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.
Subject(s)
Humans , Radiculopathy , Retrospective Studies , Spinal Cord Diseases , Transplants , Vertebral Artery , X-Ray FilmABSTRACT
Pre-operative evaluation of the anatomy of the axis, such as the size and angle of the axial isthmus, is very important to minimize complications in atlantoaxial transarticular screw fixation. To provide basic data useful for atlantoaxial transarticular screw fixation in Korean, the width and height of the axial isthmus as well as ideal insertion angle of the screw were measured in this study. Fifty seven (male, 36; female, 21) dried axes obtained from Korean adult cadavers, 60.5 years old in average, were used. The shortest distance in the width and height of the axial isthmus was measured at the level of transverse foramen by using Vernier calliper. The ideal screw insertion angle was set up as an angle between a parasagittal line and the line passing through the center of the isthmus and screw insertion point which is located 2 mm lateral to and 3 mm superior to the posteromedial end of the inferior articular surface of the axis. The mean width of the axial isthmus was 8.14 mm (8.42 mm in male; 7.86 mm in female) in the right and 8.46 mm (8.80 mm in male; 8.12 mm in female) in the left side, and 8.61 mm in male and 7.99 mm in female. Although the width of the axial isthmus was slightly greater in the left and in male, there was no significant difference between both sides or sexes. The mean height of the axial isthmus was 7.17 mm (7.49 mm in male; 6.84 mm in female) in the right and 7.43 mm (7.90 mm in male; 6.96 mm in female) in the left side, and 7.69 mm in male and 6.90 mm in female. However there was no significant difference between both sides or sexes, as like in the width. In the atlantoaxial transarticular screw fixation, the axis with isthmus lesser than 5 mm in its width or height is regarded as risk group in general. The frequency of the risk group in the width was 3.5% (2 cases) in the right and 1.8% (1 case) in the left, while that in the height was 8.8% (5 cases) in the right and 7.0% (4 cases) in the left. The mean ideal insertion angle of the screw was 5.6 degrees, 4.4 degrees in the right and left side of male, and 4.7 degrees, 5.5 degrees in the right and left side of female respectively. However the insertion angle dispersed over a wide range between 0 degree ~ 12 degrees. In conclusion, measurement of the isthmus height and insertion angle, besides the isthmus width, should be involved in the pre-operative examination, to minimize complications during the atlantoaxial transarticular screw fixation.