Bony Union Following Platelet-Rich Plasma and Focused Extracorporeal Shock Wave Therapy for Delayed Union of Bilateral Lumbar Spondylolysis in an Adolescent Gymnast: A Case Report

Lumbar spondylolysis is a stress fracture of the pars interarticularis that is common in adolescent athletes.In this report, we describe the case of a 16-year-old male competitive gymnast who presented with low back pain.Magnetic resonance imaging (MRI) demonstrated bilateral L4 spondylolysis with high signal in the pars interarticularis (right, progressive stage; left, early stage).Sport was stopped completely, and a rigid thoracolumbosacral orthosis was fitted immediately.Pain improved gradually, and the high signal on fatsuppressed T2-weighted images regressed, but the fracture lines extended rather than consolidated, and computed tomography (CT) at three months showed no bony bridging on either side.The right lesion remained at the progressive stage, and the left showed uniformly sclerotic fracture margins and no bridging trabeculae, indicating that it was approaching the terminal stage.Delayed union was diagnosed.After informed consent was obtained, focused extracorporeal shock wave therapy (f-ESWT) was delivered to the bilateral pars defects in three sessions at approximately weekly intervals, and a single injection of autologous platelet-rich plasma (PRP) was administered at the defects under fluoroscopic guidance before the second session.Transient injection-site pain was the only adverse event, and no neurological complications occurred.CT at two months showed bony bridging progressing bilaterally; a graduated return to gymnastics training was begun, and CT at five months confirmed bilateral union.At nine months, the patient had trained without restriction for four to five months without recurrence of low back pain, and MRI obtained after an acute hyperextension injury showed both pars defects still united.To our knowledge, this is the first report of PRP injected at a pars interarticularis defect in lumbar spondylolysis.Because both modalities were applied concurrently in a single patient while rigid bracing was continued, their individual contributions cannot be separated, and spontaneous union cannot be excluded.Nevertheless, the course changed from stalled to healing after the intervention, in a lesion considered unfavorable for spontaneous union.This single observation is hypothesis-generating rather than evidence of treatment efficacy, and it suggests that combined PRP and f-ESWT may merit evaluation in comparative studies of delayed-union spondylolysis that has not responded to conservative treatment.