Risk prediction model of pedicle screw loosening within 2 years after decompression and instrumented fusion surgery for degenerative lumbar disease.

Abstract

Background context: Pedicle screw loosening (PSL) after spinal fusion surgery is one of the most frequently reported complications and leads to poor clinical outcomes.

Purpose: This study aimed to develop and validate a risk prediction model for PSL within 2 years in patients undergoing lumbar instrumented fusion surgery based on their risk profiles.

Study design/setting: Retrospective, observational study.

Patient sample: Patients who underwent lumbar instrumented fusion surgery at a single academic institution between May 2015 and February 2019.

Outcome measures: Risk assessment of PSL and development of a rating score based on patient characteristics.

Methods: The demographic profiles and radiographic parameters using computed tomography were obtained. These factors were analyzed to determine possible risk factors related to postoperative PSL after 2 years. A scoring system was developed using these independent risk factors and validated using prospectively collected data from another center between May 2019 and December 2021.

Results: The occurrence of PSL within 2 years postoperation was 12.7% (40/315). PSL was significantly predicted by smoking, low Hounsfield units (HU) of the pedicle tract at the index level (P), and a low psoas-lumbar vertebral index (PLVI). The risk of PSL according to the categories of the risk score was 1.1% for those with a score of 0-1, 15.1% for a score of 2-3, and 61.5% for a score of 4-6. In validation, this model demonstrated both good discrimination and calibration results. The area under the curve was 0.887 (95% CI 0.830-0.938) for the derivation cohort and 0.835 (95% CI 0.738-0.918) for the external validation cohort.

Conclusions: This PSL risk score, including smoking, Index P HU, and PLVI, is a novel approach to predict PSL 2 years postsurgery. This approach highlights the role of factors associated with osteoporosis and sarcopenia in the development of PSL and could aid in preoperative decision-making and surgical planning.