Radiology Quiz

Radiology quiz

EUGENE C. ANANDAPPA, MD

aFall 2000

A 15-YEAR-OLD HEALTHY athletic hispanic male was referred to an orthopedic surgeon with a complaint of lower back pain. The pain started one year ago, while playing competitive soccer in school. The pain is worse while playing but does not incapacitate him. The pain does not radiate, and there are no other accompanying symptoms. Plain radiographs followed by a technitium bone scan were obtained.

QUESTIONS:
A. What are the plain film findings?
B. What are the bone scan findings?
C. What is your diagnosis?
D. What imaging modality is useful for follow-up?

ANSWERS: In the lateral view of the lumbar spine, there is a oblique lucency at the base of the laminae of L-4 vertebra. The alignment is normal, with normal lumbar lordosis.

The bone scans show intense activity focally over the pedicles of L-4 vertebra. This is best seen in the SPECT images.

DIAGNOSIS: Bilateral L-4 spondylolysis.

DISCUSSION

Spondylolysis is a common problem in sports medicine. It is a stress fracture through the pars interarticularis of L-4 or L-5. As with other stress fractures, it is more common among young athletes, especially gymnasts and football lineman. Activity-related pain is the common symptom.

Although spondylolysis means lysis of a vertebral structure, the term is used almost exclusively to refer to the interruption of the pars interarticularis, which may be either unilateral or bilateral. Spondylolisthesis refers to slippage or displacement, without regard for direction.

About 90% of these injuries occur at L-5, 8% at L-4, 1 to 2% at L-3. They are found in about 3% of the population; they do not generally occur in nonambulators. The lesion develops in children around 5 to 6 years of age with an incidence of 3.3%. A second peak occurs in the adolescent population. The highest incidence is in white males (6.4%), and the lowest incidence is in African-American females (1.1%). The injury also has a familial predisposition, with reported rates of 27% to 69% in close relatives. It is also associated with Scheuermann disease.

Plain anteroposterior, lateral and oblique radiographs of the lumbar spine should be obtained with the patient standing. When spondylolysis occurs at L-4, it is generally associated with partial or complete sacralization of L-5. The radiographic changes are variable. Initial radiographs are often negative. Later, sclerosis of the involved area may be seen on one or both sides. Oblique radiographs may show a well-marginated defect in the pars as a break in the “neck of the Scotty dog.” On plain films about 80% of the lesions are bilateral, however on CT scans unilateral defects are rare.

Single-photon emission computed tomography (SPECT) bone scintigraphy is highly sensitive (85%) for detection of “painful” spondylolysis. A functional examination, such as SPECT scintigraphy, provides an active physiologic examination that predicts whether the spondylolytic defect is likely to be the source of specific pain; the probability and progression of healing can be determined with bone scintigraphy. If increased uptake can be seen on bone scan, healing of the stress fracture is possible with conservative treatment. In patients with radiographically confirmed spondylolysis but no focal accumulation on scintigraphy, the nonunion of the stress fracture is established, and it is unlikely to heal with immobilization.

DIFFERENTIAL DIAGNOSIS: OTHER CAUSES OF BACK PAIN

Back pain in children, unlike that in adults, usually has a defined cause in 50 to 60 % of cases. A complete history, a detailed physical examination and appropriate laboratory and imaging modalities can usually pinpoint the problem.

Infection: Disk space infection, or discitis, is an inflammatory lesion of the intervertebral disk that occurs in children. The infection probably begins in one of the contiguous endplates and then involves the disk. Children usually are not systemically ill, rarely have an elevated temperature and the WBC is frequently normal; however, the ESR is usually increased. Plain radiographs will reveal end-plate irregularity of the contiguous vertebrae, with disk space narrowing. Technetium bone scans, CT, or MRI may be needed to confirm the diagnosis.

Children with vertebral osteomyelitis and tuberculosis are systemically ill and have other symptoms.

Scoliosis: Scoliosis does not cause back pain in children. If scoliosis is associated with pain, the physician should look for an entity causing both, such as osteoid osteoma or osteoblastoma, herniated disk, or an intraspinal tumor.

Patients with JRA, ankylosing spondylitis, or Reiter’s disease may also present with back pain.

The ideal imaging modality should identify the presence or absence of disease, and if present define its extent. CT, MRI, and SPECT bone scintigraphy are excellent imaging modalities. MR studies are more difficult to achieve than are CT. CT studies are not operator-dependant, and the quality of the CT examinations tend to vary little from one institution to another. In our institution, almost all of the painful spondylolysis patients are successfully followed-up with serial SPECT bone scintigraphy.

REFERENCES

1. Lucins JO, Elting JJ, Cicoria AD, et al: SPECT evaluation of lumbar spondylolysis and spondylolisthesis. Spine 1994;19:608–612.

2. Lowe J, Schachner E, Hirschberg E, et al: Significance of bone scintigraphy in symptomatic spondylolysis. Spine 1984;6:653.

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