The Effect of Spinopelvic Parameters on Anterior Bone Graft Subsidence in Surgical Treatment of Pyogenic Lumbar Spondylodiscitis.

Abstract

Study design: Retrospective cohort study.

Objectives: To evaluate the effect of spinopelvic parameters on anterior bone graft subsidence and functional outcomes after anterior interbody fusion (AIF) and posterior instrumented fusion (PIF) in pyogenic spondylodiscitis (PS).

Methods: Sixty-five patients who had received AIF+PIF for PS over July 2003 to December 2015 were enrolled. Based on the degree of bone graft subsidence, the patients were divided into groups A (minimal subsidence), B (moderate subsidence), and C (severe subsidence). Comparative analysis was performed evaluating patient demographics, spinopelvic parameters (kyphosis angle, involved segment's intervertebral height, pelvic incidence [PI], pelvic tilt, sacral slope, lumbar lordosis [LL], thoracolumbar kyphosis, and PI minus LL [PI-LL]), and clinical evaluation including Oswestry Disability Index (ODI) score and Visual Analog Scale (VAS) scores. The data were collected in a patient registry at perioperative, postoperative 3-month and 2-year to assess clinical and radiological outcomes. Receiver Operating Characteristic (ROC) analysis was applied for identification of cut-off points of LL and PI-LL in suggestion of clinical practice.

Results: The 65 included patients had a mean follow-up period of 35.09 ± 38.30 months. Generalized estimating equation analysis showed that LL and PI-LL changes in group A were significantly different from those in group C but not in group B, revealing that preoperative LL and postoperative PI-LL are bone graft subsidence type indicators. By contrast, preoperative ODI, postoperative 3-month VAS-back, preoperative VAS-leg, and postoperative 2-year VAS-leg scores were associated with bone graft subsidence type. ROC analysis identified preoperative LL < 40.79° and postoperative PI-LL > 15° as significant predictive markers for severe bone graft subsidence, providing valuable thresholds for surgical risk evaluation.

Conclusions: Among spinopelvic parameters, preoperative LL and postoperative PI-LL are important parameters associated with bone graft subsidence severity in patients who had received AIF+PIF for PS.