How to Reduce the Risk of Mechanical Failures in Adult Deformity Surgery: Comparing GAP Score and Roussouly Type Restoration

Global Spine Journal 2025, Vol. 0(0) 1–15

DOI: 10.1177/21925682251328285

This study investigates the predictors of mechanical failure in adult spinal deformity surgery, highlighting the significance of the GAP score and Roussouly type restoration in minimizing complications. A proper post-operative GAP Score and spinal alignment restoration are crucial for reducing mechanical failure rates.

Study Design and Methods

• Retrospective cohort study with a 5-year follow-up on adult spinal deformity cases.

• Inclusion criteria: Patients over 18, with at least 4 vertebrae fused.

• Data collected: Demographic, surgical, spinopelvic parameters, and complications.

Key Findings

• Mechanical Complications: Revision surgery rate was 40.6%.

• Higher post-operative GAP scores linked to increased junctional failure risk.

• Roussouly Type Restoration: Failure to restore original type increases mechanical failure risk.

Predictive Analysis

• GAP Score and Roussouly Type are top predictors for mechanical failure.

• Gradient Boosting model showed high predictive accuracy (ASE 0.073).

• Kaplan-Meier Analysis: Higher GAP scores linked to earlier junctional failures.

Recommendations

• Surgical Planning: Restore original Roussouly type and achieve proper lumbar lordosis.

• Avoid Pelvic Retroversion: Ensure proper global balance.

Statistical Analysis

• Logistic regression confirmed GAP score and Roussouly type as significant predictors.

• ROC Curves: Moderate association between GAP score and revision surgery need.

Limitations

• Retrospective design with potential selection bias.

• Asymmetrical sample size of GAP score groups.

Level of Evidence

3 retrospective cohort study