Minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) is a surgical technique that appears to minimize iatrogenic paraspinal muscle injury thereby enhancing early recovery. In 2010, Villavicencio et al. compared the outcomes of 63 open and 76 MIS TLIF patients, and they reported comparable good clinical outcomes between the two groups, but with a higher neurological complication rate in the MIS group. In a meta-analysis by Wu et al. of 16 open TLIF studies consisting of 716 patients and eight MIS TLIF studies consisting of 312 patients, the authors reported similar fusion and complication rates in both groups. Likewise, multiple studies in the literature support the comparable long-term clinical outcomes between open and MI-TLIF patients.

Muscle injury is one of the points of interest that differentiates these two procedures. Dave et. al. showed that the mean reduction in lean muscle mass of multifidus muscle was greater in open TLIF compared to MIS-TLIF. However, Min et. al. at 1-year follow-up showed that there was less change in fat infiltration percentage and cross-sectional area in the MI-TLIF but there was no significant difference between the two groups. Although percutaneous pedicle screw fixation had positive effects on postoperative trunk muscle performance, clinical outcomes were not significantly different in areas of pain score, JOA score, and patient’s opinion regarding the outcome of the surgery as concluded by Kim and his colleagues. All the above studies evaluated the muscle damage using postoperative MRI imaging at different time intervals. The muscle damage that has been quantified using late postoperative MRI will be biased because of different rehabilitation protocols and variability between individuals, which is unavoidable. However, no study has evaluated or compared the biochemical muscle damage between the open and MI-TLIF groups. We hypothesize that muscle damage in minimally invasive techniques, using retractors through small incisions causes an increase in surrounding muscle pressure in the immediate postoperative period and hence the increased muscle damage compared to the open TLIF procedure.