AP View and Common C-Spine injuries - Part 3

Long AP view checklist
While interpreting the AP view of C-Spine, address these two questions:

1. Are all the spinous processes in a straight line? (Red and Blue vertical lines)
If not, consider a rotational injury.

2. Look for approximately equal height of each vertebra and also spaces between adjacent spinous processes? (Light green arrows and small blue X marks)

Common Fractures 
Most C-spine injuries are managed with immobilisation or surgical repair. Indications for surgical intervention are:

1. Neurological Deficits
2. Severe Pain
3. Unstable Spine

Jefferson's fracture (burst # of atlas due to axial loading)
X-Ray display outward displacement of lateral masses on open-mouth view. It is treated with hallo immobilisation/ surgical repair. 

Hangman's fracture: Fracture of both pedicles of C2 that occurs due to hyperextension of neck. It is treated with halo immobilisation/ surgery. 

Odontoid (Peg) Fractures
Type 1 - Philadelphia collar
Type 2 - Halo vest/ Surgical Repair
Type 3 - Halo vest

Vertical Compression fracture (Treated with traction/immobilisation)

Unilateral facet dislocation: On a lateral view, the involved vertebral body will be displaced <50% of its width. On anterior view, there is rotation of the involved vertebra, with the affected spinous process pointing toward the side that is dislocated. 

Bilateral facet dislocation: The vertebral body is dislocated anteriorly at least 50% of its width. These injuries usually present with neurologic deficits. 

Clay Shoveler's fracture i.e. Avulsion off the end of one of the lower cervical spinous processes, classically describes with C7. Rx with a soft collar. 

Images taken from:
https://www.med-ed.virginia.edu/courses/rad/cspine/interpretation8.html
http://newnurseblog.com/2010/11/17/spinal-precautions/halo/
https://radiopaedia.org/articles/hangman-fracture
http://www.radiologyassistant.nl/en/p49021535146c5/spine-cervical-injury.html

The obsolete C-Spine X-Rays - Part 2

AP View (Peg view)

The stability of C1-2 depends mainly on the transverse ligament. When looking at peg view, watch out for these three things:

1. Vertical Alignment of lateral margins of C1 and C2 (Vertical white lines in the image below) - If there is vertical misalignment of the masses then consider four possibilities - ligament injury, burst fracture of C1 (Jefferson #), rotation or developmental variation.

Slight neck rotation can often lead to unequal appearing spaces on either side but if this is the case, then lateral masses of C1 and C2 remain normally aligned.

2. Spaces on both sides of Peg should be approximately equal (Horizontal white lines in the image below) - Normal distance between peg and the lateral masses on each side is between 3-5mm.

Laterally displaced lateral masses (Jefferson #))

Rotated film leading to unequal distance on one side of peg

3. Look if there is a fracture on the base of the peg

Peg fracture

Beware of the Mach effect - an optical illusion which appears like a fracture through the base of peg.

Make a note of the horizontal black line crossing the base of peg - MACH EFFECT

Images taken from:
http://www.mediconotebook.com/2013/05/jefferson-fracture.html
https://www.ceessentials.net/article15.html

The obsolete C-Spine X-Rays - Part 1

In this day and age, most hospitals and certainly all the trauma centres prefer to CT Cervical-spine rather than performing a series of Cervical Spine X rays. Few centres have gone a step beyond, where they perform a head to pelvis (PAN-CT) scan PRIOR to resuscitation, which is then followed by simultaneous Clinical and CT based ABCD assessment.

That said, I believe that C-Spine X rays still hold a place in the developing world where cost becomes a significant issue during management of trauma victims. Emergency Physicians often get caught up in financial discussions with patients and their families, therefore we need to choosy while ordering blood investigations and imaging studies. And also, C-Spine X-Rays is a good way to start evaluating low risk injuries. In this three part series, I intend to provide a framework and stepwise interpretation of C-Spine X-Rays. 

Trauma C Spine views:

1. AP
2. Lateral
3. Open Mouth (Peg View)

• Swimmer's view: It is named after the swimming stroke referred to as freestyle. This view can be requested in addition to standard 3 trauma views to demonstrate the upper thoracic  and the seventh cervical vertebrae.

The most common reasons for missed injuries is inadequate films (which fail to show C7-T1 junction) and poor understanding of C1-C2 anatomy.

Anatomy Review

Key Points: It is critical to understand C1-C2 anatomy. C1 vertebra lacks a body. C1 instead has a ring which incorporates the odontoid process (odontoid process = dens = peg) of C2 vertebra. Often, these three different names for odontoid process cause a bit of confusion. I am going to refer to it as "peg" for the rest of this post. 

Look at the images below to visualise C1-C2 anatomy. Peg (labelled as odontoid process of C2 in the image below) sits between the Anterior Arch of Atlas (C1 vertebra is also called as Atlas) and transverse ligament. 

Peg is labelled as Dens the all the above 3 (Ant,Post and Lateral) images

See how peg (also known as odontoid/dens) fits into the ring of C1 vertebra seen from the lateral view

Lateral View (STEPS)

1. Assess adequacy of the film (Is C7-T1 junction seen? - Avoid interpreting inadequate films. Patients with inadequate films need a CT scan. Swimmer's view can be used as an adjunct to improve visualisation due to poor body habitus. At the outset, choose a CT over X-rays in difficult body habitus and elderly. 

Inadequate film (C7-T1 not visualised)

Adequate (C7-T1 junction seen)

                                       

Swimmer's view

2. Identify the Anterior Arch of Atlas (AAA) and measure the distance between AAA and Peg (< 3mm in Adults and < 5mm in Kids) - Increased space between these two structures suggests transverse ligament injury.

Pre-dental space on X Tay

3. Identify Peg: Anterior cortex of peg should be continuous with the body of C2 (Remember, Peg itself is a part of C2) and the posterior cortex of the peg should be in continuation with the posterior cortex of body of C2. Any break in the anterior or posterior cortex indicates a Peg fracture.

Image of Left - Not the that the anterior cortex of peg continuous with the body of C2 and the posterior cortex of the peg is in continuation with the posterior cortex of body of C2. Image on Right- Obvious step in the continuity of C1-2 indicating peg #. This finding may not be very prominent. 

4. Identify Harris Ring - A white incomplete ring seen at the base of peg which is occasionally incomplete at inferior and superior aspects (This is NORMAL). If the anterior or posterior margin of the ring looks disrupted, suspect a fracture thru the base of peg or C2 body.

Harris Ring, Marked with black Arrow heads. Look at all the above images now and try to localise the harris ring.

5. Look at the THREE Lines, heights of all the vertebra and pre vertebral soft tissues: 

• Each line should run smoothly without any steps. 
• The anterior and posterior heights of vertebra should be approximately same
• Any swelling on the soft tissues shadows anterior to the vertebra indicates haemorrhage. However, the absence of swelling cannot exclude an injury. So be worried if you increase in the width of pre-vertebral soft tissues but don't be reassured completely if it looks normal. Remember these numbers (3x7=21)

Pre-dental space - < 3mm in adults
Pre-vertebral Soft tissues width at C1-4 - < 7mm

Pre-vertebral Soft tissues width at C5-7 - < 21mm

Images taken from:

• http://www.shutterstock.com/pic-415445710/stock-photo-cervical-spine-structure-vertebral-bones-cervical-bones-anatomy-of-human-bone-system-human.html
• http://www.aafp.org/afp/1999/0115/p331.html
• https://www.med-ed.virginia.edu/courses/rad/cspine/interpretation1.html
• https://www.ceessentials.net/article20.html
• http://accessemergencymedicine.mhmedical.com/searchResults.aspx?q=jefferson+fracture&f_SemanticFilterTopics=jefferson+fracture&fl_SiteID=52&fl_TopLevelContentDisplayName=Images&adv=True
• http://clinicalgate.com/cervical-spine-5/
• https://www.studyblue.com/notes/note/n/radiology-c-spine-neck/deck/8336200