ASTM F2458 Wound Closure Strength Testing of Tissue Adhesives

What the test does

A substrate is selected and kept in the moisture condition that represents its use, then cut to create the wound to be closed. The adhesive or sealant is applied exactly as the product's instructions direct and allowed its specified cure time. The two halves are gripped without crushing the substrate and separated at a constant rate until the closure fails. The failure force is recorded along with the failure mode — adhesive, cohesive or substrate — and the substrate and its condition are reported alongside every value.

What it measures, and why it matters

How much force it takes to pull a glued wound open, as a comparison between products. Tissue adhesives are increasingly used as adjuncts to sutures and staples or as replacements for them, and while the forces a real wound sees vary enormously with the indication and with the patient, all such uses depend on the material resisting mechanical force — so the adhesive properties are central to judging fitness for use. The standard is explicit that it provides a means of comparison, and with an appropriate substrate a quality-control tool, rather than a clinical prediction.

Comparison, with the substrate as the variable

The method is written for comparing products. What it is compared on is chosen, and that choice governs the number.

Purpose

Comparison of wound closure strength between tissue adhesivesA comparative method, stated as such.

Secondary use

Quality control in manufacture, with an appropriate substrate

Principle

Two substrate halves joined across a cut by the adhesive, then pulled apart

Substrate

Chosen, and decisiveA tissue analogue and real tissue do not give the same answer, and neither does one tissue against another.

Context

Adjunct to sutures and staples, or a replacement for them

Record the substrate, its source and its condition

DakWithout it the number cannot be compared with anybody else's, including your own last batch.

The standard notes that the forces involved vary greatly with the indication and with patient-specific circumstances. It compares products under one defined condition; it does not predict clinical holding strength.

Test speed

Rate

A constant rate of grip separation, fixed by the method — but the figure is in the purchased text and is published on no catalogue recordIt is on none of the records for the -05(2024), -05(2015) or -05(2010) editions and no independent source reproducing it was found, so read it from the standard rather than assume one. Published work run in analogy to this family of methods reports crosshead speeds from 20 mm/min to 50 mm/min, which is why the rate has to be reported beside the failure force.

Hold the rate across the comparison

Every specimen at the same speedPracticeSoft tissue and tissue analogues are rate-dependent. A closure strength quoted without the rate that produced it is not comparable with anyone else's.

Reported

The force at which the closure failed

Failure mode

Adhesive, cohesive or substrateA substrate tear means the adhesive outlasted the tissue — good news, and not a wound closure strength.

Keep the substrate wet if that is its service condition

DakMost tissue adhesives are used on moist tissue, and drying the substrate changes the bond fundamentally.

What the machine must be capable of

Very small forces, measured traceably. Wound closure strengths are commonly a few newtons, and an accuracy class applies only down to a stated fraction of a load cell's capacity, so a frame's own cell is almost certainly working outside the range its certificate covers — the same constraint that governs catheter, closure and label testing. Grips must hold a soft and often wet substrate without crushing it, which is a narrow window, and a substrate that slips makes the bond look weaker than it is.

The rate of grip separation is part of the method rather than a free choice, but it is one of the figures held in the purchased text: it appears on none of the catalogue records for the -05(2024), -05(2015) or -05(2010) editions, and no independent source reproducing it was found. That gap shows in the literature. Published work run in analogy to this family of tissue-adhesive methods reports crosshead speeds ranging from 20 mm/min to 50 mm/min — a factor of more than two on a substrate whose response is rate-dependent, and enough on its own to explain a disagreement between two laboratories. Read the figure from the standard, set it, hold it across every specimen in a comparison, and report it beside the failure force. A wound closure strength quoted without the rate that produced it is not comparable with anyone else's.

Grips and fixtures for this method

Standard 25 mm

Pneumatic Vice Action Grip

Light grips holding a soft, wet substrate. Whatever holds the substrate must not crush it, and on tissue or a tissue analogue that window is narrow.

Specifications

Self-identifying

Load Cells

A cell matched to a bond that fails at a few newtons, verified at that load rather than at frame capacity.

Specifications

How the test runs

1. 01Select the substrate and record its source, preparation and condition.
2. 02Keep it in the moisture state that represents its use.
3. 03Cut the substrate to create the wound to be closed.
4. 04Apply the adhesive or sealant exactly as the product's instructions direct.
5. 05Allow the specified cure or set time.
6. 06Select a load cell suited to a bond failing at a few newtons.
7. 07Verify the load cell class at that working load.
8. 08Grip the two halves without crushing the substrate.
9. 09Separate at the specified constant rate.
10. 10Record the failure force and the failure mode.
11. 11Report the substrate and its condition alongside every value.

Calculations

What the report has to contain

• Reference to ASTM F2458 and the edition
• Adhesive or sealant identification and lot
• Substrate type, source, preparation and moisture condition
• Application method, quantity and cure time
• Conditioning and test temperature
• Load cell capacity and its verified class at the working load
• Rate of grip separation
• Failure force for each specimen
• Failure mode — adhesive, cohesive or substrate
• A statement that the result is comparative

What goes wrong in practice

Reporting a value without the substrate, its source and its condition, which makes it incomparable with anyone else's result and with your own previous batch. Drying a substrate that is used wet. Averaging in substrate tears, which describe the tissue's tear resistance rather than the bond. Oversized load cells. And presenting a comparative figure as a clinical holding strength, which is exactly the reading the standard's own framing is written to prevent, since the forces a real wound sees vary enormously with the indication, the site and the patient.