Highlights
In a nationwide Danish cohort of 17,832 adults undergoing elective mesh repair of primary umbilical or epigastric hernias 10 cm or smaller, onlay mesh placement served as the reference technique and was associated with lower long-term risks of reoperation for recurrence and bowel obstruction than retromuscular repair and IPOM.
Compared with onlay placement, retromuscular mesh was associated with a higher hazard of reoperation for recurrence (HR, 1.63; 95% CI, 1.12-2.38) and bowel obstruction (HR, 2.01; 95% CI, 1.05-3.82).
IPOM was also associated with a higher risk of reoperation for recurrence (HR, 1.38; 95% CI, 1.02-1.86) and a notably higher risk of bowel obstruction (HR, 3.47; 95% CI, 2.27-5.28) compared with onlay placement.
Preperitoneal placement emerged as a clinically attractive option because the authors’ conclusion favored both onlay and preperitoneal approaches when recurrence and bowel obstruction are prioritized.
Background
Primary ventral hernias, especially umbilical and epigastric defects, are among the most common abdominal wall conditions treated by general surgeons. Mesh reinforcement has become standard for many repairs because it lowers recurrence compared with suture repair alone, particularly as defect size increases. Yet “mesh repair” is not a single operation. A central technical question remains where, anatomically, the prosthesis should be placed.
The principal mesh planes used in routine practice include onlay placement over the anterior fascia, retromuscular placement behind the rectus muscles, preperitoneal placement deep to the abdominal wall but outside the peritoneal cavity, and intraperitoneal onlay mesh (IPOM), in which mesh is placed within the abdominal cavity against the peritoneal surface. Each position presents tradeoffs. Onlay repair is technically familiar and often simpler, but historically has raised concern about wound morbidity. Retromuscular repair is often favored in complex abdominal wall reconstruction because of durable biomechanics, though it may require greater dissection. Preperitoneal repair attempts to combine anatomical reinforcement with avoidance of intraperitoneal mesh contact. IPOM, especially with laparoscopic techniques, has offered minimally invasive access but has long raised questions about adhesions, bowel complications, and the long-term consequences of intraperitoneal prosthetic material.
Evidence comparing these planes specifically for primary ventral hernias has been limited by heterogeneous techniques, single-center series, and relatively short follow-up. The new Danish nationwide analysis addresses a clinically important gap by focusing on reoperation for recurrence and bowel obstruction across mesh positions in a large real-world cohort.
Study Design and Methods
Design and data sources
This was a Danish nationwide register-based cohort study. Investigators used the Danish National Patient Register and linked it with the Danish Ventral Hernia Database and the Danish Civil Registration System. Denmark’s integrated national registries are particularly well suited to longitudinal surgical outcomes research because they support near-complete follow-up and linkage across procedural and outcome datasets.
Population
The cohort included adults aged 18 years or older who underwent elective primary ventral hernia repair between January 2014 and April 2025. Eligible hernias were umbilical or epigastric defects measuring 10 cm or smaller, repaired with mesh. Follow-up extended through November 1, 2025. The final cohort comprised 17,832 patients.
The distribution of mesh techniques was as follows: 8,764 onlay repairs, 1,239 retromuscular repairs, 4,292 preperitoneal repairs, and 3,537 IPOM repairs. Mean age was 54 years (SD, 13.5), and 4,873 patients (27.3%) were female.
Exposure and comparators
The exposure of interest was anatomical mesh placement technique. The study compared four groups: onlay, retromuscular, preperitoneal, and IPOM. Onlay mesh placement was used as the reference category in the reported hazard models.
Outcomes
The primary outcomes were reoperation for recurrence and bowel obstruction. These are clinically meaningful endpoints because they move beyond radiographic or symptom-based recurrence definitions and focus on events serious enough to require operative management. Time-to-event associations were estimated with Cox proportional hazards regression, reported as hazard ratios with 95% confidence intervals.
Key Findings
Recurrence requiring reoperation
The most practice-relevant message from this study is that onlay mesh placement compared favorably with several alternative planes. Relative to onlay repair, retromuscular placement was associated with a significantly higher hazard of reoperation for recurrence, with an HR of 1.63 (95% CI, 1.12-2.38). IPOM was also associated with a significantly increased hazard, with an HR of 1.38 (95% CI, 1.02-1.86).
These effect sizes are not trivial. A 63% relative increase in recurrence-related reoperation for retromuscular placement and a 38% increase for IPOM, if robust to confounding, would materially influence operative planning for small to moderate primary ventral hernias. The abstract does not provide a hazard ratio for preperitoneal versus onlay for recurrence, but the authors’ conclusion indicates that preperitoneal placement, like onlay, may be a preferable choice when recurrence and bowel obstruction are considered together.
Bowel obstruction
The bowel obstruction findings are equally important, and perhaps even more distinctive. Compared with onlay placement, retromuscular repair carried an HR of 2.01 (95% CI, 1.05-3.82) for bowel obstruction, while IPOM carried an HR of 3.47 (95% CI, 2.27-5.28). Thus, IPOM was associated with more than triple the hazard of bowel obstruction requiring surgical attention or meeting the registry-defined endpoint.
The signal for IPOM is biologically plausible. Intraperitoneal prosthetic material can promote adhesions despite modern barrier-coated meshes, and any adhesion burden near mobile bowel loops may increase the risk of obstruction over time. The elevated risk observed for retromuscular repair is more surprising and warrants careful interpretation. It may reflect case selection, technical heterogeneity, extent of dissection, or anatomical complexity not fully captured by registry covariates.
Why onlay and preperitoneal may matter most
The authors concluded that onlay and preperitoneal placement may be preferable options in primary ventral hernia repair. This conclusion is clinically sensible. Preperitoneal placement avoids direct contact between mesh and intra-abdominal viscera while preserving a deeper anatomic plane than onlay. Onlay placement, meanwhile, may have benefited in this cohort from broad adoption, standardized execution, or use in lower-complexity cases. Importantly, the study does not suggest that all retromuscular repairs are inferior in all settings; rather, within this national cohort of elective primary ventral hernias 10 cm or smaller, those approaches were associated with worse outcomes on the endpoints measured.
Clinical Interpretation
What should surgeons take from this study?
For routine elective repair of primary umbilical and epigastric hernias up to 10 cm, the findings argue against assuming that deeper or more technically elaborate planes necessarily yield better long-term results. In particular, the data challenge the notion that retromuscular placement, often viewed favorably in incisional hernia surgery and complex abdominal wall reconstruction, can simply be extrapolated as the best default plane for all primary ventral hernias.
The study also reinforces long-standing concerns regarding IPOM. Over the past decade, enthusiasm for intraperitoneal mesh placement has already softened in many abdominal wall practices, partly because of cost, concern about adhesions, and the growth of extraperitoneal minimally invasive approaches. The strong bowel obstruction signal seen here further supports efforts to avoid intraperitoneal prosthetic placement when an effective extraperitoneal alternative is feasible.
How might these findings affect patient counseling?
When discussing mesh repair with patients, surgeons increasingly need to explain not only whether mesh will be used, but where it will be placed. This study supports a more nuanced informed-consent discussion. For patients with primary ventral hernias amenable to several techniques, surgeons may reasonably explain that, in a large national cohort, onlay and preperitoneal approaches were associated with lower downstream risks of recurrence-related reoperation and bowel obstruction than retromuscular repair or IPOM.
That said, technique choice remains individualized. Prior surgery, obesity, rectus diastasis, defect size and shape, tissue quality, cosmetic concerns, surgeon expertise, and whether the operation is open, laparoscopic, or robotic all influence the ideal plane.
Strengths of the Study
The study has several notable strengths. First is scale: more than 17,000 patients provide far greater statistical power and external relevance than most prior comparisons of ventral hernia mesh planes. Second is the nationwide registry framework, which reduces loss to follow-up and captures real-world practice across many surgeons and institutions rather than a single high-volume center. Third is the focus on hard clinical endpoints. Reoperation for recurrence and bowel obstruction are highly meaningful to both surgeons and patients.
The long accrual window, spanning 2014 to 2025, also allows assessment across evolving clinical practice. Finally, the restriction to primary ventral hernias 10 cm or smaller improves clinical coherence by avoiding the major heterogeneity seen when primary and incisional hernias are analyzed together.
Limitations and Caveats
As with all observational registry studies, confounding by indication remains the central limitation. Surgeons do not choose mesh plane at random. Retromuscular repair may have been selected for larger, more difficult, recurrent-in-disguise, or anatomically challenging hernias that carried higher baseline risk even after adjustment. Likewise, IPOM may have been used in patients with specific prior surgical histories or minimally invasive indications that influenced outcomes independently of mesh position.
The use of reoperation for recurrence as the endpoint, while clinically robust, may underestimate total recurrence burden because not all recurrences are repaired. Some patients may decline further surgery, and thresholds for reoperation can vary by age, comorbidity, symptom severity, and surgeon preference. Similar considerations apply to bowel obstruction coding and the exact clinical pathways leading to event capture.
The abstract does not specify all covariates used in adjustment, nor does it detail whether operative approach, defect width categories, body mass index, smoking, diabetes, or concurrent rectus diastasis were fully accounted for. Those factors could influence both choice of mesh plane and long-term outcomes. In addition, registry studies cannot always capture granular technical nuances such as mesh overlap, fixation type, closure of the fascial defect, use of self-gripping prostheses, component-separation maneuvers, or specific anti-adhesive mesh coatings.
The retromuscular finding, in particular, should therefore be interpreted cautiously rather than dogmatically. It may reflect residual confounding as much as true inferiority of the plane itself for selected primary ventral hernias.
Context Within the Existing Literature
Guideline and consensus documents have generally favored mesh reinforcement over suture repair for many ventral hernias, but the ideal mesh plane has remained less settled, especially for smaller primary defects. The European Hernia Society and Americas Hernia Society guidelines on umbilical and epigastric hernias have supported mesh use and have often highlighted preperitoneal or retromuscular concepts while acknowledging variable evidence quality and technique heterogeneity. This new study adds important comparative real-world data that may shift attention toward onlay and preperitoneal approaches in straightforward primary ventral hernia cases.
More broadly, contemporary abdominal wall surgery has trended toward extraperitoneal mesh positioning whenever practical. This is evident in the growing adoption of minimally invasive retromuscular, extended totally extraperitoneal, and transabdominal preperitoneal variants. The present data fit that general extraperitoneal movement, but they also suggest that for primary ventral hernias, a simple onlay approach should not be dismissed as outdated or intrinsically inferior.
Practical Implications for Surgical Practice
For elective primary umbilical and epigastric hernias 10 cm or smaller, surgeons may wish to revisit local algorithms that preferentially favor IPOM or retromuscular placement without strong patient-level rationale. On the basis of this study, a reasonable hierarchy for many patients would prioritize preperitoneal or onlay placement when anatomically feasible and when surgeon expertise is adequate.
At the same time, practice change should be measured rather than abrupt. The best next step is likely not universal conversion to one technique, but careful audit of institutional outcomes by mesh plane, operative approach, and patient phenotype. Surgeons should also consider whether their retromuscular repairs are being performed in a distinct risk population. If so, case-mix adjustment is essential before drawing local conclusions.
Future Research
This study should stimulate several lines of inquiry. Prospective comparative studies, ideally pragmatic randomized trials where feasible, are needed to determine whether the observed advantages of onlay and preperitoneal placement are causal. Future analyses should examine absolute event rates, interactions with operative approach, and outcomes stratified by defect size, obesity, rectus diastasis, and prior abdominal surgery.
Patient-reported outcomes are also critical. Chronic pain, abdominal wall function, cosmetic satisfaction, seroma formation, surgical-site occurrence, and return to activity are not captured by recurrence and bowel obstruction alone. Cost-effectiveness analyses would further help determine whether simpler planes confer economic as well as clinical benefit.
Funding and Trial Registration
The abstract does not report a ClinicalTrials.gov registration number, which is expected given the observational registry-based design rather than an interventional trial. Funding details are not provided in the abstract and should be verified in the full article.
Conclusion
This Danish nationwide cohort provides consequential evidence that mesh plane matters in elective primary ventral hernia repair. In adults undergoing repair of umbilical or epigastric hernias 10 cm or smaller, both retromuscular placement and IPOM were associated with higher hazards of reoperation for recurrence and bowel obstruction than onlay placement. The strongest cautionary signal was seen with IPOM, particularly for bowel obstruction.
For contemporary general surgery practice, the study supports serious consideration of onlay and preperitoneal mesh placement as preferred strategies for many primary ventral hernias. The findings should not be overgeneralized to incisional or highly complex abdominal wall reconstruction, and residual confounding remains possible. Still, the message is clear: in primary ventral hernia repair, the simplest or most familiar plane may in fact be among the safest and most durable when judged by clinically meaningful long-term outcomes.
References
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2. Henriksen NA, Montgomery A, Kaufmann R, et al. Guidelines for treatment of umbilical and epigastric hernias from the European Hernia Society and Americas Hernia Society. British Journal of Surgery. 2020;107(3):171-190. PMID: 31916607.
3. Muysoms FE, Miserez M, Berrevoet F, et al. Classification of primary and incisional abdominal wall hernias. Hernia. 2009;13(4):407-414. PMID: 19636450.
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