Schmitz 1997.

Methods	Prospective randomised study with 64 participants included, comparing mesh and non‐mesh inguinal hernia repairs
Participants	All 94 participants with primary inguinal hernia were operated on, of which, according to statistical calculations and inclusion criteria, 64 were included in the study. Inclusion criteria Male and female, age: 17‐75 years, informed consent (comment: participants were told about both surgical methods), primary hernia. Exclusion criteria Acute incarceration, immune suppression, coagulation disorders, relapse, hepatosis, diabetes mellitus, malignant tumour
Interventions	Group A Tension‐free surgical treatment (n = 32) Group B Shouldice herniorrhaphy (n = 32): as per the original publication All participants were operated on with endotracheal anaesthesia. Four surgeons with long lasting Shouldice operation experience took part in the study. Mean operation duration was 43 ± 10 min in Shouldice group and 31 ± 7.5 in TF‐group
Outcomes	Surgical early complications (including hematomas, infections, seromas and testicular swelling) and wound healing were assessed till the day of discharge on the 6th postoperative day. Postoperative pain was assessed using a VAS and quantifying the amount of paracetamol taken by individual participants.
Notes	A 2 day earlier release of pain was suspected using TF‐method in comparison to Shouldice method, so a population size of n = 32 participants/group was calculated using t‐tests for unpaired samples for comparison of means (assumed standard deviation: 2 days) to calculate a level of significance P < 0.05
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Randomised by 'letter' (no details described, not described if envelopes were used) immediately before operation
Allocation concealment (selection bias)	Unclear risk	Not mentioned
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Not mentioned
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not mentioned
Incomplete outcome data (attrition bias) All outcomes	Low risk	Classification of hernia type and wound status postoperative (hematoma, infections, seroma, testicle swelling) is reported for all 64 participants. No attrition reported.
Selective reporting (reporting bias)	Low risk	Different categories of wound status (hematoma, infections, seroma, testicle swelling) are reported for the period of day 1‐6. Acetaminophen use and pain on lying, walking and sitting up were reported as diagrams, no exact numbers reported (picture 1‐4)
Other bias	Low risk	No other sources of bias found