Explaining Mechanical Failures in Adult Spinal Deformity Patients With Pelvic Incidence-Lumbar Lordosis Within 10°:...

Area of Science:

• Spine surgery
• Orthopedic surgery
• Adult spinal deformity

Background:

• Pelvic incidence-lumbar lordosis (PI-LL) is a common alignment goal in adult spinal deformity (ASD) surgery.
• However, PI-LL does not account for the distribution of lordosis.
• The Roussouly classification categorizes distinct sagittal spinal shapes.

Purpose of the Study:

• To evaluate mechanical complication rates in ASD patients with PI-LL ≤10° after spinal fusion to the pelvis.
• To determine the postoperative Roussouly type in these patients.
• To assess if the Roussouly classification can explain the occurrence of complications.

Main Methods:

• Retrospective cohort study of ASD patients (2009-2021) with ≥5-level fusion to the pelvis and 2-year follow-up.
• Independent variables included postoperative PI-LL ≤10°, Roussouly type (current and theoretical), lumbar apex, inflection point, and pelvic retroversion.
• Primary outcome was mechanical complications.

Main Results:

• 60% of 53 patients with PI-LL ≤10° experienced mechanical complications; 28% required reoperation.
• Roussouly mismatch was more frequent in patients with mechanical complications (78%) and significantly higher in those with proximal junctional failure (PJK/F) (86%).
• Patients with mechanical complications were less likely to have a postoperative lordosis apex at L4/5 (6% vs. 33%).

Conclusions:

• A PI-LL ≤10° goal is associated with high mechanical complication rates (60%) in ASD patients.
• Roussouly classification provides additional insight, with mismatch being more common in patients experiencing complications, particularly PJK/F.
• The Roussouly classification appears more valuable than PI-LL alone for predicting and potentially avoiding complications in ASD surgery.