Finite element method for nerve root decompression in minimally invasive endoscopic spinal surgery.

INTRODUCTION: Diagnosis is the key to improving spinal surgery outcomes. Improvements in the diagnosis of radiculopathy have created new indications for full-endoscopic spine surgery. We assessed the finite element method (FEM) to visualize and digitize lesions not detected by conventional diagnostic imaging.

METHODS: We used FEM in two patients: a lumbar patient and a cervical patient. The lumbar patient was a 67-year-old woman with a history of rheumatoid arthritis; she also had osteoporosis and pulmonary fibrosis. She had left L3 radiculopathy due to an L3 vertebral fracture. The cervical patient was a 61-year-old woman with left C6 radiculopathy due to C5-C6 disc herniation. We performed full endoscopic foraminotomy per the patients's request. Based on preoperative and postoperative CT Digital Imaging and Communications in Medicine data of 0.5-mm slices, 3-D imaging data were reproduced, and kinetic simulation of FEM was performed.

RESULTS: Postoperatively, both patients' radiculopathy disappeared, improving their activities of daily living and enabling them to walk and work. Also, the total contact area and maximum contact pressure of the nerve tissue decreased from 30% to 80% and from 33% to 67%, respectively.

CONCLUSIONS: A new method for perioperative evaluation and simulation, FEM can be to visualize and digitize the conditions of the lesion causing radiculopathy. FEM that can overcome both time and economic constraints in routine clinical practice is needed.