Application of an expandable pedicle screw in the severe osteoporotic spine: A preliminary study

Purpose. To investigate the clinical abstractnd radiographic outcome of multi-axial expandable pedicle screws (MEPS) in patients with osteoporosis. Methods. One hundred and twenty-five consecutive patients received MEPS from the UPASS spinal fixation system to obtain thorocolumbar or lumbosacral stabilization. All patients underwent bone mineral density (BMD) scans. The indications for use of the MEPS were spinal diseases with severe osteoporosis (degenerative diseases 46 cases, compression fractures 28 cases, lumbar tuberculosis 27 cases and revision spine surgery 24 cases). The pre-operative and three months post-operative functional evaluations were graded with JOA and VAS scoring system. One week, six months and 12 months after surgery, plain film and three-dimensional CT scans were obtained to evaluate the spinal fusion and fixation effectiveness of MEPS. Results The mean follow-up period was 18 months (ranged from 6 to 33 months). All patients suffered from severely osteoporosis with a decrease of 25.3°o in BMD. The preoperativeJOA and VAS scores were 11.3± 3.0 and 6.7±1.8 mm, respectively. Three months after operation, the JOA and VAS scores were 25.2±2.0 and 2.3± 1.7 mm. The recovery rate was 78.1±11.5% and the clinical results were satisfying. There were no instances of screw loosening or pullout of the MEPS and the screw-bone interface was excellent. The radiographic results showed that bone healing, both around the screws and inter-vertebral, was achieved. Conclusion In osteoporosis spine surgery, excellent bone-screw interface and fixation strength can be achieved by using MEPS. MEPS are a novel approach to increase the pedidc screw fixation in osteoporotic and revision spine surgeries.