To explore the imaging characteristics and new therapy of adolescent lumbar spondylolysis, in order to improve the diagnostic ability and provide the new ideas for the treatment of the disease.

Retrospective study of one patient with L₅ bilateral spondylolysis who had underwent the treatment of staphylococcal enterotoxin c injection guided by C-arm X-ray.

X-ray presented discontinuity of L₅ pedicle isthmus where appeared a visible crack that forming a typical "scotty dog sign" . CT scan presented disunion of L₅ bilateral pedicle isthmus, the hyperplasia and sclerosis of the broken edge made it uneven and serrated shaped that forming a typical "crack sign" and "fracture sign" . The diagnosis of L₅ bilateral spondylolysis was clear and the patient′s clinical signs and symptoms were significantly better than the condition before the treatment and bony union was in 1 year after the therapy of staphylococcal enterotoxin c injection guided by C-arm X-ray.

The diagnosis of lumbar spondylolysis is mainly depended on imaging examination, thus giving insight into the imaging characteristics and grasping the key points of diagnosis of lumbar spondylolysis are particularly important to make the accurate diagnosis.Moreover, the treatment is worthy of being clinically spread for its novelty, economy, convenience, security and minimal invasion.