Lumbosacral anatomy is unique in pediatric spondylolysis.

PURPOSE: To determine whether patients with L5 spondylolysis have different lumbosacral anatomy compared to patients without L5 spondylolysis.

METHODS

Computed tomography (CT) scans of pediatric patients with isolated L5 spondylolysis were identified and matched 1:4 (age, sex, BMI) to patients without spondylolysis. Sagittal parameters assessed included sacral slope angle, sacral table angle, L4-S1 and L5-S1 Cobb angles, the horizontal angle of the L5 pars interarticularis, the distances between the L4 inferior articular process (IAP) and the S1 superior articular process (SAP) and their respective individual distances to the L5 pars. Coronal parameters assessed included the percent subluxation of L4 IAP below the facet joint.

RESULTS

1084 CT scans were reviewed. 32 patients with isolated L5 spondylolysis were identified and matched to 122 patients without spondylolysis. The horizontal angle of the L5 pars was greater in spondylolysis patients (142.5 ± 10.2 vs. 119.9 ± 5.9, p < 0.05). There was less distance (mm) between L4 IAP and S1 SAP (11.3 ± 3.9 vs. 14.7 ± 2.9, p < 0.05) and less distance (mm) from both L4 IAP (2.6 ± 1.7 vs. 5.4 ± 2.2, p < 0.05) and S1 SAP (0.7 ± 0.4 vs. 1.5 ± 0.7, p < 0.05), respectively, to the L5 pars in the spondylolysis group. Pearson's analyses revealed that a larger horizontal angle of the L5 pars was strongly associated with spondylolysis (0.59).

CONCLUSION

Pediatric patients with L5 spondylolysis have a significantly more horizontal L5 pars that is closer to both the L4 IAP and S1 SAP.