Spondylolysis

Spondylolysis is a defect or fracture of the pars interarticularis, the segment of the vertebral arch between the superior and inferior articular processes. It most commonly affects the pars at the L5 level and is typically a stress fracture resulting from repetitive lumbar extension and rotation. It is most frequent in adolescents and young athletes, but can occur in adults as a fatigue injury.

Risk factors include participation in sports with repetitive lumbar extension, such as gymnastics, football, soccer, and weightlifting, and it may be more common in individuals with certain anatomical predispositions. The condition can be unilateral or bilateral; bilateral defects may progress to spondylolisthesis if instability develops.

Symptoms are usually a gradual onset low back pain that worsens with activity and improves with rest. Pain may radiate to the buttocks or thighs. On examination, there is focal tenderness over the pars interarticularis and pain with lumbar extension or contralateral rotation.

Diagnosis often starts with plain radiographs, which can be normal early. Oblique lumbar views may reveal the “Scottie dog” sign with a collar representing a pars fracture. Computed tomography is more sensitive for identifying the defect and assessing healing. Magnetic resonance imaging can detect bone marrow edema in acute injuries and helps exclude other pathology. Bone scans or SPECT can show increased uptake in stress injuries.

Treatment is usually conservative, especially in adolescents. This includes activity modification, temporary cessation of aggravating sports, bracing, and a structured physical therapy program to improve core stability and flexibility. Return to sport is gradual and guided by pain resolution and evidence of healing. Surgery is rare and reserved for persistent pain, high-grade spondylolisthesis, or when conservative care fails to relieve symptoms.

Prognosis is favorable for many adolescents who heal with conservative management, while healing potential decreases with age and when progression to listhesis occurs. Recurrence is possible if rehabilitation is incomplete or activities resume too soon.