8. Pedicle bone quality score offers superior predictive value over vertebral bone quality score for pedicle screw loosening following instrumented transforaminal lumbar interbody fusion: an MRI-based study

Abstract

BACKGROUND CONTEXT

Pedicle screw loosening (PSL) is a common complication in transforaminal lumbar interbody fusion (TLIF), leading to poor clinical outcomes such as pseudarthrosis, adjacent segment pathology, and spinal instability, often necessitating revision surgeries. Bone quality significantly impacts screw stability, traditionally assessed through computed tomography (CT) or dual-energy X-ray absorptiometry (DEXA). However, magnetic resonance imaging (MRI)-based pedicle bone quality (PBQ) and vertebral bone quality (VBQ) scores offer non-ionizing alternatives for preoperative bone quality evaluation.

PURPOSE

To compare the predictive strength of PBQ and VBQ scores for assessing PSL following TLIF and to identify key risk factors contributing to screw loosening.

STUDY DESIGN/SETTING

A retrospective cohort study evaluating MRI-derived PBQ and VBQ scores as predictors of PSL in patients undergoing TLIF.

PATIENT SAMPLE

A total of 394 patients (aged ≥ 18) were treated with TLIF for degenerative lumbar spinal conditions, with complete preoperative imaging and at least 12 months of postoperative follow-up.

OUTCOME MEASURES

Primary outcomes included the incidence of PSL and the predictive accuracy of PBQ and VBQ scores. Secondary measures included fusion rates, T-scores from DEXA, and patient-reported outcomes such as the visual analog scale (VAS) and Oswestry Disability Index (ODI).

METHODS

PBQ and VBQ scores were calculated from sagittal T1-weighted MRI images and normalized against cerebrospinal fluid intensity. Receiver operating characteristic (ROC) curves and area under the curve (AUC) values compared their predictive efficacy. Multivariate logistic regression identified independent risk factors for PSL.

RESULTS

PBQ exhibited superior predictive accuracy for PSL compared to VBQ (AUC: 0.894 vs 0.722). PBQ demonstrated higher sensitivity (75.93%), specificity (92.31%), positive predictive value (78.85%), and negative predictive value (91.03%). Significant predictors of PSL included higher PBQ scores, longer fusion constructs, lower T-scores, reduced fusion rates, and older age. PSL was associated with increased back pain but did not significantly impact ODI or leg VAS scores.

CONCLUSIONS

PBQ scores are stronger predictors of PSL than VBQ, providing a valuable non-ionizing alternative for preoperative assessment. Integration of PBQ scores into surgical planning may optimize screw fixation strategies, particularly in patients with compromised bone quality. Additional significant risk factors for screw loosening included older age, lower hip DEXA T-scores, longer fusion constructs, and lower fusion rates.

FDA Device/Drug Status

This abstract does not discuss or include any applicable devices or drugs.