Assessment of pedicle screw placement accuracy, procedure time, and radiation exposure using a miniature robotic guidance system.

STUDY DESIGN: Controlled, cadaveric implantation trial. OBJECTIVE: To evaluate the effect of a robotic guidance system on screw placement accuracy, amount of radiation exposure, and length of procedure time during percutaneous pedicle screw implantation. SUMMARY OF BACKGROUND DATA: Pedicle screws are associated with low complication rates, and several computer-assisted image guidance systems exist that facilitate accurate screw placement. However, these systems may represent substantial radiation exposure risk to patients and surgeons. METHODS: We implanted 234 pedicle screws in 12 cadavers (study group: 15 surgeons, 197 screws, and 10 specimens; control group: 2 surgeons, 37 screws, and 2 specimens). We measured procedure time, fluoroscopy time, and radiation exposure and evaluated screw placement accuracy with computed tomography scans. To evaluate the learning curve, we compared measurements with those of an experienced robotic guidance user through the 2-sample (heteroscedastic), 1-tail t test (P< 0.05). RESULTS: Relative to control, the study group had fewer screw placement deviations (average, 2.6±0.7 mm vs. 1.1±0.4 mm; P<0.0001), fewer pedicle wall breaches of 4 mm or greater (average, 5.4% vs. 1.5%), lower surgeon radiation exposure (average, 136 mrem vs. 4.2 mrem), lower fluoroscopy time per screw (average, 33.0 s vs. 0.9 s), and shorter procedure time (average, 1.98 h vs. 1.23 h). Use of robotic guidance increased the accuracy of percutaneous pedicle screw placement by 58%, thereby reducing the risk of neurologic injury (as measured by breaches >4 mm), new-user radiation exposure (by 98.2%), and procedure time (by 36%). CONCLUSIONS: The advantages associated with a robotic guidance system may make the surgeon more at ease about offering minimally invasive or percutaneous surgical options to patients and more comfortable about implementing pedicle-based fixation in general. This advanced technology may also allow inclusion of patients with complicated anatomic deformities, who are often excluded from pedicle screw-based surgery options.

Results of lumbar total disc arthroplasty in military personnel.

STUDY DESIGN: Evaluation of lumbar total disc arthroplasty (TDA) in military patients. OBJECTIVE: To evaluate the clinical and radiographic outcomes of US military personnel who have undergone TDA for degenerative disc disease and to assess the retention versus discharge rate after undergoing this procedure. SUMMARY OF BACKGROUND DATA: TDA was developed as an alternative to arthrodesis for the surgical management of degenerative disc disease with the goal of preserving motion and reducing adjacent segment disease. However, the indications and optimal candidates for this procedure are uncertain. Military members must maintain a certain level of physical fitness and be capable of meeting the demands of hazardous environments. This study reviews results of TDA performed on active duty military members. METHODS: The surgery schedules from 2005 to 2008 were reviewed to identify military members who underwent single-level or 2-level TDA for degenerative disc disease after failing at least 6 months of conservative management. All patients had a minimum of 2-year follow-up. Preoperative and postoperative clinical assessments were completed using the Oswestry Disability Index (ODI) questionnaire and the numeric rating scale (NRS). Radiographs were evaluated to determine range of motion, height, and disc position at the operated levels. The retention rate of the patients in the military was also recorded. Statistical analysis of the data was carried out with significance assumed at the P < 0.05 level. RESULTS: Thirty-eight patients, implanted with a total of 56 discs, met the criteria for retrospective analysis. Twenty patients had single-level and 18 had 2-level TDA. Mean age was 35 (23 to 56 y) years. Mean follow-up was 28 months. The overall mean preoperative ODI and NRS of 53.6 and 7.3, significantly improved postoperatively to 27.7 and 3.3, respectively (P < 0.001). There was no difference in the postoperative ODI (P = 0.19) or NRS (P = 0.18) when comparing single-level and 2-level TDA. Clinical success was achieved in 79% of patients. Mean range of motion was 6.5 degrees and the mean disc height increased by 69%. Sixty-eight percent of patients returned to full active duty. CONCLUSIONS: This study showed clinical success approaching 80% in military patients who underwent lumbar TDA. Furthermore, close to 70% were able to return to their positions within the military. TDA, while more closely reapproximating the normal biomechanics of the spine, may provide patients with an improved alternative to spinal arthrodesis for degenerative disc disease.

Clinical acceptance and accuracy assessment of spinal implants guided with SpineAssist surgical robot: retrospective study.

STUDY DESIGN: Retrospective, multicenter study of robotically-guided spinal implant insertions. Clinical acceptance of the implants was assessed by intraoperative radiograph, and when available, postoperative computed tomography (CT) scans were used to determine placement accuracy. OBJECTIVE: To verify the clinical acceptance and accuracy of robotically-guided spinal implants and compare to those of unguided free-hand procedures. SUMMARY OF BACKGROUND DATA: SpineAssist surgical robot has been used to guide implants and guide-wires to predefined locations in the spine. SpineAssist which, to the best of the authors' knowledge, is currently the sole robot providing surgical assistance in positioning tools in the spine, guided over 840 cases in 14 hospitals, between June 2005 and June 2009. METHODS: Clinical acceptance of 3271 pedicle screws and guide-wires inserted in 635 reported cases was assessed by intraoperative fluoroscopy, where placement accuracy of 646 pedicle screws inserted in 139 patients was measured using postoperative CT scans. RESULTS: Screw placements were found to be clinically acceptable in 98% of the cases when intraoperatively assessed by fluoroscopic images. Measurements derived from postoperative CT scans demonstrated that 98.3% of the screws fell within the safe zone, where 89.3% were completely within the pedicle and 9% breached the pedicle by up to 2 mm. The remaining 1.4% of the screws breached between 2 and 4 mm, while only 2 screws (0.3%) deviated by more than 4 mm from the pedicle wall. Neurologic deficits were observed in 4 cases yet, following revisions, no permanent nerve damage was encountered, in contrast to the 0.6% to 5% of neurologic damage reported in the literature. CONCLUSION: SpineAssist offers enhanced performance in spinal surgery when compared to free-hand surgeries, by increasing placement accuracy and reducing neurologic risks. In addition, 49% of the cases reported herein used a percutaneous approach, highlighting the contribution of SpineAssist in procedures without anatomic landmarks.