Microscopic features and transient contraction of palpable bands in canine muscle
PainSci commentary on Simons 1976: ?This page is one of thousands in the PainScience.com bibliography. It is not a general article: it is focused on a single scientific paper, and it may provide only just enough context for the summary to make sense. Links to other papers and more general information are provided wherever possible.
This study of trigger points in canine cadavers shows histologic changes that are consistent with theoretically predicted trigger point morphology. Specifically, it clearly showed a strongly contracted segment of muscle fibre — not the whole fiber, but just a very small part of it. The segment is clearly swollen, and the sarcomere bands are so tightly packed that individual ones can’t be seen — but they are clearly visible on either side of the contraction, and in adjacent fibres.
The authors assume that there are compressed capillaries on either side of the contraction. If so, this would probably deprive the tissue of oxygen.
The tissue examined was not symptomatic — dogs can’t tell us where it hurts. The spots were identified as taut bands with a local twitch response prior to (gulp) termination of the specimen.
While the results seem to be consistent with the MTrP construct, it was not — and could not be — correlated with the symptomatology that clinically defines it.
~ Paul Ingraham
original abstract †Abstracts here may not perfectly match originals, for a variety of technical and practical reasons. Some abstacts are truncated for my purposes here, if they are particularly long-winded and unhelpful. I occasionally add clarifying notes. And I make some minor corrections.
Ten pairs of biopsies were excised from gracilis and semitendinosus muscles of 4 mongrel dogs. These were compared with the histological findings reported in painful spots and muscle hardenings of human muscles. Test biopsies sampled a palpable band. Paired control biopsies sampled a portion of the same muscle where it showed no palpable hardening. Processed sections were randomized and read blind. Sections stained with aqueous toluidine blue showed no convincing metachromasia. Sections stained with trichrome showed no proliferation of endomysial connective tissue. Test sections stained with hematoxylin and eosin showed no proliferation of nuclei and no increase in the number of central nuclei in muscle fibers compared to control sections. No convincing histological difference was found. During surgery under Nembutal anesthesia, rubbing palpation of the exposed muscle elicited a transient contraction of a bundle of muscle fibers several milli-meters in diameter. This corresponded in time and position to the palpable band in the dog muscle. The band-like hardness palpated in these canine muscles appears to be caused by a circumscribed transient muscular contraction rather than histologically demonstrable structural changes.
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- “Accelerated muscle fatigability of latent myofascial trigger points in humans,” Ge et al, Pain Med, 2012.
- “Two-dimensional ultrasound and ultrasound elastography imaging of trigger points in women with myofascial pain syndrome treated by acupuncture and electroacupuncture: a double-blinded randomized controlled pilot study,” Müller et al, Ultrason Imaging, 2015.
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- “Ability of magnetic resonance elastography to assess taut bands,” Chen et al, Clin Biomech (Bristol, Avon), 2008.
- “Identification and quantification of myofascial taut bands with magnetic resonance elastography,” Chen et al, Archives of Physical Medicine & Rehabilitation, 2007.
This page is part of the PainScience BIBLIOGRAPHY, which contains plain language summaries of thousands of scientific papers & others sources. It’s like a highly specialized blog. A few highlights:
- Inciting events associated with lumbar disc herniation. Suri 2010 Spine J.
- Prediction of an extruded fragment in lumbar disc patients from clinical presentations. Pople 1994 Spine (Phila Pa 1976).
- Characteristics of patients with low back and leg pain seeking treatment in primary care: baseline results from the ATLAS cohort study. Konstantinou 2015 BMC Musculoskelet Disord.
- Effectiveness and cost-effectiveness of universal school-based mindfulness training compared with normal school provision in reducing risk of mental health problems and promoting well-being in adolescence: the MYRIAD cluster randomised controlled trial. Kuyken 2022 Evid Based Ment Health.
- No long-term effects after a three-week open-label placebo treatment for chronic low back pain: a three-year follow-up of a randomized controlled trial. Kleine-Borgmann 2022 Pain.