Learning Curve of Endoscopic Lumbar Discectomy - A Systematic Review and Meta-Analysis of Individual Participant and Aggregated Data

Abstract

Study design: A systematic review and meta-analysis of individual participant and aggregated data.

Objectives: To define the learning curves of endoscopic discectomies using unified statistical methodologies.

Methods: Searches returned 913 records, with 118 full-text articles screened. Studies of endoscopic lumbar spine surgery reporting outcomes by case order were included. Mixed-effects nonlinear, logistic, and beta meta-regressions prdwere conducted to define the learning curves.

Results: 13 studies involving 864 patients among 15 surgeons were included in total. For transforaminal endoscopic discectomy, the estimated operating time for the first case was 95 min [CI: 87-104], and the estimated plateau was 66 minutes [CI: 51-81]. An estimated 21 cases [CI: 18-25] were required to overcome 80% of this deficit, but near-plateau performance was expected only after 59 cases [CI: 51-70]. The estimated risk of surgical complications on the first case was 25% [CI: 11%-46%], with an 80% reduction in relative risk requiring an estimated 41 cases. The expected postoperative VAS leg pain score after the first case was 2.7 [CI: 1.8-3.8], with an 80% improvement requiring an estimated 96 cases. Similar numbers were required to overcome the learning curves in interlaminar and biportal endoscopic discectomies.

Conclusions: Approximately 60 cases are required to achieve proficiency in endoscopic lumbar spine surgery, although the greatest part of the learning curve can be overcome with 20 cases. This should be considered when designing implementation programmes for surgeons and service providers that wish to incorporate endoscopic spinal surgery into their practice.

Keywords: degenerative; degenerative disc disease; disc; disc herniation; discectomy; endoscopy; lumbar; minimally invasive.

Figure 1.

Learning curve of transforaminal endoscopic lumbar discectomy. (A) By operating time. Visualisation of the results of the non-linear meta-regression. The blue line indicates the fitted exponential curve, with the shaded area around the curve indicating the 95% CI. The coloured lines show the individual points from each surgeon series. The horizontal dashed line is the estimate of the time taken in the first case. The bars denote the expected values for first case, and the number of cases to overcome 80% and 99% of the learning curve. The error bars denote the 95% confidence interval. (B) The expected proportion of surgeons to have overcome 80% of the learning curve (blue line) or 99% of the learning curve (red line) by operating time. (C) By surgical complications. Visualisation of the results of logistic regression. The solid black line denotes the average curve between all surgeons, with the shaded grey area indicating the 95% CI. The coloured lines indicate the estimated curves of each individual surgeon series. (D) By postoperative VAS leg pain score. Visualisation of the results of logistic regression. The solid black line denotes the average curve between all surgeons, with the shaded grey area indicating the 95% CI. The coloured lines indicate the estimated curves of each individual surgeon series. (E) The expected proportion of surgeons to have 80% relative risk reduction in surgical complications (blue line), and 80% improvement in postoperative VAS leg pain score (red line).

Figure 2.

Learning curve of interlaminar endoscopic lumbar discectomy. (A) By operating time. Visualisation of the results of the non-linear meta-regression. The blue line indicates the fitted exponential curve, with the shaded area around the curve indicating the 95% CI. The coloured lines show the individual points from each surgeon series. The horizontal dashed line is the estimate of the time taken in the first case. The bars denote the expected values for first case, and the number of cases to overcome 80% and 99% of the learning curve. The error bars denote the 95% confidence interval. (B) By surgical complications. Visualisation of the results of logistic regression. The solid black line denotes the average curve between all surgeons, with the shaded grey area indicating the 95% CI. The coloured lines indicate the estimated curves of each individual surgeon series.

Figure 3.

Learning curve of biportal endoscopic lumbar discectomy. (A) By operating time. Visualisation of the results of the non-linear meta-regression. The blue line indicates the fitted exponential curve, with the shaded area around the curve indicating the 95% CI. The coloured lines show the individual points from each surgeon series. The horizontal dashed line is the estimate of the time taken in the first case. The bars denote the expected values for first case, and the number of cases to overcome 80% and 99% of the learning curve. The error bars denote the 95% confidence interval. (B) By surgical complications. Visualisation of the results of logistic regression. The solid black line denotes the average curve between all surgeons, with the shaded grey area indicating the 95% CI. The coloured lines indicate the estimated curves of each individual surgeon series.