Abstract: We included 70 studies in the review; 66 studies with 17,067 participants were included in the quantitative analysis. An additional 18 studies are awaiting classification and 12 are ongoing. Fifteen of the 18 studies awaiting classification mainly correspond to congress summaries published before 2010, in which the available information does not allow the complete evaluation of all their risks of bias and characteristics. Our main outcome was prevention of PDPH, but we also assessed the onset of severe PDPH, headache in general and adverse events. The quality of evidence was moderate for most of the outcomes mainly due to risk of bias issues. For the analysis, we undertook three main comparisons: 1) traumatic needles versus atraumatic needles; 2) larger gauge traumatic needles versus smaller gauge traumatic needles; and 3) larger gauge atraumatic needles versus smaller gauge atraumatic needles. For each main comparison, if data were available, we performed a subgroup analysis evaluating lumbar puncture indication, age and posture. For the first comparison, the use of traumatic needles showed a higher risk of onset of PDPH compared to atraumatic needles (36 studies, 9378 participants, risk ratio (RR) 2.14, 95% confidence interval (CI) 1.72 to 2.67, I2 = 9%). In the second comparison of traumatic needles, studies comparing various sizes of large and small gauges showed no significant difference in effects in terms of risk of PDPH, with the exception of one study comparing 26 and 27 gauge needles (one study, 658 participants, RR 6.47, 95% CI 2.55 to 16.43). In the third comparison of atraumatic needles, studies comparing various sizes of large and small gauges showed no significant difference in effects in terms of risk of PDPH. We observed no significant difference in the risk of paraesthesia, backache, severe PDPH and any headache between traumatic and atraumatic needles. Sensitivity analyses of PDPH results between traumatic and atraumatic needles omitting high risk of bias studies showed similar results regarding the benefit of atraumatic needles in the prevention of PDPH (three studies, RR 2.78, 95% CI 1.26 to 6.15; I2 = 51%). There is moderate-quality evidence that atraumatic needles reduce the risk of post-dural puncture headache (PDPH) without increasing adverse events such as paraesthesia or backache. The studies did not report very clearly on aspects related to randomization, such as random sequence generation and allocation concealment, making it difficult to interpret the risk of bias in the included studies. The moderate quality of the evidence for traumatic versus atraumatic needles suggests that further research is likely to have an important impact on our confidence in the estimate of effect.

Plain-language summary: We searched the medical literature for studies carried out in any setting comparing needles of different characteristics (i.e. different tip designs and sizes) for the prevention of PDPH. The evidence is current to September 2016. We included 70 studies and were able to include information from 66 of those studies (17,067 participants) in the numerical analysis. An additional 18 studies are awaiting classification and 12 are ongoing. We found that the use of needles with a traumatic tip resulted in a higher risk of PDPH when compared to needles with atraumatic tips. When we compared the different studies comparing various sizes of large and small traumatic gauges, we did not find any difference in effects in terms of the risk of PDPH. Finally, when we compared atraumatic needles with a higher gauge to those with a smaller gauge, we observed no significant differences in terms of the development of PDPH in any of the scenarios analysed. We also found no significant differences in the use of traumatic versus atraumatic needles in the development of adverse effects such as paraesthesia, backache and severe PDPH. The studies did not report clearly on aspects of their design related to randomization. (This is a method that uses the play of chance to assign participants to comparison groups in a trial). This made it difficult for us to interpret the risk of bias in the included studies. We therefore considered the quality of the evidence for most of the outcomes assessed in this review to be moderate.