Abdominal wall morphometric variability based on computed tomography: Influence of age, gender, and body mass index

The sagitta in 3D reconstruction of linea alba on routine CT scans is predictive of postoperative burst abdomen

PURPOSE

Burst abdomen (BA) is a relevant complication after abdominal surgery that causes additional surgical procedures, prolonged hospital stays and long-term morbidity. Several underlying risk factors exist and have been characterized previously. Those risk factors consist of surgical and medical factors. Recently, CT-derived body composition is of rising interest and 3D reconstruction of the linea alba has been studied. The clinical significance of those parameters is not clear. We therefore performed an analysis of linea alba 3D reconstruction measurements and their prognostic significance on the development of BA.

METHODS

An institutional data base of patients with post operative wound infections was assembled. The subgroup of patients with BA was compared to controls. If the patients had complete preoperative abdominal CT scans, their images were further analyzed and 3D reconstruction of the linea alba was performed. Subsequently, lineal alba was measured at predetermined positions. Those values were evaluated as risk factors for postoperative BA.

RESULTS

A total of 72 patients with BA and 32 controls were eligible for the analysis. We found body mass index-related significant differences as well as sex related differences in linea alba width. Furthermore, BA patients had a significantly wider linea alba and longer sagitta compared to controls. In the multivariate analysis of linea alba measurements and clinical parameters, the length of the sagitta was significantly associated with the risk of BA (OR 1.266; 95% CI 1.011-1.585; p = 0.04).

CONCLUSION

In this study of 3D reconstruction of the linea alba from routine CT scans, we could show that a longer sagitta was associated with an increased risk of postoperative BA.

Towards a better understanding of abdominal wall biomechanics: In vivo relationship between dynamic intra-abdominal pressure and magnetic resonance imaging measurements

BACKGROUND

In vivo mechanical behaviour of the abdominal wall has been poorly characterised and important details are missing regarding the occurrence and post-operative recurrence rate of hernias which can be as high as 30 %. This study aimed to assess the correlation between abdominal wall displacement and intra-abdominal pressure, as well as abdominal compliance.

METHODS

Eighteen healthy participants performed audio-guided passive (breathing) and active (coughing, Valsalva maneuver) exercises. Axial dynamic changes of abdominal muscles and visceral area were measured using MRI, and intra-abdominal pressure with ingested pressure sensor.

FINDINGS

Correlations between abdominal wall displacement and intra-abdominal pressure were specific to participant, exercise, and varying between rectus abdominis and lateral muscles. Strong correlations were found between rectus abdominis displacement and intra-abdominal pressure during breathing (r = 0.92 ± 0.06), as well as lateral muscles displacement with intra-abdominal pressure during coughing and Valsalva maneuver (r = -0.98 ± 0.03 and - 0.94 ± 0.05 respectively). The abdominal pseudo-compliance varied greatly among participants during muscular contraction, the coefficient of variation reaching up to 70 %.

INTERPRETATION

The combination of intra-abdominal pressure and dynamic MRI measurements enables the identification of participant-specific behaviour pattern. Intra-abdominal pressure and abdominal wall dynamic undergo consistent and predictable interactions. However, this relationship is subject-specific and may not be extrapolated to other individuals. Therefore, both intra-abdominal pressure and abdominal wall motion must be measured in the same participant in order to accurately characterise the abdominal wall behaviour. These results are of great importance for mesh design, surgical decision-making, and personalised healthcare.

M-mode ultrasound evaluation of lateral abdominal muscle postural response to load: an exploratory study

Aim

There is a need to evaluate the tissue deformation index of lateral abdominal muscles using M-mode ultrasound in a cohort of healthy subjects to establish a convenient reference point for clinical reasoning in patients. The aim of the study was to assess differences in the tissue deformation index between individual lateral abdominal muscles regardless of body side, compare these differences in the tissue deformation index on the right and left sides of the body, and evaluate side-to-side differences in the tissue deformation index within individual lateral abdominal muscles.

Material and methods

In a group of 126 healthy volunteers (59 females), the postural response of lateral abdominal muscles to external perturbation in the form of rapid arm abduction with load was recorded on both sides of the body, and the tissue deformation index was calculated.

Results

The mean values of the tissue deformation index form an increasing gradient from deep to superficial lateral abdominal muscles: 0.06%/ms for the transversus abdominis, 0.084%/ms for the internal oblique and 0.151%/ms for the external oblique (p <0.001). Side-to-side intra-muscle differences were significant only for the transverse abdominis (right: 0.047%/ms; left: 0.070%; p <0.01).

Conclusions

The tissue deformation index values differ significantly among individual lateral abdominal muscles and form a characteristic gradient: transversus abdominis < internal oblique < external oblique. The transversus abdominis muscle shows significant asymmetry in the tissue deformation index between the left and right sides of the body.

Shear Wave Elastography for Assessment of Changes in Abdominal Soft Tissues after Lipoabdominoplasty

BACKGROUND

The changes in the elasticity of the abdominal skin, subcutaneous tissues and muscles after lipoabdominoplasty are still unknown. The aim of this study was to provide an objective assessment of tissue elasticity after lipoabdominoplasty using ultrasound elastography.

METHODS

A total of 21 female patients (31-41 years old) who underwent lipoabdominoplasty from Oct 2019 to Mar 2022 were included in this retrospective study. The elastography values of the skin, subcutaneous tissues and abdominal muscles were obtained with the ultrasound shear wave elasticity imaging system pre-operation (Pre) and 6 months post-operation (Post) at four different points.

RESULTS

Twenty-one female patients were included. The elasticity of the abdominal skin, subcutaneous tissues, rectus abdominis and external oblique abdominis significantly increased at 6 months post-operation. The improvements in abdominal soft tissue elasticity were not uniform across the examined points.

CONCLUSIONS

Significant changes in the elasticity of the abdominal skin, subcutaneous tissues and muscles were observed after lipoabdominoplasty. Ultrasound elastographic assessment was objective and feasible for evaluating the effect of lipoabdominoplasty on abdominal soft tissue.

LEVEL OF EVIDENCE III

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Linea alba 3D morphometric variability by CT scan exploration

PURPOSE

The width of the Linea alba, which is often gauged by inter-rectus distance, is a key risk factor for incisional hernia and recurrence. Previous studies provided limited descriptions with no consideration for width, location variability, or curvature. We aimed to offer a comprehensive 3D anatomical analysis of the Linea alba, emphasizing its variations across diverse demographics.

METHODS

Using open source software, 2D sagittal plane and 3D reconstructions were performed on 117 patients' CT scans. Linea alba length, curvature assessed by the sagitta (the longest perpendicular segment between xipho-pubic line and the Linea alba), and continuous width along the height were measured.

RESULTS

The Linea alba had a rhombus shape, with a maximum width at the umbilicus of 4.4 ± 1.9 cm and a larger width above the umbilicus than below. Its length was 37.5 ± 3.6 cm, which increased with body mass index (BMI) (p < 0.001), and was shorter in women (p < 0.001). The sagitta was 2.6 ± 2.2 cm, three times higher in the obese group (p < 0.001), majorated with age (p = 0.009), but was independent of gender (p = 0.212). Linea alba width increased with both age and BMI (p < 0.001-p = 0.002), being notably wider in women halfway between the umbilicus and pubis (p = 0.007).

CONCLUSION

This study provides an exhaustive 3D description of Linea alba's anatomical variability, presenting new considerations for curvature. This method provides a patient-specific anatomy description of the Linea alba. Further studies are needed to determine whether 3D reconstruction correlates with pathologies, such as hernias and diastasis recti.

Numerical investigation of a finite element abdominal wall model during breathing and muscular contraction

BACKGROUND AND OBJECTIVE

Ventral hernia repair is faced with high recurrence rates. The personalization of the diagnosis, the surgical approach and the choice of the prosthetic implant seem relevant axes to improve the current results. Numerical models have the potential to allow this patient-specific approach, yet currently existing models lack validation. This work extensively investigated a realistic finite element abdominal wall model including the implementation of muscle activation.

METHODS

A parametric 3D finite element model composed of bone, muscle and aponeurotic structures was introduced. Hyperelastic anisotropic materials were implemented. Two loading scenarios were simulated: passive inflation of the abdominal cavity to represent, e.g., breathing, and passive inflation followed by muscular activation to simulate other daily activities such as cough. The impact of the inter-individual variability (e.g., BMI, tissue thickness, material properties, intra-abdominal pressure (IAP) and muscle contractility) on the model outputs was studied through a sensitivity analysis.

RESULTS

The overall model predictions were in good agreement with the experimental data in terms of shape variation, muscles displacements, strains and midline forces. A total of 34 and 41 runs were computed for the passive and active sensitivity analysis respectively. The regression model fits rendered high R-squared in both passive (84.0 ± 6.7 %) and active conditions (82.0 ± 8.3 %). IAP and muscle thickness were the most influential factors for the selected outputs during passive (breathing) activities. Maximum isometric stress, muscle thickness and pre-activation IAP were found to drive the response of the simulations involving muscular contraction. The material properties of the connective tissue were essential contributors to the behaviour of the medial part of the abdominal wall.

CONCLUSIONS

This work extensively investigated a realistic abdominal wall model and evaluated its robustness using experimental data from literature. Such a model could improve patient-specific simulation for ventral hernia surgical planning, prevention, and repair or implant evaluation. Further investigations will be conducted to evaluate the impact of the surgical technique and the mechanical characteristic of prosthetic meshes on the model outputs.

The relationship between urinary incontinence and abdominal muscle thickness in community-dwelling older women undergoing comprehensive geriatric assessment

PURPOSE

Urinary incontinence (UI) is one of the most common geriatric syndromes in older adults, especially in women. The aim of this study is to show the relationship between urinary incontinence and abdominal muscle thickness measured by muscle ultrasonography (US) in community-dwelling older women adults.

METHODS

Eighty-seven community-dwelling older women participated in our study. The presence and the type of UI were recorded. Clinical and demographic characteristics were collected, and a comprehensive geriatric assessment was performed on all participants. Abdominal muscle layer thicknesses were evaluated with muscle US.

RESULTS

The prevalence of UI was 55.2% (n = 48) of the study population. The median [IQR] age of the patients in the UI group was 73.0 [69.0-77.5] years and it was 69.0 [67.0-73.0] years in patients without UI (p = 0.007). Abdominal muscle thicknesses were measured smaller in patients with UI than those without UI except for internal oblique muscle thickness. The median [IQR] rectus abdominis muscle thickness was lower in patients with UI than in patients without UI, and the difference was statistically significant (p < 0.003). RA muscle was associated with UI regardless of age, polypharmacy, malnutrition, and frailty (OR: 0.58; 95% CI 0.38-0.89; p = 0.01).

CONCLUSIONS

We have shown that UI was independently related to the rectus abdominis muscle thickness, which may reflect the function and mass of the pelvic floor muscles.

A novel in vivo approach to assess strains of the human abdominal wall under known intraabdominal pressure

The study concerns mechanical behaviour of a living human abdominal wall. A better mechanical understanding of a human abdominal wall and recognition of its material properties is required to find mechanically compatible surgical meshes to significantly improve the treatment of ventral hernias. A non-invasive methodology, based on in vivo optical measurements is proposed to determine strains of abdominal wall corresponding to a known intraabdominal pressure. The measurement is performed in the course of a standard procedure of peritoneal dialysis. A dedicated experimental stand is designed for the experiment. The photogrammetric technique is employed to recover the three-dimensional surface geometry of the anterior abdominal wall at the initial and terminal instants of the dialysis. This corresponds to two deformation states, before and after filling the abdominal cavity with dialysis fluid. The study provides information on strain fields of living human abdominal wall. The inquiry is aimed at principal strains and their directions, observed at the level from -10% to 17%. The intraabdominal pressure related to the amount of introduced dialysis fluid measured within the medical procedure covers the range 11-18.5 cmH₂O. The methodology leads to the deformation state of the abdominal wall according to the corresponding loading conditions. Therefore, the study is a step towards an identification of mechanical properties of living human abdominal wall.

Shear wave elastography of the lateral abdominal muscles in C-shaped idiopathic scoliosis: a case-control study

Considering that knowledge about lateral abdominal muscles (LAM) in idiopathic scoliosis (IS) is still very limited, the aims of this study were: (a) to compare LAM thickness and elasticity between C-shaped IS and non-scoliotic population; and (b) to compare LAM thickness and elasticity between C-shaped thoracic, thoracolumbar, and lumbar IS. A total of 259 adolescents were included in the final analysis; among these, 108 were IS and 151 were non-IS. LAM thickness and elasticity were measured at rest and during isometric contraction by an Aixplorer ultrasound scanner. Out of all LAM, only OE thickness was higher on the convex body side compared to the concave side in lumbar and thoracolumbar scoliosis. It may be related with muscle’s atrophy/hypertrophy or other tissues displacement rather than different force generated by the muscle on both body sides, because an asymmetry in the elasticity of the LAM between the convex and concave side was not presented. The only TrA was stiffer in lumbar scoliosis compared to thoracolumbar and thoracic scoliosis. LAM elasticity was similar in IS and non-IS adolescents.

Correlations of the rectus abdominis muscle anatomy with anthropometric measurements

PURPOSE

The anterior abdominal muscle wall has a strong aesthetic connotation, primarily because of the classical anatomical description of the rectus abdominis muscle in the collective consciousness. However, the morphological reality of the general population considerably deviates from this description. Therefore, we investigated the anthropometric characteristics correlated with the anatomy of the rectus abdominis muscle.

METHODS

We performed a computed tomography scan anatomical study of recti abdominis muscles in 86 patients with no history of abdominal surgery. We noted the transverse and anteroposterior measurements of the rectus abdominis muscle, the transverse measurement of the linea alba, and the cutaneous and muscular abdominal perimeters. We compared these morphological elements with anthropometric data (sex, age, weight, height, and body mass index [BMI]).

RESULTS

BMI was positively correlated with cutaneous abdominal perimeter (r = 0.89, p < 0.001) and muscular abdominal perimeter (r = 0.7, p < 0.001). The correlation of BMI with cutaneous abdominal perimeter was not influenced by sex (r = 0.90 and r = 0.89 in men and women, respectively). The correlation of BMI with muscular abdominal perimeter was greater in men than in women (r = 0.80 vs. r = 0.75). The muscular abdominal perimeter was more strongly correlated with the transverse measurement of the rectus abdominis muscle in men than in women (r = 0.75 vs. r = 0.59). The muscular abdominal perimeter was more strongly correlated with the linea alba in women than in men (r = 0.51 vs. r = 0.31).

CONCLUSION

The anatomy of the anterior abdominal wall correlated with anthropometric data, including BMI. Rectus abdominis muscles and linea alba structures differed between men and women.