BROKEN NECK (ODONTOID FRACTURE)
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What is an Odontoid Fracture?
The odontoid (also known as the “dens”) is the second vertebre in your neck (you have a total of 7 vertebre in the neck, another 12 in the thoracic spine and 5 in the lumbar spine). The 2nd vertebre can be broken after a whiplash type injury (your neck is hyper extended or hyper flexed). If you over extend your neck, the vertebre shifts backward, if you over flex your neck then your vertebre shifts forward. This particular vertebre has a unique structure and there is a bump that forms a joint with the first vertebre. This bump is a weak link in the spine and can break. It can break in three locations. A type 1 fracture occurs when just the tip that breaks. Its due to an avulsion of a ligament called the alar ligament (an avulsion means the ligament is ripped off the bone and actually pulls part of the bone off with it). A type 2 fracture is a break at the base of the dens, and a type 3 fracture is when the break goes into the main portion of the second vertebre.
How is an Odontoid Fracture diagnosed?
A patient with this type of fracture comes in after a whiplash type injury complaining of worsening neck pain. Its uncommon for someone with this injury to have neurologic injury, its usually pain that patients reports.
The injury is diagnosed with x-rays, but often a CT scan is used to better understand the pattern of the broken neck bone. When looking at a spine with this type of injury, its important to evaluate the space for the spinal cord, to ensure the broken bone is not compressing the spinal cord. Doctors are concerned for spinal cord compression if the spinal canal (which is where the spinal cord travels within the spine) is narrower than 1 cm.
How is an Odontoid Fracture treated?
Treatment depends upon on where the fracture occurs within the second vertebre.
A type 1 (tip avulsion) and a type 3 (fracture through the vertebral body) typically don’t require surgery as long as there is no neurologic problem. Patients wear a hard neck collar 6-12 weeks.
A type 2 fracture (break at the base) has a lower chance of healing (only 66%l) and therefore surgery may be required.
The surgery places a single screw across the fracture, or a halo is placed around the neck to hold the bones in a stable position, or the first and second vertebre can be fused (fixed together).
A single screw or halo are effective in standard type 2 fractures.
A fusion is usually required when the bone fragment separates more than 5 mm because over 50% will not fuse. However, the problem with fusion of C1-2 is that you lose about 50% of your neck rotation.
What is the long term outcome?
The patients typically heal well with the proper treatment. Neck pain in this condition is caused by the broken bone fragments rubbing together. Once healed, the pain shoulder resolve. The most common complication following fusion is the decrease in neck motion. Overall rates of successful fusion are very high.
The importance of surgical intervention for these fractures in the elderly population (>65 years old) has been highlighted by recent studies, which have shown that the 1-year mortality (person is no longer living one year after the injury) decreases significantly when surgery is performed. This seems counterintuitive... here is this frail elderly person with a broken neck...how are they going to recover from a big surgical operation? But similar to hip fractures (where its been shown that surgically repairing a broken hip saves lives, even in people that are over 90 years old), surgery allows people to recover faster even if there is increased pain for a few days/weeks after surgery. A broken neck is incredibly debilitating, and if its not treated with surgery, it still need to be treated because the neck is painful and often times unstable (the injury can get worse if its not protected). Therefore, people that do not get surgery need to wear a big bulky neck brace 24/7 for weeks and weeks. These neck braces make eating and drinking difficult, and many times elderly people can choke or aspirate (food goes down the wrong pipe...and enters the lungs instead of the stomach), which causes pneumonia (lung infection), and puts them at a much higher risk for mortality. Therefore its been shown that surgery saves lives in the elderly population after a C2 fracture.
References
1. C2 Vertebral Fractures in the Medicare Population: incidence, outcomes, and costs. Pearson et al. JBJS 2016; 98(6): 449-56. full article. mortality differences at 90 days and 1 year, surgical intervention shows improved outcomes.