- Discussion:
- most common;
- occur thru base of odontoid process & may be caused by either hyper-flexion or hyperextension forces;
- blood supply is often comprimised in a type 2 frx
- type II frx occurs at base of dens, typically, frx plane is transverse;
- when dens displacement occurs, the C-1-dens-
transverse ligament complex usually remains intact;
- ligamentous disruption may involve thick atlantoaxial capsular lig;
-
non union:
- non union occurs in 30-50%, esp in elderly w/ > 5mm of displacement;
- greater rate of nonunion occurrs in pts who had sig displacement (angulation > 10 degrees
or translation > 5 mm) & are rxed w/
halo device compared to rx w/ arthrodesis;
- in atlanto-axial instability persists, spinal cord compression and paralysis may result;
- risk factors for non union:
- comminution at the base of the odontoid (strong negative risk factor);
- older age
- initial displacement amount > 2 mm (and especially if more than 4 mm);
- initial displacement direction (posterior worse than anterior)
- residual posterior displacement is also associated w/ more pain than w/ anteiror displacement;
- delay in dx
- redislocation in
halo;
-
ref:
- Non Union of fractures of the atlas.
LS Segal, JO Grimm, ES Stauffer. JBJS 69-A, 1987. p 1423-1434.
- Non Union of the odontoid process: An experimental investigation.
J. Schatzker, CH Rorabeck, JP Waddell.
CORR Vol 108, 1975. p 127-137.
- Radiographs:
-
prevertebral soft tissue swelling;
-
dynamic flexion & extension views ;
- thin section CT w/ saggital reformations may be necessary;
- Non Operative Treatment:
- management w/
halo vest for 3 months is used if:
- initial dens displacement is < 5 mm;
- reduction is maintained,
- pt is younger than 50 years of age;
- 93% of pts heal solidly in
halovest w/ the following conditions:
- age < 65
- anterior displacement less than 5 mm or posterior displacement less than 2 mm;
- diagnosis is made within one week;
- in the study by J. Stoney et al. 1998, management of these injuries with a halothoracic vest yielded a union rate of 82%;
- in the 18% of patients that failed to unite, there was no late neurological sequelae;
- risk factors for non union were extension type of injury, age over 65, and delay in dx;
- Operative Rx:
-
posterior atlantoaxial arthrodesis with wire and bone graft has a 95% fusion rate, although an intact C-1 posterior arch is prerequisite;
- anterior screw fixation:
- in the study by Henry et al, 81 patients with odontoid fractures underwent anterior screw fixation.
- 29 patients had type II fractures and 52 patients had type III fractures;
- 92% of patients achieved bony union at an avg of 14 weeks;
- two patients required seceondary posterior fusion;
- full range of motion was restored in 43 patients;
- ref: Fixation of odontoid fractures by an anterior screw.
AD Henry et al.
JBJS Vol 81-B. No 3. May 1999 p 472.
- Associated Frx:
-
atlas frx: (see:
Jefferenson frx)
-
halovest until the C-1 arch is healed, then a posterior C-1 & C-2 arthrodesis if the dens has not healed
- because of this association, it is prudent to obtain a CT scan of the C-spine, in all patients w/ a dens frx, esp if C1-C2 fusion is being considered;
-
transverse ligament rupture:
- may occur in 10% of patients w/ type II dens fracture;
- MRI is used to make the diagnosis;
- non operative treatment would be expected to result in atlantoaxial instability;
- references:
- Transverse atlantal ligament disruption associated with odontoid fractures.
KA Greene, CA Dickman, FF Marciano, J Drabier, BP Drayer, VKH Sonntag.
Spine. Vol 19, 1994. p 2307-2314.
- Posterior atlanto-occipital dislocation with fractures of the atlas and odontoid process: Report of a case with survival.
FJ Eismont, HH Bohlman. JBJS Vol 60, 1978. p 397-399.
New Sub-type of acute odontoid fracture (type II A).
MN Hadley, CM Browner, SS Liu, VKH Sonntag.
Neurosurgery. Vol 22, 1988. p 67-71.
Treatment of type two odontoid fractures in halothoracic vests.
J. Stoney et al.
JBJS. Vol 80-B. No 3. May 1998. p 452.
