To obtain the full benefit of acupuncture as a treatment approach one must then consider the pathology of any given condition under treatment, to clinically reason the use of the modality.
The Path of Pain
Any soft-tissue injury to the body will trigger a local inflammatory response within the damaged tissues. Inflammation, being the body’s generic response to any form of trauma, is initiated regardless of the nature of the injury. The purpose of the inflammatory response is to eliminate the initial cause of cellular injury and the subsequent removal of damaged tissue and dead cell debris. It also exists to initiate repair of the damaged tissues and promote the healing process. Acute inflammation presents with five classical signs: pain, heat, redness, swelling and loss of function.
Following an initial insult, the injured tissue creates a stimulation of the sensory receptors of small afferent nerve fibres of A delta (Aδ) and C axon size. These first-order neurons ascend to synapse mainly in the superficial dorsal horn of the spinal cord. These first-order neurons enter the spinal cord at the dorsal root entry zone, via the lateral division of the dorsal roots of the spinal nerves. It is here in the dorsal horn that they combine together to form the dorsolateral fasciculus (tract of Lissauer), which is present at all spinal cord levels. The first-order neurons of Aδ fibre type enter lamina I (and V) and synapse primarily with second-order neurons in lamina I and lamina V of the spinal cord grey matter. The first-order neurons of C fibre type enter the spinal cord and synapse with lamina I cells and lamina II interneurons. The branches of the dorsolateral fasciculus then either ascend or descend one to three spinal cord levels within this tract, to terminate in their target laminae of the dorsal horn. It is there that they synapse either with second-order neurons or interneurons. The axons of the second-order neurons pass across the midline of the spinal cord to the contralateral side in the anterior white commissure, forming the spinothalamic tract (STT).
The second-order neurons stem from the dorsal horn and from here the pain signal progresses from the dorsal horn along the ascending STT. The STT transmits pain (as well as thermal and crude touch sensations) to the contralateral ventral posterior lateral nucleus of the thalamus. Although the STT ends at the thalamus, as it ascends through the brainstem it also sends collateral connections to the reticular formation. When the STT reaches the thalamus it synapses with a third-order neuron. The third-order neurons are located within the ventral posterior lateral, the ventral posterior inferior and the intralaminar thalamic nuclei. From this level the signal then ascends from the thalamus onward via the fourth-order neurons of the STT to synapse with fourth-order neurons within the cortex. It is here that painful stimulus can be perceived at a conscious level. The projections of the fourth-order neurons of the STT can be diffusely spread to the entire cerebral cortex. This tends to support the hypothesis that pain may affect the whole brain and ‘pain centres’ are not necessarily discretely localised regions but rather a complex systemic network encompassing many neural structures (1). This is an example of one route by which pain may be experienced. If one considers this mechanism as a credible explanation for the transmission of painful stimuli and subsequently evaluates the proposed mechanisms for acupuncture, a cause and effect model for the clinically reasoned use of acupuncture can be implemente
The Analgesia Mechanism of Acupuncture
An acupuncture needle inserted through the skin into the deeper myofascial structures activates the sensory receptor in the underlying muscle. Following initial insertion of the needle an inflammatory response is initiated and causes the release of a variety of chemicals, one such being calcitonin gene-related peptide (CGRP). CGRP is a potent vasodilator and causes a local increase in circulation which may lead to visual observation of the local phenomenon known as ‘weal’ and ‘flare’ which is similar to a histamine response. This response may also cause a sensation of itchiness in some individuals (2). The increase in circulation is also documented in deeper muscular tissues, which is considered to support local tissue healing (3). The insertion of a needle is then often followed by some form of mechanical stimulus. This stimulus often takes the form of rotation of the needle in an alternating clockwise and anticlockwise manner. The response of the connective tissues to this action is termed mechanical transduction and is considered to be a beneficial component of acupuncture (4). The local mechanical stimulus triggers impulses that transmit to the spinal cord type II and III muscle afferent nerves, also known as small diameter myelinated afferents (Aδ). These cells synapse in the spinal cord with those of the anterolateral tract (ALT), which in turn communicates with three other areas. These areas, or more commonly termed ‘centres’, are the spinal cord, the midbrain and the pituitary–hypothalamic complex. Within the spinal cord, the arriving Aδ stimulus also transmits signals across collateral connections to intermediate endorphinergic cells which inhibit the substantia gelatinosa (SG)-cell activity via the release of the endorphins, enkephalin or dynorphin but not β-endorphin. Spinal cord endorphins cause presynaptic inhibition of C fibres, preventing transmission of the pain signals from the C fibres entering the dorsal horn with the STT . Within the spinal cord the enkephalins and dynorphins that are released by intermediate cells block pain signals (1). This proposed mechanism of segmental analgesia is similar to that of Melzack and Wall’s original description, which discussed the collateral inhibition of pain by the release of γ-aminobutyric acid (GABA) as initialled by Aβ fibres (5).
The Aδ fibres entering the spinal cord also communicate with the midbrain via the ALT. Ascending ALT transmission stimulates cells within the periaqueductal grey (PAG) which release β-endorphin to excite the raphe nucleus located at the lower end of the medulla oblongata, triggering impulses along the dorsolateral tract (DLT) to release monoamines (M) (serotonin and noradrenalin) within the spinal cord. Postsynaptic inhibition is modulated via noradrenalin, whereas C fibres are presynaptically inhibited via serotonin stimulating further release of met-enkephalin. Noradrenalin has an analgesic effect throughout the spinal cord as its release is diffuse and non-specific in location. Either of the two monoamines released are capable of suppressing pain transmission (1). Imaging studies have also demonstrated that the limbic system plays an important role in acupuncture-induced analgesia (6). The ascending stimulus continues to terminate in the pituitary–hypothalamic complex where it triggers the release of adrenocorticotropic hormone (ACTH) and β-endorphin into the circulation in equal measures. ACTH can then travel to the adrenal cortex where cortisol is subsequently released into the blood which produces anti-inflammatory effects (1). If the acupuncture stimulus is particularly strong, analgesia can be facilitated through the mechanism of diffuse noxious inhibitory control (DNIC), where one pain may inhibit another (7).
Acupuncture Mechanism and Needle Placement
When acupuncture is performed in a region close to the site of pain there is a primary utilisation of the segmental circuits operating within the spinal cord while also bringing in cells from the midbrain and pituitary–hypothalamic complex. When needles are placed in distal points much further away from the painful region, they activate the midbrain and pituitary–hypothalamic complex without the benefit of segmental effects (1). Therefore, it may be generalised that local segmental needling usually gives more intensive analgesia than distal non-segmental needling does because it uses all three centres. Generally, the two kinds of needling (local and distal) are used together on each patient to enhance one another. This is often the case with traditional acupuncture where local and distal points on the same ‘channel’ or ‘meridian’ are used in the treatment of musculoskeletal pain. This then uses the segmental and heterosegmental mechanisms as previously discussed. The segmental approach triggers inhibitory enkephalinergic cells in the spinal grey matter which are directly contacted by the Aδ primary afferents. The heterosegmental effect is brought about by a neurohormonal mechanism involving the release of β-endorphin and by two descending neuronal mechanisms which are serotonergic and adrenergic. There is also considered to be some involvement of DNIC in the overall analgesic effect (2).
Beyond Analgesia
Acupuncture has also been shown to induce a phenotypic switch of muscle macrophages. This causes a reduction in pro-inflammatory cells (M1 macrophages) and an increase in anti-inflammatory cells (M2 macrophages and IL-10), which reduces pain, swelling and inflammation in local tissue (8). Wang et al. (9) showed that acupuncture regulates opioid-containing macrophages and anti-nociceptive mediators in inflammatory pain, further supporting the interaction between acupuncture, pain and inflammation that speeds up healing and the recovery processes. Jeong et al. (10) suggested that acupuncture treatment has an inhibitory effect on cytokine production TWEET THIS, as the elevated levels recorded in patients suffering from headaches were reduced to those of a healthy control group following acupuncture treatment. Although this research was specifically conducted in patients with chronic headache, it may be possible to apply these results to the general population.
Torress-Rosas et al. (11) stated that sciatic nerve activation with electroacupuncture controls systemic inflammation by inducing vagal activation of aromatic L-amino acid decarboxylase, leading to the production of dopamine in the adrenal medulla. This can provide therapeutic advantages such as controlling inflammation in infectious and inflammatory disorders. This new research also goes some way to explain the biomechanical process initiated by electroacupuncture that influences sepsis.
Acupuncture is also thought to accelerate the initial inflammatory response to promote the secondary healing responses in injury, and also helps to control systemic inflammation in inflammatory and infectious disorders including sepsis.
Cost Effective
Acupuncture performed by health professionals is a cost-effective way of delivering acupuncture as the only additional cost following training is for the needles. Using the HePAG (Box 1) discount needles can cost as little as approximately £0.02 each (£2.11 per 100), and little, if any, additional treatment time is needed, meaning that there is either a minimal or no additional cost to the commissioner or service user. Acupuncture also provides an effective, cost-effective and evidence-based service for patients and maintains patient choice. Offering patient choice is a key objective of the UK government; offering acupuncture as part of existing services provides patient choice without any great cost to the NHS TWEET THIS.
Box 1: The Health Professions Acupuncture Group (HePAG)
Safety
There has been significant research in to the safety of acupuncture. MacPherson et al. (12) made a survey of 34,407 acupuncture treatments, and reported no serious adverse events (ie. ones requiring hospital admission). In total, there were 43 significant minor adverse events (including nausea, fainting, dizziness, vomiting, increased symptoms and bruising). This equates to only 0.12% (1.2 per 1000), which is an extremely low figure even in comparison to other treatments regarded as very safe, such as medication.
Figures on serious adverse events associated with acupuncture were published by White (13). This research combined data from the above studies with further reports, and included 4,441,103 treatments in total. White reported 11 serious adverse events (13). More common were mild adverse events such as tiredness and bruising, which both occurred in 3% of treatments. Further evidence of the safety of acupuncture has been provided by Xu et al. (14), who stated that four recent surveys of acupuncture safety among regulated, qualified practitioners confirmed that serious adverse events after acupuncture are uncommon. These surveys covered more than 3 million acupuncture treatments in total; there were no deaths or permanent disabilities, and all patients who suffered an adverse event fully recovered.
The more common adverse events are exceptionally minor in nature and pose very little risk to the patient. More significant adverse events are extremely rare. HePAG endorses acupuncture as an exceptionally safe treatment, when practised by a HePAG member TWEET THIS.
Application and Training
Research has shown that a range of musculoskeletal and sports injures benefit from acupuncture, including plantar fascial pain, medial tibial stress syndrome, acute and chronic low back pain, patellofemoral pain, shoulder pain, neck pain, headaches and migraine. From a clinically reasoned perspective, however, the potential exists for it to be used for the treatment of any myofascial pain and dysfunction. WMA is a practice that has its philosophies firmly based in anatomy and physiological principles. This means, therefore, that providing a prerequisite knowledge of anatomy and physiology is in place (ie. graduate sports therapist, osteopath, chiropractor, doctor, nurse, physiotherapist, etc.) a foundation level of WMA can be taught as an accelerated protocol over a few months with a little as six contact days. This is the type of acupuncture that is most commonly employed by chartered physiotherapists and other manual therapists clinically at all levels, from treating sedentary individuals to elite Olympic athletes.
The next article in the series will discuss the clinically reasoned application of WMA for a variety of common musculoskeletal conditions.
- Acupuncture initiates a variety of physiological responses that can affect pain, inflammation, healing and recovery.
- Acupuncture analgesia has three main mechanisms: local, segmental and supraspinal.
- The application of acupuncture is related to anatomical structures and local and central physiological responses.
- Evidence demonstrates that acupuncture can be an effective treatment for a number of myofascial pain conditions.
- Research shows acupuncture is a safe treatment.
- Cost analysis demonstrates acupuncture to be a cost-effective intervention.
- To obtain the full benefit of acupuncture, one must consider the pathology of the condition under treatment.
- Acupuncture triggers a vasodilatory response, increasing local circulation, which is thought to support local tissue healing.
- Research has found that a number of chemical changes occur as a result of acupuncture – locally improving healing via the release of histamine, bradykinin, and white blood cells and analgesia by increasing local endorphin and serotonin levels.
- pain relief
- the release of tight tissue – muscle, fascia, ligament and tendons
- increased circulation
- improved sleep patterns.
Acupuncture is a treatment in its own right, however, as Chartered Physiotherapists, we have the benefit of being able to add our clinical eye and supplement acupuncture with manual therapy techniques and exercises to aid recovery if indicated. This is also of benefit if at the last minute you decide it is not for you as we can provide alternatives. The total time the needles are in is guided by client response in sessions initially being a shorter period and progressing accordingly in follow up sessions.
