Study design:

This was a systematic review.

Objective:

This review evaluates the minimally invasive transforaminal lumbar interbody fusions (MIS-TLIF) learning curve in the literature and compares outcomes during and after completing the curve.

Summary of background data:

MIS-TLIF are performed for various spine conditions. Proponents cite improved clinical outcomes while critics highlight the steep learning curve to attain proficiency.

Methods:

Literature searches on Medline and Embase utilized relevant subject headings and keywords. Manuscripts reporting learning curve statistics were included. Monotonic trends of operative duration were assessed with Mann-Kendall nonparametric testing.

Results:

Nine studies met inclusion criteria. Number of patients ranged from 26 to 150 (average 83.2, median of 86). Commonly reported metrics included number of procedures to complete the curve, operative duration, blood loss, ambulation time, length of stay, complication rate, follow-up visual analogue scale (VAS) for back and leg pain, and fusion rate. Various methods were employed to determine number of cases to complete the curve, all involving operative duration. Number of cases ranged from 14 to 44. A significant negative trend for operative duration of cases during the learning curve (τ=-0.733, P=0.039) was found over the years that studies were published. Initial complication rates varied from 6.8% to 23.8%. Initial VAS-back and VAS-leg ranged from 0.8 to 2.9 and 0.5 to 2.3, respectively. While definitions of “good” fusion varied, fusion rates meeting Bridwell grade I or II during the learning curve ranged from 84.0% to 95.2%.

Conclusions:

Surgeons in their learning curve have become faster at the MIS-TLIF procedure. Clinical outcomes including postoperative pain and fusion rates showed satisfactory results, but surgeons learning the procedure should take measures to minimize complications in early cases, such as utilizing novel navigation technology or supervision from more experienced surgeons. Learning curve research methodology could benefit from standardization.