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CT-Based Characterization of Fracture Patterns in Pediatric Lumbar Spondylolysis
Vivien Chan1,2, Robert G Watkins1, Kenneth D Illingworth1
1Cedars Sinai Spine, Cedars Sinai Medical Center, Los Angeles, California.
Background:
Spondylolysis is a stress fracture of the pars interarticularis. Precise fracture morphology may help dictate management and dictate whether direct repair with an intralaminar screw is possible. The aim of this study was to characterize the specific fracture patterns of the pars interarticularis in pediatric patients with spondylolysis.
Methods:
This was a single-center retrospective cohort study. Patients were included if they were aged younger than 21 years with lumbar spondylolysis or Grade 1 isthmic spondylolisthesis on computed tomography (CT) imaging. On sagittal CT, total pars length (mm), inferior edge of inferior articular process to spondylolysis (mm), superior edge to spondylolysis (mm), size of spondylolysis gap (mm), and width of pars (mm) at fracture site were measured. The angle of the pars fractures were characterized in reference to the long axis of the pars.
Results:
There were 32 patients with 59 total spondylolyses included in this study. The mean age was 15.1 ± 1.9 years, and 44% (n = 14) were female. 7 (22%) patients had grade 1 spondylolisthesis. There were 15 fractures (25%) that had less than 0.5-mm gap, and the remaining 44 spondylolysis had a mean gap size of 2.4 ± 1.3 mm (range 0.9-6.4 mm). The mean total pars length was 37.9 ± 3.7 mm (range 31.6-45.8 mm). The mean measurement from the superior edge to the spondylolysis site was 12.1 ± 2.9 mm (range 6.1-18.8 mm). The average percentage of superior edge to spondylolysis/total pars length was 32.0% (range 17%-52%). Pars fracture angles ranged from 77° to 165° to the long axis of the pars. A majority (n = 40, 68%) of the pars fractures were between 110 and 140°. There were 12 fractures (20%) that were <110° and 7 fractures (12%) that were >140°.
Conclusions:
Pars fractures typically occur approximately one-third of the distance from the superior edge of the pars. However, considerable variability exists in their exact location along the pars. A clearer understanding of these fracture patterns may help refine surgical techniques and improve surgical outcomes for this patient population.
Level Of Evidence:
Level III. See Instructions for Authors for a complete description of levels of evidence.
