Early Postoperative Increase in Procollagen Type 1 N-Propeptide (P1NP) Predicts One-Year Pseudarthrosis Following Anterior Cervical Discectomy and Fusion: A Prospective Cohort Study.

STUDY DESIGN: Prospective cohort study. OBJECTIVE: To evaluate whether bone turnover markers (BTMs) predict pseudarthrosis after cervical spine surgery. SUMMARY OF BACKGROUND DATA: Pseudarthrosis is a major reason for reoperation after ACDF. However, prediction of pseudarthrosis remains elusive. Patient-level factors have proven unreliable, and optimization of modifiable risk factors may be precluded by urgent neurological indications for surgery. Bone turnover markers are directly modifiable and may help predict fusion before and after surgery. MATERIALS AND METHODS: Patients undergoing 1-3 level ACDF for degenerative pathology were enrolled. Exclusion criteria included metabolic bone disease, current osteoporosis treatment, inflammatory arthritis, chronic steroid use, and chronic kidney disease. Serum collagen type 1 C-telopeptide (CTX) and procollagen type 1 N-propeptide (P1NP) were used as markers of bone resorption and formation, respectively. Labs were collected preoperatively and at six weeks postoperatively for CTX and P1NP with changes in values (Δ) calculated. The primary outcome was radiographic pseudarthrosis at one year, defined as interspinous distance change >1 mm on dynamic lateral radiographs. Associations between pseudarthrosis and BTMs, demographics, comorbidities, surgical variables, and osteometabolic labs were assessed. A stepwise (Wald) logistic regression model evaluated independent predictors of pseudarthrosis. RESULTS: Fifty-eight consecutive patients were enrolled, 25 missed six‑week labs, leaving 33 patients (60 levels) for analysis. Pseudarthrosis occurred in 30% of patients. Baseline demographics, surgical factors, and laboratory values were similar between fused and pseudarthrosis cohorts. Six‑week P1NP tended to be higher in the pseudarthrosis group (95.0±84.8 vs. 55.1±23.4, P=0.074), and ΔP1NP was significantly greater (38.5±70.6 vs. -16.9±97.1, P=0.013). Logistic regression identified ΔP1NP as a significant predictor of one‑year fusion status (P=0.039), whereas BMI, 25‑hydroxyvitamin D, and number of fused levels showed borderline associations. CONCLUSION: Patients at risk for pseudarthrosis after ACDF show a larger early increase in P1NP compared to their fused counterparts while CTX levels remained comparable between the groups. Considering that these changes occur early after surgery, there may be a role for trials testing the efficacy of postoperative anabolic agents in preventing pseudoarthrosis in high-risk patients. EVIDENCE LEVEL: Level II (Prospective Cohort Study).