Early changes in bone specific turnover markers during the healing process after vertebral fracture

The present study measured longitudinal changes in bone turnover markers in elderly patients with vertebral fracture and investigated the relationship among bone turnover markers, duration of bed rest and bone mineral density (BMD).

Criteria for patient selection were 50 years in age and older, and presence of VF. Serum bone-specific alkaline phosphatase (BAP) was measured as a marker of bone formation. Urinary crosslinked N-terminal telopeptides of type I collagen (NTX) was measured as a marker of bone resorption. In principle, samples were collected just after injury, within 24 h, and 1, 2, 3, 5 and 8 weeks after. We also measured duration of bed rest and BMD.

The study population consisted of 42 cases. The average BMD of the lumbar vertebrae was 0.670 ± 0.174 g/cm2. Bed rest period was 17.9 ± 8.8 days. BAP showed significantly higher values at 2 and 3 weeks compared with the baseline value. Thereafter, BAP progressively decreased until 8 weeks. Urinary NTX was increased soon after the onset of pain with the same patterns in BAP. Urinary NTX values reached a peak at 3 weeks, and then they kept significantly higher values until 8 weeks. The peak value of serum BAP was affected by the duration of bed rest, although that of the urinary NTX was not. The peak values of serum BAP and urinary NTX showed negative correlations with the initial BMD values.

Bone turnover markers remained higher at 8 weeks, even patients symptom was healed after VF. Bone turnover markers were affected on physical activity and BMD.