Discussion
In this study, we investigated the time-related effects of the AbClo device on patients who had the abdominal wall fascia intentionally left open at the end of a laparotomy for trauma and EGS. Our findings showed that 8 hours after the index laparotomy, the percent decrease in the maximum width of the fascial defect was two times greater with early placement of the device (≤24 hours after the index laparotomy) compared with late placement (>24 hours after the index laparotomy). Moreover, a 74.5% decrease in the width of the fascial gap was achieved 24 hours after the index laparotomy, indicating a gap reduction 1.7 times greater with early placement versus late placement of the device. Myofascial reapproximation with this non-invasive approach tended to plateau at approximately 48 hours after device placement. Nevertheless, the fascial gap reduction in the early placement group was significantly better than late placement. Those findings underscore the potential advantages of a preventative approach to the lateralization of the abdominal wall in the OA. They also support the notion that cutting the linea alba disrupts the midline attachments of the fascia, resulting in rapid lateral retraction of the myofascial layers.15 33
The disruption of the linea alba causes shortening of the muscles and a reduction in elasticity which increases the fascial gap and interferes with efforts to medialize the muscles.15 33 Unloading of the abdominal wall muscles results in muscle atrophy with reduction in fiber diameter in as early as 3–5 days.34 35 Those findings are linked to the predominance of slow twitch fibers in abdominal muscles which are more susceptible to atrophy than fast twitch muscles.34 35
Primary myofascial closure rate was 98% with early placement of AbClo, and 85% with late device placement. Overall primary myofascial closure rate was 93%, similar to current closure rates for invasive fascial traction systems.6 7 10 11 14 15 21 23 27 36 37 Interestingly, an 85% rate of primary closure with late placement of AbClo reproduced the results of our group’s previous pilot study in which the device was initially placed 48 hours after the index laparotomy.28 This finding validates that the preventive care path of this technology relies on applying it before myofascial contraction and lateral retraction of the abdominal wall become too difficult to overcome non-invasively. Accordingly, recent studies showed that incorporating a gradual fascial traction strategy, as soon as possible, after the index laparotomy significantly increases the rate of primary fascial closure in OA.10 11 14 15 22 23 25 38 Delaying the application of a fascial traction method reduced fascial closure rate by 30–60%.10 11 14 15 28 38 One study also showed that approximately 80% of patients who did not achieve fascia closure experienced a delay of three or more days to undergo the application of a fascial traction method.15
Nearly all fascial traction strategies currently used for OA are invasive requiring surgical procedures to fasten retention sutures, mesh, and elastic material to the abdominal wall fascia.6 10 11 15–24 36 38 Consequently, usage of those strategies immediately after the index laparotomy can be curbed by coagulopathy, takebacks, recent gastrointestinal anastomosis, risk of abdominal compartment syndrome, fluid overload, bowel edema, injury burden, and surgical site infection.10 12 15 36–38 Invasive fascial traction in the presence of those conditions could contribute to early complications in OA.15 36–38 In contrast, a non-invasive approach that avoids direct surgical manipulation of the myofascial layers could be more suitable for early application in the OA. Accordingly, the main advantages of the AbClo device include preservation of the fascia and rapid non-invasive bedside placement, adjustment, and removal. Moreover, the pressure gauge with preset safety tension zone helps avoid abdominal compartment syndrome.
The biomechanical principles of the device hinge on the compression and shear forces generated by the rectus abdominal muscle rigid splints and the elastic binder. The resultant vector from those forces produces 44.12 pound-force (lbf) distributed tangentially over the recti abdominis pushing the myofascial layers toward the midline.28 Load response deformation of the abdominal wall is subject to mechanical laws that include the coefficients of elasticity (Young’s modulus) and of stiffness (shear modulus).39–42 At the skin level, the biomechanics of load propagation is primarily determined by collagen and elastic fibers arranged according to Langer’s lines.32 41 43 44 Previous experiments showed that skin collagen bundles realign, increase rigidity, and undergo morphological changes in the direction of external forces in 30 minutes.45 This notion supports the non-invasive midline transfer of resultant force vector generated by the rectus muscle splints and the circumferential dynamic binder of the AbClo device.28 29 32 Moreover, myofascial medialization is enhanced by the concave undersurface of the splints.28
Force transmission across the subcutaneous adipose tissue is also determined by mechanical laws that include the coefficients of elasticity and stiffness.29 46 Magnetic resonance elastography showed that compression and shear strains applied to the subcutaneous adipose tissue induced more stiffness than when applied to muscles.29 46 Those findings corroborate the process of non-invasive propagation of the resultant force vector across all layers of the abdominal wall and the retention of those layers by the AbClo device.
Several studies have shown a decreased likelihood of primary fascial closure with higher number of takebacks.9–11 47 Recent data showed that each additional takeback reduced the odds of primary fascial closure by approximately 90%.10 Furthermore, a delay to first takeback beyond 24 hours after the index laparotomy was also linked to decreased odds of primary fascial closure, with approximately 80% decrease in delays between 24.1 and 36 hours up to 98% with delays longer than 48 hours.10 12 Our findings showed that a single takeback was three times more common in the early placement group than in the late group. Considering the favorable effect of a single takeback on fascial closure, we also reassessed our data after excluding all patients that were closed on the first takeback. Despite the exclusion of those patients, our findings still showed a higher percent reduction in the fascial gap and primary fascial closure with the placement of the device compared with late placement.
Previous studies showed a higher prospect of primary fascial closure in patients who had OA for trauma than EGS.6–8 10 11 14 14 21 28 37 This is most likely due to fewer comorbidities, new adjuncts to resuscitation, and more judicious use of crystalloids in trauma, and fewer takebacks.6–8 10 11 14 14 21 28 37 However, in our study, primary fascial closure and the need for two or more takebacks were similar in EGS and trauma patients. In addition, patients’ median fluid volume status was consistently above 8 L, but fascial closure did not seem to be impacted. Those findings suggest that early application of the device could have a favorable impact in the number of takebacks and primary fascial closure regardless of the reason for the OA. That notion is supported by the capability of uncomplicated pressure-regulated fascial reapproximation at the bedside avoiding unnecessary changes of in the operating room with an estimated cost of US$5600 per device. Moreover, the same device can be reused on the same patient after each takeback. Accordingly, in a recently published cost-minimization analysis, the use of AbClo was associated with lower incremental costs of −$6012 (95% CI −19 499 to 1996) compared with NPWT alone including operating room costs.48 The mean cumulative costs per patient were $76 582 for those treated with NPWT alone versus $70 582 for those treated with the AbClo device.48
Studies showed that a BMI≥30 kg/m2 could have a negative impact on the success and timing of primary fascial closure in OA patients.47 49 50 Therefore, we specifically assessed the impact of patients’ BMI on non-invasive approach for myofascial mobilization. Our findings showed that the BMI was similar between the groups with an overall median BMI>30 kg/m2. Moreover, after adjusting for BMI and number of takebacks, our findings still showed an average fascial gap reduction and fascial reapproximation 22% higher with early AbClo placement (≤24 hours) compared with late placement. Those findings corroborate mechanical load transmission generated by the device through the subcutaneous adipose tissue.29 46
Considering the complications specifically related to the use of the AbClo device, our results showed only minor (stage 2) pressure ulcers of the skin which were treated conservatively with saline and dressings. Those ulcers were unrelated to early or late application of the device and were undoubtedly less severe than the complications reported with current surgical methods of fascial traction.1–7 A particularly important finding was the absence of abdominal compartment syndrome and elevated peak pressures, indicating the safety of the device’s safe tension zone monitoring feature (35–65 mm Hg). Moreover, there were no cases of acute fascial dehiscence, and enterocutaneous fistula related to the use of the device. The postoperative hernia rate of the patients who underwent primary fascial closure was 14.3% at 3-month follow-up.
This study has several limitations. In addition to its small sample size and non-randomized management, we did not compare the reduction in fascial gap and primary closure rates achieved with the AbClo device to that of other methods including invasive fascial traction systems. This was due to two factors: first, the non-invasive approach of the AbClo is fundamentally different from surgical procedures for fascial traction, and second, we have not used invasive fascial traction techniques in our center. Moreover, we did not specify the time to first takeback and the indications for the OA based on specific surgical findings during the index damage control laparotomy. Comorbidities and prognostic scores were not assessed for EGS patients. Furthermore, time to follow-up was very limited to provide meaningful data related to postoperative hernia formation after primary fascial closure. Finally, we did not directly assess additional factors that have been shown to promote fascial closure in OA patients including direct peritoneal resuscitation, botulin toxin injection, damage control resuscitation, and whole blood transfusion.