INFLUENCE OF HIGH PELVIC INCIDENCE ON OPERATIVE DIFFICULTY IN PATIENTS TREATED SURGICALLY FOR DEGENERATIVE LUMBAR SPONDYLOLISTHESIS

The objective of this study was to determine if the degree of pelvic incidence (PI) influenced the difficulty of surgery in patients undergoing treatment for degenerative spondylolisthesis. This is a retrospective cohort study of patients enrolled between 2015 - 2021 in the Canadian Spine Outcomes and Research Network (CSORN) multi-centred prospective study on the assessment and management of DLS who underwent decompression or decompression and fusion, and who had baseline radiographic measures. Patients were divided into two groups based on a preoperative PI of >60° or < 6 0°. Baseline demographic, clinical, radiographic, and procedure factors were compared between the groups stratified by procedure type (decompression vs. decompression and fusion). Of the patients that had a decompression alone, 85 had PI 60°. Demographic factors, chief complaint, grade of spondylolisthesis, and preoperative patient-rated outcome measures (PROM) were similar between the two groups. Blood loss was similar in both groups, but patients with a high PI had significantly longer operative times (96 minutes vs. 82 minutes). Of the patients that had a decompression and fusion, 193 had PI 60°. Demographics and preoperative PROMs were similar between the groups except more females were in the high PI group (71% vs 60%). Patients in the high PI group were also more likely to have grade II spondylolisthesis (41% vs. 26%) and were less likely to have minimally invasive surgery (16% vs. 29%). Operating time was similar between groups; however, blood loss was significantly increased in the patients that had a high PI (M = 400 vs. 300 mL). Intraoperative complications and length of stay were not different between groups, regardless of procedure. Overall, this study demonstrates that high PI is associated with increased operative time and blood loss, indicating there may be unique challenges with this population. Technical difficulties may arise due to larger exposures required and challenging angles seen in patients with a high PI. Thus, operative difficulties should be anticipated when treating patients with a PI >60°.