Asymptomatic same-site recurrent disc herniation after lumbar discectomy: results of a prospective longitudinal study with 2-year serial imaging.

Study Design: This is a prospective cohort study with serial imaging.
Objective: We set out to determine the incidence of symptomatic and asymptomatic same-level recurrent disc herniation and assess their effect on 2-year outcome.
Summary of Background Data: The reported incidence of symptomatic same-level recurrent disc herniation after lumbar discectomy varies widely in retrospective studies. To date, the incidence of radiographic same-level recurrent disc herniation has not been studied prospectively with sequential imaging. Furthermore, the clinical relevance of recurrent disc herniation on magnetic resonance imaging (MRI) after discectomy remains unknown, particularly in patients with poorly specific pain after surgery.
Methods: One hundred eight patients undergoing lumbar discectomy for a single-level herniated disc at five institutions were prospectively observed for 2 years. Computed tomography (CT) and MRI of the lumbar spine were obtained every 3 months to assess reherniation and disc height loss. Leg and back pain visual analog scale (VAS), Oswestry Disability Index (ODI), and quality of life (SF-36 physical component) were assessed 3, 6, 12, and 24 months after surgery.
Results: No patients demonstrated residual disc on postoperative MRI. By 2 years after discectomy, 25 (23.1%) patients had demonstrated radiographic evidence of recurrent disc herniation at the level of prior discectomy on serial imaging (mean ± SD, 11.8 ± 8.3 months after surgery). Radiographic disc herniation was asymptomatic in 14 (13%) patients and symptomatic in 11 (10.2%) patients. The occurrence of symptomatic recurrent disc herniation was associated with worse 2-year leg pain (VAS-LP, P=0.002) and disability (ODI, P=0.036) but not quality of life (SF-36) or disc height loss. The occurrence of asymptomatic reherniation was not associated with disc height loss or any outcome measure (VAS, ODI, and SF-36) by 2 years.
Conclusion: Nearly one-fourth of patients undergoing lumbar discectomy demonstrated radiographic evidence of recurrent disc herniation at the level of prior surgery, the majority of which were asymptomatic. Asymptomatic disc herniation was not associated with clinical consequences by 2 years. Clinically silent recurrent disc herniation is common after lumbar discectomy. When obtaining MRI evaluation within the first 2 years of discectomy, providers should expect that radiographic evidence of reherniation may be encountered and that treatment should be considered only when correlating radicular symptoms exist.