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Evaluation of Spondylolysis and Spondylolisthesis Detected Incidentally on Abdominal and Pelvic CT 2005

General Spine

Douglas M Katz, MD
Orlando Ortiz , MD, MBA, ASSR Member
Lily M Belfi , MD, Non ASSR Member


To determine the prevalence of lumbar spondylolysis and spondylolisthesis in a group of patients referred for abdominal and pelvic CT scans for reasons unrelated to the lumbosacral spine.

Methods & Materials

510 consecutive patients (ages 5-97) who underwent abdominal and pelvic CT on a single multidetector CT scanner for reasons unrelated to lower back pain were identified. The CT scans (generally imaged using 5 mm slice thickness) were retrospectively reviewed on a monitor for spondylolysis, spondylolisthesis, and associated degenerative changes by a radiology resident and a board-certified radiologist in consensus. The entire lumbar spine was reviewed using bone windows and cine viewing, but emphasis was placed on the status of the posterior elements of L4 and L5. The degree of spondylolisthesis was estimated on sagittal reformations. Attention was also paid to the presence of sclerotic changes at the L5 pedicles in patients 45 years or younger.


There were 29 cases of L5 spondylolysis, corresponding to a prevalence of 5.7 percent. Twenty-three of these cases demonstrated bilateral spondylolysis, and 6 unilateral. Sixteen of the 23 cases of bilateral spondylolysis also demonstrated spondylolisthesis, 13 of which were grade I and 3 of which were grade II. Almost all of these CT scans which were positive for spondylolysis also showed associated degenerative changes, including vacuum discs and facet hypertrophy. With respect to the 6 cases of unilateral spondylolysis, 4 had sclerosis of the contralateral pedicle, and 1 demonstrated sacralization of the contralateral side. In patients 45 years of age or younger who did not have spondylolysis or spondylolisthesis, we observed a 32.2 percent incidence of sclerosis involving the L5 lumbar pedicles. There were no cases of spondylolysis or spondylolisthesis at any of the other lumbar vertebral body levels.


The prevalence of incidental spondylolysis in patients undergoing abdominal and pelvic CT for unrelated reasons was approximately 6 percent.


No disclosures.