Definition

Thoracic strain or sprain refers to the acute or subacute onset of pain in the region of the thoracic spine due to soft tissue injury, including muscles, ligaments, tendons, and fascia, of an otherwise normal back. Sprain relates to injury in ligament fibers without total rupture, whereas strain is an overstretching or overexertion of some part of the musculature [1]. Because the thoracic cage is unified by the overlying fascia, thoracic sprain or strain can translate into pain throughout the thoracic spine.

Epidemiology

Although the scientific literature on musculoskeletal pain in the cervical and lumbar spine is abundant, similar information about the thoracic region is sparse because of its lower prevalence [2]. The lifetime prevalence in the general population of having a musculoskeletal complaint in the thoracic spine is 17% in contrast to 57% in the low back and 40% in the neck [3]. Therefore observation and characterization of such lesions are minimal, subsequently limiting the potential to improve treatment methods for thoracic sprain and strain disorders. Moreover, pain felt in the thoracic spine is often referred from the cervical spine, mistakenly giving the impression that the incidence is higher [4].

Thoracic strain or sprain may be the indirect result of disc lesions, which have been reported to be evenly distributed in incidence between the sexes and are most common in patients from the fourth to sixth decades of life [5]. Muscles adjacent to the injured disc tend to become tight in response to the local inflammatory process, which may jeopardize the local muscle equilibrium, possibly leading to ligament strains and muscle sprains in the thoracic region. Other structures that may lead to strain or sprain in the mid back due to the same inflammatory rationale are the thoracic facet joints and the nerve roots [6].

As with most nonspecific mechanical disorders of the cervical and lumbar regions, the natural history of the majority of patients with nonspecific thoracic strain or sprain is resolution within 1 to 6 months [7].

Mechanisms

The thoracic spine is considered to be the least mobile area of the vertebral column secondary to the length of the transverse processes, the presence of costovertebral joints, the decrease in disc height compared with the lumbar spine, and the presence of the rib cage. Movements that occur in the thoracic spine include rotation with flexion or extension.

Thoracic sprain and strain injuries can occur in all age groups, but there is an increased prevalence among patients of working age [8]. Intrinsic mechanisms include bone disease as well as alteration of normal spine or upper extremity biomechanics. This includes cervical or thoracic deformity from neuromuscular or spinal disease as well as shoulder or scapular dysfunction. The most common intrinsic cause of thoracic strain, however, is poor posture or excessive sitting. Poor posture may be related to development of Scheuermann disease in the young and osteoporosis in the elderly that leads to kyphosis and compression deformities seen in those patients.

Poor posture is often manifested as excessive protraction or drooping of the neck and shoulders as well as decreased lumbar lordosis or “flat back.” With the classic “slouched position” encountered in children and adolescents and often carried on through adulthood, there is excessive flexion of the thoracic spine with a decrease in rotation and extension.

Postural alterations promote increased thoracic kyphosis, resulting in the “flexed posture.” Excessive flexion results in excessive strain on the “core,” including the small intrinsic muscles of the spine, the long paraspinal muscles, and the abdominal and rib cage muscles. Excessive flexion can increase the risk of rib stress fractures as well as costovertebral joint irritation. This can cause referral of pain to the chest wall with subsequent development of trigger points in the erector spinae, levator scapulae, rhomboids, trapezius, and latissimus dorsi. Poor motion in extension and rotation can place an increased load on nearby structures, such as the lumbar or cervical spine and shoulders.

Extrinsic or environmental mechanisms include repetitive strain, trauma, and obesity. Risk factors include occupational and recreational activities characterized by repetitive motions, such as lifting, twisting, and bending. Occupations requiring manual labor or extended periods in a sitting position are predisposed to a higher incidence of such disorders [9]. Traumatic causes include falls, violence, and accidents leading to vertebral fractures, chest wall contusions, or flail chest.

Symptoms

Patients typically report pain in the mid back, which may be related to upper extremity or neck movements. Symptoms may be exacerbated by deep breathing, coughing, rotation of the thoracic spine, or prolonged standing or sitting. The pain can be generalized in the mid back area or focal. If it is focal, it is usually described as a “knot,” which is deep and aching. It may radiate to the anterior chest wall, abdomen, upper limb, cervical spine, or lumbosacral spine and may be accentuated with movement of the upper extremity or neck. As described by McKenzie [4], the location of pain in mechanical disorders of the thoracic spine is either central (symmetric) or unilateral (asymmetric).

Other symptoms include muscle spasm, tightness, and stiffness as well as pain or decreased range of motion in the mid back, low back, neck, or shoulder.

Physical Examination

The essential finding in the physical examination of thoracic sprain or strain is thoracic muscle spasm with normal neurologic examination findings. Pain may be exacerbated when the patient lifts the arms overhead, extends backward, or rotates. Rib motion may be restricted and may be assessed by examining excursion of the chest wall. This is accomplished by laying hands on the upper and lower chest wall and looking for symmetry and rhythm of movement. The upper ribs usually move in a bucket-handle motion, whereas the lower ribs move in a pump-handle motion. Restriction of specific ribs can be assessed by examining individual rib movements with respiration.

The position of comfort is usually flexion, but this is the position that should be avoided. Sensation and reflex examination findings should be normal. A finding of lower extremity weakness or neurologic deficit on physical examination suggests an alternative diagnosis and may warrant further investigation [10].

As the thoracic cage and spine are the anchors for the upper limbs, the thoracic spine influences and is influenced by active and resisted movement of the extremities, cranium, and lumbar and cervical spine [11]. Therefore, a careful spinal and shoulder examination is essential to rule out restrictive movements, obvious deformity, soft tissue asymmetry, and skin changes (that may be seen in infection or tumor). Detailed examination of other organ systems is important because thoracic pain can be referred.