Seven studies, with a total of 1,132 participants (719 with AAA and 413 with AOD), were included in the review. Three studies (n=654) were prospective and four were retrospective (n=478).
The overall incidence of incision hernia in the studies was 21% for AAA versus 9.8% for AOD.
Pooled analysis of all 7 studies showed that patients with AAA were 2.8 times more likely to experience post-operative incision hernia than patients with AOD (OR 2.79, 95% CI: 1.88, 4.13; based on 7 studies; p<0.0001). The findings were similar for inguinal hernia (OR 2.85, 95% CI 1.71, 4.77; based on 5 studies; p<0.0001). Risk factors differed between patients with AAA and patients with AOD, with the former being older and more likely to be male. However, pooled analysis of 3 studies that adjusted for these and other major risk factors showed more than five times the risk for incision hernia in patients with AAA compared with those with AOD (OR 5.45, 95% CI: 2.48, 11.94; p<0.0001).
There was clinical heterogeneity between the studies with regard to mean duration of follow-up, type of surgical closure used and follow-up measures. However, there was no statistically significant heterogeneity in the forest plots for either inguinal hernia or incision hernia (p=0.23 and p=0.99, respectively), and sensitivity analyses did not substantially change any of the pooled estimates. No evidence of publication bias was detected (p=0.33).