Biomechanics of Vertebroplasty

Osteoporosis is a skeletal disease characterized by low bone mass and deterioration of bone tissue. It affects 15–20 million women in the United States. Fractures of the vertebrae, wrist and hip are the most common. [1] In the spine, osteoporosis greatly affects the bone mass of the vertebral bodies (VB), the primary structures for transmitting loads in the spine. The VB is comprised of a shell of dense bone surrounding a more porous bony tissue called trabecular bone. Trabecular bone is a lattice-like network of trabeculae in the shape of plates or rods, depending on orientation and one’s age. When the weakened trabecular structure experiences a loss of height, acute back pain, spinal cord compression, and overall loss of mobility can ensue. A single fracture creates a region of high stress in the trabecular network, often leading to more fractures. In almost 20% of the cases one fracture in a VB may result in a secondary fracture within a one year period. [2] Many fractures go unnoticed. The high occurrence, frequent uncertainty of fracture, and gravity of subsequent injury indicate a need to improve the strength of osteoporotic vertebrae before damage can occur. It may be desirable to treat weakened bone prior to fracture. One candidate for prevention that is investigated in this study is vertebroplasty. Currently, the procedure is used to repair fractured VB by injecting acrylic bone cement into the affected level. A parametric finite element (FE) investigation and supporting experimental study was conducted to evaluate the usefulness of vertebroplasty as a preventative treatment.