ARRS Case of the Week

MUSCULOSKELETAL IMAGING: Spine

Case Author: Brian D. Petersen, MD, University of Colorado

History

42-year-old man with back pain since he was 15 years old and current constant pain radiating down his right leg.

MSK Imaging for the Practicing Radiologist

Imaging Findings

Weight-bearing lateral long format radiograph (A) shows spondylolisthesis at the lumbosacral junction and marked anterior sagittal imbalance (dashed line). Coned-down lateral radiograph of the lumbosacral junction (B) shows severe degenerative disk disease with attritional rounding of the anterior sacral promontory (white arrow) and grade 4 spondylolisthesis (black arrow). Sagittal T2-weighted MR image (C) shows marked degenerative disk disease and rounding of the sacral promontory (arrow). Sagittal reformatted CT scan (D) shows marked hypoplasia of the L5 pedicles (straight arrow) and obliteration of the L5–S1 neural foramen (curved arrow).

Diagnosis

Congenital spondylolysis and spondylolisthesis

Teaching Points

Features typical of congenital spondylolisthesis include ribbonlike pedicles and marked attritional rounding of the sacral promontory. This rare subtype of spondylolisthesis is due to incomplete embryologic formation of the neural arch. Congenital spondylolysis tend to result in higher grades of spondylolisthesis (grades 3–5).

Isthmic spondylolysis is the most common type of spondylolysis and is an acquired condition related to fatigue fracture of the pars interarticularis. If they do not heal, these fatigue fractures can lead to spondylolisthesis of variable degree.

Dysplastic spondylolysis and dysplastic spondylolisthesis are confusing terms that have been applied to thinning and stretching of an intact pars and congenital deficiency of the L5 ring, allowing L5 spondylolisthesis.

Spondylolisthesis was graded by Meyerding on a scale of 1–5 based on division of the endplate of the vertebral body into quarters: grade 1, less than 25% translation; 2, 25–50%; 3, 50–75%; 4, greater than 75%; 5, complete slip of the vertebral body (spondyloptosis).

90% of degenerative spondylolisthesis occurs at L4–L5; 90% of pars defects that allow slippage occur at L5–S1.

Suggested Readings

Ross JS, Brant-Zawadski M, Moore KR, Crim J, Chen MZ, Katzman GL. Diagnostic imaging: spine, 2nd ed. Salt Lake City, UT: Amirsys, 2007:2–47

Wiltse LL, Widell EH, Jackson DW. Fatigue fracture: the basic lesion in isthmic spondylolisthesis. J Bone Joint Surg Am 1975; 57:17–22

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