Commentary on “Comparison of minimally invasive and open TLIF outcomes with more than seven years of follow-up”

Transforaminal lumbar interbody fusion (TLIF) can be performed with open or minimally invasive (MI) surgical techniques. Most studies comparing the two approaches focus on short-term outcomes. The paper by Hong et al. [1] was a retrospective consecutive cohort study of short and long-term clinical outcomes of open versus MI TLIF.

Patients with degenerative conditions underwent either open or MI TLIF by a single surgeon (open 2011-2012, MI 2013-2014) and had ≥ 7 years of follow-up. Patients who presented with fracture, history of metastasis, infection and those on medication for rheumatoid arthritis or ankylosing spondylitis with bony changes were excluded.

Multiple perioperative parameters were assessed. The Oswestry Disability Index (ODI) was used to track disability and visual analog scale (VAS) for leg pain. Static and dynamic radiography, as well as computed tomography (CT), were performed and followed for union status and adjacent segment degeneration (ASD) which was categorized as radiographic (R-ASD), symptomatic (S-ASD), as well as operative (O-ASD).

Of an initial 118 patients, 17.8% were lost to follow up. In total, 97 patients were included in the study (open = 42; MI = 55). Demographics, comorbidities, degenerative condition, and levels addressed did not differ significantly between the groups.

Perioperatively, the MI group had lesser mean operative time, drainage, transfusion, days to ambulation, and hospital length of stay compared to those who underwent open TLIF. Both procedures resulted in significant improvement in ODI and VAS that remained significant through the follow-up and were without differences between the groups.

Union status was not different between the groups (90.5% for open and 85.5% for MI). Notably, ASD measures increased annually in both groups and were significantly different as of 5-year follow-up with the open group showing a significantly greater incidence of R-ASD (35.7% versus 21.8%) and S-ASD (28.6% versus 14.5%). However, the groups were not statistically different with regard to O-ASD at seven years (11.9% versus 7.2%).

When interpreting their findings, the authors concluded that MI TLIF had advantages over open TLIF with regard to peri-operative outcomes. This finding is not unexpected, as there is less surgical disruption required, and is consistent with prior studies. The longer-term outcomes are of particular interest. The improved R-ASD and S-ASD associated with MI TLIF may be related to decreased effect on neighboring facets. Also, it is of significant note that fusion rate was not compromised with the MI TLIF (fusion rates not found to be different between the groups).

With the advantages of MI TLIF reported by the authors in their consecutive cohorts, it must be balanced by noting that the patient reported outcome measures, VAS and ODI, were not different between the groups. In addition, although there were differences in R-ASD and S-ASD, this did not translate to differences in O-ASD in the time studied.

There are limitations to the study. As a single surgeon consecutive cohort study, the findings may not be fully generalizable. There were mixed characteristics / degenerative conditions in both groups, although the groups were overall similar. Additionally, while the groups were of moderate size, the numbers may have limited the power to detect lesser differences.

Overall, the reviewed study highlights favorable perioperative outcomes and longer-term radiographic as well as symptomatic ASD for those undergoing MI versus open TLIF, while achieving similar clinical outcomes and fusion rates. The study adds to the literature with longer term follow up of those undergoing MI TLIF in comparison to open TLIF in defined cohorts and supports the practice.

Financial disclosures/conflicts of interests

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