Tag Archives: Penetrating trauma

Best Of: How To Read A Stab Wound

Most emergency departments do not see much penetrating trauma. But it is helpful to be able to learn as much as possible from the appearance of these piercing injuries when you do see them. This post will describe the basics of reading stab wounds.

ImportantThis information will allow some basic interpretation of wounds. It will not qualify you as a forensics expert by any means. I do not recommend that you document any of this information in the medical record unless you have specific forensic training. You should only write things like “a wound was noted in the midepigastrium that is 2 cm in length.” Your note can and will be used in a court of law, and if you are wrong there can be significant consequences for the plaintiff or the defendant. This information is for your edification only.

1. What is the length of the wound? This does not necessarily correspond to the width of the blade. Skin stretches as it is cut, so the wound will usually retract to a length that is shorter than the full width of the blade.

2. Is the item sharp on one side or both? This can usually be determined by the appearance of the wound. A linear wound with two sharp ends is generally a two sided knife. A wound with one flat end and one sharp end is usually from a one-sided weapon. The picture below shows a knife wound with one sharp side.

Single edge knife wound

3. Is there a hilt mark? This can usually be detected by looking for bruising around the wound. The picture below shows a knife wound with a hilt mark.

Knife wound with hilt mark

4. What is the angle? If both edges are symmetric, the knife went straight in. If one surface has a tangential appearance, then the knife was angled toward that side. You can approximate the direction of entry by looking at the tangential surface of the wound edge. In this example, the blade is angling upward toward the right.

Angled knife entry

5. How deep did it go? You have no way of knowing unless you have the blood stained blade in your possession. And yes, it is possible for the wound to go deeper than the length of the knife, since the abdominal wall or other soft tissues can be pushed inwards during the stab.

AAST 2011: CT Evaluation of Penetrating Neck Trauma

In the old days, stab injuries to Zone 2 in the neck meant a trip to the operating room. Then it became acceptable to evaluate stable patients with this injury via endoscopy, angiography and a swallow study. Most chief residents didn’t have the patience for this and opted for OR anyway. CT now promises to simplify the evaluation process, rolling these studies into one fast and simple one.

USC+LAC and the University of Maryland directed a prospective multicenter study that looked at the sensitivity and specificity of using CT angiography of the neck to evaluate penetrating injuries.All patients underwent a structured physical examination of the neck. If hard signs of injury to the vascular tree or aerodigestive tract were present, they were immediately taken to OR (6%). Nearly all of these patients had an injury that required repair. If they had no signs, they were merely observed (51%). None had a missed injury.

The remaining 159 patients had a positive exam (minor oozing, small stable hematoma) underwent CT angio of the neck (54% stabs, 42% gunshots, 4% other). The majority were in Zone 2 (41%), but 24% were in Zone 3, 21% in Zone 1, and 14% crossed multiple zones. Overall sensitivity was 100% and specificity was 97%. CT angio was nondiagnostic in 3 patients due to missile fragment artifact.

Bottom line: CT angio of the neck is a fast and accurate exam that can be used in stable patients with an abnormal physical exam but no hard signs of injury. This fits my bias, and we have already been using the scanner this way for stabs. I would now recommend cautiously extending its use for select gunshots as well.

Hard signs of neck injury:

  • Unstable vital signs
  • Large, expanding, or pulsatile hematoma
  • Active bleeding
  • Air bubbling
  • Voice or airway disturbance
  • Hematemesis / hemoptysis
  • Thrill / bruit
  • Neurologic deficit

Reference: Evaluation of multidetector computed tomography for penetrating neck injury: a prospective multicenter study. AAST 2011 Annual Meeting, Oral Paper 61.

How To Read A Stab Wound

Most emergency departments do not see much penetrating trauma. But it is helpful to be able to learn as much as possible from the appearance of these piercing injuries when you do see them. This post will describe the basics of reading stab wounds.

Important: This information will allow some basic interpretation of wounds. It will not qualify you as a forensics expert by any means. I do not recommend that you document any of this information in the medical record unless you have specific forensic training. You should only write things like “a wound was noted in the midepigastrium that is 2 cm in length.” Your note can and will be used in a court of law, and if you are wrong there can be significant consequences for the plaintiff or the defendant. This information is for your edification only.

1. What is the length of the wound? This does not necessarily correspond to the width of the blade. Skin stretches as it is cut, so the wound will usually retract to a length that is shorter than the full width of the blade.

2. Is the item sharp on one side or both? This can usually be determined by the appearance of the wound. A linear wound with two sharp ends is generally a two sided knife. A wound with one flat end and one sharp end is usually from a one-sided weapon. The picture below shows a knife wound with one sharp side.

Single edge knife wound

3. Is there a hilt? This can usually be detected by looking for bruising around the wound. The picture below shows a knife wound with a hilt mark.

Knife wound with hilt mark

4. What is the angle? If both edges are symmetric, the knife went straight in. If one surface has a tangential appearance, then the knife was angled toward that side. You can approximate the direction of entry by looking at the tangential surface of the wound edge.

Angled knife entry

5. How deep did it go? You have no way of knowing unless you have the blood stained blade in your possession. And yes, it is possible for the wound to go deeper than the length of the knife, since the abdominal wall or other soft tissues can be pushed inwards during the stab.

How Big Was The Knife?

As part of a thorough history and physical on any trauma patient, we typically ask “How big was the knife you were stabbed with?” and “How deep did it go?”

Unfortunately, the answers you typically will get are “This big!” while they hold their hands at least 3 feet apart, and “All the way, doc!”

These answers are not very helpful, so it is not really of much use to ask the questions. The “how big” question is not helpful at all, because a long knife may barely penetrate, and a paring knife can make it all the way into the heart.

This leaves the “how deep” question. There are two ways to determine the answer. If the paramedics or police bring the weapon in, you can carefully examine it (taking proper care to preserve forensic evidence) and see if there is a blood line extending from the tip. This will show the maximum depth of penetration.

The second way is to examine the wound, either by local wound exploration or using CT.

Helpful hint: You can’t tell how large (wide) the blade is by looking at the wound. The elastic nature of the skin causes it to stretch as it is being cut during the stab. When the knife is removed, the resulting laceration will always be less wide than the blade.

To Probe or Not To Probe: Penetrating Wounds

There is considerable variability in the way that penetrating wounds are approached. Some are located over areas of lesser importance (distal extremities) or are so superficial that they obviously don’t fully penetrate the skin.

Unfortunately, some involve high-value structures (much of the neck and torso), or are too small to tell if they penetrate (ice pick injury). How should these injuries be approached?

Too often, someone just probes the wound and makes a pronouncement based on that assessment. Unfortunately, there are major problems with this technique:

  • The tract may be too small to appreciate with a finger or even a cotton-tip swab
  • The tract may be oriented in an unexpected direction, or the soft tissues may have moved after the penetration occurred. In this case, the examiner may not appreciate any significant depth to the wound.
  • Inserting an object may violate a structure that you wish it hadn’t (resulting in a hissing sound after probing a chest wound, or a column of blood after probing the neck)

A better way to approach these wounds is as follows:

  • Is the patient unstable? If so, you know the penetration caused the problem and the patient belongs in the OR.
  • Is there other evidence of deep injury, such as peritonitis with a penetrating abdominal wound? If so, the patient still needs to go to the OR.
  • Do a legitimate local wound exploration. This entails making the hole bigger with a knife, and using surgical instruments and your eyes to find the bottom of the tract. Obviously, there are some parts of the body where this cannot be done, such as the face, but they probably don’t need this kind of workup anyway.

As one of my mentors, John Weigelt, used to say, “Doctor, do you have an eye on the end of your finger?” In general, don’t use anything that doesn’t involve an eyeball in your local wound explorations!