Disc space preparation in transforaminal lumbar interbody fusion: a comparison of minimally invasive and open approaches.

ABSTRACT

BACKGROUND: Minimally invasive surgical (MIS) approaches to transforaminal lumbar interbody fusion (TLIF) have been developed as an alternative to the open approach. However, concerns remain regarding the adequacy of disc space preparation that can be achieved through a minimally invasive approach to TLIF. QUESTIONS/PURPOSES: The purpose of this cadaver study is to compare the adequacy of disc space preparation through MIS and open approaches to TLIF. Specifically we sought to compare the two approaches with respect to (1) the time required to perform a discectomy and the number of endplate violations; (2) the percentage of disc removed; and (3) the anatomic location where residual disc would remain after discectomy. METHODS: Forty lumbar levels (ie, L1-2 to L5-S1 in eight fresh cadaver specimens) were randomly assigned to open and MIS groups. Both surgeons were fellowship-trained spine surgeons proficient in the assigned approach used. Time required for discectomy, endplate violations, and percentage of disc removed by volume and mass were recorded for each level. A digital imaging software program (ImageJ; US National Institutes of Health, Bethesda, MD, USA) was used to measure the percent disc removed by area for the total disc and for each quadrant of the endplate. RESULTS: The open approach was associated with a shorter discectomy time (9 versus 12 minutes, p = 0.01) and fewer endplate violations (one versus three, p = 0.04) when compared with an MIS approach, percent disc removed by volume (80% versus 77%, p = 0.41), percent disc removed by mass (77% versus 75%, p = 0.55), and percent total disc removed by area (73% versus 71%, p = 0.63) between the open and MIS approaches, respectively. The posterior contralateral quadrant was associated with the lowest percent of disc removed compared with the other three quadrants in both open and MIS groups (50% and 60%, respectively). CONCLUSIONS: When performed by a surgeon experienced with MIS TLIF, MIS and open approaches are similar in regard to the adequacy of disc space preparation. The least amount of disc by percentage is removed from the posterior contralateral quadrant regardless of the approach; surgeons should pay particular attention to this anatomic location during the discectomy portion of the procedure to minimize the likelihood of pseudarthrosis.