INTRODUCTION: Vertebral osteoporotic fracture increases both elastic and time‐dependent ('creep') deformations of the fractured vertebral body during subsequent loading. The accelerated rate of creep deformation is especially marked in central and anterior regions of the vertebral body, and may contribute to the development of kyphotic deformity in life. We hypothesise that vertebroplasty can reduce these gradual creep deformations of damaged vertebrae.
METHODS: Fourteen pairs of spine specimens, each comprising three vertebrae and the intervening soft tissue, were obtained from cadavers aged 67‐92 yr. Specimens were loaded in increased compression until one of the vertebral bodies was damaged. Damaged vertebrae were then augmented: one of each pair underwent vertebroplasty with polymethylmethacrylate cement, the other with a resin (Cortoss). A 1kN compressive force was applied for 1 hr before fracture, after fracture, and after vertebroplasty, while creep deformation was measured in anterior, middle and posterior regions of each vertebral body, using a MacReflex optical tracking system.
RESULTS: Cement type had little influence on creep deformation, so data from all 28 specimens were pooled. After fracture, creep in the anterior vertebral body increased from 4,513 (STD 4766) to 54,107 (STD 54,845) microstrains (P<0.001), and creep in the central vertebral body increased from 885 (STD 5,169) to 34,378 (STD 40,762) microstrain (P<0.001). (10,000 microstrains = 1% deformation.) Following vertebroplasty, creep deformations were reduced by 61% (P=0.002) and 66% (P=0.006) in anterior and central regions respectively.
DISCUSSION: Creep deformations of the anterior and central regions of damaged vertebral bodies were substantially reduced by vertebroplasty. In life, vertebroplasty could help to slow or prevent the gradual development of kyphotic deformity following vertebral osteoporotic fracture, as well as increase vertebral stiffness and strength.