TRAUMATIC ATLANTOAXIAL SUBLUXATION , POSTERIOR TRANSFACET FIXATION : A CASE REPORT

Las lesiones de la columna cervical se describen comunmente como eventos neurologicamente catastroficos con una tasa de supervivencia muy baja. Las lesiones del segmento C3-C7 son las mas frecuentes (alrededor del 80%) seguidas por el segmento C1-C2 (20%). Las lesiones de la columna cervical son de gran importancia, tanto por su gravedad asi como por las implicaciones neurologicas que conllevan. Es importante tener en cuenta que de los traumatismos cervicales que no presentan dano neurologico en el momento inmediato del accidente, un 10% lo presentaran con posterioridad, por lo que todos los traumatismos cervicales se deben considerar como potenciales traumas raquimedulares, hasta que la evolucion a posterior demuestre que no hay dano medular o radicular en forma definitiva. Se ha reportado casos con presentacion sin deficit neurologico tanto en dislocaciones atlanto-occipitales como atlanto-axoideas, por lo que estas lesiones pasan desapercibidas en el servicio de urgencias. Algunas de sus manifestaciones a tener en consideracion en el momento del accidente son, dolor suboccipital a la presion axial del craneo y cuello rigido espontaneo del paciente. Tambien puede presentarse disfagia, dolor a la palpacion de la parte anterior del cuello y aumento de volumen prefaringeo visible, por lo que es importante mantener la sospecha ante todo paciente con trauma craneo cervical quien presenta estos sintomas y realizar los examenes pertinentes. En este articulo se presenta un caso de luxacion atlanto-axoidea postraumatica que no presentaba deficit neurologico en el momento del accidente pero posteriormente se desarrollo, asi como el manejo quirurgico realizado.


INTRODUCTION
Craniocervical trauma is considered life threatening, due to the devastating neurological damage it causes.Thanks to advances in modern medical systems and the care of patients with trauma, the number of patients who survive these injuries has increased.Universal precautions in the care of the vertebral spine, and bet-ter stabilization of the vertebral spine at the moment of transfer to a specialized center, have led to a better outcome. 1,2Cervical, occipitocervical, and C1/C2 injuries and their evolution present a confused clinical manifestation that can lead to diagnostic error.4][5] Injuries in 30% of cases may be combined, atlantoaxial and occipitocervical, with high mortality rates. 1 There are reports of patients with cervical injury without neurological deficit, in which delayed diagnosis and initial stabilization lead to a worse prognosis for the patient in the short to medium terms.Once the diagnosis of cervical injury, specifically atlantoaxial, has been established, reduction and early fusion are recommended as definitive treatment, to prevent the development of neurological disturbances, which may be irreversible, even placing the patient's life at risk.Although there are currently various techniques for the treatment of these injuries, the results depend on the surgical technique that the specialist spinal surgeon is familiar with. 2,3,6,7inical case General information: Male patient aged 28 years, born and residing in Guadalajara, Jalisco, a Roman Catholic, educated to high school level, working as a carpenter.Inherited diseases: Denied by the patient.Disease history: Denies chronic-degenerative diseases.No previous surgery.
Patient reports that two months previously (August 2012), prior to admission, he suffered a physical assault causing cranioencephalic and cervical trauma.He was assessed at the Hospital General de Zona, where he was diagnosed with mild cervical sprain.The patient was discharged at the same time, without neurological deficit.The patient reports that after discharge, he began to experience paresthesia of the upper limbs with intermittent onset, followed by a gradual decrease in muscle strength, prompting him to come to this center for assessment.
Patient is conscious and oriented as to time, space and person.The neurological exam presents hypoesthesia of the upper limbs, with a decrease in muscle strength, 4/5 (Daniels scale).Patient has pain on moving the neck and pain on axial compression.Denies dysphagia.
Imaging studies were performed (Figure 1) which showed, in CT image reconstruction, loss of atlantoaxial joint congruence.Figure 2 shows the lateral Radiography and the measurement of C1/C2, the ADI interval, and the Powers index.
The atlantoaxial region is marked and the dissection extends laterally until the atlantoaxial joints on both sides were visualized, as well as the joint facets.The facets of the atlas and axis were visualized directly, and distraction was performed manually, using a cranialhalo, achieving adequate alignment.Transfacet posterior instrumentation of C1/C2 was performed, (Figure 3) without using large screws, and it was seen in the radiography that the screws achieved adequate reduction.(Figure 3) The normal anatomy between C1 and the odontoid apophysis is restored, as can be seen in the postsurgical control.(Figure 4) Patient one year after surgery, with adequate evolution and without neurological deficit, stiffness, or pain on movement.(Figures 5 and 6)

DISCUSSION
Rotational lesions of the atlantoaxial joint were described for the first time by Corner, in 1907.These lesions are the result of flexion and rotation, with rupture of the transverse ligament. 1,2,81-C2 luxations are rare in adults, occurring in <1% of all spinal injuries and around 20% of lesions of the cervical spine. 1,3,9,10tlantoaxial subluxation is rare, and even more so without fracture of the dens (odontoid process) of the axis.As a result, it can sometimes be overlooked.
The intrinsic stability of the atlantoaxial complex is provided by the dens apophysis, which binds to the ventral osteoligamentous ring, formed by the anterior arch of the atlas, and dorsally by the transverse ligament. 2,6,11he transverse ligament and facet joint capsule impede the anterior translation of C1 on C2.The alar ligaments connect to the posterolateral apex of the dens with the lateral aspect of the magnum foramen bilaterally, which limits particularly anterior displacement of the atlas in the dens and excessive rotation of C1 on C2. 12 The pattern of injury is consistent with a mechanism of high-degree hyperextension. 4he diagnosis is generally difficult; the clinical manifestations are usually rare, such as suboccipital pain on axial pressure on the skull,  Figures 5 and 6.Evolution 1 year after surgery.
and on moving the skull the patient spontaneously stiffens the neck, contracting the sternocleidomastoid and trapezius muscles, with dysphagia and pain on anterior palpation of the neck 3,8 , torticollis, and occipital neuralgia.Symptoms of vertebrobasilar insufficiency may sometimes be present.,13 Early diagnosis is essential, as a longer period between the lesion and its reduction is correlated with higher rates of recurrence and failure of the reduction through non-surgical techniques 14 We believe that simple radiographic measurements (ADI and Powers Index) of the cervical spine can help in the interpretation of anomalies in segment C1/C2, as in this case, where both measurements showed values compatible with C1/C2 disassociation, as well as helping the team of the emergency unit avoid overlooking these potentially devastating entities.
The craniocervical joint is an anatomically complex functional structure that represents the transition zone between the skull and the spinal cord, enabling extension, flexion and lateral rotation of the head.In particular, the atlantoaxial segment has unique characteristics compared with the lower cervical portion, due to its ample range of rotation. 1,2here are magnetic resonance imaging tests that suggest that interruption of the alar ligament is the mechanism by which a rotatory subluxation is produced. 15,16The alar ligaments are the main structures responsible for the stability of rotation, as they limit the rotation to 45°. 5,14ielding and Hawkins 10 describe 4 types of atlantoaxial rotation with rotation of the transversal ligament.(Table 1) Our patient is classified as having a type IV lesion, in which the atlas can dislocate bilaterally forwards or backwards, with concomitant narrowing of the vertebral canal.
Dislocation in C1-C2 is a dynamic process that is generally irreducible and cannot be reduced by cervical traction.The treatment of this type of chronic and reducible dislocation is a challenge for surgeons, although improvements in surgical techniques have brought some encouraging results over the years.The main procedures reported in the literature are posterior occipitocervical/C1-C2 fusion and instrumentation, and transoral odontoidectomy.Recent improvements in the emergency diagnosis and therapeutic management have shown a higher rate of patient survival.
Fielding and Hawkins 10 describe 4 types of atlantoaxial luxation with rupture of the transverse ligament; (Table 1) this case presented a type IV lesion, therefore it was decided on reduction with transfacet screws of C2 to C1, that even without using longer screws, has achieved adequate reduction, and good results after one year of follow-up.In these cases, occipitocervical fusion is generally considered as a form of neuroprotection, and should be performed as soon as possible. 1,5,715

FINAL CONSIDERATIONS
The diagnosis of posttraumatic atlantoaxial luxation should be suspected in the presence of sprain and neck pain.However, atlantoaxial luxation can occur in the absence of any clinical symptoms, therefore this diagnosis should be systematically considered and ruled out in any patient with multiple traumas.The radiographic findings of the cervical spine, in AP and lateral views, can hinder the interpretation of luxation C1/C2, therefore the routine use of CT scan of the cervical spine should be considered in all patients with cervical cranial trauma.When instability of the C1/C2 joint is diagnosed, timely reduction and fusion is recommended as definitive treatment.