The influence and effect of MRI on the AO classification for thoracolumbar spine injury

English Keywords:Thoracolumbar spine injury  Classification  AO classification  MRI

English Abstract:

  【Abstract】 Objectives: To evaluate the influence and effect of MRI on the AO classification for thoracolubar spine injury. Methods: A retrospective analysis of 80 patients suffering from thoracolumbar injury from January 2010 to December 2013 was performed. All patients in this study accepted X-ray, CT and MRI scans. The number and level of fractures in patients were analyzed. According to AO classification, the injury morphology was classified into type A compression injury, type B distraction injury, and type C rotation injury. The status of posterior ligamentous complex(PLC) were ranked with intact, indeterminate and injured. The first evaluation was done by X-ray and CT data(CT group). Six weeks later, the second evaluation was performed by adding MRI data(CT+MRI group). The ratios of rank changes of injury in AO classificatoin were evaluated with Wilson CIs. Results: CT alone revealed 128 thoracolumbar fractures in which 98 fractures were classified as AO type A, 24 as type B, 6 as type C. CT and MRI together revealed 23 new fractures with a total of 151 fractures in which 91 fractures were classified as AO type A, 54 as type B, 6 as type C. Compared with CT group, the AO types changed in 17 patients(21.3%) in group of CT+MRI, 95% Wilson CI(0.14, 0.31); unchanged 63 patients(78.7%), and 95% Wilson CI(0.68, 0.86). Among those that changed, 15(18.75%) patients changed from AO type A to B, 95% Wilson CI(0.11, 0.27); 2(2.5%) patients changed from AO type B to A, 95% Wilson CI(0.01, 0.08). With CT alone, the status of PLC was defined as intact in 58 cases, suspect injury in 1 case, and disrupted in 21 cases. With CT and MRI, the PLC was assessed as intact in 45 cases, suspect in 2 cases, disrupted in 33 cases. Using CT and MRI data together, 63 patients(78.7%) whose PLC assessment did not change, with 95% Wilson CI(0.67, 0.88). The number of patients whose PLC assessment changed reached 17(21.3%) with 95% Wilson CI(0.13, 0.33). Conclusions: The combination of MRI can detect bone and ligament injury more clearly than CT alone, which probably leads to the change of AO classification. Ligamentous injuries revealed by MRI are mainly responsible for these changes.