Technical Strategies and Surgical Results of C1 Lateral Mass-C2 Pedicular Screw Fixation in Atlantoaxial Disorders

Choi, Hong June; Kim, Keun Su; Park, Ki Seok; Han, In Ho; Chin, Dong Kyu; Jin, Byoung Ho; Cho, Yong Eun

Abstract

OBJECTIVE
There are various posterior fusion techniques in managing C1-2 instability. The aim of this study is to evaluate surgical techniques and clinical results including complications of the C1 lateral mass and C2 pedicle screw fixation (C1-2 LMPSF) in atlantoaxial disorders.
METHODS
From February 1997 to July 2008, 24 patients were performed C1-2 LMPSF due to C1-2 instability. Pathway of vertebral artery was classified into three groups by 3D-angiogram. Diameter of C1 lateral mass and C2 isthmus on the plain X-ray and CT was measured before operation. Surgical method was divided into four groups according to fixation site (bilateral or unilateral) and bone graft (with or without graft). Stability of C1-2 fixation was postoperatively evaluated by flexion and extension cervical lateral films. We reviewed clinical data, imaging studies and old chart retrospectively as sources for analysis.
RESULTS
Among 24 patients, os odontoideum was the most common cause (16 out of 24). Four patients had anomalous vertebral artery. Mean diameters of C1 lateral mass was 9.9(range 4.2~16.4) mm at right side, 10.3 (range 3.4~14.2) mm at left side. Mean diameter of C2 isthmus was 5.8 (range 1.0~10.1) mm at right side and 5.8(range 2.1~8.2) mm at left side. Two patients showed very narrow C2 isthmus. As a result, unilateral C1-2 LMPSF was performed on 6 patients (4 for anomalous vertebral arteries and 2 for narrow C2 isthmus). 12 of 18 patients were with C1-2 interlaminar bone graft and 6 patients without bone graft. All patients showed stable C1-2 fixation by flexion and extension cervical lateral X-ray films taken at least 6 months after surgery. Five out of 8 patients who had preoperative radiculopathy only showed improved symptoms. However, Seven out of 8 patients who had myelopathy showed little neurological improvement .
CONCLUSION
For C1-2 LMPSF, preoperative 3D CT-angiogram study is mandatory to identify abnormal vertebral artery and narrow C2 isthmus. Bilateral C1-2 LMPSF without bone graft is enough to obtain stable C1-2 fixation. If there is an abnormal vertebral artery or narrow C2 isthmus, unilateral C1-2 LMPSF with bone graft and wiring is alternative successful method.