Corbey 1997.

Methods	Design: parallel‐group, 2 arms Country: Denmark Multisite: no Needle tip used: Quincke vs Whitacre Needle diameter used: 27 G Number of attempts: unknown Procedure: spinal anaesthesia Site of the puncture: L2‐3 or L3‐4 Training level of those who administered the puncture: unknown Median or paramedian technique: unknown Type of anaesthetic: Hyperbaric lignocaine 75‐100 mg, or hyperbaric bupivacaine 12.5‐15 mg,
Participants	1. 200 patients enrolled (less than 45 years of age, presenting for daycare surgery on the lower half of the body to be performed under spinal anaesthesia) Excluded patients: unclear Patients randomized to: 27 G Quincke (100, 50%) 27 G Whitacre (100, 50%) 2. 9 patients failed to return their questionnaires and 2 patients were recorded as failures 3. Main characteristics of patients: Age (range): Quincke group: 31. 77 to 32.1; Whitacre group: 31.4 to 32 Weight (mean, SEM): no reported Gender ‐ male (number): no reported
Interventions	Spinal anaesthesia with either a 27 G Quincke needle or 27 G Whitacre 27‐gauge Quincke (external diameter 0.41 mm Becton‐Dickinson [B‐D] Meylan, Spain) 27‐gauge Whitacre spinal needle (external diameter 0.41 mm [BD] Spain).
Outcomes	Outcomes were not classified as primary or secondary PDPH: postural headache, aggravated by standing, or sitting up, and relieving by lying down Postdural puncture‐related headache (PDPR‐H) Non‐specific headache Grading of severity of headache
Notes	Trial registration: not stated Funder: not stated Role of funder: not stated A priori sample size estimation: no Conducted: not stated Declared conflicts of interest: not stated
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient information to score this item as low or high risk of bias. Quote: "The patients were randomly allocated to receive spinal anaesthesia" (page 780)
Allocation concealment (selection bias)	Unclear risk	Insufficient information to score this item as low or high risk of bias
Blinding of participants (performance bias)	Low risk	Quote: "Patients were not aware of which needle had been used to perform the anaesthesia". (page 780)
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "The replies to the questionnaires were assessed by one of the authors who was not aware of which needle had been used to perform the anaesthesia". (page 780)
Incomplete outcome data (attrition bias) All outcomes	Low risk	No patients were lost to follow‐up
Selective reporting (reporting bias)	High risk	Adverse events, additional to PDPH, were not reported
Other bias	Low risk	No other biases were identified