Computer-assisted , minimally invasive transforaminal lumbar interbody fusion : one surgeon ’ s learning curve

Study Design. A retrospective study of prospectively collected clinical data. Objective. To evaluate the learning curve of using the computer assisted navigation minimally invasive spine surgery (CAMISS) and transforaminal lumbar interbody fusion (TLIF) technique for the surgical treatment of lumbar degenerative diseases. Summary of Background Data. Minimally invasive (MI) transforaminal lumbar interbody fusion (TLIF) is technique challenge and long learning curve, as complex procedure performed through tubular tractor with high complications compared with open TLIF. Intro-operative navigation could provide real-time 3 dimension anatomic structure of spine, could make the complex surgery accuracy and safety. We combined computer assisted navigation and minimally invasive spine surgery (CAMISS) to treat lumbar degenerative disease. However, the learning curve of the combine technique is unknown. Methods. Seventy-four consecutive patients with lumbar degenerative disease underwent CAMISS TLIF between March 2011 and January 2013 by a single surgeon. All patients were followed up at least 24 months, and the average follow-up time was 38 months. The learning curve was assessed via a logarithmic curve-fit regression analysis. According to the plateau of asymptote, initially 25 patients was divided as early group and remain cases were the later group. The clinical evaluation data included operative time, anesthesia time, intraoperative blood loss, day for ambulation, postoperative hospital stay, visual analog scale (VAS) leg and back pain scores, the Oswestry disability index (ODI) value, Macnab outcome scale scores, complications, radiological outcomes and rate of conversion to an open. Results. The complexity of cases increased over the series, and the complication rate decreased. There were significant different between two groups on average duration of anesthesia (p<0.001). The operative time showed a significant decrease (p < 0.001) as the case number increased, as indicated by the equation y =− 18.26 ln(x) + 219.23 (x, case number; y, operative time [min]), with a coefficient of determination R2 = 0.6435. There was no significant difference with intraoperative blood loss, day for ambulation, and post-operative hospital stay in the two groups (p>0.05). The improvement of VAS leg and back pain scores and ODI in each group was similar: there was a significant improvement (p<0.05) at 3 months, 12 months and 24 months after surgery when compared with preoperative scores, but there was no statistical difference (p>0.05) in the VAS leg and back pain scores and ODI between two groups 3 months, 12 months and 24 months after surgery. The complication rate was 12.00% for early group, 6.82% for later group, with no statistical difference (p>0.05) between groups. No significant difference was found between two groups in Macnab outcome scale scores and solid fusion rate. There was no need for conversion to an open procedure for both groups. Conclusions. Our study showed a plateau asymptote of CAMISS TLIF was reached after 25 operations. The latter patients were during shorter operative time and anesthesia duration. CAMISS TLIF is an effective and safety option in the surgical treatment of lumbar degenerative disease.