Learning Curve, Outcome Parameters, and MRI Assessment of Disc Evacuation After Transforaminal Percutaneous Endoscopic Lumbar Discectomy

Investigators reviewed clinical evaluation, C-arm shot, and post-operative MRI findings as parameters for evaluation. All data was taken from the patients' medical records with single-level LDH (Lumbar Disc Herniation) following TPELD. Patients with incomplete data and those who underwent revision surgery were excluded. The collected data were regarding the sociodemographic characteristics of the patients (age and gender), surgical time, pre-operative pain scale (1-10), postoperative pain scale, complications, and weight of the removed disc and ODI (Oswestry Disability Index) score. The preoperative pain scale was assessed within 48 hours before the surgery while the post-operative pain scale was assessed at one month and three months after the surgery. The reduction of pain was assessed, comparing the pre-operative pain scale and the post-operative pain scale at 1 month and 3 months follow up. Pre TPELD MRI data and 3 months post TPELD were collected to evaluate the percentage of disc removed referring to the quantification of the axial MRI by two independent radiology department personnel. The area of the bulging disc was measured using as many points as the user felt were necessary in order to trace a reasonable outline of disc herniation. All of the TPELD procedures are performed by a single spine surgeon with only using one type of endoscopic instrumentation in one level LDH. The surgeon was not involved during data collection and data were collected by independent assessors. The statistical analysis was performed using SPSS 23.0. investigator tested all the numeric variables with the Shapiro-Wilk test for the normality of distribution. The surgeon's learning curve was evaluated using negative curve-fit regression analysis (y = ae-bx+ c) described by Silva, et al (2013). Then all case are divided into two groups based on the surgical time: cases before and at reaching 50% proficiency (early group) and cases after reaching 50% proficiency (later group).