Similarities exist between descriptions of myofascial trigger points (MTrPs) in the western medical literature and those of the AhShi points of traditional Chinese acupuncture. Both systems utilise these points in the treatment of pain. The current teaching methodology in veterinary acupuncture focuses on traditional Chinese medicine (TCM) theory. However, many western practitioners of acupuncture use a modified technique that combines acupuncture and MTrP therapy in the treatment of pain. MTrP therapy is a more organized, systematic method for the treatment of musculoskeletal pain. The scientific basis for MTrP therapy lends itself to use by practitioners, untrained in acupuncture, in the treatment of acute and chronic musculoskeletal pain.

The following discussion examines similarities between the development of the recognition and use of MTrPs and acupuncture points. Comparisons between the definition and features of MTrPs and AhShi points suggest that these points are identical.

Historical Development of Acupuncture Points

Historically, three phases have been described in the development of acupuncture points:

 "Whatever hurts is the point"--needling or cauterising points spontaneously painful or painful on pressure palpation. Point locations were non-specific and had no names at this stage.

 Points became associated with specific diseases, through practice and experience. Distinct points were recognised that predictably affected both local and distal pain and disease. Such correlation led to point naming, in order to distinguish these points from other points of pain.

 A systematic approach grouped randomly located points according to similar functions and led to the development of the channel system. The channel and the points are interdependent concepts, and are the basis of channel theory in TCM.

Historical Development of Myofascial Trigger Points

Froriep (1843) found that treatment of extremely tender, palpable hardenings in skeletal muscle relieved patient's pain. Subsequent reports from the early 1900's found that the pain could be relieved in these tender muscles by ethyl chloride spray. Prior to 1938, few authors in the Western medical literature recognised an association between a tender spot in skeletal muscle, and the referral of pain at a distance from this area. Kellgren, beginning in 1938, provided a number of reports of characteristic referred pain patterns for many individual muscles and fascial structures. Similar patterns of referred pain were found to occur both clinically from tender points of patients, and experimentally after injection of hypertonic saline into muscle of normal individuals.

Three authors, beginning in the early 1940's, independently began to report associations between individual muscles and clinical patterns of pain in large numbers of patients. The papers by these three clinicians emphasised four cardinal features associated with these affected muscles: a palpable nodular or band-like hardness in the muscle; a highly localised area of extreme tenderness in that band; reproduction of the patient's distant pain complaint by digital pressure on that spot; and relief of the pain by pressure or injection of the tender spot. The patient's reaction when the painful muscle was palpated was termed the "jump sign". The palpably nodular/tender region of muscle was termed 'the trigger area' and later 'trigger point'. Janet Travell researched and published the most extensively of these three authors. The manifestation of her clinical work in the field of myofascial pain can be found in "Myofascial Pain and Dysfunction: the Trigger Point Manuals" the seminal work on the subject in humans. Research in myofascial pain, since the 1980's, has focused on understanding the underlying mechanisms of MTrPs.

History Repeats Itself

Clear parallels appear to exist between the development of acupuncture in TCM and MTrP therapy. Initially, in acupuncture, where there was pain there was a point, while with MTrPs, where there were characteristic palpable muscle hardenings there was pain. Treatment, in both cases, led to relief of the associated condition. Clinical practice and experience led to a second stage of development. Acupuncture developed an association between specific points and pain and disease. MTrP development led to an association between MTrPs and specific patterns of pain. Establishing associations, between particular points and pain and/or disease, led to the ability in each system to distinguish between different MTrPs and acupuncture points. Adoption of a systematic approach, in the final phase, led to the diagnostic and therapeutic development of acupuncture and MTrP theory. Further understanding, of the underlying mechanisms in both MTrPs and acupuncture, has resulted from medical research. The difference, therapeutically, between these systems is that MTrP therapy is used primarily to treat pain, while acupuncture can also be used in the treatment of a wide variety of conditions and symptoms in addition to pain.

Acupuncture Point Location

Traditional Chinese acupuncture, particularly by individuals not familiar with its details, is typically associated with charts showing acupuncture points connected by the channel (meridian) system. The most important constituents of the channel system are the 12 (bilateral) primary channels, and the midline Conception (front) and Governing (back) channels. Together, these comprise what are known as the Fourteen Channels. The channels, and the acupuncture points which lie along their paths, are the foundation of acupuncture.

The name of each channel reflects the part of the body with which the channel, and its constituent points, is therapeutically linked, i.e., the points along each channel have similar therapeutic properties. The channels serve as connecting vessels that transmit Qi (pronounced "chee") around the body. Qi in TCM terms is perceived functionally, by what it does, rather than being defined as a substance. Simplistically, Qi is considered conceptually similar to the western concept of energy.

The points that occur along the main acupuncture channels, however, are not the only type of acupuncture point. Acupuncture points are generally classified into three types: the channel points; miscellaneous (also called off channel or extra meridian) points; and AhShi points (points of pain). Some texts also include a fourth type of point, the new points.

The channel points are so named because of their location along the paths of the Fourteen Channels. Historically, as acupuncture developed and more points were discovered, a problem arose regarding locating and naming points. As a result, a second category of points, the miscellaneous points, emerged. These points have names and their own individual indications and disease associations, but are not situated along the Fourteen Channels. Clinically the miscellaneous points supplement the channel points. The channel points and miscellaneous points are located according to traditional units of measurement relative to anatomical landmarks. Thus, their locations are regarded as being anatomically fixed and the same from one individual to the next.

AhShi points (also called points of pain, unfixed points and tender points) are the general name given to sites on the body that become spontaneously tender when disease or injury occurs. The location of AhShi points is not fixed. Some authors state that AhShi points are not channel or miscellaneous points, while other authors classify any tender points as an AhShi point regardless of their location. The latter terminology may provide a source of some confusion, when the anatomically fixed location of the channel and miscellaneous points are considered to be (anatomically unfixed) AhShi points. Without specific names and definite locations, AhShi points are thought to represent the earliest stages of acupuncture evolution.

The traditional principle, of "whatever hurts is the point", seems to lead to the different interpretations of AhShi points in different texts. The confusion possibly arises from the use of the spontaneous pain or tenderness to pressure at an acupuncture point in TCM diagnosis. Acupuncture points along the channels may become spontaneously tender or painful to touch when internal disease is present. The channels, as a result, were theorised to connect the body surface and internal organs or two areas of the body. O'Connor has termed these points of "pressure pain", as distinct from AhShi points, while other authors also use the term AhShi point in reference to sensitive channel or miscellaneous points.

"Pressure pain" at channel points is particularly common with special groups of points, e.g., the Associated, Alarm and Connecting points. Acupuncture point selection for treatment, based on sensitive points along the channels, is called channel diagnosis. However, channel diagnosis is recommended only as a starting point for further examination. For example, the same channel points might be affected by different diseases, leading to other diagnostic procedures being required to make the definitive diagnosis.

New points are a recent category of acupuncture points, and their discovery has paralleled the developments of western medical practice. Knowledge of neuroanatomy, and traditional methods of observation and experimentation on patients, have both contributed to descriptions of new point locations.

MTrP Location

MTrP point location, in the veterinary literature, is consistently misreported as being in a stable anatomical location. Instead, the MTrP locations reported should serve merely as a guide to where to look. Unlike charts of classical acupuncture points, the locations of MTrPs are not thought of as immutable locations. Every muscle can develop MTrPs and many muscles have multiple locations. The site of the trigger point in a given muscle varies with the individual. The precise localisation of the MTrP responsible for the patients pain is emphasised as this is necessary for treatment and successful resolution of the pain syndrome.

AhShi and MTrPs Compared

Obvious similarities are present when comparing the clinical features of AhShi points and MTrPs. Comparisons between the definition and features of AhShi points and MTrPs suggest that these points are identical:

Spatial Distribution and Associated Pain

Melzack (1977) attempted to determine the correlation between MTrPs and acupuncture points for pain, using the two criteria of spatial distribution and the associated pain pattern. The study found a 100% correlation, based on location and an overall clinical correspondence of 71% between acupuncture and MTrPs for pain distribution. The study concluded that MTrPs are firmly anchored in the anatomy of the neural and muscular systems, while acupuncture is associated with an ancient conceptual but anatomically nonexistent system. However, the close correlation between MTrPs and acupuncture points used for pain, suggests that they are two systems discovered independently and labeled differently. The two systems represent the same phenomena and can be explained in terms of the same underlying neural mechanism. Studying the neurophysiological response to these therapies has contributed to the understanding of pain mechanisms and in devising methods of treatment for chronic pain. However, not all acupuncture points are associated with skeletal muscle, therefore not all acupuncture points are MTrPs.

Advantages of MTrP Therapy

Schoen (1992) has suggested that a disadvantage of acupuncture in the treatment of chronic musculoskeletal conditions is that it often requires continual treatment. Elimination of initiating and perpetuating factors and MTrP identification and treatment reduce both the number of treatments required and the need for ongoing treatment in chronic musculoskeletal conditions, compared with acupuncture. The trigger point system is scientifically based and, as a result, some of the fundamental knowledge needed to understand myofascial pain syndromes has already been learned by veterinarians. The functional approach provided by MTrP therapy can be learned without the requirement for also learning TCM theory, can assist acupuncturists using TCM in diagnosing MTrP location and can improve acupuncture results in the treatment of musculoskeletal pain.

References

1.  Helms JM (1995). Acupuncture Energetics: A Clinical Approach for Physicians. Berkley, Medical Acupuncture Pub.

2.  Kapchuk TJ (1983). The Web That Has No Weaver. NY, Congdon and Weed.

3.  Macdonald AJR (1989). Acupuncture Analgesia and Therapy. In Textbook of Pain. P.D. Wall, Melzack, R. eds. Churchill, Livingston: 906-919.

4.  Melzack R, Stillwell DM, et al. (1977). Trigger Points and Acupuncture Points for Pain: Correlations and Implications. Pain 3: 3-23.

5.  O'Connor J, Bwensky D, Eds. (1981). Acupuncture a Comprehensive Text. Seattle, Eastland Press.

6.  Schoen AM (1992). Acupuncture for Musculoskeletal disorders. In Problems in Veterinary Medicine. A.M. Schoen. Philadelphia, J.B. Lippincott Co. 4: 88-97.

7.  Simons DG, Travell JG, et al. (1999). Travell and Simons' Myofascial Pain and Dysfunction: The Trigger Point Manual. 2nd ed. Vol 1. Baltimore, Williams and Wilkins.

8.  Travell JG, Simons DG. Myofascial Pain and Dysfunction: The Trigger Point Manual Vols.1&2. Williams and Wilkins, Baltimore 1983 and 1992.

9.  Xinnong C. Ed (1990). Chinese Acupuncture and Moxibustion. Beijing, Foreign Languages Press.