Pedicle screws are commonly employed to restore spinal stability and correct deformities. The Renaissance robotic system was developed to improve the accuracy of pedicle screw placement. In this study, we developed an intraoperative classification system for evaluating the accuracy of pedicle screw placements through secondary registration. Furthermore, we evaluated the benefits of using the Renaissance robotic system in pedicle screw placement and postoperative evaluations. Finally, we examined the factors affecting the accuracy of pedicle screw implantation. Through use of the Renaissance robotic system, the accuracy of Kirschner-wire (K-wire) placements deviating <3 mm from the planned trajectory was determined to be 98.74%. According to our classification system, the robot-guided pedicle screw implantation attained an accuracy of 94.00% before repositioning and 98.74% after repositioning. However, the malposition rate before repositioning was 5.99%; among these placements, 4.73% were immediately repositioned using the robot system and 1.26% were manually repositioned after a failed robot repositioning attempt. Most K-wire entry points deviated caudally and laterally. The Renaissance robotic system offers high accuracy in pedicle screw placement. Secondary registration improves the accuracy through increasing the precision of the positioning; moreover, intraoperative evaluation enables immediate repositioning. Furthermore, the K-wire tends to deviate caudally and laterally from the entry point because of skiving, which is characteristic of robot-assisted pedicle screw placement.

Clinical and radiologic study evaluating the outcome after anterior corpectomy with iliac bone fusion compared with discectomy with interbody titanium cage fusion for multilevel cervical degenerated disc disease. To investigate the safety and effectiveness of interbody titanium cage with plate fixation in multilevel postdiscectomy fusion. The operation for segmental multilevel cervical degenerated disc disease remains controversial. Data on safety and efficacy of titanium cages in multilevel postdiscectomy fusion are rarely available. We investigated the safety and effectiveness of interbody fusion cages with plate fixation and compared the clinical and radiographical results between anterior corpectomy and iliac bone fusion with plate fixation and multilevel discectomy and cage fusion with plate fixation. Sixty-two patients were treated with either a multilevel discectomy and cage fusion with plate fixation (27 patients, group A) or an anterior corpectomy and iliac graft fusion with plate fixation (35 patients, group B). We evaluated the patients for cervical lordosis, fusion status, and stability 24 months postoperatively on the basis of spine radiographs. The patients' neurologic outcomes were assessed by the Japanese Orthopedic Association (JOA) scores. Neck pain was graded using a 10-point visual analog scale. Both groups A and B demonstrated a significant increase in the JOA scores (preoperatively 11.1+/-2.1 and 10.4+/-3.5, postoperatively 14.3+/-2.4 and 13.9+/-2.1, respectively) and a significant decrease in the visual analog pain scores (preoperatively 8.5+/-1.1 and 8.7+/-1.5, postoperatively 2.9+/-1.8 and 3.0+/-2.0, respectively). However, there was no significant difference between groups A and B. Both groups A and B showed a significant increase in the cervical lordosis after operation and reached satisfactory fusion rates (96.3% and 91.4%, respectively). Three patients (two 2-level corpectomies and one 3-level corpectomy) had construct failures that required a second operation. Eight of 35 patients who underwent iliac bone fusion had donor site pain. The hospital stay in group A was significantly shorter than that in group B (P=0.022). Either a multilevel discectomy and cage fusion with plating or a corpectomy and iliac bone fusion with plating provides good clinical results and similar fusion rates for cervical degenerative disc disease. However, absence of donor site complications and construct failures and shorter hospital stay make the multilevel discectomy and cage fusion with plate fixation better than corpectomy and strut graft fusion with plate fixation.

Cage-assisted anterior cervical discectomy and fusion (ACDF) has proven to be a safe and effective procedure for the treatment of one- and two-level degenerative disc disease (DDD). To the authors' knowledge, clinical results after three- and four-level interbody cage-augmented ACDF have not been reported in the literature. The authors investigated the safety and effectiveness of titanium cages used in such procedures and evaluated the results in cases with or without plate fixation. Fifty-six patients suffering from cervical DDD were divided into two groups. Group 1 included 32 patients who underwent titanium cage-assisted ACDF; Group 2 included 24 patients who underwent the same procedure, supplemented with plate fixation. The cervical DDD was confirmed by radiography and magnetic resonance imaging. The patients underwent radiographic evaluation to assess cervical lordosis, segmental height of cervical spine, the height of the foramina, and spinal stability. Neurological outcomes were assessed using the Japanese Orthopaedic Association (JOA) scores. Neck pain was graded using a 10-point visual analog scale (VAS). The follow-up period ranged from 13 to 28 months (mean 17.2 months). In both Groups 1 and 2 significant increase (p < 0.001) was demonstrated in the JOA scores (preoperatively 10.7 +/- 2.4 and 11.1 +/- 2, postoperatively 13.9 +/- 2.2 and 14.1 +/- 2.3, respectively) and VAS pain scores (preoperatively 8.8 +/- 0.9 and 8.5 +/- 1, postoperatively 3.1 +/- 2.1 and 2.8 +/- 1.8, respectively); however, there was no significant intergroup difference. A significant increase in the cervical lordosis, foraminal height, and segmental height was observed in both groups. Good stability of cage fusion was obtained in both groups 12 months postoperatively (90.6% in Group 1 and 91.7% in Group 2); however, there were no statistically significant intergroup differences. The complication rate in Group 2 was higher than that in Group 1. The hospital length of stay in Group 1 was significantly lower than in Group 2 (p < 0.001). Analysis of these findings demonstrated that titanium cage-assisted ACDF provided long-term stabilization, increased lordosis, increased segmental height, and increased foraminal height. In both groups good neurological outcomes were achieved and donor site morbidity was avoided. The lower complication rate and shorter hospital stay, however, make the cage-assisted fusion without plate fixation better than with plate fixation.

Anterior discectomy and fusion to treat cervical degenerative disc disease is the preferred procedure for many spine surgeons. The ideal device for structural reconstruction of the anterior cervical spine remains controversial. The purpose of this prospective study was to investigate the effectiveness of a non-threaded titanium cage in performing anterior spinal fusion for cervical degenerative disc disease. The clinical and radiologic data of 78 consecutive patients were reviewed. Neurologic outcome was assessed using Odom's criteria. Neck pain was graded using a 10-point visual analog scale. The cervical spinal curvature, the height of foramina, and fusion status were evaluated on preoperative and postoperative radiographs. Mean follow-up was 24.9 (range 18-35) months. An excellent or good result was found in 92% of the patients with radiculopathy, 69% of those with myelopathy, and 73% of those with myeloradiculopathy. Statistical analyses also showed improvement of cervical pain after surgery (P < 0.001) and a significant increase in foraminal height (P = 0.035). Cervical kyphosis was present in 27 (34%) patients before surgery; it was corrected to lordosis in 9. The fusion rate at 12 months and 24 months was 91% and 95%, respectively. No surgery or cage-related complication occurred in these patients. Non-threaded interbody cage fusion in this study achieved a high fusion rate and had a good neurologic outcome. These results suggest that non-threaded cage fusion is a safe and effective method for anterior cervical discectomy.