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Dissection of the thoracic paraspinal region – implications for osteopathic palpatory diagnosis: A case study
International Journal of Osteopathic Medicine 8 (2005) 69e74 www.elsevier.com/locate/ijosm
Short communication
Dissection of the thoracic paraspinal region e implications for osteopathic palpatory diagnosis: A case study Gary Fryer *, Jim Johnson School of Health Science, City Campus, Victoria University, PO Box 14428 MCMC, Melbourne 8001, Australia Received 30 January 2004; received in revised form 30 July 2004; accepted 23 December 2004
Abstract Background: Authors in the field of osteopathy have claimed that tissue texture abnormalities in the paravertebral gutter (PVG), the region between the erector spinae mass and the spinous processes, are indicators of intervertebral somatic dysfunction, but the cause of texture abnormality is unknown. Methods: The PVG was identified using manual palpation and marked with marker pins before dissection. A progressive dissection of the medial paraspinal thoracic region was performed and the anatomy of this region was reviewed. Results: Progressive dissection revealed the trapezius, spinalis, semispinalis, multifidus and rotatores muscles to be immediately deep to the marked location, and deep to these muscles, directly below the marker, was the zygapophysial joint. Discussion: The possible relevance of these medial paraspinal structures to tissue texture abnormality detected with palpation was discussed. Authors in the field of osteopathy have suggested that dysfunction of either the rotatores muscles or the underlying zygapophysial joint may be responsible for tissue texture change in the PVG, and these structures were located directly under the palpated site. Conclusion: Further research to examine the tissues associated with textural abnormalities in the PVG is warranted. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Palpation; Osteopathic medicine; Muscle; Skeletal; Thoracic wall
1. Introduction The concept of intervertebral dysfunction, a functional disturbance of the intervertebral joints and related tissues that can be detected with manual palpation and treated with manipulation, is important to osteopathic theory and practice. Authors in the field of osteopathy originally called this dysfunction the ‘osteopathic lesion’ or ‘osteopathic spinal lesion’, although latterly most authors refer to it as ‘somatic dysfunction’, ‘segmental dysfunction’ or ‘intervertebral dysfunction’.1e6 The
* Corresponding author. E-mail address: [email protected] (G. Fryer). 1746-0689/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.ijosm.2005.04.006
nature and pathophysiology of intervertebral dysfunction remains speculative.1 Authors in the field of osteopathy have claimed that segmental, paraspinal tissue texture change is a key diagnostic sign of intervertebral dysfunction, and may include abnormal hardness, bogginess or ropiness of the underlying paraspinal muscles.3,7,8 Osteopaths commonly palpate for altered tissue texture in three distinct paraspinal regions: the medial, paravertebral ‘gutter’ (PVG), which lies close to the spine between the vertebral spinous process in the midline and the erector spinae muscle group; the bulk of the erector spinae muscle group; and, more laterally, the iliocostalis muscle fibers overlying the angles of the ribs. Many authors claim that the cardinal sign of intervertebral dysfunction
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is ‘palpable hypertonicity’ of the deep, fourth layer paraspinal muscles, particularly rotatores and multifidus.3,7e10 It has been claimed that these tissue texture changes can be palpated in the PVG,3,8 and are usually found unilaterally and reported as being tender by the patient. More laterally, palpable hypertonicity of the iliocostalis muscle at the rib angle is claimed to be indicative of rib dysfunction.3 There has been much speculation on the aetiology of the manipulable spinal lesion, and various authors have implicated the paraspinal muscles,11 zygapophysial joints,12 and the intervertebral disc13,14 as the underlying cause of segmental motion restriction and tissue texture change. Korr proposed the model of the facilitated segment e a hyperactive segment of spinal cord e whereby abnormal motor output from the cord produced increased segmental muscle activity (such as rotatores and multifidus) that was proposed to cause tissue texture and joint motion change.15 Tissue texture changes in muscles have also been attributed to myofascial trigger points (MTrP), which are speculated to involve motor endplate dysfunction and result in muscle fiber ‘contraction knots’. MTrPs would be detected as small, hard and tender bands within the affected muscle, and refer pain in a characteristic pattern when manual pressure was applied.16 Fryer1 proposed a model for intervertebral dysfunction involving both patho-anatomical and functional sequelae to spinal injury, leading to a deficit in regional proprioception, changes in segmental and polysegmental muscle activity and motor control, and predisposing the segment to further strain. In this model, intervertebral sprain would initially produce paraspinal tissue abnormality due to peri-articular soft tissue inflammation and abnormal ‘pain mode’ activity of the superficial paraspinal muscles. As the dysfunction became more chronic, tissue abnormality would be caused by both overactivity of the superficial paraspinal muscles and atrophy of the deeper muscles, which may expose the underlying bony architecture to probing palpation.1 Little research exists to confirm either the existence of paraspinal tissue texture abnormalities, or their pathophysiology. In a recent study, Fryer et al.17 demonstrated that sites located in the thoracic PVG detected as abnormal to palpation by an osteopath, and reported as being tender by the subject, had a lower pressure pain threshold than sites identified as being normal and nontender above, below and opposite the dysfunctional site. This study suggested that such sites were not due to palpatory illusion,18 but had characteristics that could be objectively measured, and the authors recommended research into the nature of these regions. The aim of this case study dissection was to review the anatomy of the medial, paraspinal region, and examine what structures were present within the PVG to highlight tissues that may potentially produce abnormal texture.
2. Methods The dissection was conducted on an elderly (age unobtainable), embalmed (formaldehyde, glycerine and ethanol, prepared 12 months prior to dissection) male cadaver at the Victoria University anatomy laboratory, and performed by an experienced anatomy laboratory technician (JJ). A registered osteopath with 13 years practice experience (GF) palpated the thoracic region of the prone cadaver and attempted to locate the PVG and any apparent irregularities in the PVG (Fig. 1). Although the texture and shape of the paravertebral region was different to that of a living subject (harder and flatter), the osteopath was confident of identifying the familiar PVG, but less confident concerning the identification of a region of segmental PVG texture irregularity. Once a spot was located in the PVG, a marker pin was inserted into the site. Reference pins were also located on the lateral, superior and inferior margins of the specimen in the event the original pin and site were disturbed during dissection. The pin was removed during the process of dissection, but the small hole created by its removal assured very accurate re-location. The progressive dissection was performed in five stages. The first stage involved removal of the skin and superficial fascia to expose the trapezius muscle. The second stage involved removal of the trapezius muscle and fascia to expose the erector spinae muscle group. The erector spinae muscles were then removed to uncover the semispinalis muscle. Following removal of the semispinalis, the deepest layer of back muscles, the rotatores muscles, was uncovered. In the final stage of dissection, all muscle tissue was removed from the paraspinal region close to the marker pin to expose the vertebral lamina, articular pillar and zygapophysial joint line.
Fig. 1. Palpation of paravertebral gutter (PVG). Note that the left upper limb has been removed for teaching purposes.
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3. Results The first stage of dissection involved removal of the skin and superficial fascia from most of the trunk, using a rectangular incision, to expose the trapezius muscle (Fig. 2). The left upper limb had been previously removed for teaching purposes. The marker pin, located to the right side of the midline, clearly penetrated the lower fibers of the trapezius muscle (Fig. 2). The second stage involved removal of the trapezius muscle and fascia to expose the erector spinae muscle group. The marker pin was seen to penetrate the spinalis muscle, the most medial muscle of this group (Fig. 3). The erector spinae muscles were removed to uncover the semispinalis muscle. The marker pin penetrated the tendinous portion of the semispinalis muscle (Fig. 4). The levator costorum muscles, lateral to the transverse processes, were clearly visible. Following removal of the semispinalis (and the indistinguishable fibers of the multifidus), the deepest layer of back muscles, the rotatores muscles, were uncovered. The marker pin was present in the lateral portion of the rotatores brevis muscle, close to the common attachment of the brevis and longus muscles (Fig. 5). The intertransversarii muscles, arising from transverse process to transverse process, were clearly seen at this stage of dissection. In the final stage of dissection, all muscle tissue was removed from the paraspinal region close to the marker pin, which exposed the vertebral lamina, articular pillar and zygapophysial joint line at that level. The marker pin was seen to penetrate the joint line on the lateral third of the zygapophysial joint (Fig. 6). Rotatores muscles were seen at the segments above and below. The distance between the two transverse processes near the marker was 30 mm.
Fig. 2. Trapezius muscle. The marker pin can be seen to penetrate the lower fibers of the trapezius muscle (Tp). The latissimus dorsi (LD) can be clearly seen. X Z marker pin; Rp Z reference pins.
Fig. 3. Spinalis muscle. The marker pin penetrated the lateral fibers of the spinalis muscle (S). The other erector spinae muscle groups, longissimus (L) and iliocostalis (I), can be seen laterally. X Z marker pin.
4. Discussion This case study aimed to review the anatomy of the thoracic paraspinal region and highlight structures that could feasibly be involved in the creation of abnormal tissue texture in the PVG. Such tissue texture abnormalities are claimed by osteopaths to be a diagnostic sign of intervertebral dysfunction, but there is little evidence of what tissues potentially could be involved or palpated in this region. No conclusions can be made about the possible role of such structures from this case dissection, but it is interesting to note that the spinalis, semispinalis and rotatores muscles, as well as the zygapophysial joint itself, were located directly under the marked site in the PVG.
Fig. 4. Semispinalis muscle. The marker pin penetrated the tendinous portion of the semispinalis muscle (Ss). The levator costorum (LC) and external intercostal muscles can be seen more laterally. X Z marker pin; TP Z transverse process.
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Fig. 5. Rotatores muscles. The marker pin penetrated the rotatores brevis muscle (RB), close to the common attachment of the rotatores longus (RL). Note the intertransversarii muscles (It); TP Z transverse process; X Z marker pin.
4.1. Review of clinical anatomy The first stage of dissection removed the skin and superficial fascia to expose the trapezius muscle. The trapezius muscle is an extrinsic back muscle, and receives its motor nerve supply from the accessory nerve (CN XI). The other superficial extrinsic back muscles (latissimus dorsi, levator scapulae, and rhomboids) receive their nerve supply from cervical ventral rami (intrinsic back muscles are supplied by dorsal rami) and connect the upper limbs to the trunk and control limb movements.19 Travell et al.16 claim that MTrPs in the mid and lower trapezius may present as tender and hard bands on palpation, and would refer pain superiorly to the paraspinal region and mastoid process, with aching and tenderness into the suprascapular region.16
Fig. 6. Zygapophysial joint. The marker pin penetrated the lateral portion of the zygapophysial joint line (Z-j). RL Z rotators longus; TP Z transverse process; X Z marker pin; RB Z rotatores brevis; SP Z spinous process.
After removal of the trapezius muscle and thoracolumbar fascia, the erector spinae muscle group was exposed. The erector spinae is the most superficial group of the intrinsic back muscles, and make up the bulk of the paraspinal mass lateral to the PVG. The intrinsic thoracic back muscles are deep, innervated by dorsal rami, and are enclosed by fascia that attaches medially to the tips of the spinous processes and supraspinous ligament, laterally to the transverse processes and angles of the ribs, and extends from the pelvis to the skull. This fascia forms a thin covering for the deep muscles of the thoracic region, and a strong thick covering for muscles in the lumbar region.19 The erector spinae muscles are the chief extensors of the spine and are divided into three columns: spinalis (medially), longissimus (intermediate), and iliocostalis (laterally). The fibers of these muscles run superiorly, from spinous processes (spinalis), from ribs to transverse processes (longissimus), or angles of ribs (iliocostalis).19 In this dissection, the spinalis was found to underlie the site of palpation in the PVG. Deep to the erector spinae was the transversospinalis group, comprising semispinalis, multifidus and rotatores muscles. These muscles originate from the transverse processes and pass to spinous processes of more superior vertebrae, and occupy the ‘gutter’ region between the transverse and spinous processes.19 The semispinalis is the most superficial of the group, found only in thoracic and cervical regions, and was indistinguishable from the multifidus in the thoracic region. The marker pin in the present dissection passed through the lateral fibers of the semispinalis. Travell et al.16 have observed that MTrPs can commonly occur in the semispinalis muscle, which refers characteristic pain similar to that of the longissimus muscle, upward in the paraspinal region and to the lateral thorax. Multifidus refers pain primarily around the region of the adjacent spinous process, and may render the spinous process tender to palpation and percussion.16 In the lumbar spine, the most developed muscle of this group is the multifidus.19,20 Multifidus has been proposed to have little role in movement of the spine, but perhaps fulfils an important role in segmental stability by contracting to stiffen and protect the spinal unit from external forces during loading or movement.21 Hides et al.22 used ultrasonography to detect multifidus atrophy in low back pain patients specific to the segment and side that was painful on manual assessment. Multifidus atrophy has also been observed in subjects with chronic LBP using MRI23 and computer tomography.24 This case dissection supports the plausibility of the proposal that atrophy of semispinalis or multifidus may potentially produce texture abnormality in the thoracic PVG, insofar as these muscles lay directly under the marked site in the gutter.
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On removal of the semispinalis and multifidus, the rotatores muscles were exposed. The rotatores are the deepest muscles of the transversospinalis group, and constitute the deepest muscle fasciculi located in the groove between the spinous and transverse processes. The rotatores comprise of a brevis (attaching from the transverse process to the root of the spinous process immediately superior) and longus (spanning two segments).25 It has been suggested that rotatores muscles lack sufficient strength and leverage to produce spinal motion, and may play a greater role in spinal proprioception, acting as a ‘kinesiological monitor’.19 Travell et al. claim that involvement of rotatores MTrPs throughout the thoracolumbar spine produces midline pain and referred tenderness to tapping on the spinous process adjacent to the MTrP.16 This dissection observed the rotatores to be located directly beneath the palpated site in the PVG, and may potentially be palpable if of abnormal tissue texture (or ‘abnormal hypertonicity’), as suggested by many osteopathic authors.3,7e10 After removal of all myofascial tissue, it was found that the zygapophysial joint line lay directly beneath the marked location. The zygapophysial joint is a plane synovial joint, and thoracic joints are orientated mainly in the frontal plane. In the lower thoracic region, the joints progressively become more oriented to the sagittal plane. The proposal that inflammatory changes occurring in the zygapophysial joint and peri-articular tissues could result in tissue changes detected in the PVG,1 is consistent with the findings of this case study, because the joint was directly below the palpated PVG. 4.2. Limitations No conclusions can be made concerning intervertebral somatic dysfunction or tissue texture change in the PVG from this case study. The osteopath was confident of identifying the PVG, but not confident in identifying an abnormal area of tissue texture. The tissues of the embalmed cadaver were much firmer than the tissues of a living subject, and it was not possible to palpate deeply through the tissue layers as would be attempted in the muscles of an osteopathic patient. Furthermore, any tissue irregularity may be an artifact of the embalming process. These factors reduce the significance of the zygapophysial joint lying directly below the palpated spot within the PVG, but not the likelihood of all these structures underlying the PVG and potentially identifiable to palpation. The dissection was conducted on only one cadaver and so caution must be used when attempting to generalize from these findings. 4.3. Implications Authors in the field of osteopathy claim that segmental tissue texture abnormality located in the
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PVG is an important clinical sign of intervertebral dysfunction,3,8 but no researcher has attempted to investigate what tissues may be involved to produce the apparent abnormality. Many authors have assumed that the altered texture can be caused by abnormal contraction of the underlying rotatores and multifidus muscles,3,7e10 but there is little direct evidence to support this.2,26 It is also widely assumed that tissue texture abnormality detected by palpation represents a dysfunctional or pathological tissue, but it is possible that such ‘abnormalities’ are simply a reflection of normal muscle heterogeneity. In Fig. 4, the marker pin was amongst the fascial and tendon slips of semispinalis. It is possible that different muscle or tendon fascicles may produce irregularity to palpation. Perhaps such differences in tissue texture should only be viewed as abnormal when other characteristics e such as tenderness e are associated with them. This is consistent with recommendations from many osteopathic authors, who advocate a combination of clinical signs for the diagnosis of intervertebral dysfunction, including tissue texture change, asymmetry, altered motion and tenderness.3,8 Although the zygapophysial joint was located directly under the palpated location, caution is needed before assuming that the underlying joint may be a cause of tissue texture change in the PVG. Inflammation of the zygapophysial joint and surrounding peri-articular structures has been suggested as a cause of tissue texture abnormality,1 but the joint is very deep and it is unknown whether such changes would be detectable with palpation through the trapezius, spinalis, semispinalis, multifidus and rotatores muscles. No researcher has attempted to examine what spinal structures or paraspinal tissues can be reliably palpated on normal subjects. The close proximity of the palpated location to the rotatores muscles and the zygapophysial joint, however, does lend support to the proposal that these structures could potentially produce tissue change in the PVG. 4.4. Further investigation The exact tissues and the pathophysiology responsible for producing palpable abnormalities in the PVG require further investigation. This case study supports the proposal that deep paraspinal muscles and the zygapophysial joint are directly below the hollow of the PVG where authors recommend osteopaths to palpate for tissue texture change, and so may be involved in texture abnormalities detected in the PVG. Investigation using fresh, unembalmed cadavers, that are likely to have a tissue consistency closer to that of a living subject, could be examined for structures deep to the palpated PVG, but access and ethical clearance may be difficult for researchers.
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Tissue biopsies of normal and abnormal PVG sites may reveal differences, but biopsy sampling of the exact palpable spot is likely to present difficulties, particularly concerning the depth of penetration and accuracy of the sampling the targeted tissue. Furthermore, studies examining subjects with LBP have found mostly nonspecific differences e fiber type change, ‘moth-eaten fibers’ e that would not have an obvious influence on palpation.27 Diagnostic imaging of paraspinal structures deep to abnormal sites may help identify the tissues involved. One study failed to find signs of inflammation in subjects with LBP using diagnostic ultrasound, but this study did not use subjects with acute pain (who would be more likely to have inflammatory changes).28 Magnetic resonance imaging is likely to be more useful than ultrasonography in detecting joint and tissue inflammation, but the cost and availability of this procedure present an obstacle for most researchers. Diagnostic ultrasound may be useful to compare the relative thickness of deep muscles underlying normal and abnormal PVG sites.29 In order to determine if abnormal muscle activity is associated with the abnormally palpable sites, modern fine-wire EMG techniques could be used to record and compare activity in the deep paraspinal muscles underlying normal and abnormal sites.
5. Conclusion This case study served as a review of the anatomy of the thoracic paraspinal region and highlighted the structures that could feasibly be involved in the creation of abnormal tissue texture that may be palpated in the PVG of the thoracic region. The authors hope that studies in the future will reveal the pathophysiology of these sites, and establish the clinical relevance of such findings.
References 1. Fryer G. Intervertebral dysfunction: a discussion of the manipulable spinal lesion. J Osteopath Med 2003;6:64–73. 2. Fryer G, Morris T, Gibbons P. Paraspinal muscles and intervertebral dysfunction. Part 1. J Manipulative Physiol Ther 2004;27:267–74. 3. Greenman PE. Principles of manual medicine. 2nd ed. Baltimore: Williams & Wilkins; 1996. 4. Kuchera WA, Kuchera ML. Osteopathic principles in practice. Missouri: Kirksville College of Osteopathic Medicine Press; 1992. 5. Stoddard A. Manual of osteopathic practice. London: Hutchinson & Co; 1969.
6. Stone C. Science in the art of osteopathy. Cheltenham: Stanley Thornes Ltd; 1999. 7. Walton WJ. Texbook of osteopathic diagnosis and technique procedures. Ohio: American Academy of Osteopathy; 1970. 8. Kuchera ML, Jones JM, Kappler RE, Goodridge JP. Musculoskeletal examination for somatic dysfunction. In: Ward RC, editor. Foundations for osteopathic medicine. Baltimore: William & Wilkins; 1997. 9. Bourdillon JF. Spinal manipulation. 5th ed. Oxford: ButterworthHeinemann; 1992. 10. Stoddard A. Manual of osteopathic techniques. 3rd ed. London: Hutchinson & Co.; 1980. 11. Mitchell FLJ. In: The muscle energy manual, vol. 1. Michigan: MET Press; 1995. 12. Maigne R. Diagnosis and treatment of pain of vertebral origin. Baltimore: Williams & Wilkins; 1996. 13. McKenzie RA. The lumbar spine. Mechanical diagnosis and therapy. Wellington: Spinal Publications; 1981. 14. Cyriax J. Textbook of orthopaedic medicine, vol. 1. 7th ed. London: Balliere Tindall; 1978. 15. Korr IM. The neural basis of the osteopathic lesion. J Am Osteopath Assoc 1947;47:191e8. In: Peterson B, editor. The collected papers of Irvin M. Korr. Indianapolis: American Academy of Osteopathy; 1979:120e27. 16. Travell JG, Simons DG, Simons LS. 2nd ed. In: Myofascial pain and dysfunction, vol. 1. Baltimore: William & Wilkins; 1999. 17. Fryer G, Morris T, Gibbons P. The relationship between palpation of thoracic paraspinal tissues and pressure sensitivity measured by a digital algometer. J Osteopath Med 2004;7:64–9. 18. Lewit K, Liebenson C. Palpation e problems and implications. J Manipulative Physiol Ther 1993;16:586–90. 19. Moore KL, Dalley AF. Clinically orientated anatomy. 4th ed. Baltimore: Lippincott William & Wilkins; 1999. 20. Bogduk N. Clinical anatomy of the lumbar spine and sacrum. 3rd ed. New York: Churchill Livingstone; 1997. 21. Richardson CA, Jull GA, Hodges P, Hides JA. Therapeutic exercise for spinal segmental stabilization in low back pain. London: Churchill Livingstone; 1999. 22. Hides JA, Stokes MJ, Saide M, Jull GA, Cooper DH. Evidence of lumbar multifidus muscle wasting ipsilateral to symptoms in patients with acute/subacute low back pain. Spine 1994;19:165–72. 23. Kader DF, Wardlaw D, Smith FW. Correlation between the MRI changes in the lumbar multifidus muscles and leg pain. Clin Radiol 2000;55:145–9. 24. Danneels LA, Vanderstraeten GG, Cambier DC, Witvrouw EE, De Cuyper HJ. CT imaging of trunk muscles in chronic low back pain patients and healthy control subjects. Eur Spine J 2000;9: 266–72. 25. Cramer GD, Darby SA. Basic and clinical anatomy of the spine, spinal cord, and ANS. St Louis: Mosby; 1995. 26. Fryer G, Morris T, Gibbons P. Paraspinal muscles and intervertebral dysfunction. Part 2. J Manipulative Physiol Ther 2004;27:348–57. 27. Mannion AF, Weber BR, Dvorak J, Grob D, Muntener M. Fibre type characteristics of the lumbar paraspinal muscles in normal healthy subjects and in patients with low back pain. J Orthop Res 1997;15:881–7. 28. Nazarian LN, Zegel HG, Gilbert KR, Edell SL, Bakst BL, Goldberg BB. Paraspinal ultrasonography: lack of accuracy in evaluating patients with cervical or lumbar back pain. J Ultrasound Med 1998;17:117–22. 29. Fryer G, Morris T, Gibbons P. The relationship between palpation of thoracic tissues and deep paraspinal muscle thickness. Int J Osteopath Med 2005;8:22–8.
Short communication
Dissection of the thoracic paraspinal region e implications for osteopathic palpatory diagnosis: A case study Gary Fryer *, Jim Johnson School of Health Science, City Campus, Victoria University, PO Box 14428 MCMC, Melbourne 8001, Australia Received 30 January 2004; received in revised form 30 July 2004; accepted 23 December 2004
Abstract Background: Authors in the field of osteopathy have claimed that tissue texture abnormalities in the paravertebral gutter (PVG), the region between the erector spinae mass and the spinous processes, are indicators of intervertebral somatic dysfunction, but the cause of texture abnormality is unknown. Methods: The PVG was identified using manual palpation and marked with marker pins before dissection. A progressive dissection of the medial paraspinal thoracic region was performed and the anatomy of this region was reviewed. Results: Progressive dissection revealed the trapezius, spinalis, semispinalis, multifidus and rotatores muscles to be immediately deep to the marked location, and deep to these muscles, directly below the marker, was the zygapophysial joint. Discussion: The possible relevance of these medial paraspinal structures to tissue texture abnormality detected with palpation was discussed. Authors in the field of osteopathy have suggested that dysfunction of either the rotatores muscles or the underlying zygapophysial joint may be responsible for tissue texture change in the PVG, and these structures were located directly under the palpated site. Conclusion: Further research to examine the tissues associated with textural abnormalities in the PVG is warranted. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Palpation; Osteopathic medicine; Muscle; Skeletal; Thoracic wall
1. Introduction The concept of intervertebral dysfunction, a functional disturbance of the intervertebral joints and related tissues that can be detected with manual palpation and treated with manipulation, is important to osteopathic theory and practice. Authors in the field of osteopathy originally called this dysfunction the ‘osteopathic lesion’ or ‘osteopathic spinal lesion’, although latterly most authors refer to it as ‘somatic dysfunction’, ‘segmental dysfunction’ or ‘intervertebral dysfunction’.1e6 The
* Corresponding author. E-mail address: [email protected] (G. Fryer). 1746-0689/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.ijosm.2005.04.006
nature and pathophysiology of intervertebral dysfunction remains speculative.1 Authors in the field of osteopathy have claimed that segmental, paraspinal tissue texture change is a key diagnostic sign of intervertebral dysfunction, and may include abnormal hardness, bogginess or ropiness of the underlying paraspinal muscles.3,7,8 Osteopaths commonly palpate for altered tissue texture in three distinct paraspinal regions: the medial, paravertebral ‘gutter’ (PVG), which lies close to the spine between the vertebral spinous process in the midline and the erector spinae muscle group; the bulk of the erector spinae muscle group; and, more laterally, the iliocostalis muscle fibers overlying the angles of the ribs. Many authors claim that the cardinal sign of intervertebral dysfunction
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is ‘palpable hypertonicity’ of the deep, fourth layer paraspinal muscles, particularly rotatores and multifidus.3,7e10 It has been claimed that these tissue texture changes can be palpated in the PVG,3,8 and are usually found unilaterally and reported as being tender by the patient. More laterally, palpable hypertonicity of the iliocostalis muscle at the rib angle is claimed to be indicative of rib dysfunction.3 There has been much speculation on the aetiology of the manipulable spinal lesion, and various authors have implicated the paraspinal muscles,11 zygapophysial joints,12 and the intervertebral disc13,14 as the underlying cause of segmental motion restriction and tissue texture change. Korr proposed the model of the facilitated segment e a hyperactive segment of spinal cord e whereby abnormal motor output from the cord produced increased segmental muscle activity (such as rotatores and multifidus) that was proposed to cause tissue texture and joint motion change.15 Tissue texture changes in muscles have also been attributed to myofascial trigger points (MTrP), which are speculated to involve motor endplate dysfunction and result in muscle fiber ‘contraction knots’. MTrPs would be detected as small, hard and tender bands within the affected muscle, and refer pain in a characteristic pattern when manual pressure was applied.16 Fryer1 proposed a model for intervertebral dysfunction involving both patho-anatomical and functional sequelae to spinal injury, leading to a deficit in regional proprioception, changes in segmental and polysegmental muscle activity and motor control, and predisposing the segment to further strain. In this model, intervertebral sprain would initially produce paraspinal tissue abnormality due to peri-articular soft tissue inflammation and abnormal ‘pain mode’ activity of the superficial paraspinal muscles. As the dysfunction became more chronic, tissue abnormality would be caused by both overactivity of the superficial paraspinal muscles and atrophy of the deeper muscles, which may expose the underlying bony architecture to probing palpation.1 Little research exists to confirm either the existence of paraspinal tissue texture abnormalities, or their pathophysiology. In a recent study, Fryer et al.17 demonstrated that sites located in the thoracic PVG detected as abnormal to palpation by an osteopath, and reported as being tender by the subject, had a lower pressure pain threshold than sites identified as being normal and nontender above, below and opposite the dysfunctional site. This study suggested that such sites were not due to palpatory illusion,18 but had characteristics that could be objectively measured, and the authors recommended research into the nature of these regions. The aim of this case study dissection was to review the anatomy of the medial, paraspinal region, and examine what structures were present within the PVG to highlight tissues that may potentially produce abnormal texture.
2. Methods The dissection was conducted on an elderly (age unobtainable), embalmed (formaldehyde, glycerine and ethanol, prepared 12 months prior to dissection) male cadaver at the Victoria University anatomy laboratory, and performed by an experienced anatomy laboratory technician (JJ). A registered osteopath with 13 years practice experience (GF) palpated the thoracic region of the prone cadaver and attempted to locate the PVG and any apparent irregularities in the PVG (Fig. 1). Although the texture and shape of the paravertebral region was different to that of a living subject (harder and flatter), the osteopath was confident of identifying the familiar PVG, but less confident concerning the identification of a region of segmental PVG texture irregularity. Once a spot was located in the PVG, a marker pin was inserted into the site. Reference pins were also located on the lateral, superior and inferior margins of the specimen in the event the original pin and site were disturbed during dissection. The pin was removed during the process of dissection, but the small hole created by its removal assured very accurate re-location. The progressive dissection was performed in five stages. The first stage involved removal of the skin and superficial fascia to expose the trapezius muscle. The second stage involved removal of the trapezius muscle and fascia to expose the erector spinae muscle group. The erector spinae muscles were then removed to uncover the semispinalis muscle. Following removal of the semispinalis, the deepest layer of back muscles, the rotatores muscles, was uncovered. In the final stage of dissection, all muscle tissue was removed from the paraspinal region close to the marker pin to expose the vertebral lamina, articular pillar and zygapophysial joint line.
Fig. 1. Palpation of paravertebral gutter (PVG). Note that the left upper limb has been removed for teaching purposes.
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3. Results The first stage of dissection involved removal of the skin and superficial fascia from most of the trunk, using a rectangular incision, to expose the trapezius muscle (Fig. 2). The left upper limb had been previously removed for teaching purposes. The marker pin, located to the right side of the midline, clearly penetrated the lower fibers of the trapezius muscle (Fig. 2). The second stage involved removal of the trapezius muscle and fascia to expose the erector spinae muscle group. The marker pin was seen to penetrate the spinalis muscle, the most medial muscle of this group (Fig. 3). The erector spinae muscles were removed to uncover the semispinalis muscle. The marker pin penetrated the tendinous portion of the semispinalis muscle (Fig. 4). The levator costorum muscles, lateral to the transverse processes, were clearly visible. Following removal of the semispinalis (and the indistinguishable fibers of the multifidus), the deepest layer of back muscles, the rotatores muscles, were uncovered. The marker pin was present in the lateral portion of the rotatores brevis muscle, close to the common attachment of the brevis and longus muscles (Fig. 5). The intertransversarii muscles, arising from transverse process to transverse process, were clearly seen at this stage of dissection. In the final stage of dissection, all muscle tissue was removed from the paraspinal region close to the marker pin, which exposed the vertebral lamina, articular pillar and zygapophysial joint line at that level. The marker pin was seen to penetrate the joint line on the lateral third of the zygapophysial joint (Fig. 6). Rotatores muscles were seen at the segments above and below. The distance between the two transverse processes near the marker was 30 mm.
Fig. 2. Trapezius muscle. The marker pin can be seen to penetrate the lower fibers of the trapezius muscle (Tp). The latissimus dorsi (LD) can be clearly seen. X Z marker pin; Rp Z reference pins.
Fig. 3. Spinalis muscle. The marker pin penetrated the lateral fibers of the spinalis muscle (S). The other erector spinae muscle groups, longissimus (L) and iliocostalis (I), can be seen laterally. X Z marker pin.
4. Discussion This case study aimed to review the anatomy of the thoracic paraspinal region and highlight structures that could feasibly be involved in the creation of abnormal tissue texture in the PVG. Such tissue texture abnormalities are claimed by osteopaths to be a diagnostic sign of intervertebral dysfunction, but there is little evidence of what tissues potentially could be involved or palpated in this region. No conclusions can be made about the possible role of such structures from this case dissection, but it is interesting to note that the spinalis, semispinalis and rotatores muscles, as well as the zygapophysial joint itself, were located directly under the marked site in the PVG.
Fig. 4. Semispinalis muscle. The marker pin penetrated the tendinous portion of the semispinalis muscle (Ss). The levator costorum (LC) and external intercostal muscles can be seen more laterally. X Z marker pin; TP Z transverse process.
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Fig. 5. Rotatores muscles. The marker pin penetrated the rotatores brevis muscle (RB), close to the common attachment of the rotatores longus (RL). Note the intertransversarii muscles (It); TP Z transverse process; X Z marker pin.
4.1. Review of clinical anatomy The first stage of dissection removed the skin and superficial fascia to expose the trapezius muscle. The trapezius muscle is an extrinsic back muscle, and receives its motor nerve supply from the accessory nerve (CN XI). The other superficial extrinsic back muscles (latissimus dorsi, levator scapulae, and rhomboids) receive their nerve supply from cervical ventral rami (intrinsic back muscles are supplied by dorsal rami) and connect the upper limbs to the trunk and control limb movements.19 Travell et al.16 claim that MTrPs in the mid and lower trapezius may present as tender and hard bands on palpation, and would refer pain superiorly to the paraspinal region and mastoid process, with aching and tenderness into the suprascapular region.16
Fig. 6. Zygapophysial joint. The marker pin penetrated the lateral portion of the zygapophysial joint line (Z-j). RL Z rotators longus; TP Z transverse process; X Z marker pin; RB Z rotatores brevis; SP Z spinous process.
After removal of the trapezius muscle and thoracolumbar fascia, the erector spinae muscle group was exposed. The erector spinae is the most superficial group of the intrinsic back muscles, and make up the bulk of the paraspinal mass lateral to the PVG. The intrinsic thoracic back muscles are deep, innervated by dorsal rami, and are enclosed by fascia that attaches medially to the tips of the spinous processes and supraspinous ligament, laterally to the transverse processes and angles of the ribs, and extends from the pelvis to the skull. This fascia forms a thin covering for the deep muscles of the thoracic region, and a strong thick covering for muscles in the lumbar region.19 The erector spinae muscles are the chief extensors of the spine and are divided into three columns: spinalis (medially), longissimus (intermediate), and iliocostalis (laterally). The fibers of these muscles run superiorly, from spinous processes (spinalis), from ribs to transverse processes (longissimus), or angles of ribs (iliocostalis).19 In this dissection, the spinalis was found to underlie the site of palpation in the PVG. Deep to the erector spinae was the transversospinalis group, comprising semispinalis, multifidus and rotatores muscles. These muscles originate from the transverse processes and pass to spinous processes of more superior vertebrae, and occupy the ‘gutter’ region between the transverse and spinous processes.19 The semispinalis is the most superficial of the group, found only in thoracic and cervical regions, and was indistinguishable from the multifidus in the thoracic region. The marker pin in the present dissection passed through the lateral fibers of the semispinalis. Travell et al.16 have observed that MTrPs can commonly occur in the semispinalis muscle, which refers characteristic pain similar to that of the longissimus muscle, upward in the paraspinal region and to the lateral thorax. Multifidus refers pain primarily around the region of the adjacent spinous process, and may render the spinous process tender to palpation and percussion.16 In the lumbar spine, the most developed muscle of this group is the multifidus.19,20 Multifidus has been proposed to have little role in movement of the spine, but perhaps fulfils an important role in segmental stability by contracting to stiffen and protect the spinal unit from external forces during loading or movement.21 Hides et al.22 used ultrasonography to detect multifidus atrophy in low back pain patients specific to the segment and side that was painful on manual assessment. Multifidus atrophy has also been observed in subjects with chronic LBP using MRI23 and computer tomography.24 This case dissection supports the plausibility of the proposal that atrophy of semispinalis or multifidus may potentially produce texture abnormality in the thoracic PVG, insofar as these muscles lay directly under the marked site in the gutter.
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On removal of the semispinalis and multifidus, the rotatores muscles were exposed. The rotatores are the deepest muscles of the transversospinalis group, and constitute the deepest muscle fasciculi located in the groove between the spinous and transverse processes. The rotatores comprise of a brevis (attaching from the transverse process to the root of the spinous process immediately superior) and longus (spanning two segments).25 It has been suggested that rotatores muscles lack sufficient strength and leverage to produce spinal motion, and may play a greater role in spinal proprioception, acting as a ‘kinesiological monitor’.19 Travell et al. claim that involvement of rotatores MTrPs throughout the thoracolumbar spine produces midline pain and referred tenderness to tapping on the spinous process adjacent to the MTrP.16 This dissection observed the rotatores to be located directly beneath the palpated site in the PVG, and may potentially be palpable if of abnormal tissue texture (or ‘abnormal hypertonicity’), as suggested by many osteopathic authors.3,7e10 After removal of all myofascial tissue, it was found that the zygapophysial joint line lay directly beneath the marked location. The zygapophysial joint is a plane synovial joint, and thoracic joints are orientated mainly in the frontal plane. In the lower thoracic region, the joints progressively become more oriented to the sagittal plane. The proposal that inflammatory changes occurring in the zygapophysial joint and peri-articular tissues could result in tissue changes detected in the PVG,1 is consistent with the findings of this case study, because the joint was directly below the palpated PVG. 4.2. Limitations No conclusions can be made concerning intervertebral somatic dysfunction or tissue texture change in the PVG from this case study. The osteopath was confident of identifying the PVG, but not confident in identifying an abnormal area of tissue texture. The tissues of the embalmed cadaver were much firmer than the tissues of a living subject, and it was not possible to palpate deeply through the tissue layers as would be attempted in the muscles of an osteopathic patient. Furthermore, any tissue irregularity may be an artifact of the embalming process. These factors reduce the significance of the zygapophysial joint lying directly below the palpated spot within the PVG, but not the likelihood of all these structures underlying the PVG and potentially identifiable to palpation. The dissection was conducted on only one cadaver and so caution must be used when attempting to generalize from these findings. 4.3. Implications Authors in the field of osteopathy claim that segmental tissue texture abnormality located in the
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PVG is an important clinical sign of intervertebral dysfunction,3,8 but no researcher has attempted to investigate what tissues may be involved to produce the apparent abnormality. Many authors have assumed that the altered texture can be caused by abnormal contraction of the underlying rotatores and multifidus muscles,3,7e10 but there is little direct evidence to support this.2,26 It is also widely assumed that tissue texture abnormality detected by palpation represents a dysfunctional or pathological tissue, but it is possible that such ‘abnormalities’ are simply a reflection of normal muscle heterogeneity. In Fig. 4, the marker pin was amongst the fascial and tendon slips of semispinalis. It is possible that different muscle or tendon fascicles may produce irregularity to palpation. Perhaps such differences in tissue texture should only be viewed as abnormal when other characteristics e such as tenderness e are associated with them. This is consistent with recommendations from many osteopathic authors, who advocate a combination of clinical signs for the diagnosis of intervertebral dysfunction, including tissue texture change, asymmetry, altered motion and tenderness.3,8 Although the zygapophysial joint was located directly under the palpated location, caution is needed before assuming that the underlying joint may be a cause of tissue texture change in the PVG. Inflammation of the zygapophysial joint and surrounding peri-articular structures has been suggested as a cause of tissue texture abnormality,1 but the joint is very deep and it is unknown whether such changes would be detectable with palpation through the trapezius, spinalis, semispinalis, multifidus and rotatores muscles. No researcher has attempted to examine what spinal structures or paraspinal tissues can be reliably palpated on normal subjects. The close proximity of the palpated location to the rotatores muscles and the zygapophysial joint, however, does lend support to the proposal that these structures could potentially produce tissue change in the PVG. 4.4. Further investigation The exact tissues and the pathophysiology responsible for producing palpable abnormalities in the PVG require further investigation. This case study supports the proposal that deep paraspinal muscles and the zygapophysial joint are directly below the hollow of the PVG where authors recommend osteopaths to palpate for tissue texture change, and so may be involved in texture abnormalities detected in the PVG. Investigation using fresh, unembalmed cadavers, that are likely to have a tissue consistency closer to that of a living subject, could be examined for structures deep to the palpated PVG, but access and ethical clearance may be difficult for researchers.
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Tissue biopsies of normal and abnormal PVG sites may reveal differences, but biopsy sampling of the exact palpable spot is likely to present difficulties, particularly concerning the depth of penetration and accuracy of the sampling the targeted tissue. Furthermore, studies examining subjects with LBP have found mostly nonspecific differences e fiber type change, ‘moth-eaten fibers’ e that would not have an obvious influence on palpation.27 Diagnostic imaging of paraspinal structures deep to abnormal sites may help identify the tissues involved. One study failed to find signs of inflammation in subjects with LBP using diagnostic ultrasound, but this study did not use subjects with acute pain (who would be more likely to have inflammatory changes).28 Magnetic resonance imaging is likely to be more useful than ultrasonography in detecting joint and tissue inflammation, but the cost and availability of this procedure present an obstacle for most researchers. Diagnostic ultrasound may be useful to compare the relative thickness of deep muscles underlying normal and abnormal PVG sites.29 In order to determine if abnormal muscle activity is associated with the abnormally palpable sites, modern fine-wire EMG techniques could be used to record and compare activity in the deep paraspinal muscles underlying normal and abnormal sites.
5. Conclusion This case study served as a review of the anatomy of the thoracic paraspinal region and highlighted the structures that could feasibly be involved in the creation of abnormal tissue texture that may be palpated in the PVG of the thoracic region. The authors hope that studies in the future will reveal the pathophysiology of these sites, and establish the clinical relevance of such findings.
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