gms | German Medical Science

Objective: COSMIC^® (Ulrich) is a dynamic screw-rod system for the thoracolumbar spine. It provides stability against rotation and translation while maintaining flexibility in the sagittal plane. This study describes our experience in a prospective observational design.

Methods: Data collection completed in 95/103 treated patients (median FU: 24 months, mean age 65 years (30–88 y), 66 females/37 males). Indication for COSMIC^® was painful degenerative instability (Th11-S1). Dynamic stabilization was performed as first tier surgery in n=43 and as second tier therapy in n=60 cases. Pre-/postoperative CT-scans/radiographs (2 planes/flexion/extension) were performed in all patients. Clinical assessment using standard scales was acquired prospectively in pre-defined time intervals (VAS, ODI, SF36).

Results: In 103 patients 162 motion segments (1–3) were instrumented (n=3/512 screws needed primary revision, no hardware breakage). n=47 patients achieved mono-segmental, n=47 bi-segmental and n=9 tri-segemental instrumentation. Additional decompression was performed in n=86 cases. Significant postoperative pain relief could be documented with the VAS and ODI. (VAS preOP 65±1 to last FU 20±2; ODI preOP 51%±1 to 17%±2) and SF36 demonstrated a significant improvement in physical (pre-op:41, last FU:45) and mental health (pre-op:44, post-op:46). n=84/95 patients were satisfied with the treatment after 2 years. n=17 Patients needed revision surgery due to problems within or adjacent to the instrumented segments. (n=1 osteoporotic fracture in an adjacent vertebra, n=3 re-decompression within the instrumented segment, n=8 symptomatic degeneration of an adjacent segment, n=3 insufficient improvement with dynamic device, n=2 infection). Of those n=8 patients with symptomatic degeneration of an adjacent segment n=2 had received mono-segmental (4% of all mono-segmental) , n=5 bi-segmental (11%) and n=1 tri-segmental (11%) stabilization. Of those n=8 patients with symptomatic degeneration of an adjacent segment, n=6 (75%) initially presented with a multisegmental degeneration with spondylolisthesis before dynamic stabilization.

Conclusions: Dynamic stabilization with COSMIC^® achieved a significant improvement of pain, mobility and quality of life. An expected re-operation rate of 16,5 % and a low risk for intraoperative complications are encouraging facts. This method is best for patients with mono-segmental instability without spondylolithesis. A prospective randomized trial (spondylodesis vs. dynamic stabilization) is warranted.