Category Archives: Anatomy

What You Need To Know About Frontal Sinus Fractures

Fracture of the frontal sinus is less common than other facial injuries, but can be more complex to deal with, both in the shorter and longer terms. These are generally high energy injuries, and facial impact in car crashes is the most common mechanism. Fists generally can’t cause the injury, but blunt objects like baseball bats can.

Here’s the normal anatomy:

sinus-fracture-treatment

 

Source: www.facialtraumamd.com

There are two “tables”, the anterior and the posterior. The anterior is covered with skin and a small amount of subcutaneous tissue. The posterior table is separated from the brain by the meninges.

Here’s an image of an open fracture involving both tables. Note the underlying pneumocephalus.

frontal_sinus1

A third of injuries violate the anterior table, and two thirds violate both. Posterior table fractures are very rare. A third of all patients will develop a CSF leak, typically from their nose.

These fractures may be (rarely) identified on physical exam if deformity and flattening is noted over the forehead. Most of the time, these patients undergo imaging for brain injury and the fracture is found incidentally. Once identified, go back and specifically look for a CSF leak. Clear fluid in the nose is, by definition, CSF. Don’t waste time on a beta-2 transferring (see below).

If a laceration is clearly visible over the fracture, or if a CSF leak was identified, notify your maxillofacial specialist immediately. If more than a little pneumocephalus is present, let your neurosurgeon know. Otherwise, your consults can wait until the next morning.

In general, these patients frequently require surgery for the fracture, either to restore cosmetic contours or to avoid mucocele formation. However, these are seldom needed urgently unless the fracture is an open fracture with contamination or there is a significant CSF leak. If in doubt, though, consult your specialist.

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The Chance Fracture

Centers that take care of blunt trauma are familiar with the spectrum of injury that is directly attributable to seat belt use. Although proper restraint significantly decreases mortality and serious head injury, seat belts can cause visceral injury, especially to small bowel.

Lap belt use has been associated with Chance fracture (flexion distraction injury to the lumbar spine) since 1982. The association between seat belts and intra-abdominal injury, especially with an obvious “seat belt sign” was first described in 1987.

chance-fracture-21

Chance fracture. The vertebra appears to split in half from posterior to anterior.

Twenty years ago, orthopedic surgeons in Manitoba finally put two and two together and reported a series of 7 cases of Chance fractures. They noted that 6 of the fractures were associated with restraint use. Seat belt sign was also present in 5 of the 6 patients with fractures and three of the six had bowel injuries.

The authors noted that many provinces were mandating seatbelt use at the time, and they predicted that the number of Chance fractures, seat belt signs and hollow viscus injuries would increase. On the positive side, the number of deaths and serious head injuries would be expected to decline.

Although this was a small series, it finally cemented the unusual Chance fracture, seat belt sign, and bowel injury after motor vehicle trauma.

Thankfully, three point restraints (lap belt + shoulder harness) has been required in the seats next to doors for a long time. And since 2007, they have been mandated in the middle seat as well. Thus, these injuries seldom occur in any but the oldest (beater) cars on the road. They are seen more frequently now with sports and extreme sports injuries.

Chance fractures are frequently unstable, involving all three columns of the spine. The anterior column fails under compression, and the middle and posterior columns fail from the distraction mechanism. Usually, this fracture pattern requires operative fixation. However, if the posterior column is intact, a TLSO brace can be tried. This fracture is at risk for non-union and development of kyphosis or a flat back, which can lead to chronic pain and an abnormal posture.

Reference: Pediatric Chance Fractures: Association with Intra-abdominal Injuries and Seatbelt Use. Reid et al. J Trauma 30(4) 384-91, 1990.

 

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The Cardiac Box: Meaningful For Gunshot Wounds?

A common dogma in trauma training is: “Watch out for the box!” This area on the anterior chest is purported to indicate high risk of cardiac injury in patients with penetrating trauma.

Where is it, exactly? Technically, it’s the zone extending from nipple to nipple, and from sternal notch to xiphoid.

The cardiac box

But is the dogma true? A number of (old) papers mapped out the location and incidence of cardiac injury in stabs to the chest and upper abdomen. And there is a pretty good correlation. For stab wounds. But what about gunshots?

A team at Emory University ran a retrospective review of their trauma registry data over a three year period.

Here are the factoids:

  • They saw nearly 90 patients per year with penetrating chest wounds. Of these, 80% were gunshots (!) Many had more than one penetration.
  •  Of the 233 gunshots inside “the box”, 34% injured the heart
  • The remaining 44 gunshots outside “the box” hit the heart 32% of the time
  • The authors suggest shifting the definition of “the box” toward the left, so that it extends from anterior midline, wraps around the left chest, and ends in the posterior midline (see below)

new-cardiac-box

Bottom line: Here’s the problem. Knives are attached to a handle which tends to stay outside your patient. Thus, it can only go so deep. But a bullet will keep going until something stops it, or it runs out of gas. So it makes sense that the traditional boundaries of “the box” don’t apply. But extending it to include the left lateral chest and exclude everything on the right side? It may make statistical sense in this study, but common sense dictates that the trauma professional needs to think about the heart any time a gunshot goes anywhere near the chest or upper abdomen. Do not limit yourself to any “box!”

Reference: Redefining the cardiac box: evaluation of the relationship between thoracic gunshot wounds and cardiac injury. AAST 2016 Paper #12.

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Who Is At Risk For Blunt Cerebrovascular Injury?

Yesterday, I wrote about proper screening for blunt cerebrovascular injury (BCVI). But, as you know, it’s important to screen only when there is a significant risk of the injury being present. Screening using the shotgun approach (screen everyone for everything) yields enough false positive results to present potential danger to your patient.

A variety of authors on this topic have promoted a number of high risk criteria to trigger a screening test. Most make sense, and are related to the anatomy of the vessels in question. The carotid arteries are relatively unprotected, although a bit deep, as they course up the neck. Thus, it is possible to damage them when they suffer a direct and significantly hard blow. Once they enter the skull, they are better protected. However, fractures through key areas of the skull base and face can injure the vessels, even in these protected locations.

The vertebral arteries are deep and relatively protected as they course through the vertebral foramina. However, if the vertebrae are fractured or subluxed, vessel injury can occur.

Finally, and as always, the physical exam is important. If there are unexpected neurologic changes that can’t be explained by other injuries, or there are indications of deep vascular injury, BCVI needs to be considered.

Here is my list of indications to screen for BCVI:

  • Neurologic abnormality not explained by diagnosed injury
    †
  • Arterial epistaxis
    †
  • Seat belt sign on neck
    †
  • GCS < 8
    † (this is the most commonly forgotten one)
  • Petrous bone fracture
    †
  • C‐spine fracture (C1‐C3) or subluxation at any level
    †
  • Fracture through foramen transversum
    †
  • LeFort II or III fractures

Bottom line: Be on the lookout for any of the criteria listed above in your trauma patient. If you find one during your initial evaluation, be sure to order a CT angiogram of the neck. And keep an eye out while scanning the head and cervical spine. If any of the other radiographic indications become apparent, add on the CT angiogram at that point.

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Bucket Handle Injuries Of The Intestine

Bucket Handle Injury

A bucket handle injury is a type of mesenteric injury of the intestine. The intestine itself separates from the mesentery, leaving a devascularized segment of bowel that looks like the handle on a bucket (get it?).

These injuries can occur after blunt trauma to the abdomen. The force required is rather extreme, so the usual mechanism is motor vehicle crash. In theory, it could occur after a fall from a significant height, and I have seen once case where a wood fragment was hurled at the abdomen by a malfunctioning lathe.

The mechanics of this injury are related to fixed vs mobile structures in the abdomen. Injuries tend to occur adjacent to areas of the intestine that are fixed, such as the cecum, ligament of Treitz, colonic flexures and rectum. During sudden deceleration, portions of the intestine adjacent to these areas continue to move, pulling on the nearby attachments. This causes the intestine itself to pull off of its mesentery.

The terminal ileum is the most common site for bucket handle tears. Proximal jejunum, transverse colon, and sigmoid colon are other possible areas. The picture above shows multiple bucket handle injuries in one patient. There are 3 injuries in the small bowel, and one involving the entire transverse colon. Note the obviously devascularized segment at the bottom center of the photo.

Always think about the possibility of this injury in patients with very high speed decelerationsSeat belt marks have a particularly high association with this injury. If your patient has an abnormal exam in the right lower quadrant, or if the CT shows unusual changes there (“dirty” mesenteric fat, thickened bowel wall, extravasation), I recommend a trip to the OR. In these cases, an injury will nearly always be present.

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Source: personal archive. Not treated at Regions Hospital

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