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To the naked eye stainless steel, disposable acupuncture needles all look much the same, differing only in type of handle. But microscopically Xie and colleagues have shown some apparently shocking variations in needle-tip quality.1 A similar electron microscopic investigation 12 years ago found the same variety of faults: scratch marks, metallic scuff, lumps and irregularities of the needle surface, and stubbed, malformed or off-centre needle points (figure 1).2
The first presterilised, single-use acupuncture needles were produced by the late Man Fong ‘Benny’ Mei, a coauthor of the original investigation. He was proud of his needles and believed them to be of excellent quality, so when he saw photomicrographs showing that his needles had tips as misshapen as those of most other types he went immediately to his factory in China to reassess quality control methods. Other distributors and manufacturers were equally surprised at the appearance of their own needles.
The difficulty, of course, is the level of magnification necessary to see these needle-tip faults. Examined by the normal, naked eye, they are invisible. Xie's study used ×5000 magnification, although the earlier review had investigated a range of magnifications. With an ‘eye of faith’ the larger lumps and malformations could just be identified at lower powers, but for a reasonable view ×612.5 was used; this probably means that for effective inspection purposes about ×400 should be suitable. This is within the limits of a light microscope, although the resolution may prove adequate only for grosser malformations.
This makes one think: if needle-tip faults are visible only at high magnification, can they be considered a real clinical hazard, or is it merely a case of “shock-horror, this must be dangerous”? The original publication requested readers to look for problems that might be attributed to faulty needles and report these. The full set of photomicrographs was also displayed at an internationally attended British Medical Acupuncture Society conference with a similar request. No reports were received.
The problems associated with malformed needles have been proposed as bleeding or bruising due to an irregular needle tip scratching across a vein, sharp pain at insertion or extraction, wayward insertion due to off-centre needle point, contact dermatitis, tattooing and deposition of metallic scuff or oil residue in tissues.
Bleeding and bruising are an inevitable accompaniment of skin puncture. The surprise is that it occurs as infrequently as it does. It has been suggested that bleeding is more common if a patient is taking anti-inflammatory drugs, but no-one seems to have looked for a relation with needle type. Similarly, pain on needling occurs surprisingly infrequently and usually resolves with repositioning of the needle, so it is as likely to be due to penetration of a small nerve as to scratching with a faulty needle tip. Thus it is possible that either of these side effects of needling might be due to needle faults, but evidence would be difficult to obtain and other causes seem more likely. An intriguing possibility, however, is that an irregular needle surface might snag muscle fibres during manipulation, producing a more effective needling (de qi) sensation. This is supported by Xie's finding that the more faulty Chinese needles developed higher force amplitude during manipulation than the Japanese needles, suggesting that the mechanical load tending to resist needle motion, and thus produce needling sensation, is due to irregularities catching in muscle.
An off-centre needle point could probably cause deviation from straight insertion, but with standard-length needles this is unlikely to be of clinical importance, and is well known to occur with any flexible surgical needle. Ultrasound investigation might give more useful information on the subject.
Contact dermatitis has been noted rarely (I have seen two cases in 30 years) with red, raised, itchy lumps appearing around each needle. This has not previously been reported as occurring particularly with specific types of needle. However, a recent nickel-sensitive patient of mine exhibited the phenomenon at points on her back when I was using Chinese manufactured needles, but not when I subsequently changed to Japanese needles. This could not have been because the Japanese needles contained less nickel, since Xie found that both Chinese (12%) and Japanese (10%) needles have similar content. Furthermore, all acupuncture needles should be of the semi-austenitic precipitation hardened class of stainless steel which has a closely regulated chromium and nickel content together with low carbon, providing the characteristics of minimal corrosion, ductility (easily stretched into a wire of constant gauge) and malleability (bending without fracture). Thus it is quite possible that the sensitivity response might be due to the loose metallic lumps, which Xie has shown commonly to become detached from the surface during manipulation of Chinese needles but less often with the better quality Japanese needles.
Short-term tattooing at needle sites has been noted.2 Commercial tattoo inks contain a variety of pigments, of which carbon, iron, chromium and nickel are common ingredients. These are all constituents of the stainless steel, so the fragments detached after needle manipulation, if in sufficient quantity, will make a tiny tattoo. Health hazards, mainly allergic reactions, have been reported after commercial tattoos, but are less likely after the very small quantity of metal deposited after needling. Pigments can be absorbed into the blood stream or lymphatic drainage, particularly if tissue has been made more permeable by alcohol cleansing before needling; so the metal deposits may end up in lymph nodes or elsewhere in the body, although this is unlikely to be of clinical significance.
So the question is: do these microscopic needle faults really matter? There is possibly a small number of minor clinical hazards associated with the faults, but the question looks beyond these; it is a matter of trust, expectation and perception. We know that it is possible to produce needles of a better standard than the Chinese variety examined in Xie's study, and it is noteworthy that consistently the worst needles in the former review were also Chinese, while the best were of American manufacture. With such high output, it will never be possible for 100% perfection, but simple improvements might make a substantial difference. Ultrasonic cleaning will remove the worst of the metallic and surface residue, while spot checks with a high-powered light microscope should identify gross failures in polishing and pointing. Comparison of manufacturing processes could result in a formula for best practice, with quality control certification for reaching an approved standard. It has taken 12 years to make no progress; it is time for Western needle distributors to challenge manufacturers to improve.
Competing interests None.
Provenance and peer review Not commissioned; internally peer reviewed.
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