Distinct fusion intersegmental parameters regarding local sagittal balance provide similar clinical outcomes: a comparative study of minimally invasive versus open transforaminal lumbar interbody fusion

BACKGROUND: Most contemporary studies suggested that intersegmental parameters including disc height and local lordosis contribute to the sagittal balance of fused lumbar. Although similar clinical outcomes following MIS- and Open-TLIF were reported essentially at the early postoperative time, the comparison of local balance variables after these two different techniques was lack. The radiological differences maybe not relevant to the postoperative efficacy at an earlier post-operation stage. But during the long-term follow-up, the complications with regards to the sagittal imbalance might occur due to the distinct biomechanical properties of fusion level after MIS- and Open-TLIF. METHODS: The patients who underwent a single-level MIS- and Open-TLIF were reviewed retrospectively. The anterior disc height (ADH), posterior disc height (PDH), and segmental lordosis (SL) of the fusion segment were measured using recognition technical fluoroscopy. The mean disc height (MDH) was calculated by (ADH + PDH)/2. The relative DH was normalized by the anterior height of the upper vertebrae. The body mass index (BMI), the pain score of low back and leg visual analogue scale (VAS), Oswestry disability index (ODI), estimated blood loss, and hospital stay length was collected. RESULTS: A total of 88 patients undergoing a single-level TLIF (MIS and Open) were included. The pre- and post-operative ADH, PDH, MDH, and SL of MIS-TLIF group were 1.57 ± 0.33 cm, 0.79 ± 0.20 cm, 1.18 ± 0.21 cm, 7.36 ± 3.07 and 1.63 ± 0.30 cm, 1.02 ± 0.28 cm, 1.32 ± 0.24 cm, 10.24 ± 4.79 respectively. Whereas, the pre- and post-operative ADH, PDH, MDH, and SL of Open-TLIF group were 1.61 ± 0.40 cm, 0.77 ± 0.21 cm, 1.19 ± 0.24 cm, 9.05 ± 5.48 and 1.81 ± 0.33 cm, 0.98 ± 0.24 cm, 1.39 ± 0.24 cm, 12.34 ± 4,74 respectively. MIS- and Open-TLIF group showed no significant differences in low back VAS, leg VAS, and ODI both in pre-operation and post-operation (P > 0.05). The estimated blood loss and hospital stay length in the MIS-TLIF group were significantly lower than those in the Open-TLIF group (P < 0.05). CONCLUSION: MIS- and Open-TLIF provided similar clinical outcomes as the respect of low back VAS, leg VAS, and ODI. MIS-TLIF significantly reduced the blood loss and length of hospital stay though. The intervertebral parameters of DH and SL were both increased significantly, Open-TLIF group presented better sagittal balance in term of ADH and SL variables. The contrast investigation of intersegmental parameters may help the surgeons to figure out the further advantages of MIS-TLIF technique, and then better manage the rehabilitation and prevent the reoperation.