Can the Interspinous Distance Predict Kyphosis in Conservative Treatment in Thoracolumbar Burst Fracture? A Retrospective, Diagnostic Study

Study Design: Retrospective, diagnostic study. Objective: To verify if the interspinous distance is able to predict the risk for kyphotic collapse in thoracolumbar burst fractures treated conservatively without neurological deficit. Summary of Background Data: In patients with thoracolumbar burst fractures, the association between the amount of comminution, by using load-sharing classification (LSC), and kyphotic collapse is presented in the literature. However, LSC does not include the interspinous distance as an indirect sign to suggest biomechanical instability due to posterior ligamentous disruption in these patients in order to predict kyphotic collapse. Methods: We added the interspinous distance to the load-sharing classification (MLSC) in 50 consecutive patients with thoracolumbar burst fractures (according to Denis criteria) treated conservatively. Results: The LSC score was correlated to kyphotic collapse in the patients treated with TLSO (r = 0.312, p = 0.027; Spearman test; A = 0.668). The MLSC was similarly correlated to kyphotic collapse among TLSO-treated patients (r = 0.295, p = 0.038; Spearman test; A = 0.652). Conclusions: The interspinous distance did not contribute to the identification of worse radiographic outcomes, represented by the kyphotic collapse. This may suggest that the amount of comminution pointed out by the LSC is enough and more important than the interspinous opening in order to predict kyphotic collapse in thoracolumbar burst fractures. Possibly, the interspinous distance is much too heterogenous and multifactorial to be useful, since it reflects vertebral body height, preinjury anatomy, as well as posterior element disruption.