Nineteen trials (3,287 women) were included in the review. It appeared that 10 trials had available IPD. There were five head-to-head comparisons (744 women) of second generation devices and 14 comparisons (2,543 women) of second and first generation (hysteroscopic) devices. Fixed-effect and random-effects meta-analyses showed similar results (random-effects results presented here).
Direct comparisons showed that bipolar radio frequency ablation was associated with an increased rate of amenorrhoea compared with thermal balloon ablation (OR 4.56, 95% CI 2.24 to 9.26; Ι²=0%). Bipolar radio frequency ablation was also favourable when compared with free fluid thermal ablation where this showed a reduced rate of amenorrhoea (OR 0.36, 95% CI 0.18 to 0.73; one trial) and increased heavy bleeding (OR 4.88, 95% CI 1.32 to 18.11; one trial). There were no other substantial differences and (where more than one trial was included in the analysis) there was generally no evidence of statistical heterogeneity.
The network meta-analysis was concurrent with the direct evidence. Indirect comparisons showed increased rates of amenorrhoea in favour of radio frequency ablation when compared with cryoablation (OR 0.20, 95% CI 0.09 to 0.49) and favouring microwave ablation over thermal balloon ablation (OR 1.66, 95% CI 1.01 to 2.71; one trial) and cryoablation (OR 0.31, 95% CI 0.13 to 0.74). Radio frequency ablation was preferable to free fluid ablation in reducing heavy bleeding (OR 2.91, 95% CI 1.23 to 6.88).
In general, rates of dissatisfaction with treatment or on-going heavy bleeding were low. Direct comparisons showed reduced rates of dissatisfaction with bipolar radio frequency ablation when compared with thermal balloon ablation (OR 0.39, 95% CI 0.16 to 0.91; Ι²=0%), although this was not statistically significant in the network meta-analysis. Increased rates of dissatisfaction were noted for free fluid thermal ablation compared with bipolar radio frequency ablation (OR 9.40, 95% CI 1.14 to 77.18; one trial) and this was mirrored in the network meta-analysis. There were no other substantial differences.
Estimates of incoherence were high in the network analysis regarding rate of amenorrhoea. This was influenced by one trial that compared microwave ablation to thermal balloon ablation, but removal of this trial did not alter any directions of effect.