Recent clinical evidence suggests that preoperative pelvic morphology significantly influences the success of adult spinal deformity correction. A key study by Ritchey NP et al. has identified that pelvic incidence (PI) is a major determinant of the proximal junctional failure risk in patients undergoing long-segment spinal fusion. Understanding these parameters allows surgeons to better tailor surgical plans and mitigate mechanical complications.

The Relationship Between Pelvic Incidence and Failure Rates

The retrospective analysis involved over 200 patients who underwent long-segment thoracolumbar fusions with pelvic fixation. Researchers dichotomized the cohort into lower and higher PI groups based on a mean value of 55°. Notably, patients with higher PI demonstrated significantly lower rates of proximal junctional failure (PJF) compared to those in the lower PI group (9% vs 21%). This finding suggests that a more robust pelvic base may provide better compensatory mechanisms for the stresses placed on the upper instrumented vertebra (UIV).

Identifying Factors That Increase Proximal Junctional Failure Risk

Multivariate analysis within the study highlighted several independent predictors of mechanical failure. Besides lower PI, researchers found that choosing a lower thoracic UIV and having a previous reoperation status significantly elevated the proximal junctional failure risk. Specifically, lower thoracic UIV placement was associated with an odds ratio of 6.5, whereas reoperation status showed a staggering odds ratio of 23.8. Furthermore, Bayesian mixed-effects modeling confirmed these results, emphasizing that lower PI acts as a primary morphological risk factor that surgeons must address during preoperative planning.

In patients with an upper thoracic UIV, the rate of failure was remarkably lower in those with higher PI (0% vs 15%). Consequently, integrating PI measurements into the Schwab criteria for deformity correction could help in selecting the appropriate fusion levels. By recognizing these anatomical predispositions early, clinicians can implement preventive strategies such as the use of transverse process hooks or specific rod contouring to redistribute junctional stress.

Frequently Asked Questions

What is the clinical significance of pelvic incidence in spinal surgery?

Pelvic incidence is a fixed anatomical parameter that dictates the ideal lumbar lordosis for a patient. It is essential for determining the spinopelvic correction needed to achieve global sagittal balance and minimize mechanical strain at the fusion boundaries.

How does a lower pelvic incidence increase proximal junctional failure risk?

Patients with lower PI often require less lumbar lordosis. However, if the surgical correction does not perfectly match their unique anatomy, the resulting stiffness in the long-segment construct can lead to excessive stress and structural failure at the proximal segments.

Can surgical planning reduce the risk of PJF?

Yes. By analyzing preoperative PI and selecting a more proximal UIV (upper thoracic rather than lower thoracic) in high-risk patients, surgeons can significantly decrease the likelihood of junctional pathologies and subsequent reoperations.

Disclaimer: This content is for informational and educational purposes only and does not constitute medical advice. Refer to the latest local and national guidelines for clinical practice.

References

1. Ritchey NP et al. Use of pelvic incidence to predict proximal junctional failure in long-segment spinal fusion. J Neurosurg Spine. 2026 Apr 17. doi: 10.3171/2025.11.SPINE251010. PMID: 41996710.


2. Noureldine MHA et al. Pelvic Incidence as a Predictor of Proximal Junctional Failure in Patients Undergoing Anterior Column Realignment. World Neurosurg. 2024 Feb;182:e772-e779.


3. Yagi M et al. Proximal Junctional Failure in Adult Spinal Deformity Surgery: An In-depth Review. Neurospine. 2023 Sep;20(3):876-889.