Utility of Intraoperative Mechanical Hinging in Minimally Invasive Approach to Transforaminal Lumbar Interbody Fusion in the Correction and Maintenance of Sagittal Alignment

Introduction: Transforaminal lumbar interbody fusion (TLIF) with interbody cages is understood to have a poor restoration of lordosis in the literature. Intraoperative flexion using a hinged operating table to increase interbody spacing for cage placement followed by intraoperative extension to facilitate closure may allow a greater degree of sagittal alignment to be achieved. We add to the literature a series of TLIF cases using a minimally invasive surgical (MIS) approach with the use of the ProAxis Table.

Methods: We identified patients from 2018 to 2024 who underwent MIS-TLIF surgery from a single-surgeon database. Clinical variables collected included body mass index (BMI) and hemoglobin A1C at time of surgery. Surgical variables included levels of fusion. Radiographic variables included segmental lordosis of instrumented levels at preoperative, intraoperative, and postoperative timepoints. Post-surgical correction and 6-month correction were computed as outcome variables. Clinical and radiographic findings were analyzed with standard statistical approaches.

Results: 202 patients met inclusion criteria. The mean BMI was 27.6 kg/m2 and the mean hemoglobin A1C was 5.8. The mean preoperative SL was 14.3 degrees, the mean intraoperative SL was 20.1 degrees, the mean postoperative SL was 19.7 degrees, and the mean 6-month follow-up SL was 18.5 degrees. The mean post-surgical correction was 5.4 degrees, and the mean 6-month correction was 4.8 degrees. A significant difference was observed in lordosis between preoperative and postoperative (p < 0.0001) and between preoperative and 6-month scans (p < 0.0001). In L4/L5-TLIF a moderate negative correlation was found between preoperative SL and postoperative correction (R = -0.51) and a low negative correlation was found between preoperative SL and 6-month correction (R= -0.40). In L5/S1-TLIF, moderate negative correlations were found between preoperative SL and postoperative correction (R = -0.51) and between preoperative SL and 6-month correction (R= -0.57). In L3/L5-TLIF, a low negative correlation was found between preoperative SL and postoperative correction (R = -0.43).

Conclusion : Our study shows that the use of an intraoperative hinging surgical table during MIS-TLIF with SPO can effectively lead to an increase in and the maintenance of SL correction when compared to the typical sagittal alignment expected by conventional MIS-TLIF in the literature.