A rare case of spinal injury: bilateral facet dislocation without fracture at the lumbosacral joint

Fracture–dislocations of the lumbosacral spine are rare. Bilaterally locked facet injuries without fracture are even rarer and only 10 cases have been reported in the literature [3]. Traumatic lumbosacral dislocations are produced by high-impact trauma, and, therefore, are rarely found as isolated injuries [6]. Furthermore, many patients die soon after initial trauma, so many cases of traumatic lumbosacral dislocation remain unidentified [4, 7]. According to Watson-Jones, who first described lumbosacral dislocation, hyperextension is the main mechanism of the injury [1]. However, most authors consider a combination of hyperflexion and compression as factors responsible for causing bilateral L5–S1 dislocation [8‐11].

In our case, the patient was in a position of lumbar spinal and hip flexion when the trauma occurred (Fig. 5). We believe that hyperflexion rather than hyperextension is the most frequent mechanism of this injury. Initial screening of multiple trauma patients usually includes high-quality anteroposterior and lateral radiographs of the lumbar spine [4, 5, 10]. However, emergency room radiographs are frequently inadequate and can easily be misinterpreted as normal [4, 5]. Therefore, it is important to understand the detailed pattern of the injury. CT scan through the L5–S1 area is necessary to identify the dislocation, because it readily reveals locked or fractured facets, laminar fractures, and sacral fractures. Furthermore, MRI should be performed to assess the L5–S1 disc lesion when the general condition of the patient is stable. The MRI evaluation determines the treatment strategy [12]. Because of severe spinal and ligamentous damage, traumatic fracture–dislocation of the lumbosacral spine is rendered highly unstable [12]. Because it is a three-column injury, open reduction and internal fixation should be recommended [3, 5, 7‐9, 12‐14]. This injury results in multiple organ injury, and treatment of vital organ lesions undoubtedly remains a priority. However, early surgical treatment is necessary, especially if neurologic signs are found on physical examination [4, 6]. The time interval between trauma and surgery makes reduction difficult and physical symptoms, if present, can also affect the surgical outcome. In this case, to avoid pain prior to surgery the patient remained in the lumbar spinal and hip flexion position, and therefore, contracture of soft tissues and the hip joint had not resolved until the present time.

Most surgeons use the posterior operative approach. To achieve normal sagittal alignment, posterior reduction is required: it enables indirect decompression of the spinal canal and nerve roots, which may improve the neurologic outcome [3, 7]. If the integrity of intervertebral disc is confirmed by MRI, posterolateral fusion, only, is sufficient. However, if intervertebral disc damage is present, interbody fusion should also be performed [12]. In such cases, rigid fixation can usually be achieved by use of pedicle screws, providing immediate stability of the lumbosacral vertebrae.