Postoperative Longitudinal Outcomes in Patients with Residual Disc Fragments after Percutaneous Endoscopic Lumbar Discectomy.

Background: Residual disc fragments are observed on immediate postoperative magnetic resonance imaging (MRI) in 2.8-15% of patients after percutaneous endoscopic lumbar discectomy (PELD). Considering the known postoperative longitudinal outcomes in patients with residual disc tissue, a 'watchful waiting' strategy may be preferable to immediate re-operation in patients with asymptomatic residual disc material.

Objectives: The aim of the present study was to compare the longitudinal clinical outcomes between PELD patients in whom the complete removal of disc fragments was achieved (complete group) and those in whom residual disc fragments were observed on postoperative MRI (residual group).

Study Design: Retrospective nested case-control study.

Methods: A total of 225 patients were included (complete group, n=187 and residual group, n=38). Clinical assessments were performed using the visual analog pain score for the leg (VAS-L, x/10) and back (VAS-B, x/10) and the Korean version of the Oswestry Disability Index (K-ODI, x/45). A linear mixed-effects model was used to analyze changes during the first 24 postoperative months.

Results: One month after surgery, significant improvements in the VAS-L, VAS-B and K-ODI values were observed and were maintained during the first 24 postoperative months. No differences in these changes were noted between the groups. Early re-operation (during the first 3 postoperative months) was performed in 3 patients in the residual group (7.9%) and in 4 patients in the complete group (2.1%) (P = 0.10).

Limitations: First, the study design was retrospective. Moreover, the number of patients was relatively small and therefore insufficient to achieve robust statistical power. Second, we did not explore the radiological outcomes in patients with asymptomatic residual disc material because follow-up MRI was only obtained to document symptom recurrence.

Conclusion: When residual disc tissue is observed in asymptomatic patients, a 'watchful waiting' strategy may be preferable to immediate re-operation. However, an increased early re-operation rate is expected for patients with residual disc tissue.

Key Words: Discectomy, endoscopes, longitudinal studies, patient-reported outcome, percutaneous, reoperation, spine, residual disc.