• Pedro S Silva, Paulo Pereira, Pedro Monteiro, Pedro A Silva, and Rui Vaz.
• Neurosurgery Department, Hospital São João, Porto, Portugal. pedrodossantossilva@gmail.com
• Neurosurg Focus. 2013 Aug 1;35(2):E7.

ObjectMinimally invasive transforaminal lumbar interbody fusion (MI-TLIF) has the potential advantage of minimizing soft-tissue damage and reducing recovery time compared to open procedures. A steep learning curve has been described for the technique. The aim of the present study was to define the learning curve that describes the progress of a single surgeon performing the MI-TLIF.MethodsOne hundred fifty consecutive patients with degenerative lumbar disease who underwent 1- or 2-level MI-TLIF were included in the study. Operative time, corrected operative time per level, and complications were analyzed. The learning curve was assessed using a negative exponential curve-fit regression analysis.ResultsOne hundred ten patients underwent 1-level and 18 patients underwent 2-level MI-TLIF; the remaining 22 underwent a single-level procedure plus an ancillary procedure (decompression at adjacent level, vertebral augmentation through fenestrated pedicle screws, interspinous device at adjacent level). Negative exponential curves appropriately described the relationship between operative time and experience for 1-level surgery and after correction of operative time per level (R(2) = 0.65 and 0.57). The median operative time was 140 minutes (interquartile range 120-173 minutes), and a 50% learning milestone was achieved at Case 12; a 90% learning milestone was achieved at Case 39. No patient required transfusion in the perioperative period. The overall complication rate was 12.67% and the most frequent complication was a dural tear (5.32%). Before the 50% and 90% learning milestones, the complication rates were 33% and 20.51%, respectively.ConclusionsThe MI-TLIF is a reliable and effective option for lumbar arthrodesis. According to the present study, 90% of the learning curve can be achieved at around the 40th case.

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