Use of Shear Wave Elastography to Quantify Abdominal Wall Muscular Properties in Patients With Incisional Hernia

Soft tissue material properties based on human abdominal in vivo macro-indenter measurements

Simulations of human-technology interaction in the context of product development require comprehensive knowledge of biomechanical in vivo behavior. To obtain this knowledge for the abdomen, we measured the continuous mechanical responses of the abdominal soft tissue of ten healthy participants in different lying positions anteriorly, laterally, and posteriorly under local compression depths of up to 30 mm. An experimental setup consisting of a mechatronic indenter with hemispherical tip and two time-of-flight (ToF) sensors for optical 3D displacement measurement of the surface was developed for this purpose. To account for the impact of muscle tone, experiments were conducted with both controlled activation and relaxation of the trunk muscles. Surface electromyography (sEMG) was used to monitor muscle activation levels. The obtained data sets comprise the continuous force-displacement data of six abdominal measurement regions, each synchronized with the local surface displacements resulting from the macro-indentation, and the bipolar sEMG signals at three key trunk muscles. We used inverse finite element analysis (FEA), to derive sets of nonlinear material parameters that numerically approximate the experimentally determined soft tissue behaviors. The physiological standard values obtained for all participants after data processing served as reference data. The mean stiffness of the abdomen was significantly different when the trunk muscles were activated or relaxed. No significant differences were found between the anterior-lateral measurement regions, with exception of those centered on the linea alba and centered on the muscle belly of the rectus abdominis below the intertubercular plane. The shapes and areas of deformation of the skin depended on the region and muscle activity. Using the hyperelastic Ogden model, we identified unique material parameter sets for all regions. Our findings confirmed that, in addition to the indenter force-displacement data, knowledge about tissue deformation is necessary to reliably determine unique material parameter sets using inverse FEA. The presented results can be used for finite element (FE) models of the abdomen, for example, in the context of orthopedic or biomedical product developments.

The effect of breathing on the in vivo mechanical characterization of linea alba by ultrasound shearwave elastography

The most common surgical repair of abdominal wall hernia consists in implanting a mesh to reinforce hernia defects during the healing phase. Ultrasound shearwave elastography (SWE) is a promising non-invasive method to estimate soft tissue mechanical properties at bedside through shear wave speed (SWS) measurement. Combined with conventional ultrasonography, it could help the clinician plan surgery. In this work, a novel protocol is proposed to reliably assess the stiffness of the linea alba, and to evaluate the effect of breathing and of inflating the abdomen on SWS. Fifteen healthy adults were included. SWS was measured in the linea alba, in the longitudinal and transverse direction, during several breathing cycle and during active abdominal inflation. SWS during normal breathing was 2.3 [2.0; 2.5] m/s in longitudinal direction and 2.2 [1.9; 2.7] m/s in the transversal. Inflating the abdomen increased SWS both in longitudinal and transversal direction (3.5 [2.8; 5.8] m/s and 5.2 [3.0; 6.0] m/s, respectively). The novel protocol significantly improved the reproducibility relative to the literature (8% in the longitudinal direction and 14% in the transverse one). Breathing had a mild effect on SWS, and accounting for it only marginally improved the reproducibility. This study proved the feasibility of the method, and its potential clinical interest. Further studies on larger cohort should focus on improving our understanding of the relationship between abdominal wall properties and clinical outcomes, but also provide a cartography of the abdominal wall, beyond the linea alba.

Measuring Shear Wave Velocity in Adult Skeletal Muscle with Ultrasound 2-D Shear Wave Elastography: A Scoping Review

Ultrasound 2-D shear wave elastography (US 2D-SWE) is a non-invasive, cost-effective tool for quantifying tissue stiffness. Amidst growing interest in US 2D-SWE for musculoskeletal research, it has been recommended that shear wave velocity (SWV) should be reported instead of elastic moduli to avoid introducing unwanted error into the data. This scoping review examined the evolving use of US 2D-SWE to measure SWV in skeletal muscle and identified strengths and weaknesses to guide future research. We searched electronic databases and key review reference lists to identify articles published between January 2000 and May 2021. Two reviewers assessed the eligibility of records during title/abstract and full-text screening, and one reviewer extracted and coded the data. Sixty-six studies met the eligibility criteria, of which 58 were published in 2017 or later. We found a striking lack of consensus regarding the effects of age and sex on skeletal muscle SWV, and widely variable reliability values. Substantial differences in methodology between studies suggest a pressing need for developing standardized, validated scanning protocols. This scoping review illustrates the breadth of application for US 2D-SWE in musculoskeletal research, and the data synthesis exposed several notable inconsistencies and gaps in current literature that warrant consideration in future studies.

Comparison of the Effectiveness of Ultrasound Imaging and Perioperative Measurement in the Diagnosis and Characterization of Incisional Hernia

Background

Incisional hernia (IH) is a common complication after abdominal surgery, and there is no gold standard imaging modality for its diagnosis. Although computed tomography is frequently used in clinical practice, it has limitations such as radiation exposure and relatively high cost. The aim of this study is to establish standardization and hernia typing by comparing preoperative ultrasound (US) measurements and perioperative measurements in IH cases.

Methods

The patients who were operated for IH in our institution between January 2020 and March 2021 were reviewed, retrospectively. In result, 120 patients were included in the study, and the cases had preoperative US images and perioperative hernia measurements. IH was divided into three subtypes as omentum (Type I), intestinal (Type II), and mixed (Type III) according to the defect content.

Results

Type I IH was detected in 91 cases, Type II IH in 14 cases, and Type III IH in 15 cases. When the diameters of IH types were compared for preoperative US and perioperative measurements, respectively, there was no statistical significance (P = 0.185 and P = 0.262). According to Spearman correlation, there was a positive very strong correlation between preoperative US measurements and perioperative measurements (ρ = 0.861 and P < 0.001).

Conclusion

As stated by our results, US imaging can be performed easily and quickly, providing a reliable way to accurately detect and characterize an IH. It can also facilitate the planning of surgical intervention in IH by providing anatomical information.

Quantitative Analysis of Abdominal Muscles Using Elastography in Female Patients With Incisional Hernia

This study aimed to assess the thickness and shear wave speed (SWS) of the anterolateral abdominal wall muscles in female patients with incisional hernias of different widths, in order to analyze the biomechanical properties of abdominal wall muscles. This study included 53 patients with incisional hernia (Group A [hernia width <4 cm]: 21 patients, Group B [hernia width ≥4 cm]: 32 patients). The muscle thickness and SWS values of the external oblique (EO), internal oblique (IO), and transversus abdominis (TrA), and the hernia width were measured using Siemens Acuson S2000 ultrasound systems. Four detection points were labeled on the anterolateral abdominal wall: points 1, 2, 3, and 4, corresponding to the upper right, upper left, lower right, and lower left, respectively. The muscle thickness of the IO at point 3 was significantly different between both groups (p = 0.024). Group B had significantly higher SWS values than Group A, especially for the EO (points 1, 2, and 3), IO (points 1 and 2), and TrA (points 2 and 4) (p < 0.05). Pearson correlation analysis shows no significant correlation between muscle thickness and the SWS values of EO, IO, and TrA (all p > 0.05). Linear correlation analysis showed a significantly positive correlation between hernia width and the mean SWS value of EO, IO, and TrA (p = 0.004, 0.005, and 0.043, respectively). Muscle thickness was not reliable measure to directly reflect the biomechanical changes of the abdominal wall muscles in patients with incisional hernia. Comparatively, SWE can accurately measure the stiffness of the abdominal wall muscles and intuitively evaluate its biomechanical properties.

Muscle elasticity is different in individuals with diastasis recti abdominis than healthy volunteers

Objective

To determine the value of shear wave elastography (SWE) in assessing abdominal wall muscles, including rectus abdominis (RA), external oblique muscle (EO), internal oblique muscle, and transversus abdominis (TrA) in patients with diastasis recti abdominis (DRA) and healthy controls.

Methods

From October 2018 to December 2019, 36 postpartum DRA patients and 24 nulliparous healthy women were identified. Inter-rectus distance (IRD) measurements were taken by B-mode ultrasound. Shear wave speed (SWS) values were acquired by one operator at ten specific locations. Clinical and ultrasound variables, including demographics, IRD, muscle thickness, and muscle SWS, were compared between the two groups using Student’s t test or Fisher's exact test. Pearson correlation analyses were conducted for the variables of IRD, muscle thickness, and SWS in the 36 DRA patients.

Results

The maximum diameter of recti abdominus separation was located at the umbilicus in DRA patients (4.59 ± 1.14 cm). The SWS value was significantly lower in the RA (p = 0.003) and higher in the TrA muscle (p < 0.001) in DRA patients compared with the age-matched controls. However, SWS in both muscles (RA and TrA) showed a statistically positive correlation with IRD (p < 0.05). In addition, the SWS value in EO statistically decreased in DRA patients compared with the healthy controls (1.65 ± 0.15 vs. 1.79 ± 0.14, p = 0.001).

Conclusions

The application of SWE to abdominal wall muscles in DRA patients is feasible. The correlation between SWS value and IRD in RA should be interpreted with caution.