Outcomes of Surgical Repair of Incisional Hernia in Patients With Severe and Morbid Obesity: A Comparative Study

Introduction Incisional hernia (IH) is a common complication after open and minimal access abdominal surgery. The current practice guidelines recommend weight reduction to achieve a body mass index (BMI) < 35 kg/m2 before surgical repair of ventral hernias. However, this could be challenging to achieve, especially in emergency presentations. This study aims to assess the safety of surgical repair of IH in patients with BMI ≥35 kg/m2. Methods A retrospective comparative study has been conducted to include all patients who had surgical repair of IH on an elective and emergency basis in a UK District General Hospital. The patients were divided into two groups. Group I BMI < 35 kg/m2 and Group II with BMI ≥35 kg/m2. A comparison was made between the two groups according to demographics, comorbidities, hernia characteristics, operative data, and outcomes. Results The study included 239 patients, 181 in Group I and 58 in Group II. Morbid obesity was associated with male patients, and they were younger than Group I, p= 0.001 and 0.013, respectively. 13.8% of Group I had DM compared to 29.3% in Group II, p= 0.007. There were no significant differences in hernia characteristics or mode of surgery between the two groups. However, Group II had more overall and wound-related complications, p= <0.001 each. There were no significant differences in 30-day and 90-day mortality, recurrence rate, or 90-day readmissions. Conclusions Surgical repair of IH in patients with severe and morbid obesity is associated with more overall and wound-related complications.


Introduction
Incisional hernias (IH) in patients with morbid obesity represent a real challenge and create a vicious cycle that is hard to break.On the one hand, obesity is a known predisposing factor for developing IH after abdominal procedures [1].On the other hand, large IH could limit physical activities and lead to social isolation due to disfigurement, exacerbating obesity [2].
The surgical repair of IH is associated with symptom relief and improved quality of life [3].However, in the presence of obesity, surgical repair could be associated with an increased risk of complications and recurrence [4,5].The current practice guidelines recommend weight reduction to achieve a body mass index (BMI) < 35 kg/m2 before surgical repair of ventral hernias [6].However, this could be challenging to achieve in IH with morbid obesity, given the long waiting lists, the persistence of obesity that can lead to more complex cases and the presentation of incarceration on an emergency basis [7].This study aims to assess the safety of surgical repair of IH in patients with BMI ≥35 kg/m2.

Study design
A comparative retrospective cohort single-centre study from 2013 to 2021.

Setting
High volume acute service district general hospital in the United Kingdom.

Participants Inclusion Criteria
Study participants included all patients who had surgical repair of incisional hernia on an elective and emergency basis and had complete data.

Patients' Demographics, Comorbidities, and Risk Factors
The primary outcome parameters included all-cause and wound-related complications and mortality rates.The secondary outcome parameters included length of hospital stay, need for high-level care, unplanned 90day readmissions, and recurrence rate.The patients were divided into two groups; Group I had BMI <35 and Group II had ≥35.A comparison was made between the two groups according to the different variables examined.

Data source/bias
Data was collected from computerised records and patient case notes.

Study size
The total number of patients admitted for surgical repair of incisional hernias with complete data.

Statistical analysis
Data were analysed using the statistical software package Statistical Package for Social Sciences (SPSS), version 20.0 (IBM Corp., Armonk, NY).The Kolmogorov-Smirnov test was used to verify the normality of distribution.Continuous data were described using range (minimum and maximum), mean, standard deviation, and median.Comparisons between groups for categorical variables were assessed using the Chisquare test (Fisher or Monte Carlo).Student t-test was used to compare two groups for normally distributed quantitative variables.Mann-Whitney test was used to compare two groups for non-parametric data.Spearman coefficient was used to assess correlation.

Results
A total of 296 patients who had operations for IH were identified; 57 of them had incomplete data and were consequently excluded from the study.The analysis included 239 patients, 181 with BMI <35 (Group I) and 58 patients with BMI≥ 35 (Group II).
In Group I, 45 had emergency repair and 136 had elective repair.In Group II, 28 had emergency repair and 30 had elective repair.Moreover, in regards to gender, in Group II, 44 (75.9%) were females, compared to 94 (51.9%) in Group I, p=0.001.Group II patients were significantly younger, p= 0.013.
The comparison of the identified comorbidities showed a significant difference with diabetes mellitus (DM) only, where Group II had more patients, 17 (29.3%)with DM, compared to 25 (13.8%) in Group I, p = 0.007.Additionally, Group I included more patients with malignancy compared to Group II, p= p= 0.013.The comparison of the other comorbidities and risk factors did not show significant differences between the two groups (Table 1).Table 2 shows the comparison according to the hernia characteristics, operative details, and outcome parameters.There was a wide variation in the hernial defect size; these ranged from 1.5 by 1.5 cm to 20 by 14 cm.Additionally, there were no significant differences in hernia characteristics or mode of surgery between the two groups.A comparison of the outcome parameters showed that Group II had more overall and wound-related complications, p <0.001 each.There were no significant differences in 30-day and 90-day mortality, recurrence rate, or 90-day readmissions.

Discussion
This study compared the outcomes of the surgical repair of IH between patients with and without morbid obesity.Morbid obesity was associated with overall and wound-related complications.
Obesity and its associated comorbidities increase the risk of local wound complications and lead to a defective healing process and IH after primary abdominal surgery [4,8].Given the situation's complexity when patients with morbid obesity develop IH, there might be some inclination towards a watchful waiting strategy with this patient group.However, the safety of this approach is questionable [9].A recent study in the USA showed that obesity was associated with significantly increased odds of nonelective repair of IH [10].Additionally, nonelective repair of IH was correlated with in-hospital mortality, postoperative complications, and prolonged hospital stay [10].
Another study included 3,908 patients with IH and studied the effect of obesity, diabetes, and smoking on the outcomes [11].They found that having one or two of these comorbidities significantly increased the risk of surgical site occurrence.Moreover, patients with all three comorbidities had a two-fold increase in odds for all wound morbidity, followed similarly by obese patients with diabetes.They concluded that having multiple comorbidities was associated with the need for interventions for wound complications.This was most evident in patients with all three comorbidities and with obesity and DM.
In this series, 29.3% of the patients with morbid obesity had DM, and 56.9% had at least one medical comorbidity.This could potentially put this group at risk with any surgical intervention.However, the prevalence of malignancy was higher in Group I, 47 (26%), compared to six (10.3%) in Group II.This could be attributed to the age difference between the two groups.The mean age was 62.78 ± 14.21 in Group I and 57.53 ± 13.13 years in Group II, p= 0.013.
Studying the hernia characteristics showed that 62 (35.2%) of Group I and 14 (24.1%) of Group II presented with multiple hernial defects, and 46 (25.8%) of Group I and 16 (28.1%) of Group II had recurrent IH.Ninetytwo (51.7%) of Group I and 25 (43.9%) of Group II patients needed adhesiolysis.These findings reflect the complexity of this cohort.Comparing the outcome parameters between the two groups showed a higher complication rate of 62.1% in Group II compared to 38.7% in Group I.This has been demonstrated across all Clavien-Dindo (CD) categories.Additionally, the wound complications in Group II were three-fold (34.5%) compared to Group I (11.7%).However, the 30-day and 90-day mortality rates, hospital stay, the need for high-level care, 90-day readmissions, and recurrence rate did not show significant differences between the two groups.
The available literature presents a blurred picture of the relation between BMI and recurrence rates after ventral and IH repair.Some case series refuted any association between obesity and recurrence [12,13].On the contrary, other studies reported obesity as an independent risk factor for recurrence [14,15].A more recent study showed a recurrence rate of 10.5% for BMI> 32 versus 1.7% with BMI ≤32 after IH repair [5].In our series, the recurrence rate was 14 (7.8%) in Group I and nine (15.5%) in Group II after a mean follow-up of 55.9 SD ± 10.2 (Min -Max; 26.8 -72.4), with a median of 57.6 months.However, the difference wasn't statistically significant; p = 0.083.
Despite the safety of IH repair in patients with severe and morbid obesity, our findings highlight the importance of patient selection and optimisation preoperatively to reduce the risk of postoperative complications.

Study strengths and limitations
The limitations of this study included the retrospective nature and relatively small sample size.We endeavoured to mitigate any potential bias that could impact the outcomes.In this respect, we studied and compared the risk factors and comorbidities between the two groups to establish comparability and eliminate confounders.We only excluded patients who did not have complete necessary data that would have made the comparison impossible.Moreover, the data completion and extensive data analysis could present an accurate assessment of this case series.The extended follow-up period is a valuable strength of the study.

Conclusions
Morbid obesity was associated with the female gender, younger age, and diabetes mellitus.Surgical repair of incisional hernia in patients with morbid obesity is associated with more overall and wound-related complications.There were no significant differences in hospital stay, the need for high-level care, 30-day and 90-day mortality, recurrence rate, or 90-day readmissions.