Subluxation of one or other of the posterior rib joints is a common cause of thoracic pain. The articulating surfaces of these joints are relatively shallow and unstable, rendering them susceptible to minor subluxations. The relatively trivial incidents that provoke thoracic mechanical pain and the relative ease with which it is reduced leads us to this hypothesis. Differential diagnosis of thoracic pain is difficult because of the numerous conditions that refer pain to the area and the lesions that mimic mechanical pain.

Patients present with a sudden onset of pain; the precipitating event is usually trivial and they often feel a pop or click. More gradual onset can be associated with working in rotated postures. The pain presents a typical mechanical picture of pain aggravated by movement and posture and eased by rest. In common with a thoracic disc lesion, a deep breath often provokes the pain, presumably because the ‘bucket handle’ action of the ribs during respiration translates aggravating movements to the rib joints at the spine.

On examination there is a non-capsular pattern of limited movement involving one rotation more than the other and these simple mechanical lesions usually respond rapidly to manipulation. Provided that there are no contraindications present (see below), the manipulative techniques described in this chapter can be applied. The usual postural and management advice should also be given to prevent recurrence, which is also a typical feature.

It is important to reduce a thoracic disc displacement because of the potential for the displaced fragment to compromise the spinal cord. The thoracic vertebral canal is relatively small; therefore central prolapse poses the most threat.

In a review of the literature, Oppenheim et al (1993) reported an estimated annual incidence of one case of thoracic disc herniation per 1 million population. However, Mellion & Ladeira (2001) present a more current review of the literature which suggests that thoracic disc herniations are more common than previously thought and that in many cases these may be asymptomatic. It is primarily a condition of middle age, occurring between the third and fifth decade, and affects the lower thoracic levels more frequently. This is probably because the lower thoracic spine is free of the restriction of the rib cage, making it more mobile, and the transition to the non-rotational lumbar spine produces greater torsional stresses here. The most common level reported was T11, 12, and 75% of thoracic disc lesions occurred below T8.

Positive diagnosis of a thoracic disc lesion is difficult. There is no regular pattern to the history, signs and symptoms, as found at the cervical and lumbar spine, and it is not possible to produce a clinical model on which to base differential diagnosis. Wilke et al (2000) reported a case of shoulder pain associated with a lower thoracic disc herniation.

Central disc prolapse is most likely to compress the spinal cord and produce signs of myelopathy which include progressive paraparesis, increased reflexes, decreased sensation and bladder dysfunction. Although thoracic disc herniations are rare, Ozturk et al (2006) highlight the potential danger of their being missed as they could possibly result in the progressive myelopathy and paralysis mentioned above. A posterolateral prolapse produces segmental signs and symptoms.

To support the possible confusion arising from thoracic referred pain, Ozturk et al (2006) presented a case study of a patient with left flank pain, compatible with urinary system disorder. The cause of the pain could not be identified until magnetic resonance imaging (MRI) revealed a left T10–T11 lateral disc herniation with associated nerve root compression. They warn that thoracic disc herniation should be considered in the differential diagnosis of patients with pain more likely to be associated with visceral disorders, especially if basic diagnostic studies do not reveal the cause.

A further example is provided by Whitcomb et al (1995) who describe a patient with a 7-year history of severe disabling chronic epigastric abdominal pain attributed to chronic pancreatitis for which a 95% pancreatectomy was performed for pain control. Previous attempts to identify and treat the pain led to extensive radiographic, pharmacological, endoscopic and surgical interventions. Pain control was poor despite implantation of a continuous intrathecal morphine infusion pump. A focused physical examination eventually raised the suspicion of thoracic disc disease, which was confirmed with computed tomography. Disruption of the T7–T8 disc with protrusion into the vertebral canal and displacement of the spinal cord was identified. A microsurgicaI thoracic discectomy was performed and immediately the pain began resolving with the patient being pain-free and off all medication within several weeks.

In a review of the literature, Mellion & Ladeira (2001) highlight degenerative change, traumatic incidents, lifting, rotation, falls, exercise, rugby tackles and road traffic accidents as precipitating factors for thoracic disc lesions. The onset may be sudden and severe or insidious and slowly progressive. Mellion & Ladeira mention that Cyriax was the first author to describe the clinical presentation of a thoracic disc lesion. They suggest it may give four classical presentations: intermittent thoracic back pain which may be aggravated by sitting and relieved by standing; acute thoracic ‘lumbago’ with the thoracic spine fixed in flexion following a bending or twisting motion; thoracic root pain and paraesthesia; and symptoms of spinal cord compression. Chest pain may be constant or intermittent and may be central, localized or diffuse. A band-like dermatomal chest pain is not uncommon and abdominal referral may occur. If accompanied by cord compression, complaints of bladder involvement, lower limb paraesthesia and gait disturbance can be reported and findings may include spastic muscle weakness, hyperreflexia and a positive Babinski sign.

Mellion & Ladeira (2001) suggest that upper thoracic disc lesions are less common. Radiculopathies involving T1 share similarities with those occurring at C8, with numbness and weakness in the hand and pain in the arm and medial forearm. Weakness of the intrinsic hand muscles may be involved with T1, but this is an uncommon finding and the clinician must exclude non-mechanical causes such as Pancoast’s tumour. Horner’s syndrome (miosis and ptosis of the eye) is associated with T1 involvement but not C8. Presence of Horner’s syndrome is therefore contraindicated in manipulation or mobilization of the thoracic joints until the cause of the symptoms has been determined.

Disc lesions at the T2 and 3 levels are even less common and there are few reports in the literature of the features of involvement of T3–T8; symptoms of nerve root involvement at these levels may produce intercostal neuralgia. If there is involvement of the dura mater or dural nerve root sleeve, their mobility will be impaired and signs provoked on flexion of the cervical spine and scapular approximation. T9–T11 may produce a dermatomal pattern of pain and can include the abdomen and groin, often being confused with visceral symptoms. These lower levels may also mimic lumbar presentations including low back and leg pain.

In summary, small uncomplicated thoracic disc lesions may present with sudden or gradual onset of pain that may be felt posteriorly, anteriorly or radiating laterally. Pressure on the dura mater produces multisegmental reference of pain. The pain should have a typical mechanical behaviour, i.e. aggravated by movement and posture and eased by rest. Dural symptoms of increased pain on a cough, sneeze or deep breath may be present.

On examination, a non-capsular pattern of limited movement will be found, with one rotation being significantly more painful or limited than the other. Dural signs of pain on neck flexion and/or scapular approximation may be present if the dura mater is compromised. If there are no neurological signs and signs of cord compression are absent, the treatment techniques described in this chapter may be used. Alternatively, since lower thoracic displacements are more common, they may be treated using the techniques described for the lumbar spine.

Urgent surgical intervention is necessary for patients showing signs of spinal cord compression. Otherwise, uncomplicated thoracic disc lesions follow a path of recovery similar to that seen in cervical and lumbar disc lesions, responding to physical treatments and eventually stabilizing with time (Brown et al 1992).