Subaxial cervical spinal cord injury (SCI) is one of the most devastating injuries in medicine [1]. In Australia, 50% of traumatic SCIs reported in a 2008 cohort resulted in 136 cases of tetraplegia, amounting to annual personal care costs of approximately AUD$14.6 million [2]. Patients with subaxial facet dislocations present with the most severe neurologic deficit [3], resulting in tetraplegia in up to 87% of cases [4], [5], [6], [7], [8]. Rapid reduction is crucial, particularly in patients with a bilateral facet dislocation and a significant neurologic deficit [3]. Despite potentially devastating consequences, the spectrum of traumatic subaxial cervical facet subluxation and dislocation, herein termed distractive flexion injuries (DFIs) as described by Allen et al. [9], is significantly understudied.
Allen et al. describe four radiological stages of DFI: Stage 1, flexion sprain; Stage 2, unilateral facet dislocation; Stage 3, bilateral facet dislocation with up to 50% translation; and, Stage 4, bilateral facet dislocation with up to 100% translation [9]. Complete neurologic injury occurs more frequently following a bilateral facet dislocation [9], but by no means is this certain. Newton et al. advocates reduction of cervical facet dislocation within 4 hours of injury to prevent permanent neurologic damage following low-velocity trauma [10]. Although there is no consensus on the optimal surgical management of low- or high-velocity trauma [1], [11], [12], [13], [14], [15], [16], [17], [18], [19], in the case of SCI, prompt assessment and early intervention are crucial to optimize patient outcome [4], [10], [20], [21].
The literature pertaining to DFI comprises only small-cohort studies reporting radiographic features [5], [9], [22], [23], [24], [25], [26], [27] or the clinical outcomes of surgical or medical interventional treatment methods [3], [4], [14], [28], [29], [30], [31], [32], [33], [34]. Notably, there have been no large-scale cohort investigations of DFI, with or without concomitant neurologic deterioration, reported. In relation to clinical assessment, the neurologic examination of patients with subaxial cervical injury is often difficult, as patients commonly present with reduced levels of consciousness [35], [36]. Therefore, it is important to establish potential associations between injury epidemiology and radiographic features, and neurologic involvement. Furthermore, although qualitative radiographic analysis of cervical vertebral alignment is routinely used to provide an indication of injury severity, it is not known which (if any) of the proposed quantitative radiographic measures of subaxial spine trauma [37] are predictive of neurologic deficit. The interobserver agreement and the intraobserver repeatability of quantitative radiographic measures have not been reported for DFI.
The primary aims of the present study were to describe the epidemiology and the radiographic features of DFI in patients presenting to a major Australian tertiary hospital over a decade, and to identify which of these variables are risk factors for SCI. A secondary aim was to investigate the agreement and the repeatability of several quantitative radiographic measurements of subaxial cervical trauma severity in the context of DFI.