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 pain-related 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.