CT multiplanar reconstruction in 253 cases of lumbar spondylolysis.

Two hundred fifty-three patients with lumbar pars interarticularis defects were studied by multiplanar high-resolution computed tomographic scanning (CT/MPR). Two hundred thirty patients had one or more pars defects at L5, 21 at L4, and two at L3. Within this group of patients, 21% had more than 5 mm of disk bulge or herniation, 34% had foraminal encroachment, and 34% had indentation on the neural canal from soft-tissue or bony callus formation.