Sequential Changes of Bone Metabolism in Normal and Delayed Union of the Spine

Time-dependent changes in bone markers in delayed or nonunion of vertebral fracture were compared with those of normal union. Thirty-three patients with a fresh vertebral fracture were enrolled. Urinary Type I collagen C-terminal telopeptide, pyridinoline, deoxypyridinoline, serum C-terminal telopeptide, and N-midportion of osteocalcin (OC_N-mid) were determined at the time of hospital admission (within 24 hours after the fracture event in all cases) and at 2, 4, 12, 24, and 48 weeks thereafter. Subjects were divided into two groups according to the results of MR images taken 48 weeks after fracture. Twenty-four were normally united (Group N) and nine had delayed or nonunion (Group D) of the spine. No differences between values of bone resorption markers in Group N and Group D were observed at any time. Serum OC_N-mid in Group N started to increase at 2 weeks and reached the peak value at 24 weeks (180%); however, serum OC_N-mid in Group D increased at most 120% from baseline to 4 weeks. Values of serum OC_N-mid in Group N were higher at 24 and 48 weeks than those in Group D. Impairment of fracture healing was strongly associated with a deficit in the increase of osteocalcin in the later stage of fracture repair.