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.