title: Effect of dietary calcium on spinal bone fusion in an ovariectomized rat model.
abstract: OBJECTIVE
  To evaluate the effect of calcium supplementation on spinal bone fusion in ovariectomized (OVX) rats.
  
  
  METHODS
  Sixteen female Sprague Dawley rats underwent bilateral ovariectomy at 12 weeks of age to induce osteoporosis and were randomly assigned to two groups : control group (n=8) and calcium-supplemented group (OVX-Ca, n=8). Autologous spinal bone fusion surgery was performed on both groups 8 weeks later. After fusion surgery, the OVX-Ca group was supplemented with calcium in drinking water for 8 weeks. Blood was obtained 4 and 8 weeks after fusion surgery. Eight weeks after fusion surgery, the rats were euthanized and the L4-5 spine removed. Bone fusion status and fusion volume were evaluated by manual palpation and three-dimensional computed tomography.
  
  
  RESULTS
  The mean fusion volume in the L4-5 spine was significantly greater in the OVX-Ca group (71.80±8.06 mm(3)) than in controls (35.34±8.24 mm(3)) (p<0.01). The level of osteocalcin, a bone formation marker, was higher in OVX-Ca rats than in controls 4 weeks (610.08±10.41 vs. 551.61±12.34 ng/mL) and 8 weeks (552.05±19.67 vs. 502.98±22.76 ng/mL) after fusion surgery (p<0.05). The level of C-terminal telopeptide fragment of type I collagen, a bone resorption marker, was significantly lower in OVX-Ca rats than in controls 4 weeks (77.07±12.57 vs. 101.75±7.20 ng/mL) and 8 weeks (69.58±2.45 vs. 77.15±4.10 ng/mL) after fusion surgery (p<0.05). A mechanical strength test showed that the L4-5 vertebrae in the OVX-Ca group withstood a 50% higher maximal load compared with the controls (p<0.01).
  
  
  CONCLUSIONS
  Dietary calcium given to OVX rats after lumbar fusion surgery improved fusion volume and mechanical strength in an ovariectomized rat model.
authors.affiliation: Department of Neurosurgery, School of Medicine, Kyungpook National University, Daegu, Korea.
authors.forename: Jae-Hoon
authors.initials: JH
authors.lastname: Cho
authors.forename: Dae-Chul
authors.initials: DC
authors.lastname: Cho
authors.forename: Song-Hee
authors.initials: SH
authors.lastname: Yu
authors.forename: Young-Hoon
authors.initials: YH
authors.lastname: Jeon
authors.forename: Joo-Kyung
authors.initials: JK
authors.lastname: Sung
authors.forename: Kyoung-Tae
authors.initials: KT
authors.lastname: Kim
keywords: Calcium; Osteoporosis; Ovariectomized rat; Spinal bone fusion