Dens / Odontoid Fracture

 

Dens 1Dens 2

 

Anatomy

 

Superior projecting bony element of C2 / axis

C1 / atlas rotates around the dens to provide cervical rotation

 

Etiology / Epidemiology

 

Young - high energy injury

Elderly - low energy injury

 

Typically hyperextension injury

 

20% of all cervical spine injuries

Most common cervical fracture in the elderly

 

Classification Anderson & D'alonzo

 

Anderson Classification

 

Type 1

 

Tip avulsion

- alar ligament avulsion

- fracture off one side of tip of odontoid process

- rare

 

Type 2

 

Fracture of base of odontoid process

- most common type

- > 50%

 

Dens Fracture Type 2 Undisplaced0002Dens Fracture Type 2 Undisplaced0001

 

Type 3

 

Fracture through body of axis

 

Dens type IIIDens Type IIIDens type 3

 

Symptoms

 

Neurological injury rare due to large cross sectional area of spinal canal

Dysphagia due to retropharyngeal hematoma

Myelopathy symptoms

 

Type I Dens Fracture

 

Typically stable

 

Perform flexion / extension views

 

Type II Dens Fracture

 

Issue

 

Stability

Union

Elderly

 

Non-union

 

Vascular watershed area

- at base of odontoid

- increases risk of nonunion

 

Risk factors for nonunion

 

Koivikko et al JBJS Br 2004

- 69 patients with acute type II fractures treated with halo vest

- union 32/69 (46%)

- nonunion associated with:

- fracture gap > 1 mm

- posterior displacement > 5 mm

- delay in treatment > 4 days

 

Type 2 Dens Fracture Displaced

 

Management Type II

 

Grauer classification of Type II

Grauer 3Grauer 1Grauer 2

Type Definition Management
Type IIa

Non or mimimally displaced

No comminution

Non operative treatment
Type IIb

Displaced

Fracture line anteror-superior to postero-inferior

Potentially suitable for anterior odontoid screw
Type IIIc

Displaced

Fracture line antero-inferior to posteror-superior

Significant comminution

No suitable for screw

Posterior fixation / fusion

 

Nonoperative Management

 

Indications

 

Minimally displaced

? Elderly

 

Min displaced dens fractureDens undisplaced 2

 

Collar versus Halo-Thoracic Brace

 

Waqar et al World Neurosurg 2017

- systematic review of halo (60%) versus collar (40%) in 714 cases

- 80% type II

- similar union rates for type II fractures

- increased failure rates with collar for type III fractures

- higher complications rates with halo vest

 

Operative versus nonoperative

 

Aldrian et al Neurosurgery 2012

- anterior screw fixation (25) versus halo vest (21)

- average age 64 years

- no difference in clinical outcome between groups

- nonunion rate 13% with screw

- nonunion rate 30% with halo vest

 

Operative management

 

Indications

 

Displaced

 

Displaced DensType 2 Dens Fracture Displaced

 

Operative Options

 

1. Odontoid screw

2. C1/2 fusion

- Brook's interlaminar wire

- C1 lateral mass / C2 pedicle screws (Goel Harms)

- Mageryl transarticular screws

 

Odontoid screwodontoid screw

Odontoid screw

 

Dens Nonunion C12 fusion

C1 lateral mass / C2 pedicle screw (Goel Harms)

 

Transarticular screws

Transarticular / Magerl screws from: Koepke et al Nature Reports

 

Results

 

Shen et al Eur Spine J 2015

- meta-analysis of odontoid screw versus posterior C1/C2 fusion

- overall increased union rate with posterior fusion

- most evident > 60 years of age

- no difference < 60 years of age

 

Ondontoid Screw Fixation

 

Advantages

 

Preserves C1/C2 cervical rotation compared to C1/2 fixation

 

Contra-indications

 

Irreducible fracture

- > 6 mm displacement

- > 10 degrees angulation

- fracture gap > 2 mm

Comminution or anterior oblique fracture configuration (Grauer Type IIc)

Poor bone stock

Pathological fractures

Odontoid + transverse ligament injury - will remain unstable

Body habitus - short neck

 

Anterior Odontoid Screw Technique

 

Dens screw

 

AO Foundation Surgical Technique

 

Skull traction

Image intensifier

Smith-Robertson approach

Identify antero-inferior margin of C2

 

Results

 

Platzer et al Spine 2007

- ondontoid screw fixation in 102 patients

- nonunion rate 4% in patients < 65 years

- nonunion rate 10% in patients > 65 years

 

Lvov et al Eur Spine J 2021

- systematic review of odontoid screws

- 5% malposition

- 5% screw cut out

- 3% screw fracture rate

- nonunion 10%

 

Complications

 

Dysphagia

Difficulty swallowing

Recurrent laryngeal nerve - vocal cord paralysis

 

C1/C2 fixation

 

Indications

 

Displaced fracture

Comminution / Poor bone

? Elderly

Unstable fracture configurations

 

Technique

 

Vumedi C1/C2 fixation for Type II dens fracture

 

Vumedi C1/C2 Goel and Harms technique

 

AO Surgery Reference C1/C2 fusion

 

Results

 

Huang et al JAAOS 2019

- 77 cases type II treated with C1/C2 posterior (screw/rod) fixation

- union rate 95% on CT

 

Elderly

 

Issue

 

Most common fracture of the cervical spine in the elderly

High risk of non-union

High risk of mortality

High risk of halo-thoracic brace

High risk of failure of fixation due to poor bone

 

Mortality

 

Allia et al Orthop Traumatol Surg Res 2020

- 79 patients mean age 85

- 3 month mortality 27%, 1 year mortality 30%

- 3 month mortality 11% in undisplaced fractures

- 3 month mortality 40% in displaced fractures

 

Operative versus nonoperative

 

Schroeder et al Neurosurgery 2015

- 1233 patients > 60 year old with type II odontoid fracture

- short and long term mortality lower with operative versus nonoperative treatment

 

Sarode et al Spine J 2018

- operative versus non operative treatment 1098 patients > 65

- no difference in short term mortality

- small difference in long term mortality favoring operative treatment

 

Nonunion

 

Dens nonunion xray

 

Issues

 

Pain

Instability / myelopathy

Risk sudden death

 

Types

 

Non union - unstable on flexion extension views

Fibrous nonunion - stable on flexion / extension views

 

Fibrous union

 

Florman et al World Neurosurgery 2022

- systematic review of 141 patients with fibrous nonunion / stable nonunion

- no neurological events

- neck disability ranged from mild to severe

- good to excellent pain scores

 

Nonunion / unstable

 

Type 2 Dens Nonunion Coronal CTDens Type 2 Nonunion

 

Dens Nonunion Instability0001Dens Nonunion Instability0002

Significant instability on flexion / extension views after Type II odontoid nonunion

 

Options

 

C1/2 fusion

 

Dens Nonunion C12 fusion

 

Type III

 

Definition

 

Through the body of C2

May involve portions of C1 or C2 facets

High healing potential

 

Dens type 3 1Dens type 3 2

 

Non operative management

 

Rizvi et al Spine J 2021

- 212 patients with Type III dens fracture

- average age 72, 20% lived independently

- 95% treated nonoperatively

- 5% required surgery

 

Koshimuzi et al J Orthop 2021

- 25 patients with Type III dens fracture

- hard collar or halo vest

- 22/25 (88%) united

- nonunion associated with increased coronal tilt and lateral mass gap > 2mm