Degenerative Lumbar Disc Disease in the Mature Athlete Workup

Plain radiography

Plain radiographs traditionally have been ordered as the initial step in the workup of lumbar spine pain. The main purpose of plain radiographs is to detect underlying structural pathologic conditions. Selective criteria can be used to improve the usefulness of plain radiographs.

These studies generally are not recommended during the first month of symptoms in patients without any red flags. An exception to this would be if the low back symptoms are related to a sports-related injury where there is suspicion of fracture.

Three basic views of the spine are routinely ordered for workup of LBP: the anteroposterior view, the lateral view, and the coned-down lateral view of the lower 2 interspaces. Oblique views can be obtained to further visualize the facet joints, the pars interarticularis, and the neuroforamen.

Radiographs detect the characteristic degenerative changes of the spine, and, in some cases, they may localize a particular site of degeneration that may be causing symptoms.

Bone scanning

Bone scans can be helpful when tumor, infection, or fracture (occult or traumatic) is suspected.

Bone scans are limited by relatively poor spatial resolution of the pertinent anatomy of the spine.

Single-photon emission computed tomography scan provides superior anatomical resolution compared with uniplanar radionuclide images.

Positive bone scan findings generally should be followed by confirmatory imaging, such as MRI or CT scan, which provides for greater pathoanatomical detail of the spine.

CT scanning

CT scan of the lumbar spine provides superior anatomical imaging of the osseous structures of the spine and good resolution for disc herniation. However, its sensitivity for detecting disc herniations when used with myelography is inferior to MRI.

As with MRI, the frequency of false-positive findings in asymptomatic patients is high. CT scan is best used when a fracture is suspected, but it can be used in the detection of disc injury in patients who cannot undergo MRI. In addition, CT scan is recommended when more detailed imaging of the bony architecture is important.

Myelography

A myelogram involves penetration of the subarachnoid space and generally is not indicated in the evaluation of acute LBP. Generally, it is reserved as a preoperative test, often in conjunction with a CT scan. This provides a detailed anatomic picture, particularly of the spinal osseous elements, and can be used to correlate examination findings and assist in preoperative planning.

Myelography rarely is used in the nonoperative evaluation of patients with acute LBP, except in cases in which the clinical picture supports a progressive neurologic deficit and the MRI and electromyogram are nondiagnostic.

MRI

MRI provides high-resolution imaging and therefore allows accurate description of intervertebral disc pathology. T2-weighted images are sensitive to disc degeneration because there is a loss of signal primarily within the nucleus as a result of altered hydration status.

Sagittal sections reveal the vertebral column, intervertebral discs, spinal canal, and spinal cord. Axial views show the disc or vertebral body, the spinal cord, and the spinal roots, among other structures. Neural element encroachment seen on the sagittal view should be confirmed on the axial view.

MRI also is useful for assessment of canal encroachment and spinal stenosis. MRI is useful for imaging the broad spectrum of pathology associated with DDD in the mature athlete.

As with CT scanning, MRI is very sensitive, and not all abnormalities detected are clinically relevant. Jensen et al found in their study of 98 asymptomatic people that 64% of subjects without back pain had a bulge, protrusion, or extrusion of the intervertebral disc at one level, and 38% had an intervertebral disc abnormality at more than one level. Additionally, they found that the prevalence of disc pathology varied according to the age of the patient. In the group of asymptomatic subjects aged 60 years or older, they found that 80% had disc bulges at one or more levels. Therefore, because bulges and protrusions on MRI in people with LBP may be coincidental, each MRI study must be interpreted with regard to the patient's history, physical examination, and other diagnostic tests.

Electrodiagnosis

Electrodiagnostic studies, including nerve conduction studies, needle electromyography, and somatosensory evoked potentials, should be considered an extension of the history and physical examination and not merely a substitute for a detailed neurologic and musculoskeletal examination. These studies are helpful when the diagnosis remains unclear in patients with limb pain. They also are helpful in excluding other causes of sensory and motor disturbances, such as peripheral neuropathy and motor neuron disease. Additionally, they can provide useful prognostic information by quantifying the extent and acuity of axonal involvement in radiculopathies. Electrodiagnostic studies performed less than 3 weeks after the onset of symptoms may result in a false-negative study since evidence of denervation does not appear until 2-3 weeks postinjury.

Performing late responses, such as the H-reflex, can provide valuable information regarding the proximal nerve or nerve root involvement. The H-reflex is both a sensitive and specific marker for involvement of the S1 root and is prolonged from the time of symptom onset.

Electrodiagnostic testing usually is not necessary in patients with a clear-cut radiculopathy or in patients with isolated LBP. When imaging studies reveal multiple abnormalities, which are common in older individuals with degenerative changes, electrodiagnosis can assist in localizing the etiology of the patient's symptoms.

Discography

Discography is rarely necessary in the evaluation of LBP and is not recommended within the first 3 months of treatment. Discography can be helpful in patients who have not responded to a well-coordinated rehabilitation program or who have normal or equivocal MRI findings. In such cases, discography may have some benefit in localizing a symptomatic disc as the etiology of nonradicular back pain.

A positive discogram must include a concordant pain response. This includes reproduction of symptoms upon injection of a symptomatic disc, a nonpainful response upon injection of control discs, and observed annular pathology on postdiscography CT scan, if used.

Discography most often is used prior to contemplating intradiscal electrothermal annuloplasty, also referred to as intradiscal electrothermal therapy (IDET), or surgical fusion for unremitting pain due to a symptomatic internal disc disruption. The characteristic feature of internal disc disruption is a radial fissure extending to the innervated outer third of the annulus fibrosus.

Some have found discography followed by a CT scan to be a more precise technique to delineate discovertebral pathology with sensitivities similar to or better than MRI and CT scan/myelography.

Discography must be used with care since a significant percentage of individuals with positive discograms improve without surgery. In addition, certain groups of patients tend to overreport pain during discographic injection.

Carragee et al found that provocative lumbar discography, when performed on volunteer subjects with no history of LBP, evoked little pain in those without chronic pain conditions, compensation issues, or abnormal psychometric testing. ^[6]

They found that when this procedure was performed in subjects with abnormal psychometric testing, particularly those with somatization features, chronic pain, and ongoing compensation litigation, the subjects frequently had very painful responses to disc injections.

In light of their findings, the usefulness of discography in this latter group of patients is questionable. At the very least, their study identifies the need for a proper screening method in patients undergoing this diagnostic modality.

Despite its flaws, discography still remains the only quasi-objective provocative test for disc-mediated pain. CT discography recently has received attention because it may be a good predictor of outcome following lumbar fusion for patients with intractable back pain.