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Diagnostic Imaging

For the majority of athletes presenting with thoracolumbar pain, the initial investigation is still the plain-film anteroposterior (AP) and lateral radiographs. The AP view will depict the sagittal alignment as well as congenital anomalies at the thoracolumbar and lumbosacral junctions.

The architecture of the bodies, spinous processes, transverse processes, lamina, and pedicles also are depicted on the AP radiograph. The absence of pedicles in the painful spine is highly suggestive of neoplasia. Sclerotic bone in the area of the pars interarticularis indicates a healing attempt of a pars defect of a spondylolysis.

Sclerotic lesions with a painful scoliosis in an adolescent or young adult is suggestive of an osteoid osteoma, a type of benign bone tumor. Abnormal alignment of the spinous processes will indicate a rotatory or lateral translation of the vertebral bodies.

If this occurs after a high-energy trauma, one may suspect a significant degree of instability of the spine. Direct blows to the lumbar spine may result in fracturing of the transverse processes. The AP radiographs will depict a loss of vertebral height in both anterior compression fractures and burst fractures.

The burst fractures may show a splaying of the pedicles. The interpedicular distance gradually increases with each caudal vertebra. A sudden widening followed by a narrower normal vertebra is a classical sign of a burst fracture, which involves both the anterior and posterior halves of the vertebral body.

If an athlete sustains a sudden deceleration with his or her abdomen against a narrow restraint, such as a lap seatbelt or a guardrail, the resulting flexion–distraction forces to the spinal column may lead to a vertical separation of the spinal processes seen on the AP radiograph.

If the distraction force passes through the pedicles and the transverse processes, the fragments appear as double pedicles and double transverse processes. Any abrupt, lateral translation of the vertebral column at a fracture site on the AP radiograph would indicate a fracture dislocation injury pattern.

These relatively unstable fracture dislocations have a high incidence of neurological deficits because of shearing force across the spinal canal. Additional imaging, such as magnetic resonance imaging (MRI), usually is indicated to further delineate the status of the neural elements.

The lateral radiograph will depict the thoracic kyphosis and the lumbar lordosis as well as the contour of the vertebral bodies and the intervertebral disc spaces. The lateral view also helps to differentiate the fracture types.

Compression of the anterior half of the vertebral body with axial load but without collapse of the posterior vertebral body results in fractures known as anterior compression fractures. Loss of both anterior and posterior vertebral body height (relative to the vertebral bodies adjacent to the fracture) is indicative of a burst fracture pattern.

The acute angular deformity can be measured on the lateral radiographs focused at the level of the injuries. Any translation forward or backward in the sagittal plane of an acutely fractured vertebrae is considered to be a fracture dislocation.

The standing lateral view is helpful in following the degree of spondylolisthesis to determine if the deformity has progressed. The disc space may show progressive narrowing in the formation of significant disc degeneration. These signs include sclerotic end plates with osteophytes and the vacuum sign within the disc.

With multiple levels of disc degeneration and narrowing, the posterior elements will assume an extended position to maintain the trunk in an erect position. The subsequent abutting of the spinous processes have been labeled “kissing spines” .

If a single level of severe disc degeneration is seen in an otherwise healthy-looking spine on the lateral radiograph, the possibility of an infective discitis should lead to further investigations, such as a labeled white-cell bone scan and further blood work for infection.

The oblique plain-film radiographs of the lumbar spine demonstrate the facets and pars interarticularis area. The posterior elements form a “Scottie dog” image. The presence of a radiolucent collar indicates a defect in the pars interarticularis known as a spondylolysis.

If the collar is sclerotic, a healed pars defect or an undisplaced hypertrophic defect may be present. Further computed tomography (CT) scanning will confirm the presence of a defect. A bone scan may indicate if the defect is new or recently irritated.

The use of CT has greatly enhanced the evaluation of osseous structures. In fact, the development of the current classifications of thoracolumbar fracture was a direct result of this technology.

The degree of canal compromise by bony fragments as well as determination of the angular deformities now can be done using the various reconstruction views of the spinal column from the CT data. Plain-film radiographs do not visualize the spinal canal contents or small lytic lesions in the bone as well as CT scans do.

In trauma cases, CT scans of the thoracolumbar spine may be derived from the trauma CT series of the thorax, abdomen, and pelvis; however, CT scans should not be used as a screening tool for the entire spine. The spinal CT study should focus on the area of clinical pathology as determined by the history, physical examination, plain-film radiographs, or bone scan .

The use of CT is especially helpful in examining spondylolytic lesions in athletic patients , and use of sagittal and coronal CT reconstructions has made planar tomography obsolete in many centers.

Although CT initially was very useful in finding disc bulges and herniations, the use of MRI is now the investigation of choice to evaluate the soft tissues of the thoracolumbar spine. The MRI uses varying amounts of water content in various tissues to generate the different shades of gray that are seen in the image.

This is in contrast to CT, which relies on the radiodensity of tissue to create the scans. Adjacent soft tissues, such as the disc annulus and the nucleus pulposis, may have similar radiodensities on a CT scan; however, the nucleus may contain much more water than the annulus, allowing definition of the nucleus material to be more precise.

The presence of a new, extruded disc nucleus may have different prognostic and management factors compared with those of an old, bulging annulus or postoperative epidural scar tissue. The MRI can depict very well nerve root compression with various degrees of disc degeneration, ligamentous injury, hematoma formation, and soft-tissue tumors .

The new, high-resolution MRI can depict extremely well details such as conjoint nerve roots and small syringomyelia. Intravenous gadolinium acts as an MRI contrast agent to delineate vascular scar tissue from avascular disc material in the canal.

The use of myelography followed by CT has decreased with the advent of the noninvasive MRI. In patients with contraindications to MRI, myelography followed by CT may be the best alternative for imaging of the neural canal.

Contraindications to MRI may include having a cardiac pacemaker, an implanted neurostimulator, nonsurgical metal foreign bodies, older lens implants containing metal, as well as extreme claustrophobia.

Discography is used as a technique for pain reproduction to confirm the source of pain. The volume of dye, the pressure to dye insertion, and the containment or leakage of the dye from the nucleus will illustrate the competency of the annulus. Follow-up CT can demonstrate the location of annular tears and disc herniations.

Nuclear imaging, such as the use of bone scans and white cell–labeled scans, are very useful when fresh stress fractures, infections, or tumors are suspected in the athlete presenting with thoracolumbar spine pain. A focused radiographic correlation, usually with CT of any areas presenting with increased uptake, generally will confirm the diagnosis.

The use of a more sophisticated imaging technique known as single-photon emission CT (SPECT) allows the data to be reformatted in axial images similar to CT scans. The SPECT image localizes well the presence of recently developed spondylolytic defects.

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