Background:

Single position (SP) lateral transpsoas lumbar interbody fusion (LLIF) with posterior pedicle screw fixation (PPSF) reduces operative time compared to dual positioning. However, the learning curve has not yet been described. The purpose of this study was to define the learning curve SP LLIF with PPSF.

Methods:

This retrospective case series included the first 161 consecutive patients who underwent SP LLIF and PPSF with the senior author. Primary analysis of operative time versus case number included single level cases without adjacent level procedures. Secondary analyses included 1-3 level cases without adjacent level procedures. Operative time for 2 and 3 level procedures was normalized to single-level cases. The learning curve was assessed with linear regression, which was found to fit the data better than logarithmic regression as judged by R² values and data visualization. Perioperative outcomes as a function of case number were analyzed by least squares linear regression and Mann Whitney U-tests.

Results:

For single level surgeries without adjacent procedures (n=87), operative time decreased by a total of 28.7 (95% CI, 9.6, 47.9) minutes over the series (P<0.001). For 1-3 level cases with no adjacent procedures (n=131), normalized operative time decreased by 23.1 (7.6, 38.6) minutes (P<0.001). Post-operative change in hematocrit, length of hospital stay, post-operative change in lordosis, 90-day complications, suboptimal screw placement, and 6-week post-operative Oswestry Disability Index (ODI) score did not correlate with case number. Intraoperative fluids decreased 3.7 mL (95% CI, 0.7, 6.7) per case (P=0.015).

Conclusions:

In SP LLIF with PPSF, case number correlated with decreased operative time, but not complications. The surgeon’s prior experience with dual position (DP) LLIF likely contributed to the minimal learning curve observed. Surgeons adopting SP LLIF with minimal prior DP LLIF experience may experience a steeper curve.