2024 Volume 15 Issue 7 Pages 1002-1007
Purpose: We investigated the amount of rod bending back in circumferential minimally invasive surgery (CMIS), multi-rod using lateral lumbar interbody fusion (LLIF), and percutaneous pedicle screw (PPS) for adult spinal deformities (ASDs).
Methods: The subjects were 31 consecutive ASD patients who underwent CMIS-multi rod at our hospital since July 2022. In all cases, the fixation range was from the lower thoracic vertebrae to the pelvis. Three 5.5 mm titanium alloy rods were used in all cases. The lumbar lordosis (rod-LL), lower lumbar lordosis (rod-LLL), and thoracic (T10 to L1) kyphosis angle (rod-TK) of the rod before and after rod application were measured. Differences between the angles before and after rod application were defined as the amount of rod bending back. We also investigated the correlation between the amount of rod-LL bending back and various parameters.
Results: The average age was 75.7 years (5 males and 26 females). The Upper Instrumented Vertebra (UIV) was at T8 in one case, T9 in eight cases, T10 In 22 cases, and the LIV in the pelvis in all cases. The average various parameters were PI 47.6, LL −5.2° preoperatively and 43.7° postoperatively, and PI-LL 52.3° preoperatively and 3.9° postoperatively. Before and after rod application, rod-LL changed from 47.5° to 37.7°, rod-LLL changed from 29.0° to 23.1°, and rod-TK changed from 26.8° to 22.0°, and the amount of rod bending back was 9.8°, 5.9°, and 4.7°, respectively. The parameter with the highest correlation with rod-LL bending back was the post-LLIF PI-LL, with a correlation coefficient of 0.68. The approximate formula was rod-LL bending back = 0.47 × (PI-LL after LLIF) +8.2.
Conclusion: We investigated the amount of rod bending back in CMIS-multi-rod for ASD. The average degree of rod-LL bending back was 9.8°, and PI-LL after LLIF had the highest correlation, with a correlation coefficient of 0.68. The approximate formula is rod-LL bending amount = 0.47 × (PI-LL after LLIF) +8.2.
