Bone Healing in Adolescents with Bilateral L5 Spondylolysis with and without Preexisting Contralateral Terminal Spondylolysis.

Retrospective cohort study. To examine bone healing with conservative treatment in cases of adolescent bilateral L5 spondylolysis. We classified bilateral L5 spondylolysis, which is the most affected spinal level, by fracture stage and aimed to compare the bone healing rate according to the fracture stage and evaluate the presence of a preexisting contralateral terminal fracture at the diagnosis of fresh spondylolysis. We evaluated 48 patients (38 boys and 10 girls) with bilateral L5 spondylolysis diagnosed during or before high school. L5 spondylolysis was classified into two groups: fresh group (bilateral fresh spondylolysis cases), and terminal group (cases wherein one side had fresh spondylolysis and the contralateral side had terminal spondylolysis). We investigated the age of examination and bone healing rate in both groups. We investigated progressive-stage lesions and bone healing rate with or without progressive-stage lesions. The bone healing rate in the fresh group was significantly higher than that in the terminal group 72.0% vs. 26.1%, p=0.003). In both the groups, the bone healing rate was significantly higher in patients without progressive-stage lesions than in those with progressive-stage lesions. Bone healing of progressive-stage fresh spondylolysis was not achieved by conservative treatment when contralateral terminal spondylolysis was present in adolescents with bilateral L5 spondylolysis. Our results suggest that bilateral L5 spondylolysis treatment strategies must be determined based on the combination of the stages present.