Mechanical Complications in Adult Spinal Deformity Surgery: Can Spinal Alignment Explain Everything?

Area of Science:

• Spine surgery
• Orthopedic research
• Adult spinal deformity (ASD)

Background:

• Adequate sagittal alignment is crucial for favorable outcomes in ASD surgery.
• Mechanical complications in ASD are often linked to postoperative spinal alignment.

Purpose of the Study:

• To evaluate the predictive accuracy of the Global Alignment and Proportion (GAP) score, SRS-Schwab score, and Roussouly theoretical apex of lordosis for mechanical complications in adult spinal deformity (ASD).

Main Methods:

• Retrospective review of primary ASD cases undergoing deformity correction.
• Logistic regression and ROC curve analysis to assess the association between 6-week postoperative spinal alignment and mechanical complications.
• Evaluation of GAP score, SRS-Schwab score, Roussouly apex, pelvic tilt (PT), and sagittal vertical axis (SVA).

Main Results:

• The GAP score showed no significant discriminant ability (AUC = 0.53).
• The SRS-Schwab sagittal modifier score demonstrated a modest predictive value for mechanical complications (AUC = 0.67, P = 0.008).
• Pelvic tilt (PT) and sagittal vertical axis (SVA) at 6 weeks postoperatively were significantly associated with later mechanical complications (P = 0.03 and P = 0.01, respectively).
• The Roussouly theoretical apex of lordosis was not significantly associated with final outcomes (P = 0.47).

Conclusions:

• Mechanical failure in ASD is complex and likely multifactorial, not solely attributable to alignment measures.
• The GAP score should be used cautiously as it may not reliably predict mechanical failure across all populations.
• Future research should explore etiology, surgical technique, and patient factors to develop a more universal predictive score for ASD.