Pedicle screw-based dynamic stabilization of the thoracolumbar spine with the Cosmic®-system: A prospective observation

Object The objective of the study was to generate prospective data to assess the clinical results after dynamic stabilization with the Cosmic® system (Ulrich Medical). Patients and methods Between April 2006 and December 2007, 103 consecutive patients were treated with Cosmic® for painful degenerative segmental instability ± spinal stenosis. The preoperative workup included radiological (MRI and myelography/CT) and clinical parameters (general/neurological examination, visual analogue scale (VAS), Oswestry disability index (ODI), SF-36, Karnofsky (KPS)). At pre-defined intervals (at discharge, 6 weeks, 3 months, 6 months, 12 months, and yearly) the patients were reevaluated (X-ray/flexion/extension, neurological status, VAS, ODI, SF-36, KPS, and patient satisfaction). Data were collected in a prospective observational design. Results Data collection was completed in 100 of 103 operated patients (mean follow-up, 15±0.6 months). Dynamic stabilization was performed as first-tier surgery in 43 cases and as second-tier therapy in 60 cases. Additional decompression was performed in 83 cases. Dynamic stabilization led to significant reduction of back painrelated disability (ODI pre-op, 51±1%; Post-op, 21±1%) and improvement of pain (VAS pre-op, 65±1; Post-op, 21±2), mental/physical health (norm-based SF-36: Mental pre-op, 44; Post-op, 48; Physical pre-op, 41; Post-op, 46), and mobility (KPS pre-op, 70±1; Post-op, 82±31). Early reoperation was necessary in 12 patients (n=3 symptomatic misplaced screws, n=8 CSF pseudocele, rebleeding, or impaired wound healing, n=1 misjudged instability/stenosis in adjacent segment). Reoperations within the follow-up period were necessary in another 10 patients due to secondary screw loosening (n=2), persistent stenosis/disk protrusion in an instrumented segment (n=3), symptomatic degeneration of an adjacent segment (n= 6), or osteoporotic fracture of an adjacent vertebra (n=1), respectively. Patient satisfaction rate was 91%. Conclusions Dynamic stabilization with Cosmic® achieved significant improvement of pain, related disability, mental/physical health, and mobility, respectively, and a high rate of satisfied patients. A reoperation rate of 10% during follow-up seems relatively high at first glance. Comparable data, however, are scarce, and a prospective randomized trial (spondylodesis vs. Dynamic stabilization) is warranted based on these results.