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