Thoracic zygapophysial joint palpation.
It is widely accepted that structures in the thoracic region of the vertebral column are a potential source of pain. Palpation of thoracic zygapophysial joints is therefore frequently performed during both assessment and treatment of this region. With less research investigating the thoracic spine than either cervical or lumbar regions, its unique morphology is often not considered in detail when describing techniques of manual treatment and assessment. This article addresses vertebral and paravertebral morphology that may affect accurate palpation of the thoracic zygapophysial joints, and so highlights practical considerations for clinicians who utilise such procedures. Cornwall J, Mercer s (2006): Thoracic Zygapophysial joint palpation. New Zealand Journal of Physiotherapy 34(2): 56-59.
Keywords: thoracic zygapophysial joints, palpation, clinical anatomy.
The morphology of the thoracic zygapophysial joints leads to difficulty in accurate palpation.
Thoracic zygapophysial joints lie on the floor of the thoracic paravertebral gutter, overlaid by a series of dorsal muscles.
The orientation of the thoracic zygapophysial joints varies along the vertebral column.
Palpation of the vertebral column is routinely used in the diagnosis and treatment of disorders arising from the spine (Greenman 2003, Maitland et al 2001, Najm et al 2003). During assessment clinicians palpate spinal levels to identify painful segments, changes in joint motion and local changes in tissue texture (Greenman 2003, Maitland et al 2001, Najm et al 2003). The information gathered in this way contributes to the formation of the diagnosis. However, fundamental to an accurate diagnosis is the ability to correctly identify anatomical structures (Greenman 2003, Maitland et al 2001, Mercer and Rivett 2004,).
One of the commonly assessed and treated structures of the vertebral column is the zygapophysial joint (Maitland et al 2001), and in the thoracic region these joints have recently been documented as a source of symptoms (Dreyfuss et al 1994, Manchikanti et al 2004, Wall et al 1999). For example, a prevalence rate of 42% for pain arising from the thoracic zygapophysial joints was found in a group of patients presenting with chronic thoracic pain (Manchikanti et al 2004). Manual therapists are said to be able to diagnose conditions such as restrictions of zygapophysial joint movement (Maitland et al 2001). Treatment for such segmental dysfunction involves the application of posterior-anterior (PA) mobilisation techniques, where the motion of a restricted joint segment is purportedly restored (Greenman 2003, Maitland et al 2001). The facilitation of this restricted movement is alleged to occur through the application of targeted manual force in the plane of the joint (Maitland et al 2001). These assessment and treatment techniques require that the therapist can accurately identify the joints in question and can apply forces at the appropriate orientation.
There are a variety of factors that can influence the accuracy of palpation in each region of the spine (Cornwall & Mercer 2004, Dvorak 1998, Najm et al 2003). These factors relate to both the morphology of the vertebral segments and to the gross anatomy of the adjacent tissues (Cornwall & Mercer 2004). For palpation to be as effective as possible it must be undertaken in the context of the spinal region being assessed. This article therefore addresses the concerns that specifically arise with palpation of the thoracic zygapophysial joints. Issues that necessitate consideration when this procedure is used during manual therapy assessment and treatment are identified.
There are eleven pairs of thoracic zygapophysial joints, with one pair located between each vertebral level. These joints contribute to the floor of the 'paravertebral gutter', the region between the spinous and transverse processes (Clemente 2006, Moore et al 2006, Rosse et al 1997, Standring 2005) (Figure 1). In the cervical and lumbar regions this gutter is shallow, formed mainly by the laminae and articular pillars, whereas in the thoracic region the gutter is deeper and broader, being formed by the laminae, articular pillars and transverse processes. The thoracic transverse processes also articulate with the tubercle of the dorsal surface of the adjacent rib (Standring 2005) (Figure 1).
[FIGURE 1 OMITTED]
Due to the contour of the thoracic laminae and general orientation of the articular processes the zygapophysial joints appear to lie flat, close to the spinous processes with the prominent costotransverse joints lying more laterally (Figure 1). An informal measurement of six plastinated vertebral columns revealed that the mid-point of thoracic zygapophysial joints lay, on average, ten millimetres from the lateral edge of the adjacent spinous process. These measurements were taken in the coronal plane.
When viewed from behind the most superficial part of the zygapophysial joint is the inferior articular process of the immediately superior vertebra. At each level the articular facet of each superior articular process passes deep (or more anterior) to the inferior articular process of the vertebrae immediately above (Moore & Dalley 2006, Rosse & Gaddum-Rosse 1997, Standring 2005) (Figure 2). The distal tip of the inferior articular process therefore abuts the lamina of the immediately inferior vertebra, where the joint line is observed between the two bones (Figures 2 & 3).
[FIGURES 2-3 OMITTED]
Classic anatomical texts (Moore & Dalley 2006, Standring 2005) have stated that the angle at which the joint surfaces of thoracic zygapophysial joints articulate lies close to the coronal plane. A more precise description was provided by Davis (1959) who stated that in the thoracic spine the superior articular facets face posteriorly, slightly superiorly and slightly laterally (Figure 4). As demonstrated in Figure 2 the orientation of the articular facets in the sagittal plane varies throughout the thoracic region. Valencia (1994) reported these changes in orientation with respect to the horizontal, describing a 600 orientation in the upper thoracic region changing to 900 in the midthoracic region and almost 00 at lower thoracic levels.
[FIGURE 4 OMITTED]
Lying between the skin and zygapophysial joints are layers of subcutaneous tissue and muscle. Immediately below the subcutaneous tissue lies the lower fibres of trapezius, which attaches to all thoracic spinous processes (Johnson et al 1994) (Figure 1 & 4). Lying under the caudal half of the lower trapezius muscle are, superficial to deep, the fibres of the latissimus dorsi muscle or the aponeurotic fibres of the posterior layer of the thoracolumbar fascia (Figure 4). Further superiorly the remaining muscles to be considered are rhomboid minor and major, serratus posterior superior and splenius cervicis (Clemente 1987, Moore & Dalley 2006, Rosse & Gaddum-Rosse 1997, Standring 2005).
More intimately associated with the paravertebral gutter are the short and long rotatores, overlaid by multifidus, semispinalis cervicis and semispinalis thoracis (Hollinshead 1969). Fascicles from the rotatores, multifidus and semispinalis muscles pass between one and six segments before inserting into a transverse process (Clemente 2006, Moore & Dalley 2006, Rosse & Gaddum-Rosse 1997). While closely approximating the spinous processes, the very slender spinalis thoracis runs between the T11-L3 spinous processes to insert into a variable number of the upper thoracic spinous processes, usually between the level of T4 and T8 (Hollinshead 1969). The only additional muscle that may be considered is the longissimus thoracis, overlying the costotransverse regions but lying lateral to semispinalis thoracis (Bogduk 1994) (Figure 4). Embedded in areolar tissue the thoracic dorsal rami accompanied by arteries and veins passes over the dorsal aspect of the multifidus muscle covered by fibres of semispinalis (Chua & Bogduk 1995).
Many manual therapy techniques are based on a mechanical paradigm (Mulligan 1995, Maitland et al 2001), where restrictions in joint movement are facilitated by the application of manual force to symptomatic joints. This facilitation is said to occur when force is applied that aids the movement of contributing articular facets in the direction to which the zygapophysial joint motion is most inhibited. In this way, the joint is said to be 'mobilised' (Maitland et al 2001). Essential to this paradigm is a precise knowledge of joint margins, so that force may be directed to the symptomatic joint(s).
The plane in which the zygapophysial joint lies must also be identified. This is because facilitation of joint movement is said to be most effectively achieved through manual force that is directed parallel to the plane of the joint (Maitland et al 2001). Therefore, for facilitation of zygapophysial joint motion in the thoracic spine, PA procedures in this region should direct force in the plane of the joint, and not directly in a PA direction. The direction of applied force will also be individual to different parts of the thoracic spine, as the superior, middle and inferior regions all exhibit different orientations of the zygapophysial joints. Therefore, precise identification of both the joint line and the plane of the joint is necessary to facilitate appropriate manual therapy intervention as suggested by Maitland et al (2001) and utilised by clinicians (Mulligan 1995, Jull et al 2002, Lee 2004).
Given that the zygapophysial joints lie in the paravertebral gutter', beneath various layers of subcutaneous fat and dorsal musculature, it seems unlikely that the joint line will be readily palpable (Figures 1 & 4). In addition, the similarity in coronal plane orientation of the dorsal surface of the inferior articular facet and the adjacent laminae adds to this difficulty: distinguishing between the lamina and the projecting aspect of the inferior articular facet using palpation would be problematic. Figure 3 highlights the congruence between the laminae and zygapophysial joints, indicating the paucity of a readily palpable bony landmarks that could facilitate precise identification of the zygapophysial joints.
These clinically applied anatomical descriptions highlight the difficulty in accurately palpating structures of the thoracic spine, thereby confounding the application of PA mobilisation techniques as outlined by Maitland et al (2001). As suggested by Dvorak (1998) palpation under fluoroscopy would confirm whether the painful level was accurately located and indicate the orientation of the joint in question. Investigations into the validity of PA techniques in mobilising vertebral segments along the plane of the joint could also be undertaken.
It has been demonstrated that the thoracic zygapophysial joints are a potential source of pain (Dreyfuss et al 1994, Manchikanti et al 2004, Wall & Melzack 1999). However it is unlikely, given the morphology and location of the thoracic zygapophysial joints, that individual joints can be reliably palpated. This becomes problematic when assessing the thoracic region, or utilising techniques (such as PA mobilisations) that rely on either joint line or articular process identification. Techniques based on such approaches also need to be re-examined in light of the plane in which the joints lie, so the application and direction of any manual force is appropriately applied.
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ADDRESS FOR CORRESPONDENCE
Jon Cornwall, Department of Anatomy & Structural Biology, University of Otago, Dunedin, New Zealand. Email: firstname.lastname@example.org. Phone: 03 479 7362, Fax: 03 479 7254.
Jon Cornwall DipPhty, BSc(Physiol), MSc(Anat)
PhD Student, Department of Anatomy & Structural Biology
University of Otago
Susan Mercer BPhty(Hons), Msc, PhD
Associate Professor, School of Biomedical Sciences
The University of Queensland, Australia
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|Title Annotation:||Anatomy in Practice|
|Author:||Cornwall, Jon; Mercer, Susan|
|Publication:||New Zealand Journal of Physiotherapy|
|Date:||Jul 1, 2006|
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