Predicting postoperative imbalance in adult spinal deformity staged surgery using predictive thresholds

Area of Science:

• Orthopedic Surgery
• Spinal Deformity Correction
• Adult Spinal Deformity (ASD)

Background:

• Two-stage surgical approaches are increasingly adopted for adult spinal deformity (ASD) correction to mitigate surgical risks.
• The distinct contributions of lateral lumbar interbody fusion (LLIF) and posterior column osteotomy/posterior spinal fusion (PCO/PSF) in staged ASD correction require further elucidation.

Purpose of the Study:

• To evaluate the individual roles of LLIF and PCO/PSF in achieving deformity correction in staged ASD surgery.
• To establish predictive thresholds for spinal imbalance to guide surgical planning and improve patient outcomes.

Main Methods:

• A retrospective analysis of 151 adult spinal deformity patients undergoing staged LLIF and PCO/PSF surgeries.
• Radiographic parameters including PI-LL mismatch, pelvic tilt, C7 sagittal vertical axis (SVA), and coronal Cobb angle were assessed preoperatively, post-LLIF, post-PCO/PSF, and at two-year follow-up.
• Patient-reported outcomes using the Oswestry Disability Index (ODI) and Scoliosis Research Society-22 (SRS-22) questionnaire were evaluated.

Main Results:

• Posterior column osteotomy/posterior spinal fusion (PCO/PSF) contributed more significantly to the overall correction of PI-LL mismatch (64.5%), pelvic tilt (60.6%), C7 SVA (54.3%), and coronal Cobb angle (66.9%).
• Significant improvements in ODI and SRS-22 scores were observed at the two-year follow-up.
• Predictive thresholds for postoperative imbalance were identified: M-SVA 75.3 mm, M-PI-LL 32.5°, and M-PT 35.5°.

Conclusions:

• The second stage, PCO/PSF, plays a more substantial role in correcting spinal deformities compared to the initial LLIF.
• Established predictive thresholds can aid surgeons in optimizing planning for staged ASD correction, aiming to reduce postoperative imbalance and enhance functional outcomes.