High defect stage, contralateral defects, and poor flexibility are negative predictive factors of bone union in pediatric and adolescent athletes with spondylolysis

Purpose : To identify predisposition to spondylolysis and physical characteristics associated with “bone union” following conservative spondylolysis treatment among pediatric and adolescent athletes. Methods : We retrospectively analyzed pediatric and adolescent athletes with spondylolysis who underwent conservative treatment and rehabilitation for three or more consecutive months following sports activity cessation. Patients with terminal spondylolysis or who did not discontinue sports activities were excluded. We compared physical fitness factors in the union and nonunion groups and examined the association between bone union and spondylolysis severity by logistic regression analysis. Results : Of 183 patients with spondylolysis who underwent rehabilitation over a four-year period, 127 patients with 227 defects were included in the final analysis. Bone union was achieved in 66.5% (151/227) of the pars interarticularis defects and 70.1% (89/127) of the patients. On multivariate analysis, stage of pars interarticularis defect (odds ratio [OR], 0.26 ; p = 0.0027), stage of contralateral pars interarticularis defect (OR, 0.51 ; p = 0.00026), and straight leg-raising test (OR, 1.06 ; p = 0.028) were significantly associated with bone union. Conclusions : High defect stage, stage of the contralateral pars interarticularis defect, and poor flexibility were negative prognostic factors of bone healing in athletes with spondylolysis.