Dry needling is the use of either solid filiform needles or hollow-core hypodermic needles for therapy of muscle pain, including pain related to myofascial pain syndrome. Dry needling is sometimes also known as intramuscular stimulation (IMS). Acupuncture and dry needling techniques are similar but not the same.
The origin of the term “dry needling” is attributed to Janet G. Travell, M.D. In her book, 'Myofascial Pain and Dysfunction: Trigger Point Manual', Dr. Travell uses the term "dry needling" to differentiate between two hypodermic needle techniques when performing trigger point therapy. The two techniques she described are the injection of a local anesthetic and the mechanical use of a hypodermic needle without injecting a solution (Travell, Simons, & Simons, 1999, pp. 154–155). Dr. Travell preferred a 22-gauge, 1.5-in hypodermic needle for trigger point therapy and used this needle for both injection therapy and dry needling. Dr. Travell never used a filiform needle (aka “acupuncture” needle). Dr. Travell had access to acupuncture needles but reasoned that they were far too thin for trigger point therapy. She preferred hypodermic needles because of their strength and tactile feedback:“A 22-gauge, 3.8-cm (1.5-in) needle is usually suitable for most superficial muscles. In hyperalgesic patients a 25-gauge, 3.8-cm (1.5-in) needle may cause less discomfort, but will not provide the clear “feel” of the structures being penetrated by needle and is more likely to be deflected by the dense contraction knots that are the target… A 27-gauge needle, 3.8-cm (1.5-in) needle is even more flexible; the tip is more likely to be deflected by the contraction knots and it provides less tactile feedback for precision injection” (Travell, Simons, & Simons, 1999, p. 156).
The use of a hypodermic needle for dry needling was described by Dr. Chang-Zern Hong in his research paper on "Lidocaine Injection Verses Dry Needling to Myofascial Trigger Point”. In his research, he describes the procedure for trigger point injection and dry needling by using a 27-gauge hypodermic needle 1 ¼-in long (Hong, 1994). Both Travell and Hong used hypodermic needles for dry needling. Dr. Hong, like Dr. Travell, did not use an acupuncture needle for dry needling.
Although dry needling originally utilized only hypodermic needles due to the concern that solid filiform needles had neither the strength or tactile feedback that hypodermic needles provided and that the solid filiform needle could be deflected by "dense contraction knots", those concerns have proven unfounded and many healthcare practitioners who perform dry needling have found that the solid filiform needles not only provides better tactile feedback but also penetrate the "dense muscle knots" better and are easier to manage and caused less discomfort to patients. For that reason both the use of hypodermic needles and the use of solid filiform needles are now accepted dry needling practice. Ofttimes practitioners who use hypodermic needles also provide trigger point injection treatment to patients and therefore find the use of hypodermic needles a better choice.
The solid filiform needles used in dry needling are regulated by the FDA as a Class II medical device "intended to pierce the skin in the practice of acupuncture."  Per the Food and Drug Act of 1906 and the subsequent Amendments to said act, the FDA definition applies to how the needles can be marketed and does not mean that acupuncture is the only medical procedure where they can be used. Also the FDA definition does not mean that the FDA or any US Regulatory agency defines Dry Needling as a form of Acupuncture or that the two terms are interchangeable. Dry needling using such a needle contrasts with the use of a hollow hypodermic needle to inject substances such as saline solution, botox or corticosteroids to the same point. Such use of a solid needle has been found to be as effective as injection of substances in such cases as relief of pain in muscles and connective tissue. Analgesia produced by needling a pain spot has been called the needle effect.
Dry needling for the treatment of myofascial (muscular) trigger points is based on theories similar, but not exclusive, to traditional acupuncture; however, dry needling targets the trigger points, which is the direct and palpable source of patient pain, rather than the traditional “meridians”, accessed via acupuncture. The distinction between trigger points and acupuncture points for the relief of pain is blurred. As reported by Melzack, et al., there is a high degree of correspondence (71% based on their analysis) between published locations of trigger points and classical acupuncture points for the relief of pain. What distinguishes dry needling from traditional acupuncture is that it does not use the full range of traditional theories of Chinese Medicine. Dry needling would be most directly comparable to the use of so-called 'a-shi' points in acupuncture. The debated distinction between dry needling and acupuncture has become a controversy because it relates to an issue of scope of practice of various professions.
In the treatment of trigger points for persons with myofascial pain syndrome, dry needling is an invasive procedure in which a filiform needle is inserted into the skin and muscle directly at a myofascial trigger point. A myofascial trigger point consists of multiple contraction knots, which are related to the production and maintenance of the pain cycle. Deep dry needling for treating trigger points was first introduced by Czech physician Karel Lewit in 1979. Lewit had noticed that the success of injections into trigger points in relieving pain was apparently unconnected to the analgesic used.
Proper dry needling of a myofascial trigger point will elicit a local twitch response (LTR), which is an involuntary spinal cord reflex in which the muscle fibers in the taut band of muscle contract. The LTR indicates the proper placement of the needle in a trigger point. Dry needling that elicits LTRs improves treatment outcomes, and may work by activating endogenous opioids. Inserting the needle can itself cause considerable pain, although when done by well-trained practitioners that is not a common occurrence. No study to date has reported the reliability of trigger point diagnosis and physical diagnosis cannot be recommended as a reliable test for the diagnosis of trigger points.
Chan Gunn introduced a type of dry needling called intramuscular stimulation in the 1980s that moved away from using trigger points. Gunn believed that the peripheral muscle spasm was not the origin of pain, but instead a tight multifidi was causing spinal nerve compression, radiculopathy, and nerve damage running peripherally. This spinal nerve damage eventually reached the associated muscle, causing spasm and transformation to a trigger point. Therefore, Gunn recommended a needle be placed in the paraspinal muscles in addition to the distally affected muscle. Peter Baldry developed a version called superficial dry needling in 2005, in which the needle is inserted about 5–10 mm into the tissue above the trigger point. Baldry practiced deep dry needling until he had a patient in the early 1980s with a trigger point in his anterior scalene muscle. Baldry decided to only penetrate the skin for fear of puncturing a lung. Baldry has such success with this technique that he applied it throughout the body by simply puncturing the skin superficially over a trigger point without actually reaching it.
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Just like there are various methods to dry needling, there are various theories concerning the mechanism of action in how or why the procedure may work. Many of the studies published about dry needling are not strong; either the studies were not randomized, contained small sample sizes, had high dropout rates, used active interventions in the control group, did not follow the minimally acceptable criteria for diagnosing a myofascial trigger point, or did not clearly state that myofascial trigger points were the sole cause for the pain. For example, in a systematic review on needling therapies in the management of myofascial trigger points, only 8 of the 23 trials described the minimally acceptable criteria for diagnosing a trigger point. Locating the trigger point for dry needling is the basis for performing dry needling and should therefore be documented in each study performing this technique. In the same review, two studies tested the efficacy beyond placebo of dry needling in the treatment of myofascial trigger point pain, but, in one, the dropout rate was 48% and it was neither blinded nor randomized, and the other study used potentially active interventions in the control group.
Another systematic review concluded that dry needling for the treatment of myofascial pain syndrome in the lower back appeared to be a useful addition to standard therapies, but that clear recommendations could not be made because the published studies are small and of low quality. A 2007 meta-analysis examining dry needling of myofascial trigger points concluded that the effect of needling was not significantly different to that of placebo controls, though the trend in the results could be compatible with a treatment effect. One study (Lorenzo et al. 2004) did show a short-term reduction in shoulder pain in stroke patients who received needling with standard rehabilitation compared to those who received standard care alone, but the study was open-label and measurement timings differed, limiting the use of the study. Again the small sample size and poor quality of studies was highlighted. A recent systemic review and meta analysis released by JOSPT on "effectiveness of dry needling for upper-quarter myofascial pain" recommends the usage of dry needling, compared to sham or placebo, for decreasing pain immediately after treatment and at 4 weeks in patients with upper quarter myofascial pain syndrome./url=http://www.jospt.org/doi/pdf/10.2519/jospt.2013.4668 However the authors caution that "the limited number of studies performed to date, combined with methodological flaws in many of the studies, prompts caution in interpreting the results of the meta-analysis performed"
Dry needling is practiced by physical therapists in many countries, including South Africa, Bangladesh, the Netherlands, Spain, Switzerland, Canada, Chile, Ireland, the United Kingdom, Australia and New Zealand.
In the United States of America, physical therapists in most states perform the technique including Alabama, Alaska, Arizona, Arkansas, Colorado, District of Columbia, Georgia, Illinois, Iowa, Kansas, Kentucky, Louisiana, Maryland, Mississippi, Montana, Nebraska, New Hampshire, New Jersey, New Mexico, Nevada, North Carolina, Ohio, Oklahoma, Pennsylvania, Rhode Island, South Carolina, Tennessee, Texas, Vermont, Virginia, Washington, West Virginia, Wisconsin, and Wyoming. Physical therapists are prohibited from penetrating the skin or specifically from practicing dry needling in California, Hawaii, New York, and Florida, though many states have no regulations on dry needling. Oregon Bd of Appeals recently ruled, January 2014, the Oregon Board of Chiropractic Examiers did not have the statutory right to determine this in their scope of practice. But the Court made no ruling that Chiropractors do not have the training needed to perform dry needling. Additionally, chiropractors are legally allowed to practice dry needling in many states including Alabama, Colorado, Connecticut, Delaware, Florida, Illinois, Maryland, New Hampshire, New Mexico, North Carolina, Rhode Island, South Carolina, Texas, Utah, Virginia, and West Virginia as well as in many countries.
Many physical therapists and chiropractors have asserted that they are not practising acupuncture when dry needling. They assert that much of the basic physiological and biomechanical knowledge that dry needling utilizes is taught as part of their core physical therapy and chiropractic education and that the specific dry needling skills are supplemental to that knowledge and not exclusive to acupuncture. However, the originators and proponents of dry needling acknowledged that certain aspects of this techniques were inspired by acupuncture although they also acknowledge that the medical basis for it is purely Western Medicine in nature and therefore is not validly a subset of acupuncture and is a separate medical process. Many acupuncturists have argued that dry needling appears to be an acupuncture technique requiring minimal training that has been re-branded under a new name ("dry needling"). Whether dry needling is considered to be acupuncture depends on the definition of acupuncture, and it is argued that trigger points do not correspond to acupuncture points or meridians. They correspond by definition to the ad hoc category of 'a-shi' acupoints. It is important to note that this category of points is not necessarily distinct from other formal categories of acupoints. In 1983, Janet Travell et al. described trigger point locations as 92% in correspondence with known acupuncture points. In 2006, Peter T. Dorsher, acupuncturist at the Mayo Clinic, concludes that the two point systems are in over 90% agreement. In 2009, Dorsher and Fleckenstein conclude that the strong (up to 91%) consistency of the distributions of trigger point regions’ referred pain patterns to acupuncture meridians provides evidence that trigger points most likely represent the same physiological phenomenon as acupuncture points in the treatment of pain disorders. An article in Acupuncture Today (May 2011, p. 3, “Scope and Standards for Acupuncture: Dry Needling?”) further corroborates the 92% correspondence of trigger points to acupuncture points. The North Carolina Acupuncture Licensing Board has published a position statement asserting that dry needling is acupuncture and thus is covered by the North Carolina Acupuncture Licensing law, and is not within the present scope of practice of Physical Therapists, and Physical Therapists are not among the professions exempt from the law. But that is a matter of opinion and not a matter of law. The Attorney General was asked for an opinion by the North Carolina Acupuncture Licensing Board which he gave dated Dec 1st 2011 saying that "In our opinion, the Board of Physical Therapy Examiners may determine that dry needling is within the scope of practice of physical therapy if it conducts rule-making under the Administrative Procedure Act and adopts rules that relate dry needling to the statutory definition of practice of physical therapy."  The PTs proposed such rules but these were rejected by the Rules Review Committee because they found no statutory authority for the proposed rule. The PT board subsequently decided that "the Board believes physical therapists can continue to perform dry needling so long as they possess the requisite education and training required by N.C.G.S. § 90-270.24(4), but there are no regulations to set the specific requirements for engaging in dry needling." 
The Founder of Integrative Systemic Dry Needling (ISDN), Dr. Yun-Tao Ma PhD, L.Ac., has been spearheading the "dry needling" movement in the United States. Dr. Ma states, "Although ISDN originated in traditional Chinese methods, it has developed from the ancient empirical approach to become modern medical art rooted in evidence-based thinking and practice."  Dr. Ma then contradicts himself stating, "Dry needling technique is a modern Western medical modality that is not related to Traditional Chinese acupuncture in any way. Dry needling has its own theoretical concepts, terminology, needling technique and clinical application."  Dr. Ma realizing both the self contradictions and the legal ramifications of dry needling being rooted in acupuncture and Chinese medicine has since taken down all information in his bios regarding his education in Chinese Medicine and being a Licensed Acupuncturist in the United States. 
In May 2011 the Oregon Board of Chiropractic Examiners ruled to allow "dry needling" into the chiropractic scope of practice with 24 hours of training. In July 2011 the Court of Appeals of the State of Oregon issued an injunction, preventing chiropractors from practicing dry needling until the case is heard in court. The document issued by the court states that "dry needling" is "substantially the same" as acupuncture and that the "respondent has not explained how 24 hours of training, with no clinical component, provides sufficient training to chiropractors to adequately protect patients." In September 2011, the Oregon Board of Chiropractic Examiners And Oregon Attorney General appealed said order on the grounds that they feel the commissioner who issued the order was mistaken in his assertion. On November 10, 2011, The Court of Appeals of the State of Oregon issued an Order Denying the Motion for Reconsideration. The effect of said ruling is that the entire Appeals Court will now determine if the stay was appropriate. The stay is relevant only in the State of Oregon.
In January 2014, The Oregon Court of Appeals ruled that the Oregon Board of Chiropractic Examiners did not have the statutory authority to include Dry Needling in the scope of practice for Chiropractors in that state. The ruling did not address whether Chiropractors have the medical expertise to use dry needling or whether the training they were being given was adequate. Pending further discussion of training requirements the Oregon Physical Therapist Licensing Board has advised all Oregon physical therapists against practicing dry needling. They have not changed their ruling that dry needling is within the scope of practice for Oregon Physical Therapists.
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