Transversus Abdominis Release (TAR) Procedure: Experience of An Abdominal Wall Reconstruction Group.

Complex abdominal wall defects are important conditions with a high morbidity, leading to impairment of patients physical condition and quality of life. In the last decade, the abdominal wall reconstruction paradigm has changed due to formation of experienced and excellence groups, improving clinical outcomes after surgery. Therefore, our study shows the perspective and outcomes of an abdominal wall reconstruction group (AWRG) in Colombia, focused on transverse abdominis release (TAR) procedure.


Background
Abdominal wall defects are considered a complex pathology with increasing prevalence in the surgical practice [1]. Patients that underwent laparotomy have a 22-55% risk of herniation [1,2]. Numerous risk factors have been described in abdominal wall defects, such as emergency procedure, longevity, and comorbidities like chronic pulmonary obstructive disease (COPD), renal impairment, immunosuppression, mal-nutrition, and diabetes mellitus (T2DM) [2]. Frequently, patients that underwent abdominal surgical procedures due to critical illness, have to endure complex abdominal wall defects that directly impact their quality of life after survival [3]. Additionally, failure of hernia repair comprises between 25-54% of cases, resulting in an increment of costs, morbidity, and impact on quality of life [4][5][6][7][8]. Therefore, the need for further surgical procedures to correct abdominal wall defects, represents a challenge even for experienced surgeons, seeking a reliable, safe and durable repair [2][3][4].
Novitsky et al in 2012, presented a novel technique that modi ed the traditional surgical approach (Usually Rives-Stopa procedure) for patients with important abdominal wall defects [5]. As a result, the Total abdominis muscle release (TAR) was proposed, showing good results in terms of recurrence, and postoperative and intraoperative complications [5]. TAR technique is based on the principal goals of an abdominal wall reconstruction: restoration of abdominal wall functionality preserving autologous tissue, and reinforcement by a durable mesh with less proportion of complications [5,6]. After the presentation of this novel technique, numerous centers started its implementation as part of their regular practice reporting similar results, such as Appleton et al and Pujani et al, nding low incidence of recurrence, and morbidity [1][2].
Surgical expertise is the result of experience associated with the volume of procedures and hours of training, and the impact it may have on postoperative outcomes [9]. Relationship between surgeon volume and postoperative outcomes have been established in different studies in terms of abdominal wall hernia repair, de ning low volume as < 12 hernia repairs , intermediate 12-23 procedures, high [24][25][26][27][28][29][30][31][32][33][34][35] surgeries, and very high > 36 procedures [10]. Aquina et al found a positive association between surgeons with intermediate, high and very high volume and a decrease in hernia recurrence, postoperative complications and hospital costs [10]. Hence, excellence centers and groups with experienced surgeons have been created through the years with the goal of achieving better results, as presented by Giron et al, this specialization may result in better outcomes [11][12][13][14]. Therefore, we present the experience of an abdominal wall reconstruction group (AWRG) outcomes with total abdominis release procedure for complex ventral hernias.

Study population
With the Institutional (Hospital Universitario Mayor Méderi) Review Board's approval, and following Health Insurance Portability and Accountability Act (HIPAA) guidelines, a retrospective review of a prospectively collected database was conducted. All patients over 18 years of age that underwent TAR procedure between January 2014 and December 2020 were included. Patients with no surgical description and missing data were excluded. Ethical compliance with the Helsinki Declaration, current

Statistical analysis
Descriptive statistics were reported in terms of variable nature. Qualitative analysis was performed in terms of frequencies and percentages, while quantitative analysis was done in terms of mean and standard deviations of normally distributed data and medians and interquartile ranges (IQRs) for nonnormally distributed data. Bivariate analysis was performed. Qualitative variables were analyzed using chi-square statistics (Fisher's exact test when appropriate). Quantitative variables were analyzed, based on normality, with Spearman's or Pearson's associations correlation coe cients accordingly. Bivariate analysis between qualitative and quantitative variables was performed using Mann-Whitney test or the ttest for independent samples. For associations between categorical variables, odds ratios with 95% con dence intervals were provided. Multivariate analysis was performed, including all variables that showed association with signi cant statistical value of p < 0.2 based on bivariate analysis, also, multivariate results were analyzed with p <0.05 cut off point.

Surgical Technique
Midline incision is performed, based on preoperative CT assessment, in order to avoid inadvertent enterotomy. In midline defects, dissection of the Hernial sac is performed to free it from adjacent soft tissue. Lysis of parietal adhesions is accomplished using blunt and sharp dissection. Abdominal cavity is packed with warmed compresses for visceral protection. Posterior rectus sheath is divided, on one side, medial to linea alba. Blunt dissection (hydrodissection) of adhesions is performed until lateral neurovascular bundles are visualized medial to semilunar line. On the other side, super cial pass of the hernial sac allows access to retro rectus space. Retro rectus dissection is performed as on the previous side. Falciform is dissected of línea alba and posterior rectus sheath (PRS). Medial edges of PRS are divided (extra-peritoneally) until rostral ends at the xiphoid within the fatty triangle of Schumpelick [2].
Due to the complexity in the management of complex abdominal wall defects, creation of surgical groups specialized has arisen as a feasible option seeking achievement of better postoperative outcomes, such as morbidity, mortality and recurrence rate reduction in these patients. , being these results akin to those found in our population, where recurrence rate at 12-month follow up was 4%, with a mean follow up of 35,72 months. Surgeon expertise and high/intermediate volume centers are related with better postoperative outcomes, and lees nancial burden in hernia surgery (9)(10)(11)(12)(13)(14); in our institution, a protective factor in terms of surgical site infection, with a OR 0.07 IC (p=0,2) was found if patients underwent TAR procedure performed by AWRG, conversely to a 13-fold risk increase in SSI if the procedure was not performed by AWRG.
Abdominal wall defect procedures are designed aiming to not only repair the defect but also to restore the functionality of the abdominal wall, in uencing patient's self-esteem, emotional and mental health, being life quality an important quality indicator in hernia surgery [35][36][37]. In our study, life quality evaluation showed great results with 93.8 pts in change of health, 88.5 in social function, 83.8 in role limitation (Table 6 -See appendix), measured by the -ShortForm36- [38]. Based on these results we can assert that a multidisciplinary and specialized group can offer better postoperative outcomes, reduce in-hospital costs, and have a positive impact on the life quality of our patients with complex abdominal wall defects.
Among the limitations of this study are its retrospective nature and the lack of previous studies to compare our results in terms of abdominal group versus non-specialized surgical team. Although studies have appeared in recent years regarding this topic, further prospective studies are needed to validate our results.

Conclusion
Transverse Abdominis Release (TAR) procedure for complex abdominal wall defects under speci c clinical conditions including emergency scenarios is viable. Specialized and experienced groups can offer better postoperative outcomes and lessen surgical site infection with great results in terms of life quality. Further prospective studies are needed to con rm our results.

Declarations
Compliance with Ethical Standards: (In case of Funding) Funding: This study does not receive any funding.
Con ict of Interest: Authors do not have any con ict of interest.
Ethical approval: All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
Informed consent: Informed consent was obtained from all individual participants included in the study, and reposes in clinical history