THE MANAGEMENT OF UNILATERAL LATERAL MASS FACET FRACTURES OF THE SUBAXIAL CERVICAL-SPINE - THE USE OF MAGNETIC-RESONANCE-IMAGING TO PREDICTINSTABILITY/

Study Design. Retrospective review of the clinical course and cervical spine plain radiographs, computed tomography, and magnetic resonance imaging of 24 consecutive patients for a 2-year period with a unilater al lateral mass/facet fracture. Objective. To propose a treatment algo rithm for the management of unilateral lateral mass/facet fractures of the subaxial cervical spine based on ligamentous injury detected by m agnetic resonance imaging. Summary of Background Data. There have been no previous reports of the use of magnetic resonance imaging to predi ct clinical instability. Methods, A retrospective review of the clinic al course of all unilateral mass/facet fractures identified over a 2-y ear period was conducted. All cervical spine plain radiographs, comput ed tomography scans, and magnetic resonance images were reviewed by a neuroradiologist blinded to the clinical course of the patient. Magnet ic resonance T1-weighted and inversion recovery images were used to ev aluate the integrity of the facet region, interspinous ligament, anter ior longitudinal ligament, and posterior longitudinal ligament. Result s. Twenty-four unilateral lateral mass/facet fractures were identified . Only six initial cervical spine series demonstrated a bony abnormali ty at the level of the fracture. The fractures were identified by comp uted tomography and were almost all nondisplaced or minimally displace d. Less than half of the fractures extended ventrally to involve the t ransverse process or foramen transversarium or dorsally to involve the lamina. Twelve fractures were nonoperatively treated and 12 were trea ted surgically for stabilization. Ten patients in the operative group presented with or developed a subluxation. Nine of these patients had injury to at least three of the four ligaments evaluated by magnetic r esonance imaging. In the nonoperative group, only three patients had e xtensive ligamentous injury at the level of the fracture. All three of these patients were lost to follow-up. Conclusions, Plain radiographs of the cervical spine lack sensitivity to detect the presence of late ral mass/facet fractures. The appearance of the fracture on computed t omography does not indicate instability. The degree of ligamentous inj ury at the level of the fracture demonstrated on magnetic resonance im aging correlates with instability in this series. Operative stabilizat ion may be indicated for unilateral lateral mass fractures that presen t with a subluxation or that have injury to at least three of the foll owing ligaments: the facet region, the interspinous ligament, the ante rior longitudinal ligament, and the posterior longitudinal ligament. H owever, before a definitive management plan can be formulated, results from this small series require further validation.