Case Author(s): Tate Allen, M.D. and Farrokh Dehdashti, M.D. , 7/29/98 . Rating: #D2, #Q4

Diagnosis: Bilateral Spondylolysis at L5

Brief history:

Low back pain

Images:

Delayed bone scintigraphy, anterior and posterior images

View main image(bs) in a separate image viewer

View second image(bs). SPECT axial and coronal images at L5

View third image(xr). Lateral and bilateral oblique radiolgraphs at L5

Full history/Diagnosis is available below

Diagnosis: Bilateral Spondylolysis at L5

Full history:

A 13-year-old male presents with low back pain exacerbated by physical activity.

Radiopharmaceutical:

17.9 mCi Tc-99m MDP i.v.

Findings:

Focal increased activity is present within the posterior elements bilaterally at L5 on both the planar and SPECT images. These abnormalities correspond with bilateral pars interarticularis defects seen at L5 on lumbar radiographs.

Discussion:

Spondylolysis is a defect in the pars interarticularis commonly found in the lumbar spine at L4 and L5. Frequently, the etiology for this defect is a stress fracture, although, there may be a congenital weakness in the osseous matrix of pars interarticularis that predisposes some individuals to the development of spondylolysis. Individuals commonly affected are male athletes presenting with back and radicular pain, however, some patients are asymptomatic. Spondylothisthesis or slippage of a vertebral body onto another can be associated.

Spondylolysis is usually diagnosed with radiographs of the lumbar spine. Oblique views which show the "scottie dog" are helpful. Bone scintigraphy shows increased uptake at the pars defect. In the early stages of spondylolysis, bone scintigraphy demonstrates a poorly defined, slightly increased activity that occurs when rapid osteoclastic resorption exceeds the osteoblastic response). In addition, contralateral uptake in a unilateral pars defect probably represents a physiological response or stress fracture in the presence of an unstable neural arch. The intensity of uptake depends upon the degree of bone repair. Absence of uptake can be seen in old or stabilized, nonsymptomatic pars defects. SPECT is superior to planar imaging for detection and accurately localizing vertebral arch abnormalities.

Reference: Resnick D: Bone and Joint Imaging. Philadephia, WB Saunders Co, 1996.

Major teaching point(s):

SPECT is especially useful in evaluation of lumbar spine because it allows for precise localization of a lesion to the vertebral body, disc space , or vertebral arch.

ACR Codes and Keywords:

References and General Discussion of Bone Scintigraphy (Anatomic field:Spine and Contents, Category:Effect of Trauma)

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Case number: bs094

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