The Engineering Genealogy of Blunt-Tip Needles

Introduction

Percutaneous pain intervention has produced, over the past several decades, a steady stream of specialized needle-based instruments, each carrying its own trademarked name. In South Korea, two independent lineages illustrate this pattern: one in which the cutting edge of the acupotomy (a needle-knife descended from traditional Korean medicine) has been removed and design-patented, and another in which a dissection needle purpose-built for adhesiolysis was developed within anesthesiology and pain medicine and formally published in international journals. The two lineages emerged from different clinical traditions, yet they converge on the same intermediate form: an instrument that is inserted like a needle but, lacking a cutting edge, does not transect tissue.

This article traces the design logic of both domestic lineages, establishes that the same underlying principle has long been formalized in the Western pain-medicine literature on nerve-block needles, and then compares the three lineages on engineering and evidentiary grounds. Rather than naming specific products or practitioners, the aim is to map the genealogy and evidentiary standing of "blunt-tip needle" as a design category in its own right.

Classifying minimally invasive percutaneous instruments by transection mechanism is not a novel move original to this piece. A recent international review classified the several minimally invasive instruments used in carpal tunnel release by cutting direction (retrograde, antegrade, or bidirectional) and by the presence or absence of a safety mechanism (Korenblit M, et al. 2026), demonstrating that transection mechanism is a decisive variable governing instrument selection, procedural safety, and the learning curve. This article applies the same line of inquiry to percutaneous adhesiolysis and pain procedures.

Discussion

1. Classifying invasive instruments along a cutting-power spectrum

Percutaneous invasive instruments can be sorted, roughly, into three categories by tip geometry.

• Filiform needle (毫鍼): thin and sharp. It has no cutting function; its purpose is acupoint stimulation.
• Blunt-tip needle: as thick-bodied as an acupotomy or as slender as a nerve-block needle, but with a rounded, non-cutting tip. It penetrates the skin but does not transect tissue.
• Acupotomy / needle-knife (針刀): a needle-gauge shaft terminating in a wedge-shaped flat blade (刀刃, roughly 0.8 mm). It both penetrates and transects.

Both domestic patented lineages examined here fall into the second category. This is frequently misunderstood, because a rounded tip is often mistaken for an instrument incapable of skin penetration. The same logic that surgeons invoke in distinguishing blunt from sharp dissection applies here: a blunt-tip needle pushes through weakly bonded planes — adhesions, fascial interfaces — while displacing, rather than transecting, resilient structures such as nerves and vessels.

2. Domestic patented blunt-tip needles derived from acupotomy

A category of domestically patented percutaneous needles exists in which the wedge-shaped cutting edge of an acupotomy has been removed and the tip machined into a rounded form. Such instruments are typically registered as design patents — a patent category that protects the shape itself rather than any novel material or mechanism — implying that the basis of novelty lies in the morphological modification of "an acupotomy without a blade," not in a new therapeutic principle.

According to the literature on domestic acupuncture-related patent trends, invasive acupuncture-related instruments, including the acupotomy lineage, constitute an area in which a substantial number of patents have been filed domestically, with numerous derivative forms registered primarily as shape variations. Within the scope of this inquiry, however, the precise dimensions (diameter, length) of individual patented instruments could not be confirmed through the academic literature; cross-checking the original patent specifications remains a task for follow-up work.

This opacity around specification is not unique to the domestic context. Recent literature on the specification and standardization of acupotomy-type instruments notes that tip geometry, length, material, and multifunctional structural design vary considerably across practitioners and manufacturers in clinical practice, and that appropriate instrument-specification selection is essential both to enhance therapeutic efficacy and to reduce procedural risk (Jing Y, et al. 2026). In other words, morphological modification — including the presence or absence of a cutting edge — is common across the broader acupotomy family, but independent validation of the safety and efficacy of each individual variant remains uncommon.

3. A domestically developed instrument published in international journals: fluoroscopy-guided interventional microadhesiolysis

A separate domestic lineage was developed and formally published in international journals. A paper reporting a nonsurgical adhesiolysis technique for adhesive capsulitis of the shoulder specified the exact dimensions of three purpose-built needles as follows.

"The Round and Flexed Round needles are 1.2 mm in diameter and 80 mm long. Ahn's Needle is 0.7 mm in diameter and 65 mm long." (Ahn K, Lee YJ, Kim EH, Yang SM, Lim TK, Kim YS, Jhun HJ. Interventional microadhesiolysis: A new nonsurgical release technique for adhesive capsulitis of the shoulder. BMC Musculoskeletal Disorders. 2008;9:12.)

During the procedure, the thickest needle is inserted through skin over the middle of the supraspinatus and advanced beneath the acromion and acromioclavicular joint, sliding along the fascial plane under real-time fluoroscopic guidance to release subacromial adhesions. No medication is injected; the physical movement of the needle itself constitutes the treatment.

This technique was subsequently extended to the spine, and a clinical report applying it to lumbar spinal stenosis was published in a domestic anesthesiology journal (Han SS, Lee SJ, Lee CJ, Lee SC. The Effects of Fluoroscopy Guided Interventional Microadhesiolysis and Nerve Stimulation (FIMS) in Lumbar Spinal Stenosis. Korean Journal of Anesthesiology. 2006;51(1):82-88).

4. The Western pain-medicine literature on blunt-tip nerve-block needles

The safety rationale for blunt-tip design had already accumulated within anesthesiology and pain medicine well before the domestic cases above were published. The core literature is as follows.

Selander D, Dhunér KG, Lundborg G. Peripheral nerve injury due to injection needles used for regional anesthesia. An experimental study of the acute effects of needle point trauma. Acta Anaesthesiologica Scandinavica. 1977;21:182-188.

Using a rabbit sciatic-nerve model, this study reported that although short-bevel (blunt-type) needles produced a lower overall frequency of nerve injury than long-bevel (sharp) needles, the severity of injury, once it occurred, could be greater. This finding indicates that a blunt tip should be understood not as eliminating injury altogether but as reducing its probability.

Sala-Blanch X, Ribalta T, Rivas E, Carrera A, Gaspa A, Reina MA. Structural injury to the human sciatic nerve after intraneural needle insertion. Regional Anesthesia and Pain Medicine. 2009;34:201-205.

Microscopic examination of 520 stained fascicles in cryopreserved human sciatic nerve specimens, following needle insertion, found that no fascicles were damaged by blunt needles, whereas 3.2% were damaged by sharp needles. This is direct experimental evidence for the design goal — "the nerve is not cut" — that the domestic instruments above claim to embody.

Heavner JE, Racz GB, Jenigiri B, Lehman T, Day MR. Sharp versus blunt needle: A comparative study of penetration of internal structures and bleeding in dogs. Pain Practice. 2003;3:226-231.

In a canine model, blunt (short-bevel) needles were less likely than sharp (long-bevel) needles to puncture internal structures such as blood vessels or to cause bleeding. One co-author of this paper shares his name with the inventor credited for a separate epidural adhesiolysis catheter technique, illustrating that, within Western pain medicine itself, the concepts of "blunt-tip design" and "percutaneous adhesiolysis" have long belonged to a single line of inquiry.

Prakash S, Kumar A. Needle tip and peripheral nerve blocks. Journal of Anaesthesiology Clinical Pharmacology. 2018;34(1):129-130.

This review synthesizes the studies above and recommends commercially available short-bevel nerve-block needles as the standard for peripheral nerve blockade. In short, the design principle — "the tip is blunt enough to penetrate skin, yet displaces rather than pierces the nerve" — has already become close to common knowledge within standard anesthesiology training.

5. The evidentiary standing of acupotomy

A substantial number of systematic reviews on acupotomy have been published in international journals. Kwon et al. (2019) synthesized eleven systematic reviews (including sixty-nine randomized controlled trials) on the clinical effectiveness and safety of acupotomy, reporting significant effects for frozen shoulder, cervical spondylosis, third lumbar transverse process syndrome, trigger finger, knee osteoarthritis, and lumbar spinal stenosis (Kwon CY, Yoon SH, Lee B. Clinical effectiveness and safety of acupotomy: An overview of systematic reviews. Complementary Therapies in Clinical Practice. 2019;36:142-152). The same paper notes, however, that because acupotomy is more invasive than acupuncture, more systematic safety surveillance is warranted.

This suggests that the acupotomy lineage — including blunt-tip patented derivatives with the cutting edge removed — is not evidence-free; rather, it occupies a stage in which "evidence for the parent technique continues to accumulate, while independent clinical research on individual derivative patented instruments remains comparatively thin."

Comparison

Conclusion

The two domestic lineages of patented blunt-tip percutaneous needles arose independently from different clinical traditions — the acupotomy lineage within Korean medicine, and the adhesiolysis lineage within anesthesiology and pain medicine — yet they converge, at the engineering level, on the same design principle: a rounded tip that penetrates without transecting. This principle is not itself new. Western pain medicine has, since the 1970s, accumulated experimental evidence that short-bevel (blunt) needles reduce nerve injury, and this evidence has become a standard recommendation for peripheral nerve blockade today.

The substantive difference between the two domestic lineages lies not in tip geometry but in procedural protocol and the level of publicly disclosed evidence. Western nerve-block needles function as a conduit for delivering medication through a blunt tip, whereas the domestic lineages, for the most part, treat the physical movement of the needle itself — without any drug — as the therapeutic agent. The two also differ in evidentiary standing. The internationally published lineage (B) disclosed its methodology and needle specifications in a peer-reviewed paper, and its parent concept — adhesiolysis via a blunt-tip instrument — is broadly supported in the Western pain-medicine literature. The acupotomy-derived lineage (A) is backed, at the level of its parent technique, by numerous systematic reviews, but no independent clinical research on the individual patented instrument itself was identified in this inquiry.

In sum, when a percutaneous invasive instrument appears under a new name, it is worth distinguishing whether it embodies a genuinely new mechanism or whether it applies an already-established engineering principle — the blunt-tip needle — to a new indication under a new label. Both domestic lineages examined here leaned toward the latter. This does not, in itself, negate the clinical value of either procedure; but in clinical application, evaluation is better anchored to "which protocol, and at what level of evidence, applies the established blunt-tip principle" than to the rhetorical weight of "a newly patented instrument."

References

1. Ahn K, Lee YJ, Kim EH, Yang SM, Lim TK, Kim YS, Jhun HJ. Interventional microadhesiolysis: A new nonsurgical release technique for adhesive capsulitis of the shoulder. BMC Musculoskeletal Disorders. 2008;9:12. DOI: 10.1186/1471-2474-9-12.
2. Han SS, Lee SJ, Lee CJ, Lee SC. The Effects of Fluoroscopy Guided Interventional Microadhesiolysis and Nerve Stimulation (FIMS) in Lumbar Spinal Stenosis. Korean Journal of Anesthesiology. 2006;51(1):82-88.
3. Selander D, Dhunér KG, Lundborg G. Peripheral nerve injury due to injection needles used for regional anesthesia. Acta Anaesthesiologica Scandinavica. 1977;21:182-188.
4. Sala-Blanch X, Ribalta T, Rivas E, Carrera A, Gaspa A, Reina MA. Structural injury to the human sciatic nerve after intraneural needle insertion. Regional Anesthesia and Pain Medicine. 2009;34:201-205.
5. Heavner JE, Racz GB, Jenigiri B, Lehman T, Day MR. Sharp versus blunt needle: A comparative study of penetration of internal structures and bleeding in dogs. Pain Practice. 2003;3:226-231.
6. Prakash S, Kumar A. Needle tip and peripheral nerve blocks. Journal of Anaesthesiology Clinical Pharmacology. 2018;34(1):129-130. PMCID: PMC5885433.
7. Kwon CY, Yoon SH, Lee B. Clinical effectiveness and safety of acupotomy: An overview of systematic reviews. Complementary Therapies in Clinical Practice. 2019;36:142-152. DOI: 10.1016/j.ctcp.2019.07.002.
8. Jing Y, Qin Y, Tong Y, Qiao H, Yu H, Zhang Y, Liu F, Guo C, Yang J, Liu Q, Yang X. Status and prospects of acupotomy tool specifications and standardization. Guidelines and Standards of Chinese Medicine. 2026;4(1). DOI: 10.1097/gscm.0000000000000094.
9. Korenblit M, Haas EJ, Esch EM, Orfahli L, Mares O, Greyson M. A Mechanism-Based Classification and Review of Endoscopic and Ultrasound-Guided Carpal Tunnel Release. Journal of Clinical Medicine. 2026;15(16):6130. DOI: 10.3390/jcm15166130.