- See:
-
Occipital-Atlanto-Axial Anomalies:
- Anatomy of
C1 /
C2
- Discussion:
- more common children, since the pediatric occipital condyles are small and almost horizontal & lack inherent stability;
- this injury is usually but not invariably fatal 2nd to respiratory arrest caused by injury to the lower brain stem;
- caused by severe
hyperextension Injury w/ distraction;
- ligaments opposing occipital condyles to superior articulating facets of atlas (tectorial ligaments) are disrupted, resulting
in either anterior translation (hyperflexion), posterior translation (hyperextension), or longitudinal distraction;
- along w/ joint capsules, tectorial membrane is torn;
- dissociation may be complete (dislocation) or incomplete (subluxation);
- detection of this injury is difficult in cases of partial disruption or if reduction occurs after the initial subluxation;
- non traumatic atlanooccipital subluxation may occur, most frequently in Down's syndrome &
rheumatoid arthritis;
- in the report by K Kenter et al, the authors report on 5 children with traumatic AOD;
- average distance from the dens to the basion was 9.8 mm; and average ratio of Powers was 1.38
- there were three survivors, two having a concomitant spinal cord injury;
- all survivors underwent a posterior occipitovertebral fusion;
- 3 cases initially went undiagnosed;
- ref: Pediatric Traumatic Atlanto-Occipital Dislocation: Five Cases and a Review.
Keith Kenter M.D. et al. JPO 2001;21:585-589
- Exam:
- cranial nerve disfunction is common;
- myelopathic changes may be present;
- Radiographs: 
- increased distance between clivus & dens, w/ disruption of basilar line of Wackenheim;
- Wachenheim's line
- usded to determine anterior / posterior subluxation
- this line is drawn down the posterior surface of the clivus and its inferior extension should barely
touch the posterior aspect of the odontoid tip;
- this relationship does not change in flexion and extension;
- thus if this line runs behind the odontoid, posterior subluxation has occured and vice versa;
- in children that atlantooccipital distraction has occurred if distance
between the occiput &
Atlas is > 5 mm at any point in joint;
- Atlanto-Occipital Condyle Distance:
- should be less than 5 mm regardless of age;
- Powers Ratio:
- identifies anterior subluxation & is described as ratio of BC/OA;
- BC is the distance from the basion to the midvertical portion of posterior laminar line of the atlas;
- OA is distance from opisthion to midvertical portion of posterior surface of anterior ring of
Atlas;
- if this ratio is greater than 1, anterior subluxation exists;
- Treatment:
- initially it is essential to avoid flexion of C-spine, which can occur on standard adult trauma boards;
- ensure that the matress allows the child's head to remain in an anatomic position;
- head is immobilized w/ sandbags (or equivolent);
- traction is contraindicated because of this severe instability & potential for injury to vertebral arteries & spinal cord;
- rigid immobilization of the patient in
halo allows adjustment to obtain reduction, & maintains position during and after operation;
- fusion involves occiput to
C2 fusion;
Occipito-atlantal instability in children. A report of five cases and review of the literature.
The pathological anatomy of fatal atlanto-occipital dislocations.
Atlanto-axial fusion with transarticular screw fixation.
Occipital-cervical instability.
The pathological anatomy of fatal atlanto-occipital dislocations.
Atlanto-occipital Dislocation: A report of three patients and a review.
D. Chattar-Cora and CP Valenziano.
JTO. Vol 14, No 5. p 370.
Traumatic dislocation of the atlanto-occipital joint.
Traumatic Atlanto-Occipital Dislocation in Children.
