Odontoid = A peg-like part of the second bone in the neck
Fracture = A break in a bone
A type II odontoid fracture is a break that occurs through a specific part of C2, the second bone in the neck.
Bones of the spine are called vertebrae. The bone involved in odontoid fracture is the second vertebra, C2, high up in the neck. The joint between C2 and the vertebra above, C1, has an outstanding range of motion. This is the joint that allows the head to rotate from side to side, bend forward and bend backward.
One of the unique features of this joint is a peg of bone called the odontoid process (sometimes called the dens). It is about the size of the tip of a pinky finger. The odontoid process sticks up from the front of C2 and fits into a groove in C1.
In an odontoid fracture, that peg of bone is broken. In a Type I odontoid fracture, just the tip of the bone is broken. In a Type II fracture, the most common type, the peg is broken at its base. In a Type III fracture, the bone is broken below the base of the peg.
Some fractures are considered stable, and some are unstable. In a stable fracture, the bone does not move out of its normal anatomical position and alignment. A stable fracture may “set” and heal itself. In an unstable fracture, the bone is more likely to move out of its normal position and alignment. Type II fractures are considered the least stable of the odontoid fractures. This makes them the most likely to require surgery.
A fracture that compresses the spinal cord may injure its delicate fibers. This type of injury to the spinal cord is called myelopathy, and it may lead to neurological symptoms like pain or numbness in the back, legs, and arms.
Causes and Risk Factors
Type II odontoid fractures occur when the cervical spine is hyperflexed (bent severely backward) or hyperextended (bent severely forward). Hyperflexion and hyperextension can be caused by trauma such as a fall or whiplash from a motor vehicle accident.
Age plays a big role in the incidence of odontoid fractures–they are the most common type of cervical spine fractures in patients older than 70. This is probably due to the increased risk of falls in the elderly, as well as the greater incidence of osteoporosis (a condition of weak and brittle bones).
Type II odontoid fractures can also occur in younger patients, most commonly as the result of trauma from a motor vehicle accident.
Tests and Diagnosis
The doctor will take a complete medical history and perform a complete physical examination.
If a Type II Odontoid Fracture is suspected, the doctor may order the following diagnostic procedures:
- X-rays – test that uses invisible electromagnetic energy beams to produce images of internal tissues, bones, and organs on film.
- Magnetic resonance imaging (MRI) – a diagnostic procedure that uses a combination of large magnets, radiofrequencies, and a computer to produce detailed images of organs and structures within the body.
- Computed tomography scan (CT scan) – a diagnostic imaging procedure that uses a combination of X-rays and computer technology to produce detailed images of the body. A CT scan shows detailed images of any part of the body, including the bones, muscles, fat, and organs. CT scans are more detailed than general X-rays.
- Nuclear bone scan – a diagnostic procedure in which a radioactive substance is injected into the body to measure activity in the bones. (The amount of radiation is small–less than the radiation in half of one CT scan.) This scan helps identify damaged bones.
Treatment options for type II odontoid fractures can be nonsurgical or surgical. Nonsurgical measures include immobilization, prevent or restrict movement, in a cervical collar or halo vest.
Surgery may be required if the fracture has resulted in neurologic symptoms and/or the spine has become unstable. One surgical option is a procedure called anterior screw fixation. During this procedure, the surgeon approaches the vertebra from the front of the neck (an anterior approach) and places an internal fixation, like screws, to hold the vertebrae in place while the bone heals.
Another option is a similar procedure performed from the back of the neck (a posterior approach). During this procedure, the surgeon fuses C1 and C2, the first and second vertebrae.
The treatment of stable odontoid fractures remains controversial. The surgeon will determine the best treatment for each patient and each situation.