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Trigger-point dry needling is an invasive procedure where a fine needle or acupuncture needle is inserted into the skin and muscle. It targets myofascial trigger points (MTrPs) - hyperirritable spots palpable as nodules in the taut bands of skeletal muscles.[1] Trigger point dry needling can be performed at either superficial or deep tissue levels.
Pathophysiology of MTrPs
Trigger points are attributed to an excessive release of acetylcholine from specifc motor endplates. They can be categorised into Active and Latent MTrPs[2][3].
Active MTrPs can spontaneously trigger local or referred pain. They cause muscle weakness, restricted [[Range of Motion
|range of motion (ROM)]] and autonomic phenomena.
Latent MTrPs do not cause pain unless they are stimulated. They may alter muscle activation patterns and restrict ROM.
Active and latent MTrPs cause allodynia at the trigger point site and hyperalgesia away from the trigger point in response to applied pressure[4].
MTrPs form due to the development of a taut band within the muscle. This band is caused by excessive acetylcholine from the motor endplate, combined with the inhibition of acetylcholine esterase and an up-regulation of nicotinic acetylcholine receptors.
Taut bands initially form as a protective physiological response to actual or potential muscle damage. These bands are believed to develop in reaction to unaccustomed eccentric or concentric loading, sustained postures, and repetitive low-load stress. However, their persistence contributes to prolonged pain.
Pain associated with MTrPs is due to hypoxia and decreased blood flow. This results in decreased pH, activating muscle nociceptors for homeostasis restoration, leading to peripheral sensitisation.
MTrPs also play a role in central sensitisation. While the mechanism is not fully understood, MTrPs sustain nociceptive input into the dorsal horn, thereby contributing to central sensitisation.
Deep VS Superficial Dry Needling
Superficial dry needling involves inserting the needle up to 10 mm into the subcutaneous tissue, its benefits include ease of administration, decreased risk of significant tissue trauma, reduced risk of nerve and visceral injury and patient comfort.
Deep dry needling involves the insertion of the needle beyond the subcutaneous tissue into the muscle to reach MTrPs[5].
Mechanisms of Action
Dry needling has been shown to immediately increase pressure pain threshold and ROM, decrease muscle tone, and decrease pain in patients with musculoskeletal conditions[6]. The suggested mechanisms of action include:
Local Twitch Response: Dry needling can elicit a ‘local twitch response’ which is an involuntary spinal reflex resulting in a localised contraction of the affected muscles that are being dry-needled. Local twitch response can lead to alteration in the length and tension of muscle fibres and stimulate mechanoreceptors like A Beta fibres[7].
Effects on Blood Flow: Sustained contraction of taut muscle bands in trigger points might cause local ischemia and hypoxia. Dry needling causes vasodilation in the small blood vessels leading to increased muscle blood flow and oxygenation[7].
Neurophysiological effects: Dry needling can elicit local and central nervous responses, promoting homeostasis at the trigger point site and leading to a decrease in both central and peripheral sensitisation to pain[6].
Remote Effects: Dry needling of distal MTrP has been found to have an analgesic effect on proximal MTrP. The literature has conflicting evidence regarding the contralateral effect[7]
Dry needling (DN) therapy should be avoided in patients under the following circumstances [12][13]:
Unwilling or unable to give consent due to fear, believes, communication, cognitive, age-related factors.
Medical emergency or acute medical condition.
Local infection
Over an area or limb with lymphedema as this may increase the risk of infection/cellulitis and the difficulty of fighting the infection if one should occur.
The effectiveness of this treatment depends greatly on the skill of the therapist to accurately palpate myofascial trigger points as well as kinaesthetic awareness of the anatomical structures.
A review study concluded that dry needling, particularly in combination with other therapies, has moderate evidence for reducing pain severity in people diagnosed with low back pain. However, it also stated that the follow-up effects of dry needling and its clinical superiority in improving functional disability are ambiguous.[14]
According to a systematic review study of 16 studies, 7 of which were RCTs, the use of DN alone or with other interventions generally resulted in improvement in spasticity level, pain intensity, and ROM in stroke survivors.[15]
Another systematic review study concluded that DN reduced the severity of myofascial pain, which is usually associated with trigger points, in patients with temporomandibular joint dysfunction. However, it was also stated that there is a low level of evidence on this subject and that trials with bigger sample sizes and a lower risk of bias are needed.[16]
A systematic review of 23 trials considering needling therapies for myofascial trigger point pain concluded that direct dry-needling (where MTrPs were directly targeted) was as beneficial as wet needling.[17] There is no clear evidence that it is beneficial above placebo. More studies of higher quality with reproducible diagnostic criteria and a valid placebo are needed to draw firm conclusions on this.
A systematic review and meta-analysis with level 1a evidence concluded that:[18]
Dry needling applied by a physical therapist has very low to moderate quality evidence for superiority over no treatment or sham dry needling in reducing pain and improving pressure pain threshold in patients with musculoskeletal pain in the immediate to 12-week follow-up period.
Dry needling in improving functional outcomes has low-level evidence for superiority over no treatment and sham dry needling but no difference with other physical therapy treatments.
There is insufficient evidence for the long-term benefit of dry needling.
Electrical Dry Needling
Electrical dry needling (EDN) is a technique in which two needles are inserted as electrodes for passing an electric current. One of the main advantages of using EDN in clinical practice or acupuncture research is its capacity to set stimulation frequency and intensity objectively and quantifiably.
In clinical practice, both low- and high-frequency electrostimulation are used often for diverse conditions. Low-frequency stimulation is specifically recommended for muscular atrophy [19], whereas high-frequency stimulation is recommended for spinal spasticity[20].On animals for example EDN with 2-Hz stimulation seems to induce acupuncture analgesia by the release of endomorphin, β-endorphin and enkephalin binding to μ and δ opioid receptors. EDN with 100-Hz stimulation, however, enhances the release of dynorphin binding to the opioid receptor in the spinal cord dorsal horn to produce an acupuncture analgesic effect[21].
Most studies demonstrated a broad neuro matrix response that involved the limbic system and limbic-related brain structures including the amygdala, hippocampus, hypothalamus, cingulate, prefrontal and insular cortices, basal ganglia, and cerebellum[21]. On human infact results demonstrated a greater effect on the limbic and limbic-related brain structures with real EDN than with nonspecific or placebo stimulation. Specifically, the hemodynamic response produced a signal increase in notable limbic-related regions such as the insula, thalamus, cerebellum, and the anterior middle cingulate cortex. Interestingly, however, the subgenual anterior cingulate showed a signal decrease[22].
EDN and upper cervical and upper thoracic HVLA thrust spinal manipulation were shown to be more effective than non-thrust mobilisation and exercise in patients with chronic headaches, and the effects were maintained at 3 months. [25]
EDN combined with cervicothoracic manipulation c resulted in greater reductions in pain, disability, and medication intake than nonthrust peripheral joint/soft tissue mobilisation, exercise, and interferential current in patients with subacromial pain syndrome. The effects were maintained at 3 months.[26]
References
↑Dommerholt J, Mayoral del Moral O, Gröbli C. Trigger point dry needling. Journal of Manual & Manipulative Therapy. 2006 Oct 1;14(4):70E-87E.
↑ 6.06.1Gattie E, Cleland JA, Snodgrass S. The effectiveness of trigger point dry needling for musculoskeletal conditions by physical therapists: a systematic review and meta-analysis. Journal of Orthopaedic & Sports Physical Therapy. 2017 Mar;47(3):133-49.
↑Cagnie B, Dewitte V, Barbe T, Timmermans F, Delrue N, Meeus M. Physiologic effects of dry needling. Current pain and headache reports. 2013 Aug;17:1-8.
↑ 11.011.1Dommerholt J., Fernandez-de-las-Penas C. Trigger Point Dry Needling. An Evidenced and Clinical-Based Approach. Edinburgh: Churchill Livingstone-Elsevier, 2013
↑Australian Society of Acupunture Physioterapists Inc. Guidelines for safe acupuncture and dry needling practice, 2007.
↑White, A., Cummings M., Filshie, J. Evidence of safety of acupuncture. An introduction to Western medical acupuncture. Edinburgh: Churchill Livingstone, 2008.
↑Liu G.Techniques of acupuncture and moxibustion. Beijing: Huaxia Publishing House. 1998:177 p.
↑Yuan Y, Yan S, Chen X, Han JS X: The effect and mechanism of electroacupuncture in treating spinal spasticity: a clinical study. Nat Med J Chin, 1992;73:5932.
