Magnetic Resonance Imaging Findings and Clinical Outcomes in the Early Postoperative Period after Full Endoscopic Diskectomy for Lumbar Disk Herniation

This prospective case-control study aimed to establish the normal spectrum of early magnetic resonance imaging (MRI) findings in patients whose symptoms resolve after full endoscopic diskectomy (FED). We examined the changes in postoperative MRI findings and their relation to early clinical symptoms. In total, 33 patients underwent FED under local anesthesia. Clinical assessments and MRI examinations were performed preoperatively and immediately (within 1 week) and late (at 3 and 12 months) postoperatively. Residual disk bulging after surgery was classified into four grades compared with preoperative MRI findings: none (grade A), <25% (grade B), 25-75% (grade C), and >75% (grade D). MRI at postoperative week 1 showed grade B residual disk bulging in 9 patients, grade C residual disk bulging in 8 patients, and grade D residual disk bulging in 16 patients. Improvement was seen at postoperative month 3 (grade A in 18 patients, grade B in 10 patients, and grade C in 5 patients) and at postoperative month 12 (grade A in 29 patients, grade B in 3 patients, and grade C in 1 patient). Visual analog scale scores and the Japanese Orthopaedic Association scores showed significant differences at 1 week, 3 months, and 12 months after surgery. Postoperative MRI findings within 1 week of FED showed grade C or D residual disk material in 24 of 33 patients (73%). Clinical symptoms improved in the early postoperative period, even though residual disk bulging was present. Persisting residual bulging in the early stage following surgery may not correlate with clinical symptoms.