Analysis of cervical sagittal alignment after screw-rod fixation

The use of posterior instrumentation constructs is well established for subaxial cervical stabilizations/fusions. The importance of global and regional sagittal alignment has become increasingly recognized.

To perform an analysis using computed tomography scans to determine the effect of posterior instrumentation on postoperative cervical sagittal alignment at long-term follow-up.

Over a period of 6 years, 56 consecutive patients (38 male and 18 female patients; mean age, 47 years) underwent cervical screw-rod fixation. Plain radiographs, computed tomography scans, and magnetic resonance images were analyzed preoperatively to assess sagittal alignment (C2-C7). Postoperatively, computed tomography scans and serial radiographs were obtained in all patients. With the use of independent observers, changes in sagittal alignment were determined by comparing the preoperative and postoperative imaging studies.

In total, 390 screws were placed in the cervical spines of 56 patients. Definitive radiographic fusion was detected in all 56 patients (100%). There were no incidences of instrumentation failures or lucencies surrounding any screws. Patients with preoperative kyphosis (n = 19; mean, +9.9°) improved their sagittal alignment by 6.5° (final mean, +3.4°), whereas patients with preoperative lordosis (n = 37; mean -15.44°) maintained their lordosis (final mean, -15.3°). Mean duration of follow-up was 32.5 months.

Radiographic analysis showed lateral mass fixation to be safe and effective. Certain operative techniques allowed substantial deformity correction and maintenance of long-term correction of deformity. Screw-rod fixation may be an effective method for maintaining lordotic cervical alignment in previously lordotic patients and for significantly correcting kyphotic deformity in patients with a preoperative kyphosis.