Non-Absorbable (Non-Dissolvable) Sutures

What the classification actually says

A suture is non-absorbable when the body does not break it down and metabolise it. That is the whole of the definition, and it is worth being strict about, because the term is routinely read as if it meant “stays in” — and it does not. Whether a strand is removed after two weeks or left in place for the rest of the patient’s life is a decision about the closure. The classification describes what the material is and how tissue acts on it; it says nothing about the plan.

Keeping those two apart matters because they are decided on different grounds. The material is a fixed property of what is on the spool. The plan depends on the tissue, the site and the case, and the data that inform it — how long a given product holds its strength — are product-specific and stated in the instructions for use rather than derivable from the material class.

The classification is also not a claim that the material is unchanging. Two of the materials in this class demonstrably change in tissue over time: polyamide hydrolyses slowly, and silk loses strength. Both remain non-absorbable, because the category turns on metabolism, not on permanence. That is a nuance of definition rather than a contradiction, and it is one of the more genuinely interesting things about the class.

The families

The class divides on origin. The synthetics are the largest group: polypropylene, a linear polyolefin extruded as a monofilament; polyamide — nylon — a macromolecule of repeating units joined by amide bonds; polyester, in practice polyethylene terephthalate, braided and commonly coated; and the fluoropolymers PVDF and PTFE. The single natural member is silk, a protein fibre that is degummed and braided into a surgical strand. The metallic member is stainless steel wire, drawn from the 316L alloy.

Each family carries its own chemistry, and each has its own article in this cluster. What they share is only the classification: none of them is metabolised by the body in the way an absorbable suture is.

The construction axis

Cutting across the families is a second distinction that has nothing to do with chemistry: whether the strand is one filament or many.

A monofilament is extruded as a single continuous filament. It has no interstices, and therefore no capillarity — no route for fluid to wick along the strand. It tends to carry more memory, meaning it holds the shape it was packaged in, which is a real demand on knotting technique.

A multifilament, or braid, is many fine filaments braided into one strand. Braiding is what gives a suture pliability and the way it seats a knot. The same construction leaves interstices between the filaments and gives the strand surface texture, which is why braided sutures are commonly coated — on non-absorbable braids, typically with silicone or wax. The coating is a response to the construction rather than an addition to it.

These two axes — chemistry and construction — are independent, and reading a material along both is more useful than reading either alone. Polypropylene and silk are both non-absorbable; one is a synthetic monofilament and the other a natural braid, and almost everything a surgeon notices in the hand follows from the second fact rather than the first.