Prediction of Pedicle Screw Loosening Using an MRI-Based Vertebral Bone Quality Score in Patients with Lumbar Degenerative Disease

Abstract

Objective: To explore a new magnetic resonance imaging (MRI)-based bone quality assessment method for predicting pedicle screw loosening in the lumbar spine.

Methods: We reviewed 174 patients aged ≥50 years who were treated for lumbar degenerative diseases using posterior lumbar interbody fusion. All patients were followed-up for ≥12 months. Based on the presence of radiolucent areas on follow-up MRI images, the patients were divided into loosening and nonloosening groups. The vertebral bone quality (VBQ) score was calculated using T1-weighted MRI images. Demographic data, health history, and radiological parameters were also recorded and compared between the 2 groups. Logistic regression analysis was used to predict the independent risk factors affecting screw loosening.

Results: Screw loosening occurred in 29.88% (52/174) of patients. A total of 83 screws (9.18%, 83/904) were loosened. There were differences in the age, fixation length, fixation at S1, preoperative and postoperative PI-LL, PT, preoperative LL, lowest bone mineral density (BMD), and VBQ scores (P < 0.05) between the nonloosening and loosening groups. In the logistic regression, the VBQ score (OR = 1.02 per point; 95% CI: 1.01-1.03; P < 0.001) was identified as an independent factor influencing screw loosening.

Conclusions: As an independent risk factor for screw loosening after lumbar spine fusion, the VBQ score provides a new noninvasive protocol for assessing bone quality during surgical planning.

Keywords: Lumbar degenerative; Magnetic resonance imaging; Pedicle screw loosening; Sagittal alignment; Vertebral bone quality.