Choice of pedicle screw fixation in patient with congenital fusion of cervical 2/3 vertebra

English Keywords:C2/3 congenital fusion  Pedicle Screw  3-dimensional CT

English Abstract:

  【Abstract】 Objectives： To evaluate the choice of optimal fixation segment and feasibility of posterior pedicle screw instrumentation in C2/3 congenital fusion. Methods: From January 2007 to June 2011, 28 patients with upper cervical diseases and congenital cervical 2/3 fusion(C2/3 block vertebrae), including 16 males and 12 females, were managed in our hospital. It included 22 cases of basilar impression and atlantoaxial dislocation and 6 cases of odontoid fractures. The mean age was 46.5(24-64) years. Posterior fixation and fusion surgery were performed to manage these patients. Anterior trans-oral release procedure was added on 1 case. The fused segments of C2 and C3 were evaluated with 3-dimensional CT to analyze the pedicle screw trajectories of C2 and C3. The widths and heights of the pars interarticularis(or pedicle) of C2 and pedicle of C3 were measured and the trajectory was defined as narrowing when the value was less than 4mm. The pedicle screws were placed in the C2 or C3 according to the measurement of trajectories and should be avoided to place in the narrowing trajectories. Specifically, if the both C2 and C3 pedicles were narrow, the pedicle screws were placed in the C4 segment instead. The patients were followed up in terms of fixation status postoperatively. Results: Narrowing of C2 pedicle was identified in 15 patients(53.6%), while it was identified in 6 patients(21.4%) in C3, including 3 cases(10.7%) with both-level narrowing at the same side. During the operation, 7 patients were managed with pedicle screws fixed in C2, 16 in C3 and 3 in C4. In 2 patients, screws were placed in C2 on one side and in C3 on the other. Postoperative CT analysis showed 1 internal breach and 2 external breaches of screw trajectories in the 16 C2 pedicle screws, and 2 internal breaches and 3 external breaches in the 34 C3 screws. No iatrogenic injury of vertebral artery or spinal cord developed. 24 patients were followed up for a mean of 3.2(1.5 to 5) years and no breakage or loosening of fixation occurred. Conclusions: The incidence of pedicle narrowing in C2 is significantly higher than that in C3. C3 pedicle screw fixation is feasible in most patients with C2/3 congenital fusion and it can serve as a reliable substitute in those patients with narrowing C2 pedicles.