Cervical spine injuries associated with lateral mass and facet joint fractures: diagnosis and treatment strategies

Abstract

Purpose of study: The objectives of this study were to analyze the surgical results of cervical spine injuries associated with lateral mass and facet joint fractures retrospectively and to clarify the surgical indication and treatment strategies for these injuries.Methods used: From 1991 to 1999, 30 patients including 20 lateral mass fractures and 8 facet joint fractures received surgical treatments in our institution. The average age at surgery was 46 years. The injury types according to Allen's classification were compressive-extension in 26, lateral flexion in 3, and distractive-flexion in 1 patient. All patients, except one who required osteosynthesis for the separation fracture of the lateral mass, received exclusive posterior fusion with cervical pedicle screw system. From X-rays and magnetic resonance imaging (MRI) analyses, the fractures were classified into subtypes. The translation of fractured and adjacent vertebrae in the sagittal and coronal planes, vertebral body destruction and signal changes of disc and spinal ligaments (ALL, PLL, SSL and ISL) on MRI were evaluated. The number of stabilized segments and the spinal alignment were also evaluated at follow-up.of findings: The lateral mass fractures were divided into the following four subtypes: separation fracture in 11, comminution type in 4, split type in 5 and traumatic spondylolysis in 2. The superior and inferior articular process fractures and combination of both fractures were seen in six, one and one patient, respectively. The anterior translation of fractured vertebra was demonstrated in 77% of lateral mass fractures, whereas 24% and 10% of anterior translation was observed even in cephalad and caudal adjacent vertebrae, respectively. The alignment change in coronal plane was detected in 33% of lateral mass fractures. On MRI, the signal changes in ALL and disc were demonstrated in 76% and 25% of caudal and cephalad segments adjacent to fractured vertebra, respectively. The number of stabilized segments were 1.4, 1.67 and 2 in separation, comminution and split type, respectively. The fusion was completely achieved in all patients. However, the preservation of spinal segments resulted in fusion with the mild anterior translation in six patients.Relationship between findings and existing knowledge: Little is known about the detailed fracture type of lateral mass/facet fractures, initial instability, and a frequency of soft tissue injury. This study first analyzed these parameters.Overall significance of findings: The evaluation of spinal instability as well as the assessment of soft tissue injury on initial MRI was essential for the diagnosis and treatment of lateral mass and facet fractures. We successfully saved the stabilized segments in separation fractures or fractures with mild comminution based on the adjacent disc and ligaments evaluation. However, severely comminuted lateral mass fractures with coronal plane malalignment required two-level posterior fixation. The exclusive posterior stabilization with cervical pedicle screw system provides a short fusion as well as a normal spinal alignment even in the lateral mass fractures with severe spinal instability.Disclosures: Device or drug: cervical pedicle screw. Status: not approved.Conflict of interest: No conflicts.