Cervical facet injury

Spine Subaxial Injury with facet injury

AOSpine subaxial cervical spine injury classification system:

There was significant variability in diagnostic accuracy for F1 facet fracture through F3-type fractures, whereas almost universal agreement was achieved for F4-type injuries ¹⁾.

Considerable agreement exists between surgeon preferences with regard to unilateral facet fracture management with few exceptions. F2N2 fracture subtypes and subtypes with radiculopathy (N2) appear to be the threshold for operative treatment ²⁾.

F1 facet fracture. Non displaced facet fracture.

see Cervical facet dislocation

see Cervical unilateral locked facet.

Spine surgeons generally requested additional radiological evaluations in facet injuries, and MRI was the most common. Dynamic radiographs had a higher prevalence for F1/F2 fractures; vascular studies were more common for F3/F4 especially among surgeons with fewer years of experience. Private hospitals had a lower spine trauma cases/year and requested more MRI and more dynamic radiographs in F1/F2. Neurosurgeons had more vascular studies and dynamic radiographs than orthopedic surgeons in all facet fractures ³⁾.

see Cervical facet injury treatment.

Bilateral cervical facet dislocation (BFD) with facet fracture (Fx) often causes tetraplegia but is rarely recreated experimentally, possibly due to a lack of muscle replication. Intervertebral axial compression (due to muscle activation) or distraction (due to inertial loading), when combined with excessive anterior translation, may influence inter-facet contact or separation and the subsequent production of BFD with or without Fx. This paper presents a methodology to produce C6/C7 BFD+Fx using anterior shear motion superimposed with 300 N compression or 2.5 mm distraction. The effect of these superimposed axial conditions on six-axis loads, and C6 inferior facet deflections and surface strains, was assessed. Twelve motion segments (70 ± 13 yr) achieved 2.19 mm of supraphysiologic anterior shear without embedding failure (supraphysiogic shear analysis point; SSP), and BFD+Fx was produced in all five specimens that reached 20 mm of shear. Linear mixed-effects models (a=0.05) assessed the effect of axial condition. At the SSP, the compressed specimens experienced higher axial forces, facet shear strains, and sagittal facet deflections, compared to the distracted group. Facet fractures had similar radiographic appearance to those that are observed clinically, suggesting that intervertebral anterior shear motion contributes to BFD+Fx ⁴⁾.