Dynamic Neutralization of the Lumbar Spine After Microsurgical Decompression in Acquired Lumbar Spinal Stenosis and Segmental Instability

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Study Design.Prospective clinical study.Objective.To report the outcome, radiologic findings, and complications in patients undergoing microsurgical radicular decompression and implantation of Dynesys (Zimmer Spine, Münsingen, Switzerland).Summary of Background Data.The currently available peer-reviewed English-language medical literature addressing the use of the dynamic stabilization systems is limited. Indications, clinical results, and implant failure of Dynesys after microsurgical decompression are still controversial.Methods and Results.This study included a total of 37 consecutive patients (mean age 58 years) presenting with acquired lumbar stenosis, signs of segmental instability, and degenerative disc disease underwent lumbar microsurgical decompression and implantation of Dynesys in 1 (n = 11), 2 (n = 17), 3 (n = 9), and 4 segments (n = 1). One patient was lost to follow-up. Lumbar and radicular pain was present in 33 patients (92%). Clinical evaluation included visual analogue scale (leg and back), distribution and severity of pain (%), Prolo Functional and Economic Status, Stauffer Coventry Scale, patient's self evaluation, and radiologic assessment preoperative and postoperative at 3 and 12 months. Leg and back pain (visual analogue scale) improved at 12 months from 8.4 ± 2.1 to 3.1 ± 1.4 and from 6.7 ± 2.8 to 4 ± 2.8, respectively. Overall pain severity improved due to reduction of radicular pain from 59.2% to 27.3% after microsurgical decompression. Meanwhile, lumbar pain deteriorated from 40.8% to 47.8%. Twenty-seven percent (patient's self-evaluation) and 29.7% (Stauffer Coventry Scale) of the patients described a fair or poor outcome. Moreover, 51% and 54% of the patients had a Prolo Economic Status and Prolo Functional of 4 or 5, respectively. Complications included 4 broken and 2 misplaced screws from a total of 224 screws implanted, 2 loosen systems, and 1 cerebrospinal fistula. At 1-year, a total of 7 patients (19%) required surgical revision.Conclusion.The reported biomechanical principles of Dynesys do not reflect advantages in outcome compared with none or others stabilization systems after microsurgical radicular decompression reported in the literature.

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