Application of C2 subfacetal screws for the management of atlantoaxial dislocation in patients with Klippel-Feil syndrome characterized by a narrow C2 pedicle and high-riding vertebral artery

Abstract

Objective This study aims to investigate the clinical application and feasibility of C2 subfacetal screws in patients with Klippel-Feil syndrome (KFS), narrow C2 pedicles, and high-riding vertebral arteries (HRVAs). Methods The clinical data of seven patients with KFS, atlantoaxial dislocation, narrow C2 pedicles, and HRVAs treated with C2 subfacetal screws were analyzed in this retrospective study. The internal height, isthmus height, and pedicle width of C2 vertebra were measured using preoperative computed tomography (CT). Subfacetal screws were inserted for 7 patients (12 sides). The position and length of the screws were observed using postoperative CT. Intraoperative dura mater and vertebral artery (VA) injuries were recorded. Bone fusion was observed using follow-up CT. Results The internal height was 10.5 ± 3.2 mm, the isthmus height was 3.7 ± 1.8 mm, the pedicle width was 3.0 ± 1.4 mm, and the screw length was 19.7 ± 1.5 mm. All patients had HRVAs and narrow pedicles. No injury to the dura mater and vertebral artery (VA) occurred in this group of patients. Bone fusion was achieved in all patients during follow-up. Conclusions In patients with KFS, HRVA, and a narrow C2 pedicle, there is sufficient space below the C2 articular surface for screw insertion. When the pedicle is narrow and the C2 pedicle screw is not suitable for placement due to possible injury to the VA, subfacetal screws are a feasible alternative.

Clinical and Surgical Characteristics of Patients with Atlantoaxial Dislocation in the Setting of Sandwich Fusion

“…Sakamoto et al reported on a patient with sandwich fusion and AAD, a retro-odontoid pseudotumor, and intramedullary hyperintensity 15 . Hou et al described the use of a C2 subfacet screw as a salvage technique in the surgical treatment of a series of 7 patients with sandwich AAD 16 .…”

Influence of Variations of Craniovertebral Junction Anatomy on Safe C1 Lateral Mass and C2 Pedicle Screw Insertion: A Cadaveric and Radiologic Study

“…It is thought that C2 transpedicular screwing can be safely done by directing the screw with an average of 20° medially and 25°-28° cranially. Since an appropriate screw thickness cannot be achieved in narrow pedicles, the use of translaminar, subfacetal or transfacet screws is recommended to reduce the risk of neurovascular complications [11]. Contrarily, extra caution should be taken in cases with dominant VA for both the C1 lateral mass screw and C2 transpedicular screw techniques.…”