Biomechanics of the abdominal wall before and after ventral hernia repair using dynamic MRI

TL;DR

Using a semi-automatic methodology, an in-depth analysis of the biomechanics of the abdominal wall was conducted, highlighting the importance of a patient-specific assessment.

Abstract

Purpose: This study aims to investigate the use of dynamic MRI to assess abdominal wall biomechanics before and after hernia surgery, considering that such evaluations can enhance our understanding of physiopathology and contribute to reducing recurrence rates. Methods: Patients were assessed using dynamic MRI in axial and sagittal planes while performing exercises (breathing, coughing, Valsalva) before and after their abdominal hernia surgery with mesh placement. Rectus and lateral muscles, linea alba, viscera area, defect dimensions and hernia sac were contoured with semi-automatic process to quantify the abdominal wall biomechanical temporal modifications. Results: This study enrolled 11 patients. During coughing, the axial area of the hernia sac increased by 128.4 $\pm$ 199.2%. The sac increased similarly in axial and sagittal planes during Valsalva. Post-surgical evaluations showed a 26% reduction in inter-recti distance and a lengthening of all muscles (p $\le$ 0.05). The post-operative rectus abdominis thickness change was negatively correlated with defect width during breathing (p $\le$ 0.05). The largest change in linea alba displacement was observed in the surgical site (p = 0.07). Post-operatively, lateral muscles had a larger inward displacement during Valsalva (p $\le$ 0.05). Rectus abdominis had a larger outward displacement during breathing (p = 0.09), reduced with the mesh size (p $\le$ 0.05). A large inter-individual variability was observed. Conclusion: Using a semi-automatic methodology, an in-depth analysis of the biomechanics of the abdominal wall was conducted, highlighting the importance of a patient-specific assessment. A broader study and consideration of recurrence would subsequently complete this methodological work.

Figures (9)

• Figure 1: Selection of axial and sagittal planes for dynamic acquisitions, example of a pre-operative MRI Legend: a) Axial plane b) Sagittal plane The pink lines represent the respective placements of sagittal and axial planes The white arrow represents the defect dimension measurements (width and height) at rest in axial and sagittal planes respectively The yellow circular arc represents the inter-recti angle (only done on axial MRI), i.e., the angle formed from the aorta/iliac arteries barycenter to the inner tips of rectus abdominis muscles
• Figure 2: Segmentation masks of axial MRI, at rest and during Valsalva contraction Legend: a) Raw MRI b) Hernia sac (for pre-operative stage only) c) Visceral area d) Abdominal muscles: lateral muscles (LM) and rectus abdominis (RA)
• Figure 3: Axial displacement of the abdominal muscles of a preoperative patient performing the Valsalva maneuver The abdominal wall was at rest; i.e., without contraction; at the beginning and end of the exercise
• Figure 4: Segmentation masks in sagittal pre-operative MRI, at rest and during Valsalva contraction Legend: a) Raw MRI b) Hernia sac (for pre-operative stage only) c) Visceral area d) Linea alba segmentation e) Linea alba sections (supra, hernia-scar, infra)
• Figure 5: Sagittal displacement of the linea alba of a preoperative patient performing the Valsalva maneuver The abdominal wall was at rest; i.e., without contraction; at the beginning and end of the exercise