In this pseudo-randomized controlled trial, Shunwu et al. compared perioperative and medium term outcomes and complications between 30 patients undergoing traditional open TLIF and 32 patients undergoing minimally invasive TLIF. The authors should be applauded for conducting a comparative study of these two techniques in an effort to determine if there is a measurable clinical benefit for MIS-TLIF. Unfortunately, the answer to this difficult question remains elusive despite their strong effort. The MIS group had less blood loss, ambulated a couple of days sooner and stayed in the hospital a few days less than the open group, though it is difficult to interpret the clinical significance of these findings. In comparison to the time to ambulation and time to discharge to which we are accustomed in the United States, these authors report relatively long periods of time in bed and in the hospital for both groups. Given that the benefit of MIS is most likely in the very short term, it would have been useful if the authors provided more objective pain and function data over the first few weeks following surgery (i.e. amount of narcotic use, pain scale data, etc.). While they suggest a long-term functional benefit of MIS-TLIF, inspection of the ODI and VAS data reveal that the differences were quite small (i.e. 2-4 points on the ODI and less than 1 point on the VAS). In light of the fact that the open group had a baseline ODI that was 2 points higher than the MIS group, these differences—though statistically real—are not clinically meaningful. While the clinical benefit of MIS-TLIF remains questionable, the fact that there were no major and relatively few minor complications suggest that both procedures were safe in the hands of this surgeon. There were two cases of screw malposition in the MIS group (none that needed revision), supporting our suspicion that MIS-TLIF is technically more difficult.
So how can this paper assist us in balancing the risks and benefits of MIS-TLIF? It suggests that in experienced hands the complication rate of MIS-TLIF can be acceptably low. This technique might lead to a short term clinical benefit, though this was not rigorously examined in this study. Patients treated with MIS-TLIF probably have similar medium term functional outcomes as those treated in the traditional open manner. Investigators considering a future study on this topic should strive to reach the level of methodologic rigor employed by Arts et al. in their important RCT comparing open and tubular discectomy (1).
Read the accompanying commentary from Dr. Xiangqian, the senior author for this study. Let us know your thoughts on MIS techniques and how this paper will affect your practice.
1. Arts MP, Brand R, van den Akker ME, Koes BW, Bartels RH, Peul WC. Tubular discectomy vs. conventional microdiscectomy for sciatica: a randomized controlled trial. JAMA 2009;302:149-58.
Adam Pearson, MD, MS