Improved Surgical Correction Relative to Patient-Specific Ideal Spinopelvic Alignment Reduces Pelvic Nonresponse for Severely Malaligned Adult Spinal Deformity Patients.

Background: Persistent pelvic compensation following adult spinal deformity (ASD) corrective surgery may impair quality of life and result in persistent pathologic lower extremity compensation. Ideal age-specific alignment targets have been proposed to improve surgical outcomes, though it is unclear whether reaching these ideal targets reduces rates of pelvic nonresponse following surgery. Our aim was to assess the relationship between pelvic nonresponse, age-specific alignment, and lower-limb compensation following surgery for ASD.
Methods: Single-center retrospective cohort study. ASD patients were grouped: those who did not improve in Scoliosis Research Society-Schwab pelvic tilt (PT) modifier (pelvic nonresponders [PNR]), and those who improved (pelvic responders [PR]). Groups were propensity score matched for preoperative PT and assessed for differences in spinal and lower extremity alignment. Rates of pelvic nonresponse were compared across patient groups who were undercorrected, overcorrected, or matched age-specific postoperative alignment targets.
Results: A total of 146 surgical ASD patients, 47.9% of whom showed pelvic nonresponse following surgery, were included. After propensity score matching, PNR ( N = 29) and PR ( N = 29) patients did not differ in demographics, preoperative alignment, or levels fused; however, PNR patients have less preoperative knee flexion (9° vs 14°, P = 0.043). PNR patients had inferior postoperative pelvic incidence and lumbar lordosis (PI-LL) alignment (17° vs 3°) and greater pelvic shift (53 vs 31 mm). PNR and PR patients did not differ in rates of reaching ideal age-specific postoperative alignment for sagittal vertical axis (SVA) or PI-LL, though patients who matched ideal PT had lower rates of PNR (25.0% vs 75.0%). For patients with moderate and severe preoperative SVA, more aggressive correction relative to either ideal postoperative PT or PI-LL was associated with significantly lower rates of pelvic nonresponse (all P < 0.05).
Conclusions: For patients with moderate to severe baseline truncal inclination, more aggressive surgical correction relative to ideal age-specific PI-LL was associated with lower rates of pelvic nonresponse. Postoperative alignment targets may need to be adjusted to optimize alignment outcomes for patients with substantial preoperative sagittal deformity.
Clinical Relevance: These findings increase our understanding of the poor outcomes that occur despite ideal realignment. Surgical correction of severe global sagittal deformity should be prioritized to mitigate these occurrences.
Competing Interests: Declaration of Conflicting Interests: Peter G. Passias reports other financial or material support from Allosource; research support from the Cervical Scoliosis Research Society; paid presenter or speaker for Globus Medical and Zimmer; paid consultant for Medicrea, Royal Biologics, SpineWave, and Terumo. Daniel Sciubba reports paid consultant for Baxter, DuPuy Synthes, K2M, Medtronic, Nuvasive, and Stryker. Themistocles Protopsaltis reports IP royalties from Altus; paid consultant for Globus Medical, Medicrea, Nuvasive, and Stryker; stock or stock options from Spine Align and Torus Medical. Aaron J. Buckland reports paid consultant for Nuvasive and Stryker. Frank J. Schwab reports research support from DePuy Synthes; paid consultant for Globus Medical, K2M, Medicrea, Medtronic, and Zimmer; paid presenter or speaker for Globus Medical, K2M, Medtronic Sofamor Danek, and Zimmer; IP royalties from K2M, Medtronic Sofamor Danek, and Zimmer; research support form Nuvasive and Stryker; board or committee member for the Scoliosis Research Society and the International Spine Society Group. Renaud Lafage reports stock or stock options from Nemaris. Virginie Lafage reports paid presenter or speaker for DePuy Synthes and The Permanente Medical Group; editorial or governing board for European Spine Journal; paid consultant for Globus Medical; IP royalties for Nuvasive; and board or committee member for the International Spine Study Group and the Scoliosis Research Society. The remaining authors have no disclosures.
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