Tag Archives: stab

Retained Foreign Objects After Penetrating Injury

Recently, a Chinese man was in the news after having a four inch knife blade removed from his head after four years. What is the best way to deal with a problem like this?

First, get in the habit of imaging any body part with a penetrating injury. Retained objects can be as simple as gravel or as complicated as the knife blade above. And remember, some patients who have been stabbed present with a simple laceration but don’t want to tell you how they got it. Image before you close it!

Next, don’t remove it. This is common knowledge, but innocent looking objects (pencils, nails) can penetrate arteries and keep them from bleeding while embedded. Unpleasant and sometimes fatal bleeding can ensue if pulled out.

If you do not have specialists versed in the body regions involved in the injury, transfer immediately with the object secured in place. For objects penetrating minimally complex areas like the extremities, surgeons may opt to carefully remove it in the emergency department, or may elect to do so in the operating room.

Injuries to complex areas should undergo high resolution CT scanning so that 3D reconstruction can be performed if needed. The surgical specialists can then plan the operative approach. This is dictated by the anatomy of the area(s) involved and the architecture of the object (think about hooks and barbs). For objects located near critical areas, an operative exposure must be selected that provides access to all portions of it, and allows for rapid vascular control if needed.

This patient had a knife blade break off after he had been stabbed under the chin. It remained partly within the nasopharynx and the tip came to rest behind his left eye. His symptoms included headaches, stuffy nose and bad breath. The picture below shows the badly corroded blade in front of some of his radiographic images.

Knife in head

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.

Penetrating Injuries to the Extremities

Simple penetrating injuries to the arms and legs are often over-treated with invasive testing and admission for observation. Frequently, these injuries can be rapidly evaluated and disposed of using physical examination skills alone.

Stabs and low velocity gunshots (no rifles or shotguns, please) should be thoroughly examined. This includes an examination of the entire, unclothed body. If this is not carried out, there is a risk that additional penetrating injuries may be missed.

For gunshots, look at the wounds and the estimated trajectory to try to demonstrate that the object stayed clear of neurovascular structures. This exam is imprecise, and must be accompanied by a full neurovascular exam and evaluation of the bones and joints. If there is any doubt regarding bony involvement, plain radiographs with entry markers should be performed. Any abnormal findings will require more in-depth evaluation and inpatient admission.

If the exam is negative but the trajectory is “in proximity” to a major vessel, an arterial pressure index (API) should be measured. This test involves the calculation of the ratio of the systolic pressure in the injured extremity to the contralateral uninjured extremity. It should not be confused with the ankle brachial index (ABI) which compares the systolic pressure in the ipsilateral uninjured arm  or leg.

The magic ratio is 0.9. If the API is less than this, there is some likelihood that a vascular injury is present. If the API is higher, there is virtually no chance of injury.

The final test that must be performed before discharge is a function test. If the injured extremity is too painful to use or walk on, the patient may need to be admitted for pain management and therapy. Patients managed in this way can avoid arteriography, CT angiography or admission and save thousands of dollars in hospital charges.

Reference: Journal Am Coll Surgeons 2009;209:740-5.

How Good Is The Spine Exam In Penetrating Injury?

Examination of the spine in trauma patients is typically not very helpful. We always look for stepoffs. swelling and tenderness, but the correlation with actual injury is poor. A recent paper presented at the American Medical Student Association Annual Convention showed that it actually can be helpful in victims of penetrating injury.

A prospective study of 282 patients was carried out at a Level I Trauma Center, specifically focusing on penetrating trauma. Half had gunshot wounds, and 8% sustained spinal injury with one third left with permanent disability. Stab wounds never led to a spinal cord injury. The most common patterns for cord injury in gunshot wounds was a single shot to the head or neck, or multiple shots to the torso. 

The examiners looked for pain, tenderness, deformity and neurologic deficit. They found that the sensitivity was 67%, the specificity was 90%, the positive predictive value was 95% and the negative predictive value was 46%. These numbers are much better than those found during spine examination after blunt trauma. They also determined that prehospital immobilization after penetrating injury would not have helped, which I have also written about here.

The bottom line: a good spine exam in victims of penetrating trauma can accelerate definitive management prior to defining the exact details of the injury with radiographic or MRI imaging. This is particularly helpful in patients who present to non-trauma centers, where imaging or image interpretation may not be readily available. 

Reference: American Medical Student Association (AMSA) 60th Annual Convention: Abstract 26: Presented March 11, 2010

Use of Abdominal CT in Stab Wounds to the Anterior Abdomen

In general, stab wounds to the anterior abdomen (like any penetrating injury to the area) demand further evaluation to make sure there are no significant injuries. In the old days, a stab to the abdomen mandated a trip to the operating room. Fortunately, we recognized that more than half of these operations led to negative explorations.

Nowadays we can be much more selective. Here is my approach to evaluating these patients.

First, are there any indications that the patient needs to go to the OR right now?Check the vital signs. If there is any hemodynamic instability, operate! Check the abdomen. If there is obvious peritonitis, or significant tenderness more distant from the actual stab site, off you go to the OR!

Next, after finishing all of the usual ATLS protocol it’s time to evaluate further.Several options exist:

  • Observation – this is good for busy trauma centers that have lots of penetrating injury and busy ORs
  • DPL – not used too much any more, but certainly is legitimate. I recommend that your RBC count threshold be reduced to 25,000 or 50,000
  • Local wound exploration – this works in thinner people. Doing a LWE on an obese patient requires an incision that approaches the size of a small laparotomy. Might as well do it in the OR. Look for any violation of the anterior fascia.
  • CT scan – the new kid on the block

To use CT, the patient must be stable (remember, they should be in the OR if otherwise) and have had a full ATLS evaluation. They should also not be terribly thin. Too little fat makes it difficult to gauge depth of the injury.

The entry site(s) should be marked with a small marker to minimize streak artifact. Resist the temptation to just scan the area around the stab itself. Do a full IV contrast (no GI needed) abdomen/pelvis scan.

Look closely for blood outlining the wound tract. If it reaches the anterior abdominal fascia, the exam is positive. You do not need to see specific injury to the muscle or abdominal viscera. Violation of the anterior fascia is an absolute indication to proceed to the OR. On occasion, the knife will not penetrating the posterior fascia, or penetrates but does not injury any organs. In these cases it is best to have operated and found nothing rather than delaying and increasing the risk of intra-abdominal complications or infections.

Scan 1 shows blood tracking to the anterior fascia, as well as an increase in size of the rectus muscle.

Scan 2 shows penetration of the posterior rectus sheath with intra-abdominal fat herniating into it. The transverse colon is only 2 cm away deep to it. Scan 1 alone is enough to prompt you to take the patient to the OR!