The relationship between radiologic parameters and transverse atlantal ligament injury obtained from MRI scans in patients with an isolated atlas burst fracture: A retrospective observational study

The treatment of an atlas burst fracture depends on whether transverse atlantal ligament (TAL) injury is present. We compared the radiologic parameters associated with the presence of a TAL injury as detected using magnetic resonance imaging (MRI), and verified whether the lateral mass displacement (LMD) criteria currently used to diagnose TAL injuries in atlas burst fractures are reliable or need revision. Thirty patients who presented with isolated atlas burst fractures were included in this retrospective observational study. We measured radiologic parameters, including LMD, atlanto-dental interval, basion-dens interval, internal lateral mass displacement, and external lateral mass displacement, in each patient at the time of initial presentation. The presence of TAL injury was evaluated using MRI. We compared the radiologic parameters and characteristics of patients who presented with TAL injury. We also determined the sensitivity and specificity of an LMD test to accurately diagnose TAL injury based on MRI. Finally, we compared the radiologic parameters according to the presence of surgical treatment and patient union status. Twenty patients presented with an intact TAL, while 10 patients had a TAL injury on MRI. LMD was significantly higher in patients with TAL injury (9.61 vs 3.73 mm, P < .001). In multivariable logistic regression analysis, LMD was also significantly higher in patients with TAL injury. The sensitivity and specificity of LMD for diagnosing TAL injury based on MRI in patients with isolated C1 fractures were 90% and 100%, respectively. The incidence of an LMD greater than 8.1 mm was statistically higher in patients than in those without TAL injury (90% vs 0%, P < .001). Nine patients underwent surgery for isolated atlas burst fractures, and 21 did not. LMD (9.56 vs 4.03 mm, P < .001) and fracture gap (7.96 vs 4.01 mm, P < .001) were significantly higher in patients who underwent surgery. Among the various radiologic parameters, LMD closely correlated with the presence of TAL injury, as patients with an LMD greater than 8.1 mm were more likely to have a TAL injury in the case of atlas burst fractures. LMD is a good method for predicting the presence of TAL injury if MRI is not available.