Evaluation of the serum ionic fluoride concentration as a biomarker of bone metabolism post-spinal fusion surgery

Bone union after spinal fusion surgery with instrumentation has been determined only with imaging studies. We evaluated the usefulness of the serum ionic fluoride (SIF) concentration as a biomarker of the bone union status. We enrolled 25 patients who underwent spinal surgery in our institution, and we divided patients into three groups with and without instrumentation (G1, G2, and G3). We collected the fasting serum level preoperatively and on day 1 (D1), week 1 (D7), week 2 (D14), month 1 (D30), month 3 (D90), and month 6 (D180) postoperatively, and measured SIF concentrations using the flow injection method with an ion-selective electrode. Although preoperative SIF concentrations were similar among the 3 groups, postoperative SIF concentrations were different among the groups. SIF concentrations in groups with instrumentation (G2 and G3) increased between D14 and D90 postoperatively and decreased at D180 postoperatively. SIF concentrations in the group without instrumentation (G1) decreased between D30 and D180 postoperatively. An SIF concentration that is higher postoperatively than preoperatively may indicate unstable bone union, whereas a lower SIF concentration postoperatively than preoperatively may indicate stable bone union. We concluded that the SIF concentration may be useful for diagnosing bone union. •Usefulness of the SIF level as a biomarker of the bone union status is unclear.•The SIF concentration may be useful for diagnosing bone union.•A higher SIF level postoperatively than preoperatively may indicate unstable union.•A lower SIF level postoperatively than preoperatively may indicate stable union.