Extent of Decompression of Lumbar Spinal Canal after Endoscopic Surgery.

 Endoscopic techniques are being used in lumbar disk disease and lumbar canal stenosis to decompress the spinal canal. The present study analyzed pre- and postoperative magnetic resonance imaging (MRI) measurements of the lumbar canal.  This was a prospective study of 30 lumbar levels. Patients < 18 years of age with unilateral compression, previous surgery at the same level, and spinal instability were excluded. Endoscopic posterior decompression was used. Pre- and postoperative MRIs of all the patients were performed. Anteroposterior (AP), transverse, interfacet diameter, canal surface area, and height and angle of the lateral recess were measured.  Mean ages of male and female patients were 42.1 ± 10.3 and 45.0 ± 9.9 years, respectively. Pathologies were at L4-L5, L5-S1, and L2-L3 levels in 16, 13, and 1 patient, respectively. There was significant improvement in AP diameter (4.75 ± 1.75 mm to 10.33 ± 2.11 mm), interfacet distance (12.70 ± 4.86 mm to 18.92 ± 3.53 mm), and canal surface area (76.45 ± 25.36 mm to 187.13 ± 41.04 mm) after decompression. Significant improvement was noted in mean height and angle of lateral recess after surgery of both sides suggesting that effective decompression of the bilateral canal was possible using a unilateral approach. Most of the patients (90%) showed excellent and good improvement after surgery. Postoperative canal surface area and AP diameter in patients who did not have any pain after surgery or had pain requiring occasional medication was higher compared with patients who continued to complain of pain and required continuous pain medication.  Although the number of patients was small with a short follow-up, the endoscopic technique was effective in improving AP diameter, interfacet distance, canal surface area, lateral recess height, and lateral recess angle, suggesting that an endoscopic technique using a unilateral approach is effective in bilateral decompression of neural elements.