Assessment of the Learning Curve for Microendoscopic Decompression Surgery for Lumbar Spinal Canal Stenosis through an Analysis of 480 Cases Involving a Single Surgeon

Abstract

Study design: Retrospective study.

Objective: To assess the learning curve of microendoscopic decompression surgery for lumbar spinal canal stenosis (LSCS).

Methods: Four hundred eighty LSCS cases involving 753 stenotic lesions limited to the intraspinal canal were treated with microendoscopic decompression by a single surgeon at an institution between November 2006 and January 2015. They were numbered chronologically, and the operating time, intraoperative blood loss, and perioperative complications were investigated. Surgical outcomes were evaluated using the Japanese Orthopedic Association (JOA) score for low back pain before and 1 year after the operation.

Results: The mean operating time per level was 66.1 minutes. There was a progressive reduction in the operating time through the case series, and the approximate curve seemed to be y = - 9.4Ln(x) + 115.0. The blood loss per level, which showed a mean value of 15.0 mL, was more than 50 mL in only 2.7% of the cases after case no. 30 and in 20% of the cases before it. There were 10 (2.1%) cases of perioperative complications, which occurred even after the surgeon had gained mastery of the procedure. The median JOA score improved significantly from 17 points preoperatively to 26 points postoperatively.

Conclusions: The learning curve of microendoscopic decompression surgery for LSCS has been defined with data for a single surgeon in an institution. The operating time seems to decrease along a natural logarithmic function. The intraoperative blood loss stabilizes after the first 30 cases, whereas perioperative complications can occur at any time even after mastery of the technique.

Keywords: learning curve; lumbar spinal canal stenosis; microendoscopic decompression; minimally invasive surgery; spinal surgeons.

Fig. 1

Scatterplot showing the learning curve of microendoscopic decompression surgery for lumbar spinal canal stenosis as depicted by operating time per level. When the approximate curve was determined with a natural logarithmic function, its contribution rate (R ²) was 0.20.

Fig. 2

Scatterplot as depicted by intraoperative blood loss per level. The vertical broken line is drawn at case no. 30 and the horizontal one is at 50 mL of the intraoperative blood loss per level.