Novel Predictive Scoring System for Bone Union Rate After Conservative Management of Lumbar Spondylolysis

Study Design. A single-center retrospective cohort study. Objectives. To develop a predictive scoring system for bone union after conservative treatment of lumbar spondylolysis and assess its internal validity. Summary of Background Data. Lumbar spondylolysis, a common stress fracture in young athletes, is typically treated conservatively. Predicting bone union rates remains a challenge. Methods. This study included patients aged ≤18 years with lumbar spondylolysis undergoing conservative treatment. A multivariable logistic regression analysis was used to develop a scoring system containing six factors: sex, age, lesion level, main side stage of the lesion, contralateral side stage of the lesion, and spina bifida occulta. The predictive scoring system was internally validated from the receiver operating characteristic (ROC) curve using bootstrap methods. Results. The final analysis included 301 patients with 416 lesions, with an overall bone union rate of 80%. On multivariable analysis, the main and contralateral stages were identified as factors associated with bone union. The predictive scoring system was developed from the main side stage score (prelysis, early=0, progressive stage=1) and the contralateral side stage score (none=0, prelysis, early, progressive stage=1, terminal stage=3). The area under the curve was 0.855 (95% confidence interval: 0.811–0.896) for the ROC curve, showing good internal validity. The predicted bone union rates were generally consistent with the actual rates. Conclusions. A simple predictive scoring system was developed for bone union after conservative treatment of lumbar spondylolysis, based on the stage of the lesion on the main and contralateral sides. The predicted bone union rate was approximately 90% for a total score of 0–1 and ≤30% for a score of 3–4. This system demonstrated good internal validity, suggesting its potential as a useful tool in clinical decision making for the management of spondylolysis.