Bone Turnover Markers as a New Predicting Factor for Nonunion After Spinal Fusion Surgery.

STUDY DESIGN: Retrospective observational study.

OBJECTIVE: We investigated whether bone turnover markers could be a useful indicator for prediction of nonunion.

SUMMARY OF BACKGROUND DATA: Nonunion is a major complication of lumbar spinal fusion surgery. The involvement of bone turnover in the process of bony union in spinal fusion surgery is, however, poorly understood.

METHODS: Of the 74 patients analyzed, 13 were diagnosed with nonunion. We evaluated the significance of the following risk factors: age, sex, number of fused segments, serum levels of total alkaline phosphatase, procollagen type 1 amino-terminal propeptide (P1NP), tartrate-resistant acid phosphatase 5b (TRACP-5b), and albumin, and history of diabetes mellitus, cigarette smoking, or alcohol use. We also defined the bone turnover ratio (BTR) as a value that equals serum TRACP-5b concentration divided by serum P1NP concentration to evaluate patients' individual bone turnover balance and investigated the significance of BTR as a risk factor.

RESULTS: Univariate analysis showed that older age, malnutrition, and lower P1NP are risk factors for nonunion. Stepwise logistic regression analysis revealed that in the presence of lower P1NP, higher TRACP-5b becomes a risk factor. Furthermore, we identified BTR as the most significant risk factor for nonunion. The optimum cut-off value of BTR by receiver-operating characteristic curve was 11.74.

CONCLUSION: These findings show a relation between bone turnover and nonunion after spinal fusion surgery. The measurement of bone turnover markers could potentially be used to predict nonunion after spinal fusion surgery.

LEVEL OF EVIDENCE: 4.