Is a postoperative mismatch between theoretical and actual Roussouly lordosis apex associated with worse outcomes following adult spinal deformity surgery?
Neurosurgery Resident Vanderbilt University Medical Center Vanderbilt University Medical Center Nashville, TN, US
Disclosure(s):
Tyler Zeoli, MD: No financial relationships to disclose
Introduction: In patients undergoing ASD surgery, we sought to determine the impact of a mismatched lordosis apex to the corresponding theoretical Roussouly apex on: 1) mechanical complications, 2) reoperations, and 3) 2-year patient-reported outcome measures (PROMs).
Methods: A single-institution, retrospective cohort study was performed for patients undergoing ASD surgery from 2011-21. Inclusion criteria were: ≥5-level fusion, sagittal/coronal malalignment, instrumented to the ilium, and 2-year follow-up. The primary exposure variable was a difference in lordosis apex compared to the ideal theoretical Roussouly apex, divided into two groups: 1) Type 1/2 = PI < 50° with appropriate apex at L4, L4/5, L5, and 2) Type 3/4 = PI>50° with appropriate apex at L3/4, L3, L2/3 disc. Postoperative outcomes included mechanical complications, reoperations, and 2-year PROMs. Multivariable analysis controlled for age, BMI, and osteoporosis as defined by T-score <-2.5.
Results: In 170 patients undergoing ASD surgery and instrumented to the pelvis, mean age was 68.7±11.4, 40 (23.5%) were males, and instrumented levels was 10.5±3.0. Theoretical Roussouly was Type 1/2 (N=52, 30.1%) and Type 3/4 (N=118, 69.9%). Roussouly 1-2: A mismatched apex was found in 14 (7.6%) patients, including L1 (N=1, 7.1%), L2 (N=1, 7.1%), L3 (N=5, 35.7%), L3/4 disc (N=7, 50.0%). No significant association was found between patients with a mismatched apex and mechanical complications, reoperations, or PROMs. Roussouly 3-4: A mismatched apex was found in 69 (37.3%) patients, including L4 (N=39, 56.5%), L4/5 disc (N=16, 23.2%), and L5 (N=14, 20.3%). No significant association was found between patients with a mismatched apex and mechanical complications, reoperations, or PROMs.
Conclusion : In patients undergoing ASD surgery, a mismatched lordosis apex was significantly more common in Roussouly Type 3/4 patients than Type 1/2. However, failure to achieve a postoperative apex corresponding to the ideal theoretical Roussouly apex did not have a significant impact on postoperative complications and PROMs. Lumbar apex may not be as useful a predictor of outcomes as other Roussouly principles, such as magnitude of lower lordosis arch and pelvic retroversion.