Prognostic potential of markers of bone turnover in delayed-healing tibial diaphyseal fractures

Introduction: Clinical and radiographic examinations detect delayed or nonunion only after the event has occurred. Biochemical markers of bone turnover (BTMs) are promising laboratory tools that offer an early insight into the likelihood of delayed union. We hypothesized that BTMs display temporal variations following fractures and the behavior of BTMs differ between normal and delayed union of fractures.

Methods: This was a prospective study of patients with closed fracture of tibia treated with intramedullary, interlocking nailing. BTM assays (NTX, BSAP, P1NP and osteocalcin) and clinical and radiographic assessments were obtained preoperatively and postoperatively at 8,12, 24, 36 and 72 weeks. Temporal trend of elevation of serum levels of BTMs post-fracture was the primary assessment criterion and radiographic and clinical assessment of fracture union were the secondary assessment criteria.

Results: The average time for fracture union was 15.24 weeks (range 15-19 weeks). The values of both bone formation and resorption markers peaked at the eighth week following the fracture. Resorption markers returned to baseline by 36 weeks. Among the formation markers, BSAP levels showed the smallest increase and returned to baseline earlier (36 weeks) than P1NP and osteocalcin (72 weeks). P1NP showed the most dramatic change, increasing to 2.5 times the mean baseline level at 8 weeks in normal union of fractures. The levels of bone formation markers (BSAP, OC, PINP) were significantly lower in patients with delayed union. There was no significant difference in the levels of the resorption marker (NTX) between normal and delayed union patients.

Conclusion: Serial monitoring of biochemical markers of bone turnover can be used as an adjunct to clinical and radiological observations to predict delayed union LEVEL OF EVIDENCE: Level 2 (prospective observational study).