Skeletal Radiol 12002) 31:529-531 DOI 10.1007/S00256-002-0540-.X
S. Sud S. Chaturvedi T.B.S. Buxi S« Singh
Received- 12 March 2001 Revised: 13 May 2002 Accepted: 14 May 2002 Published online: 5 July 2002 © ISS 2002 S. Sud (S3) ¦ S. Chaturvedi • T.B.S. Buxi Department of CT & MRI, Sir Ganga Ram Hospital, Old Rajender Nagar, New Delhi - 110060, l-mail:
[email protected] S. Singh
Posterior atlantoaxial dislocation without associated fracture
Abstract We report on a 38-yearKeywords • Atlas • Dislocation • old man with post-traumatic posted- Posterior ¦ CT • MRI or displacement of the atlas with respected to the axis without any associated fracture or neurological deficit caused by the displacement. Radiographs, computed tomography (CT) and magnetic resonance imaging (MRI) revealed posterior displacement of the atlas with the odontoid peg lying anterior and to the right of the anterior arch of the atlas.
Department of Neurosurgery, Sir Ganga Ram Hospital, New Delhi, India
Introduction Posterior atlantoaxial dislocation without any associated fractures is exceedingly rare [1]. Magnetic resonance imaging (MRI), computed tomography (CT) with multipla nar reconstruction (MPR) and three-dimensional reconstruction provide excellent visualisation of the rare dislocation discussed in this report. Case report A 38-year-old man was admitted to our hospital after a road accident, following which he was unable to move his right upper limb or turn his neck to the right side. On examination, the patient was well oriented in time and space and his higher motor functions were normal. Movements of his right shoulder were absent in all direc tions. Flexors and extensors of the right elbow had grade 0 force. The right wrist extensors and flexors had grade IV-V force. Hand movements were normal. All other limbs had grade V force. Right biceps jerk was absent. ^- j .ateral scanogram of the neck revealing posterior displace All biochemical investigations were within normal lim- ment 0 the atlas. Note the disruption of the spinolaminar lin< its.
(closed irrowhead)
-------- 286---------
Fig. 3 Axial CT scan displayed in the bone window setting showing the odontoid peg (open arrow) placed anterior and to the right of the arch of the atlas
Radiographs of the neck revealed posterior displacement of the atlas with respect to the axis, resulting in dis ruption of the spinolaminar line (Fig. 1). CT scan of the cervical spine with MPR in the coro nal and sagittal planes along with three-dimensional re construction revealed posterior atlantoaxial dislocation with atlantoaxial rotation. The odontoid peg was seen anterior and to the right of the anterior arch of the atlas. No fracture was visualised (Figs. 2, 3). MRI of the cervical spine confirmed the CT findings. A haematoma was present within the spinal canal, leading to kinking of the cervico-medullary junction; however, no evidence of any cord oedema was visualised (Fig. 4). MRI of the brachial plexus revealed contusion injury to the right-sided peripheral nerves, trunks and divisions. The patient was put on halo traction with an 8-kg weight, but started developing quadriparesis and was
-------- 287
Fig. 5 Post-operative lateral scanogram showing posterior fixation screw. No displacement of the atlas is seen
therefore given surgical treatment. Partial odontoidectomy with posterior fixation was performed (Figs. 5, 6). The patient did well post-operatively and showed good neurological recovery over a period of 3 months during which he was seen at follow-up in the outpatient department.
Discussion Isolated post-traumatic atlantoaxial subluxation is a rare injury [2]. Non-traumatic atlantoaxial subluxation is far
531
cause enough displacement to produce major cord damage with immediate death. In this event, a lesion at this level might well be missed in a routine post-mortem examination. Posterior dislocation without fracture may therefore occur more frequently than reported [3]. Measurements of the atlantoaxial distance are reliable only when the odontoid process is intact and attached to the C2 body. Concomitant displacement of the spinolaminar line relative to C2 is also seen. The distance between the anteritfr arch of Cl and the dens can be as sessed using CT. MRI affords a more sensitive method to assess the degree of cord compression, soft tissue inju ries such as haemorrhage, disc herniation and nerve impingement [6]. Neurological deficits are invariably present, even in patients with dramatic displacement and atlantoaxial widening. However, a significant amount of displacement can be tolerated in this region owing to the large size of the spinal canal [3], In 1990, Wong reported a case of more frequent. Almost all cases of atlantoaxial displace - posterior dislocation of Cl with respect to C2 [7]. In this ment manifest anterior dislocation of the atlas relative to patient, the only complaint was intermittent numbness the axis. Cases of rheumatoid arthritis, connective tissue and tingling in the trunk from the T7-8 level in the distal disorders and variety of congenital anomalies including direction. Our patient had no significant neurological defDown's syndrome have been commonly associated with icits pertaining to C1-C2 dislocation either. The mechanism of injury suggested by Haralson and atlantoaxial dislocation showing anterior dislocation of Boyd [2] and [7] also seem to be applicable in our pa the atlas relative to the axis. A rare variation of ligamentous Cl-2 dislocation with a pure craniocaudal distrac- tient. These authors speculated that their patient was struck from behind while the cervical spinal muscles tion injury has also been reported [3]. Anterior and posterior displacements of up to 5 or were relaxed. The force of the collision applied to the even 10 mm can develop after isolated transverse liga - trunk cassed the body to be thrown forward at a greater ment rupture; further displacement requires inefficiency velocity than the head. This resulted in extreme hyperexof the alar and other secondary ligaments [4]. Separation tension of the atlantoaxial joint, resulting in dislocation of Cl and C2 without fracture or rotation requires dis - without fracture of the odontoid. All patients with posterior dislocation of the atlas ruption of the apical, alar, cruciate and posterior longitu dinal ligament [5]. In our patient, all the ligaments were with respect to the axis previously reported Caroll et al. [3] and Wong [7] had successful reduction with traction. found during surgery to be torn. Posterior atlantoaxial dislocations without fracture are In our patient, however, the patient's condition worsened exceedingly rare, and only isolated cases have been re - with traction and posterior surgical fusion was required. Patients with atlantoaxial dislocation associated with ported [2]. The rarity of this dislocation is no doubt largely due to the configuration of the interlocking atlantoaxial fracture may survive, and there are few or no -long term articular processes, a configuration which would clearly neurological effects [7]. Reduction by traction is possitend to cause fracture of the odontoid. However, it also ble, but marked instability can be present. Posterior surseems likely that trauma sufficient to produce such a dis - gical fusion is usually necessary because of residual in stability or incomplete reduction, as in our patient. location without fracture of the odontoid would tend to References 1. Haralson RH, Boyd HB. Posterior dislocation of the atlas on the axis without fracture. J. Bone Joint Surg [Am] 1969; 51:561. 2. Bohlman HH. Acute fractures and dislocations of the cervical spine. J. Bone Joint Surg [Am] 1979; 61:1119.
3. Caroll AE et al. Traumatic atlantoaxial 6. Ellis. Imaging of the atlas (Cl) and axis distraction injury, a case report. Spine (C2). Emerg Med Clin North Am 1991; 2001; 26:454-457. 9:719-732. 4. Steel HH. Anatomical and mechanical 7. Wong DA, Mack RP, Craigmile TK. consideration of the atlantoaxial articuTraumatic atlantoaxial dislocation withlation. J. Bone Joint Surg [Am] 1968; out fracture of the odontoid. Spine 1991; 50:1691. 16:587-589. 5. Daniel L, Silbergeld et al. Two cases of fatal atlantoaxial distraction injury without fracture or rotation. Surg Neurol 1991; 35:546.
-------- 288 ---------
