On-site testing of sutured organs: An experimental set up to cyclically tighten sutures

Ex vivo biomechanical evaluation of polyester and polyblend suture techniques to perform equine laryngoplasty

OBJECTIVE

To validate the use of a polyblend tape suture in equine laryngoplasty (PL).

STUDY DESIGN

Experimental study.

ANIMALS

Thirty-two cadaveric larynges.

METHODS

Each larynx was randomly assigned to 1 of 4 groups: PL with polyblend tape suture (TigerTape), without (TT) or with a cannula (TTC) in the muscular process of the arytenoid cartilage, and PL with polyester suture (Ethibond), without (EB) or with a cannula (EBC). Construct stiffness, total migration, creep, and drift values were measured after 3000 cycles. The specimens were then loaded to failure to assess their residual properties: load at failure, total energy, displacement, and 2 stiffness coefficients.

RESULTS

After cyclic testing, the total migration and creep were lower in TTC (6.36 ± 1.20 mm; 1.35 ± 0.38 mm/s) than in EB (11.12 ± 4.20 mm; 3.39 ± 2.68 mm/s) and in the TT constructs (11.26 ± 1.49 mm; 3.20 ± 0.54 mm/s); however, no difference was found with EBC (9.19 ± 3.18 mm; 2.14 ± 0.99). A correlation was found between total migration and creep (R = .85). The TTC constructs failed at higher loads (129.51 ± 33.84 N) than EB (93.16 ± 18.21 N) and EBC (81.72 ± 13.26 N) whereas the EB and EBC constructs were less stiff than TT and TTC (P < .001).

CONCLUSION

Biomechanical properties were generally superior for the TTC constructs tested under cyclical loading. The TT and TTC constructs failed at a higher load than EB and EBC constructs. The cannula in TTC and EBC reduced the failure at the muscular process.

CLINICAL SIGNIFICANCE

These results provide evidence to support the in vivo evaluation of the polyblend tape suture with or without a cannula in the muscular process for laryngoplasty in horses.

Design of a loading system for cyclic test on sutured organs

The design of loading systems to test biologic samples is often challenging, due to shape variability and non-conventional loading set-ups. In addition to this, large economic investments would not be justified since the loading set up is usually designed for one single or for a limited range of applications.

The object of this work is the development of a loading set-up finalised to on-site testing of sutures whose main function is applying a localised tensile load. The main challenges of this design process can be so summarized:•

Applying cyclic tensile loads on the suture wire, mimicking the physiologic condition where both suture anchorage points have a certain compliance;

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Designing a loading system as versatile as possible, in order to be able to accommodate organs with different geometries and sizes;

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Keeping low both the complexity and costs of realization.

All these considerations and the design calculi are here reported in detail, discussing the novelty of the system, and its main advantages.

Data from cyclic tensile tests on sutured organs to evaluate creep behaviour, distraction, and residual thread strength

A number of applications in the surgical practice are based on tensile sutures aimed to keep soft tissues in place and compensate the exit of neuropathies, prolapses or general tissue relaxation. Long-term behaviour of these constructs need to be carefully examined in order to define tensile forces to be applied and to compare different suture anchors. Data here reported refer to equine laryngoplasties, where a suitable loading system has been designed in order to be able to test sutures in-sito, applying known forces ("On-site testing of sutured organs: an experimental set up to cyclically tighten sutures" (Pascoletti et al., 2020 [1])). The loading protocol was made of two steps: in the first step, 3000 loading cycles have been performed; in the following step, a tensile test up to rupture was performed. Cyclic load/displacement curves allow evaluating suture distraction, as a consequence of suture migration and/or soft tissues creep. Tensile curves allow evaluating the residual thread strength and its ultimate displacement. These data can provide a detailed insight of long-term suture behaviour and can be a reference to compare different threads and/or suture anchors.