Spine (Phila Pa 1976). 2015 Jan 23. [Epub ahead of print]
Metzger MF1, Kanim LE, Zhao L, Robinson ST, Delamarter RB.
Study Design. An in vivo dosing study of vitamin D in a rat posterolateral spinal fusion model with autogenous bone grafting. Rats randomized to four levels of Vitamin D adjusted rat chow, longitudinal serum validation, surgeons/observers blinded to dietary conditions, and rats followed prospectively for fusion endpoint.
Objective. To assess the impact of dietary and serum levels of Vitamin D on fusion success, consolidation of fusion mass, and biomechanical stiffness after posterolateral spinal fusion procedure.Summary of Background Data. Metabolic risk factors, including vitamin D insufficiency, are often overlooked by spine surgeons. Currently there are no published data on the causal effect of insufficient or deficient vitamin D levels on the success of establishing solid bony union after a spinal fusion procedure.
Methods. 50 rats were randomized to four experimentally controlled rat chow diets: normal control, vitamin D-deficient, vitamin-D insufficient, and a non-toxic high dose of vitamin D, four weeks prior to surgery and maintained post-surgery until sacrifice. Serum levels of 25(OH)D were determined at surgery and sacrifice using radioimmunoassay. Posterolateral fusion surgery with tail autograft was performed. Rats were sacrificed 12 weeks post-operatively and fusion was evaluated via manual palpation, high resolution radiographs, μCT, and biomechanical testing.
Results. Serum 25(OH)D and calcium levels were significantly correlated with vitamin-D adjusted chow (p<0.001). There was a dose dependent relationship between vitamin D adjusted chow and manual palpation fusion with greatest differences found in measures of radiographic density between high and deficient vitamin D (p<0.05). Adequate levels of vitamin D (high and normal control) yielded stiffer fusion than inadequate levels (insufficient and deficient) (p<0.05).
Conclusions. Manual palpation fusion rates increased with supplementation of dietary vitamin D. Biomechanical stiffness, bone volume and density were also positively-related to vitamin D, and calcium.