Hidden and overall haemorrhage following minimally invasive and open transforaminal lumbar interbody fusion

BACKGROUND: Hidden haemorrhage has been proved to be significant in joint surgery. However, when referring to lumbar interbody fusion, it is often ignored because of its invisibility. This randomized controlled study aimed to calculate and compare hidden haemorrhage following minimally invasive and open transforaminal lumbar interbody fusion (MIS-TLIF and open TLIF). Meanwhile, its clinical significance was also analyzed. MATERIALS AND METHODS: A total of 41 patients were included in this study, then they were randomized to receive MIS-TLIF or open TLIF, 21 and 20, respectively. For each case, total volume loss of red blood cell (RBC) was calculated by Gross' formula based on perioperative haematocrit change, then perioperative visible volume loss of RBC was calculated through haemorrhage volume and weight. After deducting it from total volume loss of RBC, hidden volume loss of RBC was obtained. Absolute amount of hidden haemorrhage and its ratio upon total haemorrhage, as well as indicators assessing clinical outcomes, including visual analogue scale (VAS) for back and leg, Oswestry disability index (ODI), interbody fusion rate and complication incidence were compared and analyzed. RESULTS: Mean hidden volume loss of RBC in MIS-TLIF was significantly reduced compared with open TLIF (166.7 versus 245.6 ml). Besides, both mean total and visible volume loss of RBC in MIS-TLIF were also statistically less than those in open TLIF (355.3 versus 538.6 ml; 188.6 versus 293.0 ml). While mean ratio of hidden haemorrhage upon total haemorrhage was 46.7% for MIS-TLIF and 44.5% for open TLIF, respectively, showing no statistical significance. At one week postoperatively, more significant improvements of VAS for back and leg, as well as ODI were seen in MIS-TLIF compared with open TLIF. While at final follow-up of at least 2 years, all parameters continued to improve and revealed no statistical difference between both surgeries. Similar interbody fusion rate and complication incidence were observed in both series. CONCLUSIONS: Besides reduced visible haemorrhage and improved clinical outcomes, MIS-TLIF also owns the superiority of less hidden haemorrhage, offering another advantage over open TLIF. LEVEL OF EVIDENCE: Level II.