iCT Navigation for Transpedicular Screw Fixation in the Thoracolumbar Spine: Experience in 100 Consecutive Cases.

Background: Various guidance techniques have been developed for optimal pedicle screw placement. We present our initial experience with intraoperative CT (iCT) navigation for transpedicular screw fixation in the thoracolumbar spine. Objective: This study aimed to describe the accuracy and reliability of iCT navigation for transpedicular screw fixation. Material and Methods: One hundred consecutive patients underwent thoracolumbar pedicle screw fixation under iCT navigation. After iCT registration of the local bony anatomy with a firmly attached spinous process tracker, pedicle screw placement was performed under navigation with an infrared camera and infrared reflectors on insertion instruments. Screw trajectories of the intraoperative verification CT were matched against the navigation paths. Radiological and clinical follow-up was prospectively documented and retrospectively analyzed. The study included 47 women and 53 men with a mean age of 66 years. Indications for thoracolumbar pedicle fixation were degenerative instability with stenosis, cyst or disc herniation (82), spondylolytic instability (9), scoliosis with stenosis (6), and traumatic fractures (3). A total of 443 pedicle screws were inserted: 22 in the thoracic spine, 371 in the lumbar spine, and 50 in S1. Results and Conclusions: Four hundred thirty-five out of 443 screws (98%) were correctly placed. Misplacement was explained by loosened infrared reflectors on pedicle awl or probe, or by the displacement of the spinous process tracker; misplaced screws were re-inserted intraoperatively and showed correct placement on the second verification CT. Based on our first 100 cases, iCT navigation for transpedicular screw fixation in the thoracolumbar spine seems to be very accurate and reliable.

Dynamic neutralization of the lumbar spine after microsurgical decompression in acquired lumbar spinal stenosis and segmental instability.

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.