Lai 2011

Bias / Authors' judgement / Support for judgement
Random sequence generation (selection bias) / Low risk / "Eligible patients were randomized in 1 of 2 groups (SILC group and conventional 4-port LC) using sealed opaque envelopes containing computer-generated random numbers."
Allocation concealment (selection bias) / High risk / "The randomization was performed 1 week before surgery during a preoperative assessment in a surgical day ward."
Blinding of participants and personnel (performance bias) / Unclear risk / Insufficient information to permit judgement.
Blinding of outcome assessment (detection bias) / Unclear risk / Insufficient information to permit judgement.
Incomplete outcome data (attrition bias) / Low risk / No such evidence.
Selective reporting (reporting bias) / Low risk / No such evidence.
Other bias / Unclear risk / Conflicts of interest were not disclosed.

Pan 2013

Bias / Authors' judgement / Support for judgement
Random sequence generation (selection bias) / Low risk / "Eligible patients were randomized into two groups (SILC and TPLC) using sealed opaque envelopes which contained a computer-generated random number."
Allocation concealment (selection bias) / Unclear risk / Insufficient information to permit judgement.
Blinding of participants and personnel (performance bias) / Unclear risk / Insufficient information to permit judgement.
Blinding of outcome assessment (detection bias) / Unclear risk / Insufficient information to permit judgement.
Incomplete outcome data (attrition bias) / Low risk / No such evidence.
Selective reporting (reporting bias) / Low risk / No such evidence.
Other bias / Unclear risk / Conflicts of interest and source of funding were not reported.

Saad 2013

Bias / Authors' judgement / Support for judgement
Random sequence generation (selection bias) / Low risk / "A sequence with block sizes of three and six in random order was generated by computer (
Allocation concealment (selection bias) / Low risk / "Patients were randomized to CL, ML or SP cholecystectomy by drawing sequentially numbered, opaque, sealed envelopes that had been prepared earlier by a third party. Envelopes were opened by a surgical investigator on the evening before the day of operation. Operating room staff were informed of the planned procedure 1 h before the start of surgery."
Blinding of participants and personnel (performance bias) / Low risk / "After completion of cholecystectomy, all patients received non-transparent waterproof dressings at four sites on the abdomen, reflecting the incisions necessary for CL cholecystectomy...This blinding was preserved until the morning of the third day after surgery. Change of dressings during the blinded period was not necessary in any patient."
Blinding of outcome assessment (detection bias) / Low risk / "After completion of cholecystectomy, all patients received non-transparent waterproof dressings at four sites on the abdomen, reflecting the incisions necessary for CL cholecystectomy. This ensured that patients, ward doctors and nurses responsible for the postoperative evaluation and care of patients were unaware of which procedure had actually been performed. The operating surgeons and operating room staff were excluded from postoperative treatment and evaluation. This blinding was preserved until the morning of the third day after surgery. Change of dressings during the blinded period was not necessary in any patient."
Incomplete outcome data (attrition bias) / Low risk / No such evidence.
Selective reporting (reporting bias) / Low risk / No such evidence.
Other bias / Low risk / No such evidence.

Zheng 2012

Bias / Authors' judgement / Support for judgement
Random sequence generation (selection bias) / Low risk / "The computer-generated randomisation was concealed with the sealed envelope method until the patient entered into the operation room."
Allocation concealment (selection bias) / Low risk / "The computer-generated randomisation was concealed with the sealed envelope method until the patient entered into the operation room."
Blinding of participants and personnel (performance bias) / Unclear risk / Insufficient information to permit judgement.
Blinding of outcome assessment (detection bias) / Unclear risk / Insufficient information to permit judgement.
Incomplete outcome data (attrition bias) / Low risk / No such evidence.
Selective reporting (reporting bias) / Low risk / No such evidence.
Other bias / Unclear risk / Source of funding was not reported.

B. Curved instruments

Bucher 2011

Bias / Authors' judgement / Support for judgement
Random sequence generation (selection bias) / Low risk / "Patients were allocated to LESS or CL cholecystectomy using a randomization table after their preoperative visit by the surgeon."
Allocation concealment (selection bias) / High risk / "Patients were allocated to LESS or CL cholecystectomy using a randomization table after their preoperative visit by the surgeon."
Blinding of participants and personnel (performance bias) / Unclear risk / Insufficient information to permit judgement.
Blinding of outcome assessment (detection bias) / Unclear risk / Insufficient information to permit judgement.
Incomplete outcome data (attrition bias) / Low risk / No such evidence.
Selective reporting (reporting bias) / High risk / Operative complications were not reported, as would be expected.
Other bias / Unclear risk / Conflicts of interest and source of funding were not reported.

Chang 2014

Bias / Authors' judgement / Support for judgement
Random sequence generation (selection bias) / Low risk / "Each patient was randomized to one of two study arms by the closed envelope technique."
Allocation concealment (selection bias) / Unclear risk / Insufficient information to permit judgement.
Blinding of participants and personnel (performance bias) / Low risk / "All patients received dressings at the umbilicus, epigastrium, right flank, and the right hypochondrium, regardless of which procedure they had received; this concealed the procedure performed from both the patients as well as the post-operative assessor."
Blinding of outcome assessment (detection bias) / Low risk / "All patients received dressings at the umbilicus, epigastrium, right flank, and the right hypochondrium, regardless of which procedure they had received; this concealed the procedure performed from both the patients as well as the post-operative assessor."
Incomplete outcome data (attrition bias) / Low risk / No such evidence.
Selective reporting (reporting bias) / Low risk / No such evidence.
Other bias / High risk / Instrumentation provided by the industry.

Deveci 2013

Bias / Authors' judgement / Support for judgement
Random sequence generation (selection bias) / Low risk / "...were randomly assigned to undergo SILS cholecystectomy (group 1, n=50) or TPCL cholecystectomy (group 2, n=50) according to a computer-generated table of random numbers."
Allocation concealment (selection bias) / Unclear risk / Insufficient information to permit judgement.
Blinding of participants and personnel (performance bias) / Unclear risk / Insufficient information to permit judgement.
Blinding of outcome assessment (detection bias) / Unclear risk / Insufficient information to permit judgement.
Incomplete outcome data (attrition bias) / Low risk / No such evidence.
Selective reporting (reporting bias) / Low risk / No such evidence.
Other bias / Unclear risk / Source of funding was not reported.

Emre-Telciler 2014

Bias / Authors' judgement / Support for judgement
Random sequence generation (selection bias) / Unclear risk / Insufficient iformation to permit judgement.
Allocation concealment (selection bias) / Unclear risk / Insufficient iformation to permit judgement.
Blinding of participants and personnel (performance bias) / Unclear risk / Insufficient iformation to permit judgement.
Blinding of outcome assessment (detection bias) / Unclear risk / Insufficient iformation to permit judgement.
Incomplete outcome data (attrition bias) / Low risk / No such evidence.
Selective reporting (reporting bias) / Low risk / No such evidence.
Other bias / Unclear risk / Source of funding was not reported.

Herrero Fonollosa 2012

Bias / Authors' judgement / Support for judgement
Random sequence generation (selection bias) / Low risk / "[A sequence with block sizes of 4 in random order was generated by computer.]"
Allocation concealment (selection bias) / Low risk / "[...informed the surgeon on the day of the procedure of the patient’s designation.]"
Blinding of participants and personnel (performance bias) / Unclear risk / Insufficient information to permit judgement.
Blinding of outcome assessment (detection bias) / Unclear risk / Insufficient information to permit judgement.
Incomplete outcome data (attrition bias) / Low risk / No such evidence.
Selective reporting (reporting bias) / Low risk / No such evidence.
Other bias / Low risk / No such evidence.

Luna 2013

Ma 2011

Bias / Authors' judgement / Support for judgement
Random sequence generation (selection bias) / Low risk / "Eligible patients were then randomized 1:1 to receive either SPLC or CLC using a computerized mathematical algorithm."
Allocation concealment (selection bias) / Unclear risk / Insufficient information to permit judgement.
Blinding of participants and personnel (performance bias) / Unclear risk / Insufficient information to permit judgement.
Blinding of outcome assessment (detection bias) / Unclear risk / Insufficient information to permit judgement.
Incomplete outcome data (attrition bias) / Low risk / No such evidence.
Selective reporting (reporting bias) / High risk / Operative complications were not reported, as would have been expected.
Other bias / Unclear risk / Conflicts of interest were not disclosed.

Madureira 2013

Bias / Authors' judgement / Support for judgement
Random sequence generation (selection bias) / Unclear risk / Insufficient iformation to permit judgement.
Allocation concealment (selection bias) / Unclear risk / Insufficient iformation to permit judgement.
Blinding of participants and personnel (performance bias) / Unclear risk / Insufficient iformation to permit judgement.
Blinding of outcome assessment (detection bias) / Unclear risk / Insufficient iformation to permit judgement.
Incomplete outcome data (attrition bias) / High risk / The authors did not follow the intention-to-treat principle: "Two cases at the beginning of the series required the use of additional trocars. In these two operations, we were surprised by scleroatrophic cholecystitis and by a hydropic gallbladder. These cases were excluded from the study."
Selective reporting (reporting bias) / Low risk / No such evidence.
Other bias / Unclear risk / Source of funding was not reported.

Noguera 2013

Bias / Authors' judgement / Support for judgement
Random sequence generation (selection bias) / Low risk / "Patients were randomized following the Johns Hopkins Oncology Center’s Block Stratified Randomization program. Data collected for randomization included sex, age, ASA, and body mass index (BMI)."
Allocation concealment (selection bias) / Unclear risk / Insufficient information to permit judgement.
Blinding of participants and personnel (performance bias) / Unclear risk / Insufficient information to permit judgement.
Blinding of outcome assessment (detection bias) / Unclear risk / Insufficient information to permit judgement.
Incomplete outcome data (attrition bias) / Low risk / No such evidence.
Selective reporting (reporting bias) / Low risk / No such evidence.
Other bias / Low risk / No such evidence.

Pappas-Gogos 2014

Sasaki 2012

Bias / Authors' judgement / Support for judgement
Random sequence generation (selection bias) / Low risk / "…were randomly assigned to either the SPLC group or the MPLC group according to computer-generated random numbers."
Allocation concealment (selection bias) / Unclear risk / Insufficient information to permit judgement.
Blinding of participants and personnel (performance bias) / Unclear risk / Insufficient information to permit judgement.
Blinding of outcome assessment (detection bias) / Unclear risk / Insufficient information to permit judgement.
Incomplete outcome data (attrition bias) / Low risk / No such evidence.
Selective reporting (reporting bias) / Low risk / No such evidence.
Other bias / Unclear risk / Source of funding was not reported.

Sinan 2012