Recurrence risks in randomized trials of laparoscopic versus open inguinal hernia repair: to pool or not to pool (this is not the question)

Meta-analyses suggest that, with regard to relative risks of hernia recurrence, there is a net benefit in the use of synthetic mesh rather than the surgical approach. Considering important arguments raised by both conventional and laparoscopic surgeons, we set out to explore other sources of variability across individual studies.

We abstracted all publications of randomized trials of laparoscopic versus open inguinal hernia repair included in the EU Hernia Trialists meta-analyses. We applied meta-regression to identify variables that are likely to alter the relative risk of hernia recurrence with either route.

We included 41 randomized trials (7,446 patients), two of which were identified by a systematic literature search. There was significant statistical heterogeneity across studies (χ² test P=0.029). Meta-regression was limited because of scarce information provided in the original papers, and small sample sizes. Results varied internationally, with trials from the UK, southern Europe and Australia favouring open hernioplasty (analysis of variance, P=0.0047). Large numbers of surgeons contributing to the open hernioplasty group predicted better results with endoscopic hernia repair [risk ratio (RR)] 0.99 with any additional surgeon, 95% confidence interval (CI) 0.98–1.00, P=0.005]. Non-significant trends were observed towards reduced recurrence risks with increasing mesh sizes. Training procedures performed before patient enrollment slightly reduced the relative risk of recurrence with endoscopic hernioplasty.

Because of the diversity in the size of effect, it is doubtful whether data from the available hernia trials should be compiled into a single summary measure. Efficacy estimates in hernia surgery are susceptible to technical issues, which need further scientific appraisal on a larger scale.