The 'AbdoMAN': an artificial abdominal wall simulator for biomechanical studies on laparotomy closure techniques

Abstract

Purpose: Incisional hernia remains a frequent complication after abdominal surgery associated with significant morbidity and high costs. Animal and clinical studies have exhibited some limitations. The purpose of this study was to develop an artificial human abdominal wall (AW) simulator in order to enable investigations on closure modalities. We hypothesized that a physical model of the human AW would give new insight into commonly used suture techniques representing a substantial complement or alternative to clinical and animal studies.

Methods: The 'AbdoMAN' was developed to simulate human AW biomechanics. The 'AbdoMAN' capacities include measurement and regulation of intra-abdominal pressure (IAP), generation of IAP peaks as a result of muscle contraction and measurements of AW strain patterns analyzed with 3D image stereo correlation software. Intact synthetic samples were used to test repeatability. A laparotomy closure was then performed on five samples to analyze strain patterns.

Results: The 'AbdoMAN' was capable of simulating physiological conditions. AbdoMAN lateral muscles contract at 660 N, leading the IAP to increase up to 74.9 mmHg (range 65.3-88.3). Two strain criteria were used to assess test repeatability. A test with laparotomy closure demonstrated closure testing repeatability.

Conclusions: The 'AbdoMAN' reveals as a promising enabling tool for investigating AW surgery-related biomechanics and could become an alternative to animal and clinical studies. 3D image correlation analysis should bring new insights on laparotomy closure research. The next step will consist in evaluating different closure modalities on synthetic, porcine and human AW.

Keywords: Abdominal wall; Biomechanics; Incisional hernia; Laparotomy closure.

Fig. 1

‘AbdoMAN’ device. a Schematic overview showing all different components. b Side view showing three lateral muscle actuators connected to the mounted sample and the cranial/caudal jaws used to mount the sample. c Top view showing an intact sample mounted on the ‘AbdoMAN’ using jaws on all four sides

Fig. 2

Abdominal wall samples. a Shape of a sample prior to mounting. b A mounted sample on the ‘AbdoMAN’ device with fixation in four directions

Fig. 3

Synthetic abdominal wall stiffness testing. Each sample was tested in two directions (D1 and D2)

Fig. 4

‘AbdoMAN’ test setup repeatability results. a Synthetic abdominal wall stiffness determined by tensile machine testing of a small piece of each sample. b Peak intra-abdominal pressure during cough cycle of the samples mounted on the ‘AbdoMAN’. c Mean strain over surface area of the samples mounted on the ‘AbdoMAN’. d Mean strain over transversal line of the samples mounted on the ‘AbdoMAN’

Fig. 5

3D stereo correlation criteria of intact samples. a Exemplary strain image of an intact synthetic abdominal wall sample at peak intra-abdominal pressure. b Schematic image of used strain analysis areas for 3D stereo correlation: linear strain in the muscle force direction and area strain of a larger surface area

Fig. 6

3D stereo correlation criteria of 5 × 5 mm suture modality. a Mean maximum strain around suture points. The areas are indicated in the white circles. b Peak-to-peak normalized strain profile through the suture points. Maximum and minimum peaks are indicated and connected with the green lines. c Maximum opening length of the incision. This is indicated with the red line

Fig. 7

Midline closure repeatability results. a Mean maximum strain around suture points as indicated in Fig. 6a. b Peak-to-peak normalized strain profile through the suture points as indicated in Fig. 6b. c Maximum opening length of the incision as indicated in Fig. 6c