Risk factors for rod fractures in circumferential minimally invasive surgery using multi-rod constructs for adult spinal deformity

<p>Purpose: We investigated risk factors for rod fractures (RFs) in correction surgery using extreme lateral interbody fusion (XLIF), percutaneous pedicle screws (PPSs), and multi-rod constructs for adult spinal deformity (ASD).</p><p>Methods: One hundred and two ASD patients underwent correction surgery with XLIF, PPS, and multi-rod constructs between 2018 and 2020 and were followed up for a minimum of 24 months. In all patients, the range of fixation was from the lower thoracic spine to the pelvis. The mean age of patients was 72.1 years, and the mean follow-up period was 54 months. Three rods of 5.5 mm titanium alloy were used in all surgeries. The percentage of RF, the timing of RF, and RF levels were investigated, and various pre- and postoperative parameters were compared between the RF group (RF group) and the group without RF (non-RF group).</p><p>Results: Thirteen patients experienced RF. The RF levels were L3/4 in one patient, L4/5 in nine patients, and L5/S1 in three patients. Of the nine patients with RF at L4/5, two patients experienced RF after bone fusion. Of the 13 patients who experienced RF, seven patients experienced anterior longitudinal ligament (ALL) rupture. There were no significant differences in age, gender, rod material, rod diameter, and number of rods between the two groups. Patients in the RF group had significantly larger pre- and post-operative PI, pre- and post-LLIF, post-operative PI-LL, pre- and post-LLIF 2/3 PI-LLL, LLL change with PPS (PPSΔLLL), and postoperative PT. Patients in the RF group had significantly smaller preoperative LLL and preoperative TK. Multivariate analysis included seven independent variables with P<0.01, namely pre- and postoperative PI, postoperative PI-LL, pre- and post-LLIF 2/3 PI-LLL, PPSΔLLL, and ALL rupture. PPSΔLLL and ALL rapture were detected as risk factors for RF, and the cut off value for PPSΔLLL was 8 degrees in the ROC analysis.</p><p>Conclusion: PPSΔLLL and ALL rapture were identified as risk factors of RF in circumferential minimally invasive surgery with multi-rod constructs for ASD.</p>