VALIDITY OF THE 3-COLUMN THEORY OF THORACOLUMBAR FRACTURES - A BIOMECHANIC INVESTIGATION

Study Design. This study validated the three-column theory of fracture s by correlating the multidirectional instabilities and the vertebral injuries to each of the three columns, using a biomechanic trauma mode l. Objectives. The objective was to validate the three-column theory a s applied to the thoracolumbar fractures. Summary of Background Data, The widely used three-column theory of fractures for classification an d evaluation was based on retrospective analysis of radiographs. No bi omechanic study, using realistic spinal fractures and multidirectional instability measurements, was available. Methods. Using 16 fresh cada veric thoracolumbar human spine specimens, two groups of burst fractur es were produced by either simple axial compression or flexion-compres sion, using a high-speed trauma model. Multidirectional flexibility wa s measured before and after the trauma, thus quantifying the instabili ty of the burst fracture. Computed tomography scans were taken after t he fracture, and a new developed injury Scoring scheme quantified the injuries to the anterior, middle, and posterior columns, Statistical c orrelations were obtained:between the flexibility parameters and injur ies to each of the three columns. Results. In the axial compression gr oup, the middle column injury, compared with the other two columns, sh owed the highest correlations to eight of the nine flexibility paramet ers (average R(2) = 0.77). In the flexion-compression group, again the middle column injury showed the highest correlations to eight of the nine flexibility parameters (average R(2) = 0.85). Conclusions. The re sults of this study supported the three-column theory of the thoracolu mbar fractures and bolstered the concept of the middle column being th e primary determinant of mechanical Stability of this region of the Sp ine.