Biomechanical comparison of canine fascia lata and thoracolumbar fascia: an in vitro evaluation of replacement tissues for body wall reconstruction

Stapled fascial suture: ex vivo modeling and clinical implications

BACKGROUND

Recently, in the field of abdominal wall repair surgery, some minimally invasive procedures introduced the use of staplers to provide a retromuscular prosthetic repair. However, to the knowledge of the authors, there are little data in the literature about the outcomes of stapled sutures adoption for midline reconstruction. This study aims to investigate the biomechanics of stapled sutures, simple (stapled), or oversewn (hybrid), in comparison with handsewn suture. From the results obtained, we tried to draw indications for their use in a clinical context.

METHODS

Human cadaver fascia lata specimens, sutured (handsewn, stapled, or hybrid) or not, underwent tensile tests. The data on strength (maximal stress), ultimate strain (deformability), Young's modulus (rigidity), and dissipated specific energy (ability to absorb mechanical energy up to the breaking point) were recorded for each type of specimens and analyzed.

RESULTS

Stapled and hybrid suture showed a significantly higher strength (handsewn 0.83 MPa, stapled 2.10 MPa, hybrid 2.68 MPa) and a trend toward a lower ultimate strain as compared to manual sutures (handsewn 344%, stapled 249%, hybrid 280%). Stapled and hybrid sutures had fourfold higher Young's modulus as compared to handsewn sutures (handsewn 1.779 MPa, stapled 7.374 MPa, hybrid 6.964 MPa). Handsewn and hybrid sutures showed significantly higher dissipated specific energy (handsewn 0.99 mJ-mm3, stapled 0.73 mJ-mm3, hybrid 1.35 mJ-mm3).

CONCLUSION

Stapled sutures can resist high loads, but are less deformable and rigid than handsewn suture. This suggests a safer employment in case of small defects or diastasis (< W1 in accord to EHS classification), where the presumed tissutal displacement is minimal. Oversewing a stapled suture improves its efficiency, becoming crucial in case of larger defects (> W1 in accord to EHS classification) where the expected tissutal displacement is maximal. Hybrid sutures seem to be a good compromise.

Strain Assessment of Deep Fascia of the Thigh During Leg Movement: An in situ Study

Fascia is a fibrous connective tissue present all over the body. At the lower limb level, the deep fascia that is overlying muscles of the outer thigh and sheathing them (fascia lata) is involved in various pathologies. However, the understanding and quantification of the mechanisms involved in these sheathing effects are still unclear. The aim of this study is to observe and quantify the strain field of the fascia lata, including the iliotibial tract (ITT), during a passive movement of the knee. Three fresh postmortem human subjects were studied. To measure hip and knee angles during knee flexion-extension, passive movements from 0° to around 120° were recorded with a motion analysis system and strain fields of the fascia were acquired using digital image correlation. Strains were computed for three areas of the fascia lata: anterior fascia, lateral fascia, and ITT. Mean principal strains showed different strain mechanisms depending on location on the fascia and knee angle. For the ITT, two strain mechanisms were observed depending on knee movement: compression is observed when the knee is extended relative to the reference position of 47°, however, tension and pure shear can be observed when the knee is flexed. For the anterior and lateral fascia, in most cases, minor strain is higher than major strain in absolute value, suggesting high tissue compression probably due to microstructural fiber rearrangements. This in situ study is the first attempt to quantify the superficial strain field of fascia lata during passive leg movement. The study presents some limitations but provides a step in understanding strain mechanism of the fascia lata during passive knee movement.

Acute Surgical Injury Alters the Tensile Properties of Thoracolumbar Fascia in a Porcine Model

Recent work utilizing ultrasound imaging demonstrated that individuals with low back pain (LBP) have increased thickness and decreased mobility of the thoracolumbar fascia (TLF), an indication that the TLF may play a role in LBP. This study used a porcine injury model (microsurgically induced local injury)-shown to produce similar results to those observed in humans with LBP-to test the hypothesis that TLF mechanical properties may also be altered in patients with LBP. Perimuscular TLF tissue was harvested from the noninjured side of vertebral level L3-4 in pigs randomized into either control (n = 5) or injured (n = 5) groups. All samples were tested with a displacement-controlled biaxial testing system using the following protocol: cyclic loading/unloading and stress relaxation tests at 25%, 35%, and then 45% of their resting length. Tissue anisotropy was also explored by comparing responses to loading in longitudinal and transverse orientations. Tissues from injured pigs were found to have greater stretch-stretch ratio moduli (measure of tissue stiffness), less energy dissipation, and less stress decay compared to tissues from control pigs. Responses across these variables also depended on loading orientation.

CLINICAL SIGNIFICANCE

these findings suggest that a focal TLF injury can produce impairments in tissue mechanical properties away from the injured area itself. This could contribute to some of the functional abnormalities observed in human LBP.