Elsevier

World Neurosurgery

Volume 143, November 2020, Pages 471-479
World Neurosurgery

Literature Review
Learning Curve for Transforaminal Percutaneous Endoscopic Lumbar Discectomy: A Systematic Review

https://doi.org/10.1016/j.wneu.2020.08.044Get rights and content

Background

Transforaminal percutaneous endoscopic lumbar discectomy (TPELD) has become an alternative and minimally invasive surgical technique for soft lumbar disc herniation. However, the learning curve has been relatively long and difficult. In the present study, we have summarized the characteristics of the learning curve of TPELD, including the number of cases required to achieve technical proficiency, and discussed the strategies to improve the learning curve.

Methods

The PubMed, Embase, Cochrane Library, and KoreaMed databases were searched for reports describing the learning curve for TPELD. Clinical studies involving human patients and evaluating the learning curve of TPELD with quantitative data were included. A strict quality assessment was completed, and descriptive statistics were calculated.

Results

Of the 6884 screened titles and abstracts, 10 full-text reports, including 958 cases, were included in the analysis. All were cohort studies, which were grouped into early and late groups according to surgeon experience with TPELD. The most commonly used cutoff to differentiate between these groups was 20 (mean, 24.70 ± 18.99 cases; range, 10–72 cases). The most widely used measure was the operative time. Although most studies had reported better results in the operative time or pain scores in the late group, only 1 study had proposed a bona fide learning curve.

Conclusions

We found insufficient evidence to support a cutoff point of 20 or other numbers of cases for determining when the learning curve has reached a plateau. Therefore, these numbers should be interpreted with great care, and high-quality prospective studies evaluating the actual learning curve are required.

Introduction

Transforaminal percutaneous endoscopic lumbar discectomy (TPELD) is regarded as an effective minimally invasive spinal surgery for soft lumbar disc herniation (LDH). The TPELD technique can provide relevant clinical results with the typical benefits of minimally invasive spinal surgery, including less tissue trauma, a lower complication rate, and an early return to work.1, 2, 3, 4 Some randomized trials have demonstrated that the effectiveness of TPELD is comparable to that of the conventional open lumbar discectomy technique.5, 6, 7, 8, 9 Recently, some investigators have reported meta-analyses or systematic reviews of the effectiveness of TPELD.10, 11, 12, 13 The results of these meta-analyses have shown that TPELD is not inferior to conventional surgery in terms of clinical success, complications, and recovery.

The transforaminal endoscopic approach to LDH is a unique technique compared with the conventional open posterior approach. This posterolateral approach provides direct access to the disc pathology through the intervertebral foramen and avoids trauma to the normal tissue, such as a large skin incision, muscle retraction, laminectomy, and neural tissue retraction. The transforaminal endoscopic approach can be performed with the patient under local anesthesia or conscious sedation. However, despite its benefits of minimal invasiveness, most spine surgeons are not comfortable nor familiar with this technique, and the learning curve has been relatively long and difficult. Thus, some surgeons, even expert surgeons, might desist learning the procedure during the learning curve period. Such surgeons might criticize TPELD as “minimally effective” or a delusive procedure. Therefore, knowledge of the learning curve for TPELD and a proper training system are essential to achieve clinical success.

Some investigators have reported studies evaluating the learning curve of TPELD. However, no firm consensus has been reached regarding the characteristics of the learning curve and the strategies to improve the learning curve. Therefore, the objective of the present study was to systematically review the characteristics of the learning curve for TPELD, including the number of cases required to achieve technical proficiency, and discussed how to improve the learning curve period.

Section snippets

Literature Search Strategy

The PubMed, Embase, Cochrane Library, and KoreaMed databases were used to search for the related studies. Trial registries (ClinicalTrials.gov and Controlled-Trials.com) were explored to identify any ongoing studies or trials. The institutional review board certified the present study as exempt (approval no. GFIRB2018-422). The search terms “learning curve,” “training curve,” “endoscopic,” “endoscope,” “lumbar disc herniation,” “percutaneous endoscopic lumbar discectomy,” “transforaminal lumbar

Study Identification and Quality Assessment

The literature search for potentially available information for inclusion yielded 5587 studies, after removal of 1297 duplicates from 6884 reports. After a preliminary review of the titles and abstracts, another 4795 were excluded. After the full-text screening, 10 reports had met the inclusion criteria for the final analysis.17, 18, 19, 20, 21, 22, 23, 24, 25, 26 The detailed procedure of study identification is presented in Figure 1.

All studies were cohort studies, with the patients divided

Technical Aspects of TPELD and Methods to Reduce the Learning Curve

The fundamental principle of the “transforaminal” approach is direct access to the pathologic disc through the intervertebral foramen. In conventional open lumbar discectomy, routine posterior approach procedures will include a considerable skin incision, paravertebral muscle retraction, a wide laminectomy, removal of the ligamentum flavum, and dural sac retraction, which are essential to surgically treat LDH. These serial procedures are traumatic to normal tissues. A transforaminal approach

Conclusions

Significant improvement was found in the clinical and radiographic measures between the early and late stages of a surgeon’s experience of TPELD. However, the evidence was insufficient to support a cutoff point of 20 or any other number of cases at which the learning curve would have reached a plateau. Therefore, these numbers should be interpreted with great care.

Acknowledgments

The authors would like to thank Jae Min Son and Sang Gu Lee for their valuable support and technical assistance.

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    Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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