Specification builder · Tier B
Suture needle attachment (pull-out) and tensile strength tester with suture diameter gauge
A suture needle attachment tester is a small motorised tensile tester with a needle holder and suture grips that pulls the suture out of its swaged needle and records the force, as required by USP <871> and the Ph. Eur./BP suture monographs. With knot-pull grips and a dead-weight gauge the same set-up also checks suture tensile strength (USP <881>) and diameter (USP <861>). It is bought by drug and device testing laboratories, local suture manufacturers and universities.
What this equipment will do
- Suture types: absorbable and non-absorbable sutures, monofilament and braided, with swaged (eyeless) needles, straight or curved (USP <871>, Ph. Eur. monographs 0324, 0666, 0667).
- Needle attachment (pull-out) force: the force needed to pull the suture out of the needle, held with the swaged part exposed and in line with the pull, for standard and removable needles (USP <871>; Ph. Eur. needle attachment test).
- Straight-pull tensile strength (breaking load) of the suture at a constant rate of extension of 30 +/- 5 cm/min (USP <881>; Ph. Eur. minimum breaking load).
- Knot-pull tensile strength, with the knot tied consistently over the specified rubber tubing (USP <881>). (with the optional module)
- Displacement (stretch) at break and batch statistics: mean, minimum, maximum and SD per batch.
- Automatic pass/fail against USP and Ph. Eur. limit tables by suture size, checking both average and individual values and applying the retest rule (USP <871>, USP <881>). (with the optional module)
- Very fine sutures (7-0 and finer) and removable needles that detach at under 1 N, measured on a load cell of 10 N or less. (with the optional module)
- Suture diameter with a dead-weight thickness gauge, to place each suture in the right size class (USP <861>). (with the optional module)
- Suture elongation over a marked gauge length without touching the strand (non-contact extensometer). (with the optional module)
- Sutures tested wet in saline or buffer at 37 +/- 1 deg C. (with the optional module)
- Unattended testing of a batch of sutures loaded automatically from a magazine. (with the optional module)
Not covered: Needle sharpness (penetration force through a membrane) of suture needles needs the needle penetration force tester.; Needle dimensions and point/bevel inspection (burrs, hooks) need the optical measuring microscope.; Sterility and bacterial endotoxins of sutures need the microbiology laboratory (sterility testing isolator and endotoxin test system).
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Standards this specification draws on
- USP <871> Defines the needle attachment (pull-out) test, the fixed-clamp needle position and the average and individual limits by suture size for standard and removable needles.
- Ph. Eur. suture monographs 0324, 0666, 0667 Sterile non-absorbable and synthetic absorbable (monofilament and braided) suture monographs, used through the BP in Pakistan, with needle attachment, minimum breaking load and diameter tests and limits.
- USP <881> Sets the tensile tester design used for USP suture tests: constant rate of extension, clamp types and sizes, 30 +/- 5 cm/min at 125-200 mm gauge length and the knot-pull procedure.
- USP <861> Defines the dead-weight gauge, presser foot, load and measuring points for suture diameter.
- IEC 61010-1 Basic electrical and mechanical safety for laboratory test equipment.
- IEC 61326-1 EMC requirements so the tester neither disturbs nor is disturbed by other lab equipment.
- ISO 7500-1:2018 Method and accuracy classes for verifying the force-measuring system of tensile testing machines.
- ASTM E4 US practice for force verification of testing machines, accepted as an alternative to ISO 7500-1.
- ISO/IEC 17025:2017 Competence requirements for testing and calibration labs; governs the calibration certificates and the DTL's own accreditation.
- 21 CFR Part 11 Requirements for trustworthy electronic records and signatures when test results support batch release or regulatory decisions.
Common mistakes in tenders for this equipment
- Specifying only a large frame capacity (for example 5 kN) with one load cell, so fine sutures are measured at well under 1% of capacity where the reading is not accurate; ask for a 50 N or smaller load cell with stated accuracy.
- Copying one maker's grip names, travel figures or exact speed table so only that brand complies; state the USP <881> rate (30 +/- 5 cm/min), grip type and minimum travel instead.
- Buying grips for flat specimens only, with no needle holder for curved needles, so the pull-out test cannot be run as USP <871> requires.
- Accepting a factory calibration that covers force only, or is not from an ISO/IEC 17025 accredited lab; crosshead speed and displacement must also be verified.
- Calling software 'USP compliant' without checking that it evaluates both average and individual limits, applies the retest rule and lets the analyst discard clamp breaks.
- Leaving out the air compressor, spare jaw faces and knot-tying jig, so the tester stands idle or gives jaw breaks on slippery coated sutures.
- Paying before an acceptance test on the lab's own finest and heaviest sutures.
- Asking for 21 CFR Part 11 software in a teaching lab where it only adds cost and narrows the field.