Does pelvic incidence tell us the risk of proximal junctional kyphosis in adult spinal deformity surgery?

Advantages of Combined Use of Claw Hooks and Sublaminar Wires as the Upper Foundation of Long Fixation from the Thoracic Spine to the Pelvis in Osteoporotic Cases: A Finite Element Analysis of Proximal Junction Stress

Introduction

This study aimed to compare the biomechanical stress at the proximal junctional aspect between the conventional pedicle screw (PS) fixation (PSF) and the low PS density fixation (LPF) method.

Methods

This study involved 10 patients, half of whom have non-osteoporosis and the other half have osteoporosis. We made two types of intact models (one is from the upper thoracic-to-pelvis model, and the other is from the lower thoracic-to-pelvis model). From the intact models, we constructed two kinds of fusion models: (1) PSF and (2) LPF. The LPF method was as follows: The claw hooks (the combination of the down-going transverse process hooks and facet hooks) were set at the upper instrumented vertebra (UIV) and sublaminar wires at the thoracic spine and PSs at the lumbo-pelvis.

Results

Upper thoracic to pelvis fixation model In non-osteoporosis, no significant difference between the PSF and LPF is found. In osteoporosis, the von Mises stresses of the vertebra body at UIV, UIV+1, and disc were significantly lower in LPF than in PSF. Lower thoracic-to-pelvis fixation model In non-osteoporosis, the average von Mises stress of the vertebral body at UIV+1 and the maximum stress at UIV were lower in LPF than in PSF; however, no significant difference was found in the others. In osteoporosis, the von Mises stress was significantly lower in LPF than in PSF.

Conclusions

The claw hooks stabilized the vertebra body at UIV firmly, and sublaminar wires reduced load translation from the fixed spine.

Impact of Adjacent Muscular Anatomic Preservation on Proximal Junctional Kyphosis and Failure

BACKGROUND

Surgical intervention is a cornerstone of adult spinal deformity (ASD) management. However, there remain burdens from complications, including proximal junctional kyphosis (PJK) and proximal junctional failure (PJF). Posterior anatomic preservation at the uppermost instrumented vertebra has emerged as an accessible approach to potentially reduce PJK/PJF risk.

METHODS

We assembled an institutional cohort of patients with ASD evaluated between 2017 and 2022 who had spinal fusion performed with a modified subperiosteal dissection at and immediately below the uppermost instrumented vertebra. Through a meta-analysis with a random-effects model, we compared our incidence of PJK/PJF against other prophylactic interventions.

RESULTS

Ninety patients were identified, (median age, 64 years; average follow-up, 19 months). Most had scoliosis and/or spinal stenosis with a median of 8 levels fused (40% revision cases). 6.7% and 3.3% of patients developed PJK and PJF, respectively, with the most common clinical correlate being a minor neurologic deficit such as numbness (37.8%). PJK/PJF and non-PJK/PJF patients had similar postoperative complication profiles. Radiographic parameters varied: the PJK/PJF cohort had greater preoperative pelvic incidence/pelvic tilt and postoperative pelvic incidence-lumbar lordosis mismatch as well as smaller operative correction of the thoracolumbar Cobb angle. In the literature, prophylactic interventions broadly reduced the incidence of PJK/PJF, with a pooled estimate of 19% compared with 36% in patients who did not receive any additional intervention.

CONCLUSIONS

Preservation of posterior anatomic structures likely has a role in reducing the rate of PJK/PJF. Linking radiographic parameters to PJK/PJF and studying techniques that keep posterior structures intact may be steps toward improving ASD correction outcomes.

Comparison of Global Alignment and Proportion (GAP) Score and SRS-Schwab ASD Classification in the Analysis of Surgical Outcomes for Adult Spinal Deformity

Study design

The GAP score predicted post-operative mechanical complications more effectively whereas SRS-Schwab classification improved evaluation of postoperative PROMs.

Objective

The study compared the GAP Score and SRS-Schwab Classification in predicting surgical outcomes for adult spinal deformity (ASD) and elucidated whether both systems should be included in the preoperative planning.

Materials and methods

Radiographic measurements and health-related quality of life scores at baseline, 6 weeks after surgery, and the last follow-up were collected from a cohort of 69 ASD patients subjected to long segment spinal fusion surgery after they were grouped by GAP score and SRS-Schwab classification respectively. Fisher's exact test and receiver operator characteristic (ROC) curve analysis was used to compare the incidence of mechanical complications and the discriminant capacity during revision surgery between the two groups. Postoperative patient-reported outcomes measures (PROMs) were compared by one-way ANOVA, and the proportions of MCID achieved for PROMs compared by chi-square test between the two groups.

Results

The overall incidence of mechanical complications and revision surgery were 42% and 8.7%. Both GAP score and its categories predicted mechanical complications and revision surgery, but the GAP score system could not predict the improvements of PROMs. The SRS-Schwab classification could predict the occurrence of postoperative mechanical complications and improvements of postoperative PROMs between the aligned, moderately misaligned and severely misaligned groups (P < 0.05).

Conclusion

Hence, a comprehensive surgical strategy for postoperative planning may improve patients' quality of life and minimize mechanical complications.

Graphical Abstract