Key Points

Question听 What is the incidence of and long-term outcomes after component separation use for elective abdominal wall hernia repair?

Findings听 In this cohort study involving 218鈥�518 Medicare beneficiaries, 10-year operative recurrence rates were lower for patients who underwent hernia repair with component separation vs without. Operative recurrence was lower for the top 5% of surgeons by component separation volume vs the bottom 95% of surgeons.

Meaning听 Component separation appears to have a protective effect on long-term operative recurrence; however, surgeon volume was associated with only a minor reduction in recurrence rates.

Importance听 Component separation is a reconstructive technique used to facilitate midline closure of large or complex ventral hernias. Despite a contemporary surge in popularity, the incidence and long-term outcomes after component separation remain unknown.

Objective听 To evaluate the incidence and long-term outcomes of component separation for abdominal wall hernia repair.

Design, Setting, and Participants听 This cohort study examined 100% Medicare administrative claims data from January 1, 2007, to December 31, 2021. Participants were adults (aged 鈮�18 years) who underwent elective inpatient ventral hernia repair. Data were analyzed from January through June 2024.

Exposure听 Use of component separation technique during ventral hernia repair.

Main Outcomes and Measures听 The primary outcomes were the incidence of component separation over time and operative recurrence rates up to 10 years after surgery for hernia repairs with and without component separation. The secondary outcome was rate of operative recurrence after component separation stratified by surgeon volume.

Results听 Among 218鈥�518 patients who underwent ventral hernia repair, the mean (SD) age of the cohort was 69.1 (10.9) years; 127鈥�857 patients (58.5%) were female and 90鈥�661 (41.5%) male. A total of 23鈥�768 individuals had component separation for their abdominal wall hernia repair. The median (IQR) follow-up time after the index hernia surgery was 7.2 (2.7-10) years. Compared with patients who did not have a component separation, patients undergoing repair with component separation were slightly younger; more likely to be male; and more likely to have comorbidities, including obesity, and had surgeries that were more likely to be performed open and use mesh. Proportional use of component separation increased from 1.6% of all inpatient hernia repairs in 2007 (279 patients) to 21.4% in 2021 (1569 patients). The 10-year adjusted operative recurrence rate after component separation was lower (11.2%; 95% CI, 11.0%-11.3%) when compared with hernia repairs performed without component separation (12.9%; 95% CI, 12.8%-13.0%; P鈥�=鈥�.003). Operative recurrence was lower for the top 5% of surgeons by component separation volume (11.9%; 95% CI, 11.8%-12.1%) as opposed to the bottom 95% of surgeons by volume (13.6%; 95% CI, 13.4%-13.7%; P鈥�=鈥�.004).

Conclusions and Relevance听 This study found that component separation was associated with a protective effect on long-term operative recurrence after ventral hernia repair among Medicare beneficiaries, which is somewhat unexpected given the intent of its use for higher complexity hernias. Surgeon volume, while significant, had only a minor influence on operative recurrence rates.

Advances in technology, development of new techniques, and financial opportunities have played a large role in driving surgical innovation in the last decade. Nowhere has this been more apparent than within abdominal wall hernia repair and, more specifically, the use of component separation for abdominal wall hernia. This reconstructive technique, which is used to facilitate midline closure for large or complex abdominal wall hernias, was first described in the early 1990s and then repopularized with the modified posterior approach (transversus abdominus release) in the early 2010s.^1,2 Component separation has garnered contemporary media attention for both its surge in popularity and the potential harm that accompanies its inappropriate use by inexperienced surgeons.³

Despite recent attention, knowledge regarding the use of component separation and its associated long-term outcomes remains limited. Current use of the technique in comparison with historic rates remains undercharacterized, with most recent published data suggesting rates of 2% to 6%.^4-6 Additionally, most existing work evaluating outcomes after component separation is limited to single institution case series from surgeons who specialize in abdominal wall repair.^7-10 Prior population-level or multi-institutional studies either do not evaluate long-term hernia recurrence, lack contemporary data, or do not directly quantify recurrence rates outside of reporting odds ratios.^5,6,11,12 Finally, even as component separation has diffused out of specialized centers into the greater community, there remain a paucity of population-level data evaluating the importance of surgeon experience on long-term outcomes. The relationship between higher volume and improved outcomes has long been established for other complex, morbid operations such as esophagectomy or rectal cancer resection^13,14 but remains largely understudied in complex abdominal wall reconstruction.^15,16

This study sought to understand the contemporary use of component separation and its associated long-term operative recurrence in a national cohort of Medicare beneficiaries. The use of Medicare enabled a population-level view of surgeons鈥� use of component separation and the ability to measure long-term operative hernia recurrence because of Medicare鈥檚 near universal, continuous enrollment and low disenrollment rates. Additionally, we used surgeon volume as a proxy for experience to evaluate if a volume-outcome relationship exists for operative recurrence rates after complex abdominal wall repair. A better understanding of the use of component separation and its associated outcomes will be critical to inform policy initiatives, such as the centralization of complex hernia care.

This study was exempt from regulation by the University of Michigan institutional review board. We followed the Strengthening the Reporting of Observational Studies in Epidemiology () reporting guideline.

We used 100% data from the Medicare Provider Analysis and Review Part A and B files to identify initial (index) operations for patients 18 years or older who underwent elective, inpatient ventral hernia repair from January 1, 2007, through December 31, 2021. Ventral hernia included all anterior abdominal wall hernias coded in claims as ventral, incisional, umbilical, or epigastric hernia repair. Patients were identified initially using procedure codes from the International Classification of Diseases, Ninth Revision, and International Statistical Classification of Diseases and Related Health Problems, Tenth Revision (ICD-9/10), which were cross-referenced with the corresponding ICD-9/10 diagnosis codes (eTable 1 in Supplement 1). Patients were excluded from the index cohort if they had a prior hernia repair in at least the 2 years leading up to the initial operation or if it was associated with Current Procedural Terminology (CPT) codes for repair of a recurrent ventral hernia (49565, 49566, 49656, 49657). All subsequent admissions for a ventral hernia operation after the index repair were excluded from the index cohort. Patients were excluded if they were not enrolled in Fee-for-Service Medicare because of the lack of accurate follow-up. Patients were also excluded if they lacked a concurrent CPT code for hernia repair (eTable 1 in Supplement 1). A flow diagram with detailed stepwise patient inclusion/exclusion is shown in eFigure 1 in Supplement 1.

The primary outcomes were the annual number of hernias repaired with and without component separation over the study period and long term-operative recurrence up to 10 years after surgery for each cohort of patients. Patients undergoing component separation were identified using CPT code 15734 (myofascial release) in conjunction with the previously mentioned ICD-9/10 and CPT codes for a concurrent ventral hernia repair. Operative recurrence was used as a proxy for true clinical recurrence, which cannot be measured in Medicare claims data alone. The total number of ventral hernia repairs performed with and without component separation were tabulated for each year. Consistent with previous work, operative recurrence was identified by a subsequent hernia repair using the same CPT and ICD-9/10 codes used to identify the initial hernia repair and/or the presence of specific hernia recurrence CPT codes 49565, 49566, 49656, and 49657.^17,18

The secondary outcome was long-term operative recurrence stratified by surgeon component separation volume. Surgeons were included if they performed at least 1 component separation during the study period. When multiple surgeons were listed on the day of the index surgery, the primary surgeon was identified by the type of service rendered (modifier 鈥�2鈥� in CMS_TYPE_SRVC_TB) and/or as the surgeon with the highest reimbursement amount for the hernia repair. Consistent with previous work, cumulative Medicare surgeon volume over the study period was then inflated to reflect true volumes by dividing raw cumulative volume in a given year by the proportion of a hospital鈥檚 total number of year-specific Medicare discharges by total admissions from the American Hospital Association survey and then summed across years.^19,20 For example, if a surgeon performed 4 component separations in a hospital with a 33% Medicare discharges over total admissions in a given year, then this surgeon would be assigned a volume of 12 component separation repairs for that specific year. To better identify surgeons who were not independently practicing throughout the entire study period, we designated the first year a surgeon performed any elective anterior abdominal wall hernia repair (with or without component separation) as their year of entry into the dataset. Annual surgeon component separation volume was calculated by dividing inflated cumulative component separation volume by the number of years present in the dataset. The distribution of annual component separation surgeon volume was severely skewed toward lower volumes (eFigure 2 in Supplement 1); thus, using equal terciles of surgeons would not adequately discriminate levels of surgeon experience. To increase the specificity of the surgeon volume variable, we stratified surgeons into 2 groups: the top 5% by annual volume (high volume) and the bottom 95% by annual volume (low volume).

Explanatory variables included in our models were consistent with previously published work on hernia and included patient age, sex, race and ethnicity (see eMethods in Supplement 1 for race and ethnicity identification in Medicare claims data), Elixhauser comorbidities, year of surgery, approach (robotic-assisted, laparoscopic, or open), mesh use, the use of component separation, and hernia subtype (ventral/incisional or umbilical).^11,18 Age was treated as a continuous variable. All others were treated as categorical.

Because of the binary, nonlinear outcome of operative hernia recurrence, we performed time to event analysis using a Cox proportional hazards model. The Cox model was constructed to calculate the cumulative incidence of operative hernia recurrence while adjusting for the following covariates: age, sex, race and ethnicity, comorbidities, hernia subtype, operative approach, component separation use, mesh use, and year of surgery. Our primary model included all ventral hernia repairs, with and without component separation, and accounted for clustering at the hospital level. Our secondary model to evaluate operative recurrence after component separation by surgeon volume only included patients undergoing component separation, included an additional variable for surgeon volume strata (low or high volume) along with the above listed covariates, and accounted for clustering at the surgeon level. Patients were censored if they died, disenrolled from Medicare, or reached the end of the study period. Cumulative incidence of operative recurrence numbers were estimated using the Cox models with covariates set to their mean values. Proportional hazards assumptions were tested using Schoenfeld residuals. We included an interaction term with the logarithm of time for variables that violated this assumption, which included component separation use, laparoscopic and open approaches, mesh use, age, sex, congestive heart failure, peripheral vascular disease, chronic pulmonary disease, kidney failure, deficiency anemias, psychoses, and obesity.²¹

All analyses were performed using SAS version 9.4 (SAS Institute) and Stata version 18 (StataCorp). Tests were 2-sided and significance set at P鈥�<鈥�.05. Cox models accounted for clustering, and robust standard errors were used to account for heteroscedasticity. Analysis was performed from January through June 2024.

From 2007 to 2021, 218鈥�518 patients underwent ventral hernia repair, of which 23鈥�768 (10.9%) were performed with component separation and 194鈥�750 (89.1%) were performed without component separation (Table 1). The mean (SD) age of the cohort was 69.1 (10.9) years; 127鈥�857 patients (58.5%) were female and 90鈥�661 (41.5%) male. The median (IQR) follow-up time after the index hernia surgery was 7.2 (2.7 to 10) years. While the total number of inpatient ventral hernia repairs decreased from 17鈥�661 to 7330 from 2007 to 2021, the proportion of inpatient ventral hernia repairs that used component separation increased from 1.6% (279 patients) to 21.4% (1569 patients) (Figure 1 and eTable 2 in Supplement 1).

The 23鈥�768 patients who underwent repair with component separation were slightly younger (mean [SD] age, 68.1 [10.3] vs 69.2 [10.9] years, respectively) and more likely to be male (10鈥�445 [43.9%] vs 80鈥�216 [41.2%], respectively) than those undergoing repair without component separation (n鈥�=鈥�194鈥�750). Patients with component separation were more likely to have comorbid conditions such as depression (3040 [12.8%] vs 20鈥�253 [10.4%], for those without component separation), diabetes with chronic complications (1637 [6.9%] vs 9653 [5.0%], respectively), concurrent fluid and electrolyte disorders (4440 [18.7%] vs 23鈥�626 [12.1%], respectively), and obesity (6010 [25.3%] vs 39鈥�781 [20.4%], respectively). They were more likely to have repair procedures with an open approach (21鈥�907 patients with component separation [92.2%] vs 138鈥�421 [71.1%] without) and procedures that used mesh (19鈥�825 [83.4%] vs 127鈥�628 patients [65.5%], respectively) (Table 1). Most differences in baseline characteristics between the 2 groups outside of those mentioned above, despite statistical significance, were not clinically meaningful.

After adjustment for patient and operative factors, cumulative operative recurrence rates for patients undergoing ventral hernia repair with component separation were 0.7% (95% CI, 0.7%-0.8%) at 1 year, 4.2% (95% CI, 4.1%-4.2%) at 3 years, 6.8% (95% CI, 6.7%-6.8%) at 5 years, and 11.2% (95% CI, 11.0%-11.3%) at 10 years postoperatively (Figure 2). In comparison, patients undergoing repair without component separation had higher recurrence rates at 1 year (0.9%; 95% CI, 0.9%-0.9%), 3 years (4.9%; 95% CI, 4.9%-4.9%), 5 years (7.9%; 95% CI, 7.9%-7.9%), and 10 years (12.9%; 95% CI, 12.8%-13.0%).

Surgeon-specific data was available for 23鈥�627 component separations (99.4%) in the sample with a total of 6480 individual surgeons identified. After proportional Medicare volume adjustment, 4692 surgeons (72.4%) performed fewer than 2 component separations per year and 6307 surgeons (97.4%) performed fewer than 5 annual component separations (eFigure 2 in Supplement 1). Stratification of surgeons into low (bottom 95%) and high (top 5%) annual inflated volume of ventral hernia repairs with component separation yielded median (range) of annual number of repairs of 1.2 (0.1-3.7) for the low-volume and 4.9 (3.8-62.5) for the high-volume groups. Patient characteristics by surgeon volume are shown in Table 2. Notably, patients undergoing component separation from high-volume surgeons were less likely to have chronic pulmonary disease or diabetes without chronic complications, more likely to have kidney failure, and more likely to receive mesh during their operation. At 10 years postoperatively, surgeons in the top 5% of component separation volume had lower operative recurrence rates (11.9%; 95% CI, 11.8%-12.1%) than surgeons in the bottom 95% of component separation volume (13.6%; 95% CI, 13.4%-13.7%; P鈥�=鈥�.004) (Figure 3).

This study of Medicare beneficiaries found that component separation is associated with reduced long-term operative recurrence rates after ventral hernia repair. Interestingly, surgeon volume was associated with only a minor reduction in recurrence rates. This has considerable implications given the nearly 14-fold increase in use of component separation over the past 15 years combined with the large proportion of surgeons performing a very small number of these operations annually. Despite this, our data suggest that component separation has a protective benefit as it is currently being applied by surgeons at the population level.

The protective effect of component separation on operative recurrence requires further discussion. While the absolute difference in operative recurrence rates of 1.7% at 10 years after index surgery may seem small at face value, it鈥檚 important to note that patients requiring a component separation typically have larger, complex, and/or multiply recurrent hernias that carry a higher baseline risk of recurrence.^12,22 Thus, even achieving a comparable operative recurrence rate to hernia repairs performed without component separation is evidence that the technique provides an effective repair. Moreover, our outcome measure of operative recurrence is thought to underestimate true clinical recurrence by as much as 4- to 5-fold.²³ These findings are consistent with previous population-based work suggesting that component separation is associated with reduced rates of recurrence.^11,12 However, this study expands on previous work by directly quantifying the difference in recurrence rates while using a nationally representative population that includes surgeons of all experience levels.

The finding of lower operative recurrence rates with higher surgeon volume is consistent with the large body of evidence demonstrating a volume-outcome relationship for major operations.^13,24 However, the absolute difference in 10-year operative recurrence rates of less than 2% between high- and low-volume surgeons was relatively minor. Previous studies have suggested lower odds of recurrence after complex abdominal wall reconstruction when performed by a highly experienced surgeon; however, the magnitude of these differences was not reported.¹⁵ This study not only quantifies the effect size of additional volume but uses population-level data from nearly 6500 surgeons in various practice settings across the country. In total, these data suggest that localization of complex abdominal wall reconstruction to the highest-volume surgeons may not yield clinically significant improvements in long-term outcomes.

The relatively small difference we found in operative recurrence rates by surgeon volume is particularly salient when accounting for the heavily skewed use of component separation by low-volume surgeons over the study period. Even after volume inflation, most surgeons in our data did not perform a large volume of component separations, as more than 90% of surgeons performed fewer than 3 of the procedures annually. This distribution of usage may be motivated by multiple factors. First, no consensus guidelines exist for when a surgeon should use component separation, which leads to wide variation in how surgeons are performing the technique, and may lead to both underutilization and overutilization.²⁵ Increased awareness and popularity of component separation, which experienced a resurgence in the mid-2010s after modification of the posterior component separation procedure (known as the transversus abdominus release), and more recently with laparoscopic and robotic adaptations of the technique, may play a role in contemporary adoption patterns.^2,4 Furthermore, there is a considerably higher reimbursement for the procedure vs a simple hernia repair, creating potentially nefarious incentives to use component separation even for small or straightforward hernias that could otherwise be repaired without the technique.²⁶ In fact, 1 recent study found that roughly 15% of component separations performed in Michigan were for hernias less than 4 cm in width.²⁷ In the absence of clear guidelines for its use, it remains unclear if component separation is being appropriately applied, particularly in light of alternative strategies that may obviate the need for component separation, such as a preperitoneal repair with wide mesh overlap or the use of preoperative botulinum toxin A to facilitate midline fascial closure.^28,29

This work should be interpreted within the context of several important limitations. First, the Medicare population may not be generalizable to all patients undergoing hernia surgery. Some patients may be denied an operation or reoperation because of advanced age and comorbidity burden, which would affect our operative recurrence rates. Despite this, hernia repair is more common in older adults both because of aging and the higher likelihood of developing an incisional hernia from a prior operation.³⁰ Second, Medicare claims lack nuanced patient and operative characteristics that may drive the decision to perform a technique like component separation, such as hernia size, and cannot differentiate between technical variants such as anterior vs posterior component separation. However, a strength of this study was the ability to evaluate component separation as it was being applied at the population level, not just among experienced surgeons at specialized centers. Third, the surgeon volume analysis should be interpreted within the context of our ability to project all-payer patient volume from individual surgeon Medicare patient volume. To address this, we used the best available methods from previously published studies to inflate Medicare volume by the proportion of a hospital鈥檚 Medicare admissions to total number of discharges. This methodology assumes that an individual surgeon鈥檚 payer mix reflects a particular hospital鈥檚 payer mix, which is a reasonable assumption given that hernia repairs performed with component separation are primarily performed in the inpatient setting. Finally, inappropriate use of component separation may have a paradoxical effect on operative recurrence. For example, a surgeon who uses component separation to repair a small hernia, which would otherwise have a lower recurrence rate than larger defects, may have lower than average recurrence rates because of this inappropriate use. Thus, surgeon volume alone does not tell the full story, and more granular data are necessary to both inform guideline creation and measure adherence.

This study has important implications for surgeons and policymakers. While there is a push for hernia fellowship specialization in response to the increasing incidence and complexity of hernia care,^31,32 this study suggests that additional efforts to centralize complex abdominal wall hernia care to high-volume surgeons may provide only marginal gain with regard to long-term hernia recurrence. Continual diffusion of new operative techniques, mesh technology, and the emergence of the robot in hernia procedures have typically outpaced the availability of high-quality evidence suggesting relative advantages and disadvantages for their use. This leads to wide variation in practice patterns and decision-making, even among expert hernia surgeons.³³ Medicare claims data give us an important aerial view within hernia research and are particularly unique in their ability to track longitudinal operative recurrence given the near universal enrollment and low disenrollment rates. However, clinical registries remain a crucial complement to administrative data through collection of nuanced patient, hernia, and operative characteristics, which are then paired with clinical and patient-reported outcomes. There are currently 2 active hernia registries in the US, the Abdominal Core Health Quality Collaborative and the Michigan Surgical Quality Collaborative Core Optimization Hernia Registry. Registry data have the potential to greatly improve understanding of which patients would benefit from different operative techniques and would help inform the creation of consensus, evidence-based guidelines for the use of component separation, which are currently lacking.²⁵

This study found that component separation repair had lower rates of long-term operative recurrence than hernia repairs performed without component separation, a somewhat unexpected finding given the intent of component separation use for higher complexity hernias. Surgeon volume, while significant, had only a minor influence on long-term operative recurrence rates.

Accepted for Publication: September 1, 2024.

Published Online: November 13, 2024. doi:10.1001/jamasurg.2024.5091

Corresponding Author: Brian T. Fry, MD, MS, Department of Surgery, University of Michigan Center for Healthcare Outcomes & Policy (CHOP), 2800 Plymouth Rd, NCRC-016-100N-29, Ann Arbor, MI 48109 (brianfry@med.umich.edu).

Author Contributions: Drs Fry and Telem had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.

Concept and design: Fry, Schoel, Howard, Kappelman, Hallway, O鈥橬eill, Rubyan, Shao, Telem.

Acquisition, analysis, or interpretation of data: Fry, Howard, Thumma, Hallway, Ehlers, O鈥橬eill, Shao, Telem.

Drafting of the manuscript: Fry, Howard, Thumma.

Critical review of the manuscript for important intellectual content: All authors.

Statistical analysis: Fry, Howard, Thumma.

Obtained funding: Telem.

Administrative, technical, or material support: Kappelman, Hallway, Rubyan, Telem.

Supervision: Howard, O鈥橬eill, Shao, Telem.

Conflict of Interest Disclosures: Dr Fry reported grants from the National Institute on Aging (T32AG062403), SAGES (AWD023313), and support from an NIA loan repayment award (L30AG079448-01) outside the submitted work. Dr Schoel reported salary support from NIA (T32AG062403). Ms Kappelman reported graduate student support from the National Institute of Neurological Disorders and Stroke (T32GM007863) and unrelated graduate student funding from the National Institute on Minority Health and Health Disparities (R01MD016046). Dr Ehlers reported grants from the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) outside the submitted work. Dr Shao reported consulting/speaking honoraria from AbbVie outside the submitted work. No other disclosures were reported.

Funding/Support: This work was supported by a grant from the NIDDK (R01DK128179-01A1; Drs Telem and Rubyan).

Role of the Funder/Sponsor: The funder had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

Data Sharing Statement: See Supplement 2.