Hernia width explains differences in outcomes between primary and incisional hernias: a prospective cohort study of 9159 patients.

Data on primary (PH) and incisional hernias (IH) are often pooled, even though several studies have illustrated that these are different entities with worse outcomes for IHs. The aim of this study is to validate previous research comparing PHs and IHs and to examine whether hernia width is an important contributor to the differences between these hernia types. A registry-based, prospective cohort study was performed, utilizing the French Hernia Club database. All patients undergoing PH or IH repair between September 8th 2011 and May 22nd 2019 were included. Baseline, hernia and surgical characteristics, and postoperative outcomes were collected. Outcomes were analyzed per width category (≤ 2 cm, 3–4 cm, 5–10 cm and > 10 cm). A total of 9159 patients were included, of whom 4965 (54%) had PH and 4194 (46%) had IH. PHs and IHs differed significantly in 12/15 baseline characteristics, 9/10 hernia and surgical characteristics, and all outcomes. Overall, complications and re-interventions were more common in patients with IH. After correcting for width, the differences between PH and IH were no longer significant, except for medical complications, which were more common after IH repair compared to PH. After correcting for hernia width, most outcomes do not significantly differ between PH and IH, indicating that not hernia type, but hernia width is an important factor contributing to the differences between PH and IH.