Indirect ballistic injuries

[Michael Courtney]

One key issue in terminal ballistics is whether all projectile effects are local or bullets can create remote effects in tissue. The main published author of the local view is Martin Fackler. In arguing against remote pressure wave effects by citing his own unpublished data and shifting the discussion from the published experiments of Suneson et al. to claiming that remote effects have never been documented in humans (See Annals of Emergency Medicine 28:2 August 1996 p 194-203, quote from p 198), Fackler states:

To date, no study has scientifically or objectively demonstrated any change in the human gunshot victim that cannot be explained by the well-recognized wounding mechanisms of tissue crush resulting from a direct hit by the penetrating projectile or tissue displacement resulting from temporary cavitation.

In fairness to Dr. Fackler, many of the papers documenting remote wounding in humans are from later studies (Treib et al, 1996; Sturtevant 1998; etc.) However, there is at least one reference that Fackler knew about (cited as reference 55 in Fackler’s own paper) that describes remote wounding in humans. The Textbook of Military Medicine, Part I: Warfare, Weaponry, and the Casualty, Vol. 5, Conventional Warfare: Ballistic, Blast, and Burn Injuries published by the Surgeon General of the Department of the Army in 1990, edited and authored by the most experienced Army experts in wound ballistics states (TMM p 146-149):


The post-traumatic pneumatoceles that occurred in a few combat casualties in the Vietnam War show that projectiles with high energy transfer are capable of causing indirect damage to lungs.

The mechanism by which a penetrating projectile causes pulmonary injury is sometimes difficult to understand. The following example from the WDMET database may be an example of just such an injury: A soldier sustained a through-and-through of the shoulder made by an AK47 bullet fired from about 50 m away (Figure 4-39). A roentgenogram made about 1 hour after wounding (Figure 4-40) shows that the lung nearest the wound has an extensive pulmonary contusion. The cause of this injury is not clear. If temporary cavitation were the cause, some evidence of chest-wall damage or even a fracture of the humerus might be found. Certainly, the soft-tissue injury shows no evidence (such as ecchymosis) of the effects of massive temporary cavitation that would be necessary to have caused this distant lung injury. Could this observed injury be a manifestation of stress waves?

Lung has another distinctive biophysical property; it is perhaps the only organ in the body in which the speed of sound (50 m/s is likely to be less than the velocity of a penetrating projectile.) Thus, the potential exists for a projectile penetrating through lung to be associated with a true shock whether or not this has biophysical or medical ramifications is unclear.

The recent papers showing that bullets stopped by armor can cause EEG depressions sufficient for incapacitation, lung injury, and even death in a significant fraction (50%) of human-sized animals certainly demonstrates that remote wounding in the lungs is a significant wounding factor. (J Trauma 2007; 63:405-413, Mil. Med. 2007; 172: 1110-1116).

Michael Courtney

 

[Michael Courtney]

In another article arguing against remote wounding effects, Fackler claims (Journal of Trauma 29(10):1455; 1989):

A review of 1400 rifle wounds from Vietnam (Wound Data and Munitions Effectiveness Team) should lay to rest the myth of “distant” injuries. In that study, there were no cases of bones being broken, or major vessels torn, that were not hit by the penetrating bullet.

This is a surprising claim since an authoritative published analysis of that same data suggests as many as 10% of fractures included in the data set are due to indirect effects (TMM p 153-154):


Indirect fractures (that is, those that occur in penetrating wounds in which the projectile appears not to have had physical contact with the bone) are possible in extremity wounds. These fractures, which are caused when bone is displaced by the expanding temporary cavity, have been demonstrated in laboratory experiments since Harvey’s pioneering work in the 1940s . . .

Indirect fractures, in contrast to fractures caused by direct contact with the projectile, might be simple linear fractures. About 10% of the fractures in the WDMET database are listed as ”transverse (no displacement)” and “linear.” These may be indirect fractures (Figures 4-46 and 4-47).

(Figure captions for photograph and x-ray
Fig. 4-46. This casualty, who was shot through his calf with an M93 ball fired by an M16, has a large wound of exit. The wound of entrance is barely visible at the medial edge of the calf.
Source: Wound Data and Munitions Effectiveness Team

Fig.4-47. This roentgenogram of the wound shown in Figure 4-46 shows a hairline linear fracture in the tibia about 2 inches proximal to the ankle. Pieces of lead are visible near the wound of exit. It is likely that the fragmented as it exited the calf and the associated temporary cavitation caused an indirect fracture. Source: Wound Data and Munitions Effectiveness Team


Citing the WDMET data and a personal communication, Fackler goes on to say (Journal of Trauma 29(10):1455; 1989):

In only two cases, an organ that was not hit . . . suffered some disruption.


However, published findings based on the WDMET data show a larger number of significant injuries to organs not directly struck by the bullet. In addition to the remote lung injury already discussed, the report discusses five cases where abdominal organs (spleen, caecum, colon, jejunum, and liver) were damaged by bullets which did not even enter the abdominal cavity and suggests (TMM p 149-152):


Many more casualties probably sustain indirect intra-abdominal injuries similar to the ones shown in Figures 4-42 and 4-43 (that is, the injuries occur at sites remote from the projectiles’ intra-abdominal trajectories).


Remote effects in the CNS are also documented (TMM p 155):

Experimental data, also dating back to Harvey, suggest that electromechanical effects-perhaps produced when nerves are deformed by nearby cavitation-may cause depolarization and consequent neurodysfunction. The WDMET database contains at least one possible example of this phenomenon. A soldier sustained a perforating gunshot wound of the trapezius muscle in his neck. He stated that for 5 minutes after he was wounded, his body felt numb and he was unable to move any of his extremities. The subsequent physical examination revealed only tissue damage to the muscle. Despite its anecdotal nature and the possibility that this was actually a combat-stress reaction, one is tempted to believe that the stress wave passing through the soft tissue of the soldier’s neck indirectly caused a transient cord dysfunction.


In summary, Fackler’s assertions that the WDMET data base does not provide evidence for indirect wounding does not agree with authoritative published findings based on that data. The WDMET data base shows cases of indirect wounding in the lungs, liver, spleen, caecum, colon, jejunum, and CNS.

Michael Courtney

 

[rocpyro]

Thanks for posting. I'm an EMT, and gun shot wounds are one of the most interesting things I've dealt with. There's alot of contradicting data out there, it's hard to sort though at times.

 

[brickeyee]

Experimental data, also dating back to Harvey, suggest that electromechanical effects-perhaps produced when nerves are deformed by nearby cavitation-may cause depolarization and consequent neurodysfunction.

The doubters must never have 'bumped there funny bone'.
It does not take a lot of pressure to affect nerve function.
Teddy Kennedy is about to find this out.

The changes in intra cranial pressure to produce symptoms in the CNS are painfully small in the overall scale of pressure, let alone the temporary pressures produced by bullet impact and passage through tissue.

You should talk with some neurologists about what it takes to interfere and even damage nerve function from disease, let alone trauma.

 

[Michael Courtney]

The Textbook of Military Medicine has a lot of useful information on wound ballistics.

http://www.bordeninstitute.army.mil/published_volumes/conventional_warfare/conventional_warfare.html


Chapter 4 is particularly useful for understanding wounding effects, but all the chapters on projectile wounding (Ch 2-5) are interesting. It's a lot of material, and does not include new results after 1990, but it is the best introduction to wound ballistics that I have seen.

 

[Phil DeGraves]

Even Fackler says that if it is an organ that is not elastic (the liver, for example), you are more likely to get disruption than in an organ that is elastic and can move with the "wave". He talks a lot about that in the videotape "Deadly Effects".

 

[LaEscopeta]

Thanks for posting, especially the link to “The Textbook of Military Medicine.”

There's alot of contradicting data out there, it's hard to sort though at times.

That’s my feeling as well. Science understands internal (what happens from the chamber to the muzzle) and external (what happens from the muzzle to the target) ballistics very well, but terminal ballistics (what happens when the projectile hits the target) are not well understood. Thus the need for testing in ballistics media (because of formulae or model can predict as well as an actual test.) Also the reason for endless caliber debates that cannot be settled one way or the other.

 

[Michael Courtney]

Even Fackler says that if it is an organ that is not elastic (the liver, for example), you are more likely to get disruption than in an organ that is elastic and can move with the "wave". He talks a lot about that in the videotape "Deadly Effects".

It seems that one of Fackler's mistaken presuppositions is that there has to be macroscopic movement of tissue for there to be an injury of physiological dysfunction. In other words, he focused on direct crush and stretch as injury and ignored the possibility of compressive or microscopic shear stresses acting at a distance. It is now known that these forces can be important beyond the reach of temporary cavitation.

Michael Courtney

 

[La Pistoletta]

What about brain damage from a spike in blood pressure induced by a shot to a limb?

 

[Mr_Rogers]

Reported field experience in game animals suggests that a bullet velocity of around 1200 fps is required to produce any type of "hydraulic" damage. Two bullets following the same path are likely to produce two different effects.

The difficulty of researching bullet effects is emphasized in Col. Chamberlin's circa WW2 researches. He found that if you restrict the subject sufficiently to allow precise, repeatable, bullet placement you remove the conditions that allow realistic tissue damage.

 

[RyanM]

I stopped following your discussions with Dr. Roberts on Tac Forums way back when, about halfway through 'em, but I still remember making a few observations that got ignored. A lot of people really seem unwilling/unable to consider new ideas.

Anyway, one thing that got bandied about fairly often, early on, was that there are numerous veterans of various wars who were hit in the lungs with high-energy rifle bullets, and are walking around today with no noticable brain damage.

But that's a ridiculous comparison. As Fackler noted in his early career, military FMJ ball is worlds apart from expanding/fragmenting ammo, in wounding effect. Also, incapacitation due to impacts to the brain does not necessarily result in long-term trauma, or every single person who's ever been knocked out by a blow to the head would also exhibit "noticable" dain bramage. Finally, the people that did suffer severe remote brain damage would most likely have died in short order, and there wouldn't have been anything particularly outstanding about the injury, to a combat medic. Shot in the chest, fell over, died. Nothing unusual there.

One thing I still think would be worth further research later on, however, is how bullet expansion speed affects interaction with tissue. A bullet which expands all at once should be more efficient at wounding/incapacitating, even if the same amount of energy is expended in deformation compared to a slower one. However, the maximum non-deforming velocity is a factor, thus materials such as copper and harder lead alloys should be looked into.

Vb = velocity of the center of the bullet's leading face
Ve = velocity of the outermost edge of the bullet relative to the center

A bullet that is still in the process of expanding essentially behaves as though it were a smaller or more aerodynamic one, wounding less efficiently.

 

[brickeyee]

Anyway, one thing that got bandied about fairly often, early on, was that there are numerous veterans of various wars who were hit in the lungs with high-energy rifle bullets, and are walking around today with no noticable brain damage.

Lungs are mostly air.
The survivors probably did NOT get hit in the larger blood vessels in the lungs.
If they did they would have bled out I a very few minutes.

Also, incapacitation due to impacts to the brain does not necessarily result in long-term trauma, or every single person who's ever been knocked out by a blow to the head would also exhibit "noticable" dain bramage.

And ‘punch drunk’ boxers have exactly that, long term damage.
It even shows on x-rays as shrinkage of the brain tissue.
Since the damage is cumulative, that would imply that every blow does SOME permanent damage.

Think about the pressures we are talking about from a blow to the head that results in loss of consciousness.
It does not take very much pressure to force a nerve to depolarize, a process driven by osmotic gradients between the interior of the nerve and the exterior.
After the cell wall ‘gates’ open to allow the depolarization of the nerve to occur, the ‘ion pumps’ in the nerves cell wall re-create the osmotic gradient by pumping ions back into the nerve.

 

[Jeff White]

An interesting curiosity......

If indirect ballistic injuries occur, what good can this knowledge do us? There obviously isn't any evidence that this indirect trauma occurs frequently enough or causes enough injury to incapacitate an opponent with any kind of reliability. So what great strides in tactics, techniques and procedures can make now that we know this?

Jeff

 

[JesseL]

Jeff,

That's the same thought I had in reading through this. These studies are probably much more useful to medical professionals than shooters.

 

[.cheese.]

Here is a good resource I've looked through before. It might have some information you all could benefit from.

http://www.forensicmed.co.uk/firearms.htm

 

[RyanM]

And ‘punch drunk’ boxers have exactly that, long term damage.
It even shows on x-rays as shrinkage of the brain tissue.
Since the damage is cumulative, that would imply that every blow does SOME permanent damage.

Think about the pressures we are talking about from a blow to the head that results in loss of consciousness.
It does not take very much pressure to force a nerve to depolarize, a process driven by osmotic gradients between the interior of the nerve and the exterior.

Right, that's why I said "noticable" brain damage. It takes quite a few blows to the head (or one of considerable force) to cause enough brain damage to really notice it.

One single incident may not be enough to cause noticable brain damage, though it be enough to incapacitate in the short term. Like in the FBI Miami firefight, SA McNeil (I believe) was shot in the neck with a .223, and was paralyzed from the neck down for an hour or so. However, he recovered fully and no loss of mental capacity has been noted.

In other words, the simple fact that people who were incapacitated by gunshots do not exhibit "noticable" brain damage is not evidence against the indirect injury theory.

 

[brickeyee]

If indirect ballistic injuries occur, what good can this knowledge do us? There obviously isn't any evidence that this indirect trauma occurs frequently enough or causes enough injury to incapacitate an opponent with any kind of reliability. So what great strides in tactics, techniques and procedures can make now that we know this?

It would explain the significant differences seen between higher power rifle wounding effects and the lesser effects seen from almost all handgun rounds.

The entire thing reminds me of the effects of drag on subsonic and supersonic bullets.
The basic equations change when the speed of sound is approached and passed.
The Bernoulli equation is NOT valid above the speed of sound since standing pressure waves exist.

The behavior of tissue, and the possibility of remote effects on the CNS conducted through pressure waves in the blood supply may well be in the same category.
At lower impact energies the pressure wave could easily be small enough to NOT cause significant effects at 'remote' tissue.
As the magnitude of the energy increases, the transfered energy will increase.
There ARE thresholds to many effects, and this may be one.

While a handgun injury to an extremity may only effect the nerves in the immediate area, the higher energy of a rifle round could allow the energy transfered to travel to more remote location and produce an observable effect.

At some point we know that pressure alone has an effect.
The overpressure wave from air fuel explosives (or nuclear weapons) is lethal over a limited area.
No other injury is required.
Just the overpressure causes what appears to be near instant death.

 

[Cosmoline]

When you're dealing with expanding projectiles at over 2,200 fps or so then yes the temporary cavity can cause serious injuries to tissue not touched by the bullet. This "explosive" effect on flesh was first noticed in the Spanish-American war when the higher velocity 7x57 rounds hit our soldiers. Or in day-to-day experience, witness the bruising on surrounding tissues inside game shot with high powered rifles. Witness the smaller animals that simply detonate when the TC exceeds their diameter! I'd call that a pretty good demonstration. It's the difference between a hole bored through the face and the entire head exploding like a melon. The first may be survived, the second not so much.

So what great strides in tactics, techniques and procedures can make now that we know this?

We already did, over 100 years ago, by shifting from slower larger projectiles in combat arms to smaller faster ones as smokeless powder and new ballistic designs made this possible. Military arms could be even more lethal if it weren't for the antiquated absurdities of the Hague Convention. But it's not difficult to get a first-hand demonstration of modern high velocity terminal ballistics. Just go hunting and shoot something with a modern high powered rifle.

 

[La Pistoletta]

This is what I was referring to:

http://en.wikipedia.org/wiki/Hydrostatic_shock#Energy_Transfer_Required_for_Remote_Neural_Effects

 

[Jeff White]

While a handgun injury to an extremity may only effect the nerves in the immediate area, the higher energy of a rifle round could allow the energy transfered to travel to more remote location and produce an observable effect.

If the observable effect isn't enough to quickly incapacitate, this knowledge is just wound ballistics trivia. Go down to the library and spend some time reading military history. There are countless examples of people shot with high powered rifles in the extremities who aren't quickly incapacitated. For that matter, there are plenty of examples of people shot in the torso and head with high powered rifle rounds who weren't immediately incapacitated.

The overpressure wave from air fuel explosives (or nuclear weapons) is lethal over a limited area.
No other injury is required.
Just the overpressure causes what appears to be near instant death.

Overpressure is the big killer in any explosion, not just those caused by FAE. The problem is the physics involved in designing a hand held weapon of a reasonable weight and portability that will create enough overpressure to kill. And don't forget, you have to localize that overpressure to cut down on collateral damage.

Jeff

 

[Cosmoline]

For that matter, there are plenty of examples of people shot in the torso and head with high powered rifle rounds who weren't immediately incapacitated.

That's the shortcoming of the FMJ spitzer. There's a real easy fix--make the round expand. This allows the full shockwave to express itself and multiples the amount of direct tissue damage. Nobody gets up from that hit. Nobody. Their chest is just gone.

 

[JesseL]

The entire thing reminds me of the effects of drag on subsonic and supersonic bullets.
The basic equations change when the speed of sound is approached and passed.
The Bernoulli equation is NOT valid above the speed of sound since standing pressure waves exist.

The behavior of tissue, and the possibility of remote effects on the CNS conducted through pressure waves in the blood supply may well be in the same category.
At lower impact energies the pressure wave could easily be small enough to NOT cause significant effects at 'remote' tissue.
As the magnitude of the energy increases, the transfered energy will increase.
There ARE thresholds to many effects, and this may be one.

That sounds reasonable, bet remember that the speed of sound in water (and similarly flesh, which is mostly water) is nearly 5000 fps. I'm not aware of any physical threshold encompassed by the spectrum of normal bullet velocities that would have an impact on terminal ballistics.

 

[Michael Courtney]

Anyway, one thing that got bandied about fairly often, early on, was that there are numerous veterans of various wars who were hit in the lungs with high-energy rifle bullets, and are walking around today with no noticable brain damage.

Lots of people experience mild concussions (sports injuries, for example) with no noticable long-term effects.

Most survivors of well-placed penetrating rifle wounds to the chest are cases where energy transfer is minimal because the bullet does not tumble, fragment, or expand.

The Textbook of Military Medicine explains the absence of indirect injury in survivors as follows:


Body parts other than soft tissue have unique wound-ballistics characteristics that influence the relative importance of direct (cutting) and indirect (shear and stress waves) effects as sources of injury. Controversy exists regarding the relative importance of these effects, but it is probably safe to say that in most casualties who are candidates for surgical care, injury results from the direct effects of the projectiles. That is not to say that indirect effects are inconsequential. They are important in the overall context of wound ballistics, but less so as a source of surgical treatment problems. Casualties with wounds of the head, chest, and abdomen, in whom indirect effects are prominent, are frequently not candidates for surgery: Such casualties are usually killed outright.

One thing I still think would be worth further research later on, however, is how bullet expansion speed affects interaction with tissue. A bullet which expands all at once should be more efficient at wounding/incapacitating, even if the same amount of energy is expended in deformation compared to a slower one. However, the maximum non-deforming velocity is a factor, thus materials such as copper and harder lead alloys should be looked into.

Vb = velocity of the center of the bullet's leading face
Ve = velocity of the outermost edge of the bullet relative to the center

A bullet that is still in the process of expanding essentially behaves as though it were a smaller or more aerodynamic one, wounding less efficiently.

It is a good point that the relative motion between bullet and tissue determines the retarding force and energy transfer. However, the forward movement of the tissue is a bigger factor than the relative retreat of the bullet's leading edge. The bullet's leading edge might retreat 4-5mm. In contrast, tissue might be translated 20-30 mm before the bullet stops and the tissue springs back. This occurs in gelatin also.

Michael Courtney

 

[Michael Courtney]

If indirect ballistic injuries occur, what good can this knowledge do us? There obviously isn't any evidence that this indirect trauma occurs frequently enough or causes enough injury to incapacitate an opponent with any kind of reliability. So what great strides in tactics, techniques and procedures can make now that we know this?

The relevance is mostly related to desig and selection of ammunition.

There is a growing body of evidence that indirect effects can hasten incapacitation for levels of energy transfer near 500 ft-lbs, but the local rate of energy transfer (rather than the total energy transfer) seems more important.

The implications for bullet design and load selection are:

1. More impact energy can increase bullet effectiveness.
2. Optimal effectiveness requires transferring energy rapidly while meeting penetration requirements.
3. Bullets that fragment transfer energy more rapidly than bullets which do not fragment.
4. Various factors influence the rate of energy transfer, and velocity alone is not a reliable indicator of expected bullet effectiveness.

Michael Courtney

 

[Phil DeGraves]

Bullets that fragment transfer energy more rapidly than bullets which do not fragment.

"Energy transfer" is really NOT a significant factor. Why? Because if the bullet is breaking apart, that energy is being transferred to the destruction of the bullet, not to the target. Same with expansion. What is important is the wound channel. how big it is and what it destroys. Now greater energy will result in deformation which results in a larger wound channel. It isn't the "transfer of energy" that creates tissue destruction. Also, flat bullets have greater impact effect than spitzer bullets. So you can get a "splash" from a flat or blunt bullet at less velocity than you could with a pointed bullet. I've always heard that with the spitzer type bullets, you need a velocity of 2600 fps to actually get an effective hydraulic reaction. Anything less than that would require a blunter bullet. Of course, you give up range when you give up your ballistic coefficient.