Association between decreased disc signal intensity in preoperative T-2-weighted MRI and a 5-year outcome after lumbar minimally invasive discectomy

A total of 39 patients who had undergone microdiscectomy or percutaneous nu cleotomy for lumbar disc herniation were examined after a follow-up of 5 ye ars. The overall outcome was satisfactory in 80% of the patients treated, a nd only 1 (3%) patient had been reoperated during the follow-up. Clinical s igns and symptoms of lumbar instability were detected in 10 (26%) patients. All these 39 patients had been examined with lumbar magnetic resonance ima ging (MRI) on the day preceding the operation; the presence of disc degener ation was graded as severe, mild or non-existent depending on the visual br ightness of the discs on T-2-weighted images, as compared to the signal int ensity of the lumbar vertebrae. None of the 12 patients with no preoperativ e disc degeneration in MRI suffered from postoperative clinical signs and s ymptoms of instability as compared to 10 (37%) of the 27 patients with mild or severe disc degeneration suffering from instability (p = 0.04). Thus, t he results of the present study imply that the grade of the disc degenerati on in preoperative T-2-weighted MR images significantly predicted the occur rence of postoperative clinical instability.