A novel preoperative trajectory evaluation method for L5-S1 transforaminal percutaneous endoscopic lumbar discectomy

L5-S1 transforaminal percutaneous endoscopic lumbar discectomy (PELD) is a demanding procedure because of structures such as iliac crest, L5 transverse process, hypertrophic L5-S1 facet joint, and sacral ala. There has been no definite preoperative evaluation method to evaluate the surgical validity of L5-S1 transforaminal PELD. The authors report a new preoperative trajectory evaluation method for L5-S1 transforaminal PELD using magnetic resonance imaging (MRI) or computed tomography (CT) examinations. This is a technical report study. Patients who were diagnosed L5-S1 soft disc herniation were included in the present study. Success rate of transforaminal PELD according to height of iliac crest was measured. Twelve patients who were diagnosed L5-S1 disc herniation were preoperatively evaluated with this new method. A skin marker is attached to patient's back as a tentative skin entry point, which was determined by usual preoperative MRI or CT. A new tilted axial and coronal MRI or CT scan is performed according to axis of L5-S1 transforaminal working channel. The images show good relationship between working channel and iliac crest. Six patients underwent a transforaminal PELD, and the results were successful. The other six patients were considered to be “unsuitable” for transforaminal PELD because of the probable blockade by iliac crest. The tilted MRI or CT provides precise evaluation for L5-S1 transforaminal PELD trajectory and may achieve good outcome.