Study design: Cadaveric biomechanical study and retrospective chart review.
Objective: Biomechanical comparison of segmental versus nonsegmental fixation of lumbar burst fractures and clinical analysis of short-term radiographic outcomes.
Summary of background data: Traditional short nonsegmental posterior fixation of thoracolumbar burst fractures suffers from high rates of failure. Construct stability may be improved by inserting additional screws at the fracture level.
Methods: Six intact human spines (L1-L3) were biomechanically tested in flexion-extension, lateral bending, and axial torsion. The inferior half of the L2 vertebral bodies and L2-L3 discs were resected to mimic an unstable L2 burst fracture with loss of anterior column support. Pedicle screws were inserted in L1 and L3 for the control group (nonsegmental fixation). Screws were inserted at all levels for the experimental group (segmental fixation). Construct stiffness and L1-L2 disc pressure were analyzed. Twelve patients with thoracolumbar burst fractures treated with this type of segmental fixation were reviewed.
Results: Construct stiffness during axial torsion was significantly higher for segmental constructs compared with nonsegmental constructs (P < 0.02) with no differences between flexion-extension and lateral bending. Disc pressure fluctuations during flexion-extension were significantly higher for segmental compared with nonsegmental constructs (P < 0.02), with no differences in lateral bending and torsion. Mean preoperative kyphotic deformity was 9 degrees and improved by 15 degrees after surgery. Follow-up films on 9 patients showed 5 degrees of kyphosis correction loss. Mean anterior vertebral body height was 58% of normal before surgery. After surgery height was 89% of normal and at final follow-up, 78%.
Conclusions: Segmental fixation of burst fractures with screws at the level of the fracture offers improved biomechanical stability. Theoretically, segmental fixation provides for additional fixation points that may aid in fracture reduction and kyphosis correction. This specific parameter is not evaluated in this study but will be an important outcome measure for a planned randomized controlled trial.