Radiological and anatomical evaluation of the atlantoaxial transarticular screw fixation technique

Abstract

Sixty-one patients treated with C1-2 transarticular screw fixation for spinal instability participated in a detailed clinical and radiological study to determine outcome and clarify potential hazards. The most common condition was rheumatoid arthritis (37 patients) followed by traumatic instability (15 patients). Twenty-one of these patients (one-third) underwent either surgical revision for a previously failed posterior fusion technique or a combined anteroposterior procedure. Eleven patients underwent transoral odontoidectomy and excision of the arch of C-1 prior to posterior surgery. No patient died, but there were five vertebral artery (VA) injuries and one temporary cranial nerve palsy. Screw malposition (14% of placements) was comparable to another large series reported by Grob, et al. There were five broken screws, and all were associated with incorrect placement. Anatomical measurements were made on 25 axis bones. In 20% the VA groove on one side was large enough to reduce the width of the C-2 pedicle, thus preventing the safe passage of a 3.5-mm diameter screw. In addition to the obvious dangers in patients with damaged or deficient atlantoaxial lateral mass, the following risk factors were identified in this series: 1) incomplete reduction prior to screw placement, accounting for two-thirds of screw complications and all five VA injuries; 2) previous transoral surgery with removal of the anterior tubercle or the arch of the atlas, thus obliterating an important fluoroscopic landmark; and 3) failure to appreciate the size of the VA in the axis pedicle and lateral mass. A low trajectory with screw placement below the atlas tubercle was found in patients with VA laceration. The technique that was associated with an 87% fusion rate requires detailed computerized tomography scanning prior to surgery, very careful attention to local anatomy, and nearly complete atlantoaxial reduction during surgery.

Risk of vertebral artery injury: comparison between C1–C2 transarticular and C2 pedicle screws

“…Placement of either C1-C2 transarticular or C2 pedicle screws has a potential risk of vertebral artery injury [1][2][3][4][5][6][7][8][9][10][11][12][13][14]21]. The risk of vertebral artery injury by these two techniques needs to be carefully analyzed so as to allow the surgeon to choose the appropriate screw insertion method.…”

“…Posterior C1-C2 transarticular screw fixation can result in vertebral artery injury, with potentially catastrophic results such as vertebrobasilar insufficiency, brain stem and posterior fossa infarct, and even death [1][2][3]. The rate of vertebral artery injury has been reported to be as high as 8.2% [1][2][3].…”

“…The rate of vertebral artery injury has been reported to be as high as 8.2% [1][2][3]. Vertebral artery injuries commonly occur if a drill, tap, or screw perforates or occludes the vertebral artery in the vertebral artery groove of C2, which is located on the lower surface of C2 and lateral to the pedicle ( Fig.…”

“…Vertebral artery injuries commonly occur if a drill, tap, or screw perforates or occludes the vertebral artery in the vertebral artery groove of C2, which is located on the lower surface of C2 and lateral to the pedicle ( Fig. 1) [1][2][3][4][5][6][7][8]. It has been suggested that C2 pedicle screw combined with C1 lateral mass screw placement is inherently safer than C1-C2 transarticular screw fixation in view of the risk of vertebral artery injury at C2, as the medially directed trajectory of the C2 pedicle screw carries the screw away from the vertebral artery, which normally is located lateral to the screw [9][10][11].…”

“…Two anatomic variations have been suggested to be associated with vertebral artery injury. First, it is well known that the risk of vertebral artery injury during C1-C2 transarticular screw placement increases with a high-riding vertebral artery [2,5,6,15,16]. However, we are unaware of any reports comparing the risk of vertebral artery injury by C1-C2 transarticular screw versus C2 pedicle screw in those with a high-riding vertebral artery, and no references on the topic could be found in a computerized search using MEDLINE.…”