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Needle breakage, although rare, is a potential adverse event of acupuncture, which has been highlighted by systematic reviews of case reports in the Western,1 Chinese2 and Japanese3 literature. A Western review of case reports between 2000 and 2011 identified two cases of needle breakage,1 while a Chinese review between 1980 and 2009 found only one.2 By contrast, a Japanese review found a total of 48 needle breakage events from 1987 to 1999, of which 16 were accidental.3
Needle breakage can be potentially life threatening if the broken needle is left in the body, and an operation may be required to remove the embedded needle. The WHO4 has suggested that the most common site of needle breakage is the root of the needle. Suggested causes of needle breakages included poor quality manufacture, erosion between the shaft and the handle, strong muscle spasm or sudden movement of the patient, incorrect withdrawal of a stuck or bent needle, and prolonged use of galvanic current.5 From a review of the literature, to our knowledge, no study has explored the maximum compression force the acupuncture needle can withstand before breakage, and common sites of breakage. Hence, the aim of our study was to address these gaps in knowledge by conducting a pilot study.
We conducted our study using a filiform acupuncture needle, which is the most common type of needle used in our current clinical setting. The filiform needle is made of stainless steel and consists of five parts: (1) tail; (2) handle; (3) root; (4) body; and (5) tip (figure 1A). Needle sizes are based on diameter and length (mm). We tested acupuncture needles of three different diameters and lengths (A star, Shanghai, China): (1) 0.25×40 mm (long needle); (2) 0.30×25 mm (medium needle); and (3) 0.18×13 mm (short needle).
Static compression testing was conducted using an Instron 3343 single column universal testing system (Instron Corp, Canton, Massachusetts, USA). The needles were placed vertically onto a pair of pneumatic grippers with a blasted clamping surface (figure 1B). The upper clamp grasped the needle handle 1.5 cm from the tail, while the lower clamp grasped the needle body 0.5 cm from its tip. The compression rate was 10 mm/min. Load (N) versus displacement (mm) of the needles under compression was plotted.
Needle breakage did not occur, but the needle was permanently bent. Based on the load-displacement curve, the long needle required a load that was one order lower (×10−1 N) than the other two needles in order to bend. The displacement increased linearly with the increase in load. The medium-sized needle required a higher load than the short needle in order to compress. The load was highest at the beginning (displacement <1 mm) as more energy was required to bend the needle. After the needle had been bent, the required load gradually decreased, as less energy was needed to maintain the momentum (figure 2).
In this study, we found that the acupuncture needles did not break when exposed to high compression forces. Hence, we conclude that needle breakage is unlikely to occur even during strong muscle spasm, sudden movement of the patient, aggressive manipulation, or in the hands of an untrained practitioner. It is potentially reassuring for patients that there is little possibility of needle breakage during manipulation if the needles used are produced by certified manufacturers.
Although needle breakage is unlikely, it is nevertheless important to advise patients to visit a certified acupuncture practitioner to ensure that a safe yet adequate amount of manipulation is provided, as overly aggressive stimulation could lead to other adverse events, such as damage to muscle fibres, nerves and/or blood vessels.2 Other safety precautions include the single use of needles, as the needles used in our experiment were pristine. In some rural areas, needles might be sterilised and reused.2 Repeated reheating might cause a needle to become brittle over time, which could theoretically predispose it to breakage. Future studies should explore the effects of heat/electricity on acupuncture needles, and how force affects bending of the needle.
Contributors MQHL and TC conceptualised the study. MQHL performed data analysis. YRW performed the biomechanical testing. All authors were involved in manuscript writing.
Competing interests None declared.
Provenance and peer review Not commissioned; internally peer reviewed.
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