Spine - 2026-04-15 - Journal Article
How Does the Lordosis Apex, Lordosis Arcs, and Inflection Point According to Roussouly Predict Outcomes After Adult Spinal Deformity Surgery?
Jain H, Sarikonda A, Chanbour H, Younus I, Zeoli T, Wegner AM, Abtahi AM, Stephens BF, Zuckerman SL
Topics
Key Takeaway
In 202 ASD patients, cranial lordotic apex shift (occurring in 71% of apex-change cases) was associated with 6.3° less L4-S1 lordosis and greater 2-year back pain, while a preoperative inflection point outside T12/L1 increased spinopelvic complication risk by OR 2.04 (inverse of OR=0.49).
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Summary
This study evaluated whether Roussouly-based lordosis parameters—apex location, upper/lower arc vertebral count, and inflection point—predict mechanical complications, reoperations, and PROMs after ASD surgery with ≥5-level fusion. Postoperatively, 61.9% of patients had an apex shift, 71% cranially, which correlated with reduced L4-S1 lordosis (6.3° decrease) and higher 2-year NRS back pain scores. A preoperative inflection point outside T12/L1 was independently associated with spinopelvic complications (38.8% vs. 22.1%, OR=0.49), and postoperative T12/L1 inflection point was associated with higher radiographic PJK rates (56.0% vs. 40.8%, OR=1.96).
Key Limitation
Retrospective single-center design prevents determination of whether cranial apex shift and inflection point abnormalities are causes of poor outcomes or markers of more severe or rigid deformity that was inadequately correctable.
Original Abstract
STUDY DESIGN
Retrospective cohort study.
OBJECTIVES
In adult spinal deformity (ASD) surgery patients, we sought to: (1) report preoperative/postoperative lordosis apex, number of vertebrae in lower/upper lordosis arc, and inflection point, and (2) determine their impact on postoperative outcomes.
SUMMARY OF BACKGROUND DATA
The impact of lordosis apex, arcs, and inflection point on postoperative outcomes remains unclear.
MATERIALS AND METHODS
ASD patients (2009-2021) with ≥5-level fusion, sagittal/coronal deformity, and ≥2-year follow-up were analyzed. Primary exposures were pre/postoperative lordosis apex, vertebrae in upper/lower arcs, and inflection point. Outcomes included mechanical complications, reoperations, patient-reported outcome measures, and postoperative alignment. Multivariable regression controlled for age, body mass index (BMI), and comorbidities.
RESULTS
Among 202 patients (mean age: 64.4±16.7 yr, 77.2% females): Lordosis apex: the most common preoperative apex was L5 (32.7%), followed by L4 (20.3%). Postoperatively, 125 (61.9%) had an apex change-89 (71%) cranially-directed and 36 (29%) caudally-directed. Cranially shifts led to 6.3±14.1° decrease in L4-S1 lordosis, caudal change showed 3.7±13.9° increase ( P =0.002). Lordosis arcs: mean vertebrae in lower and upper lordotic arcs were 1.4±1.0 and 2.6±1.1, which postoperatively increased by 0.2±0.8 and 0.5±1.5 ( P =0.043), respectively. Greater increase in upper-arc vertebrae correlated with higher two-year numeric rating scale (NRS)-back pain (ρ=0.020, P =0.030; β=0.40, 95% CI: 0.03-0.78, P =0.036). Inflection point: preoperatively, 86 (42.6%) patients had a T12/L1 inflection point, of which 72 (83.7%) remained at T12/L1 postoperatively. Of 116 (57.4%) patients with an inflection point above/below T12/L1, 59 (50.9%) transitioned to T12/L1 postoperatively. Preoperative inflection point above/below T12/L1 was linked to more spinopelvic complications (38.8% vs . 22.1%, P =0.012; OR=0.49, 95% CI: 0.25-0.94, P =0.033). Postoperative T12/L1 inflection was associated with higher radiographic proximal junctional kyphosis (PJK) (56.0% vs . 40.8%, P =0.041; OR=1.96, 95% CI: 1.03-3.72, P =0.040).
CONCLUSION
After ASD surgery, most patients showed a cranial lordotic apex shift, with a greater increase in upper than lower arc vertebrae-highlighting the difficulty of restoring lordosis caudally. Cranial apex shift was associated with smaller L4-S1 lordosis and greater two-year back pain, while a preoperative inflection point outside T12/L1 increased the risk of spinopelvic complications. Incorporation of Roussouly principles may help spine surgeons improve outcomes and mitigate complications.