Purpose

In stabilisations of atlantoaxial instabilities it holds risks to injure the A. vertebralis as well as neurological structures. Furthermore the posterior approach of the upper part of the cervical spine requires a huge and traumatic preparation of the soft tissue. However the anterior transarticular C1-2 fusion (ATF) is less traumatic and offers almost the same strengh of the stabilisation.

Introduction: In recent years, navigated surgical procedures in spinal surgery have been established due to an increasing demand for precision. Especially 3D-C-arms connected with navigation systems are being used more often and can be utilized intraoperatively for planning as well as controlling of screw positions. This study analyses our experiences with 3D-based navigation in the posterior cervical and high thoracic spine.

Methods: A 3D-C-Arm (Vision Vario 3D, Ziehm) was connected with a navigation system (Vector vision, Brainlab) and since 10/2007 used for the placement of overall 350 Screws at 51 Patients. Of those 9 Patients had to undergo operations in the posterior cervical spine, of 53 screws Judet- (n=8), Massa lateralis- (n=27) and pedicle-screws (n=18) were placed. Indications for instrumentation were traumatic fractures (n=3), spon-dylodiscitis (n=1), multiple metastases with high-grade instability (n=4), and degenerative rheumatic stenosis of the spinal canal (n=1). Concerning the high thoracic spine (T1–10) 42 interventions were made with the method, 297 pedicle- screws were implanted. Indications in this area were traumatic fractures (n=24), metastases (n=14) and spondylodiscites (n=4).

Results: Scan-time intraoperatively took 60 seconds on average, data-transfer to the navigation-system another 10 seconds. Application-time including anti-collision-check needs approx. 6 minutes [5;18]. In total 260/350 (74%) screws could be inserted assisted with navigation, 194/350 (55%) were controlled intraop-eratively. Regarding the cervical spine in 44/53 (89 %) of the screws the navigation procedure was uneventful. Positioning of 37/53 (70%) of the screws was checked immediately postoperatively. In the upper thoracic spine 216/297 (73%) could be placed with navigation, 157/297 (53%) were controlled intraoperatively. Occasionally, scan-setup was problematic, in addition, we experienced technical problems. Correct placement was seen for each screw, thus correlating well with the intraoperative findings.

Conclusions: The application of the combination of intraoperative 3D-imaging and navigation for posterior instrumentation of the cervical and the upper thoracic spine is technically feasible and reliable in clinical use. User- and software-dependant sources of error could be solved during the first course of the series. Image-quality at the cervical spine is depending on individual bone density, and possible metal artifacts. With undisturbed visibility of the vertebral body, the reliability of 3D-based navigation at the cervical spine is comparable to that of CT-based procedures. Additionally, it has the advantage of skipping preoperative acquisition of data as well as the matching-process. Furthermore, exposure to radiation is reduced due to the possibility of sparing pre- and postoperative CT.

Purpose: The posterior transarticuar screw fixation C1-2 (Magerl) is a demanding procedure to treat atlanto-axial instabilities. In spite of a high primary instability it holds risks to injure the A. vertebralis as well as neurological structures. Furthermore the posterior approach of the upper part of the cervical spine requires a huge and traumatic preparation of the soft tissue. However the anterior transarticular C1-2 fusion is less traumativc and offers approximately the same strengh of the stabilisation.

Methods: Since the beginning of 2007 17 multimorbid patients with atlanto-axial instabilities of different entities were treated via the anterior transarticular fusion, were regular examined radioogicaly (x-ray/CT) and the procedure critically judged.

Results: C1-2 fusions were performed in 17 patients (13f, 4m, average 81,6 years (68.95)). The main symptoms was pain radiating in the upper cervical spine and the occiput, 2 Patients complaining radiating pain with paraesthesia in both upper extremities, whereas the neurology was predoinant inconspicious. The average operation-time took 64,5 min. On the left side the screws of Ø 39,5mm (32–44mm), on the right side of 36mm (32–44mm) were inserted in addiction to the point of access and the angle of insertion (mediolateral angle Ø 32,0°, ventrodorsal Ø17,6°). There were no intraoperative complications concerning the ceratin procedure, postoperative one revision had to be done because of p.o. bleeding, another because of screw dislocation with clinical relevance 21 days after the first operation. The postoperative x-ray and CT control of the upper cervical spine showed 21/34 screws in 17 patients in correct position (61,7%), 7 (20,6%) screws were too long, 6 (17,7%) screws were placed too anterior and too medial compared to the oppinion of literature. position in the literature. 3 additional positionated dens-screws were in correct position. After a clear learning curve both screws of the 6th patient were positoinated correct. In this connection it could be shown, that two aspects are important for success: A correct entry point as well as the right insertion of the angle of the screws in the coronar and sagittal view. A low intraoperative blood loss, a non traumatic access as well as an immediate postoperative pain decrease have to be valued positively for this procedure.

Conclusions: The gentle procedure of the anterior transarticular C1-2 fusion requires-despite of the huge experience in anterior surgery of dens fractures – a learning curve, because of the more proximate insertion point, the flat insertion angle and the closeness of the A. vertebralis. If these aspects are going to be noticed, failed screw positioning and excessive length as well as injuries of the A. vertebralis can be avoided.