Disclaimer: The information presented below is for educational purposes only.
This is the first in a series of articles under the banner ‘The Med Cell”. The aim of The Med Cell is to help combat practitioners understand how and why injuries occur as a result of close combat. In order to do this we have to consider what type of force is applied to cause injury and what happens to a particular target zone when that force is applied. In the ensuing series of articles the med cell will examine each body region in turn, providing a comprehensive look at combat injuries as they relate to that particular body region. The following regions will be examined:
- Foot
- Ankle and lower leg
- Knee
- Thigh and Hip
- Hand
- Wrist and forearm
- Elbow and upper arm
- Shoulder
- Thorax (chest)
- Abdomen
- Pelvis
- Head (including scalp and face)
- Neck
- Spine
Each article will look at specific kinds of force (e.g. punching, stabbing, shooting etc), what types of injuries arise when these forces are applied (based on speed and direction), and how to diagnose and give first aid to victims of those injuries. Each article will also contain real life examples of injuries being discussed, aided by digital photographs, x-rays and CAT scans to illustrate various points. Finally, articles will be supplemented with references to books, journal articles, and internet web sites so that readers can pursue the subject in more depth if desired.
In order to accomplish these aims, it is important to familiarise readers with some terms that will be used extensively in the med cell. Therefore, this first article will serve to define various medical terms, give a brief background into mechanisms of injury and describe basic physiology relevant to combat.
ANATOMIC POSITION
When describing the anatomy of the human body, it is always assumed that the body in question is standing facing forward, eyes looking forward, arms by side with palms facing forward and feet pointing forward, like so:
ANATOMIC DESCRIPTORS
The following terms are useful in describing the site of injury and also the direction of force used to inflict an injury:
- ANTERIOR: toward the front of the body
- POSTERIOR: toward the back of the body
- MEDIAL: closer to the midline
- LATERAL: further from the midline
- PROXIMAL: closer to the heart
- DISTAL: further from the heart
- SUPERIOR: above or towards the head
- INFERIOR: below or towards the foot
- SUPERFICIAL: closest to the outside of the body (skin is superficial to muscle)
- DEEP: further from the skin toward the centre of the body (muscle is deep to skin)
To put some of these definitions into practice, the big toe is MEDIAL to the little toe, and so the little toe is LATERAL to the big toe. If a strike was to come from the outside of the knee, the knee would be struck on its lateral aspect (furthest from the midline) and the strike itself would be directed medially (towards the midline).
Similarly, a strike to the ANTERIOR portion of the lower leg would be to the front of the shin, and a strike to the POSTERIOR portion of the lower leg would be to the calf or back of the lower leg.
Finally, a strike to the DISTAL portion of the lower leg will involve the lower portion i.e. the ankle, whereas a strike to the PROXIMAL portion of the lower leg will involve the higher portion i.e. the knee.
Just remember to relate everything back to the guy standing in the anatomic position.
ANATOMIC MOVEMENTS
These describe movements of joints and body structures
- FLEXION: bending the joint, thereby closing the angle between two structures.
- EXTENSION: straightening the joint, thereby opening the angle between two structures.
- ABDUCTION: moving one structure away from another laterally (away from the anatomic position). Remember that to ABDUCT someone is to take them away.
- ADDUCTION: moving one structure toward another medially (toward the anatomic position). You ADD together.
When referring to the foot, the terms are slightly different. Remembering that the PLANTAR surface is the sole of the foot, INVERSION or PRONATION is moving the plantar surface medially (towards the midline). EVERSION or SUPINATION is moving the plantar surface away from the midline. PLANTARFLEXION is therefore moving the ankle joint so that the toes point down and DORSIFLEXION (DORSUM meaning the top part) is moving the ankle joint so that the toes point upwards
When referring to the forearm, PRONATION means rotating the forearm medially so that the palm faces posteriorly or backwards (from the anatomic position, move your thumb medially towards your body). Conversely, SUPINATION means rotating the forearm in the opposite direction, or laterally, so that the palm is returned to the anatomic position.
Next, we need to know what tissues and structures are going to be injured as a result of force.
REGIONAL ANATOMY:
TISSUES AND STRUCTURES
The human body is composed of four basic tissues – epithelium, connective tissue, muscle and nerve. All parts of the body are composed of either one or any combination of these basic tissues.
SKIN
The skin forms a barrier both to mechanical injury and fluid loss. The outer or dead layer of skin varies in thickness throughout the body, and is thickest on the soles of the feet and the palms, and thinnest on protected parts such as the scrotum and the eyelids. This is significant as more force will be required to penetrate the thicker parts such as in a stab wound. Below this outer layer is living skin being made up of the epidermis which has no blood vessels, and the dermis which contains blood vessels, nerves, and other structures such as sweat glands, and hair follicles. Below this is the subcutaneous or fatty (adipose) layer, containing arteries, veins and nerves.
The nail and nailbed also fall under the heading ‘skin’, but will be discussed more fully in articles on the foot and hand when injuries to the nail and nailbed are dealt with.
Rule of Nine’s: At this point it is worth bringing up a rule used in trauma for assessing burns, but which could equally be applied to assessing target zones in combat. This is known in trauma settings worldwide as ‘The rule of 9’s’. Simply put, the surface area of the skin over different regions of the body can be estimated by the rule of 9’s:
Head = 9% of total body surface area
Each upper limb = 9 %
Each lower limb = 18% (2×9%)
Front of chest and abdomen = 18%
Back of chest and abdomen = 18%
Thus burns involving both arms and the front of the chest and abdomen will affect 9 + 9 +18 = 36% of total body surface area, a very serious burn.
FASCIA
A sheet or band of connective tissue that separates or binds muscles or organs, and is very sensitive. Fascia not only covers the muscle, separating muscles from one another and allowing frictionless motion, but also extends beyond the muscle to form the tendon of that muscle.
LIGAMENTS
These connect bone to bone, being made of connective tissue, mainly collagen
TENDONS
These connect muscle to bone, being made of connective tissue, mainly collagen
CARTILAGE
Cartilage is connective tissue that arises in 3 forms to make up structures such as the nasal septum, the trachea, knee cartilages and so on. It is not as strong as bone, and is elastic in nature.
MUSCLE
There are three types of muscle in the human body:
- SMOOTH muscle e.g. that found in gut,
- CARDIAC muscle comprising the heart,
- SKELETAL muscle.
Skeletal muscle is attached to bone by tendons. The fibres run parallel to the action of the muscle. The bulk of the muscle is enveloped by a surrounding layer of connective tissue or fascia. Skeletal muscles have a rich blood supply. Nerves pierce the surrounding fascia and supply the muscle.
Skeletal muscles act in groups during movements of the skeleton. In flexing the elbow, the biceps is known as the prime mover (produces desired effect), while the triceps is the antagonist (produces the opposite effect).
A strain is a partial or incomplete tear of a muscle or ligament, while a sprain is a partial or incomplete tear of a tendon.
BONE
Bone is a very dense connective tissue. Looking at human bone we can divide it into two forms, compact and cancellous. Compact bone is hard and dense. It forms the outer layer of bone, and is thicker in the shafts of long bones. Cancellous bone is more sponge-like though still hard, and the bone is arranged in a pattern to resist strains and stresses. The relative quantity of these two tissues varies in different bones
The outer surfaces of bones are covered in a thick layer of connective tissue called the periosteum
This leads us to ask “what mechanical and biological forces lead to bones being broken?”
Bone deforms when basic forces are applied to them. These forces are compression, transverse loading, torsion, bending and shearing. A compressive force leads to shortening of the length of the bone, while tension elongates it. Torsion causes rotation of bone, while bending it causes it to bow in the centre. Shearing distorts its length. Bone is weakest in tension and strongest in compression.
The determinants of bone stiffness or that of other materials is arrived at in a complicated way and it will not be dealt with here. However, the defining term is elastic modulus. This simply means that for a given material of the certain size and shape, it can be compared to another material of the same size and shape. Let’s look at the relative strengths of some materials using the elastic modulus (units are megapascals)
| Cartilage | 20 |
| Tendon | 400 |
| Cortical bone | 15000 |
| Cancellous bone | 1000 |
| Pure cold worked titanium | 100,000 |
| Stainless steel cold worked | 200,000 |
It can be seen that cortical or compact bone is about 15% or one seventh as strong as cold worked titanium.
The diameter (more specifically the radius) of a structure is also important in determining strength. It works out that a material shaped like a rod which is twice the diameter of another rod of the same material is actually 4 times as strong. This is important when considering combat injuries as obviously a certain force e.g. leg stamp applied to the tibia in the lower leg will not break it, but will in fact break the fibula when that same force is applied.
The load at failure of a whole bone will depend on bone size and shape, distribution of cortical and cancellous bone, mechanical properties of cortical and trabecular bone, loading rate, mode of loading (compression, tension, shear) and direction of loading and point of application. Fractures usually result from tension and/or shear forces.
The following table shows the strength of bone compared to other materials under different types of force.
| Material | Strength in pounds per square inch | ||
| Tension | Compression | Shear | |
| Oak | 12,500 | 7000 | 4000 |
| Compact bone | 15,000 | 21,000 | 9000 |
| Steel | 65,000 | 60,000 | 40,000 |
Obviously these numbers are absolute values, so cannot be taken on their own to calculate forces required to break human bones. Other variables mentioned above come into play. In the med cell articles on specific regions I will attempt to give the force required to fracture bones from different directions while considering these variables.
FRACTURE DEFINITIONS:
OPEN (COMPOUND) fractures mean the fracture site communicates with the outside world, whereas CLOSED (SIMPLE) fractures leave the overlying skin and soft tissue intact.
COMPLETE fractures result in bone fragments that are separated from each other. The x-ray below is of a young female pedestrian hit by a car, which resulted in a complete fracture of her femur.
COMMINUTED fractures are complete fractures where the bone is broken into many fragments. The following image is that of a male involved in a road accident. His head hit the windscreen resulting in a comminuted skull fracture of his frontal bone (this is his forehead). In this case it is also a depressed skull fracture, meaning bone has been forced inwards toward the brain.
INCOMPLETE fractures leave the continuity of the bone intact (e.g so called greenstick fracture).
DISPLACED fractures mean the bony fragments are not aligned.
Common early complications of fractures include bleeding, vascular injury, nerve injury, tendon injury, compartment syndromes, fat embolism, and infection if the fracture is compound.
DISLOCATION:
This means the bones of a joint are no longer in their normal position and this is usually the result of a sudden forceful impact. Almost always the ligaments of the joint will be partially or completely torn. Below are two x-rays of a young person who fell, fracturing their distal fibula and dislocating their tibia. The first x-ray is taken from front to back, in other words, from anterior to posterior. Thus it is called an antero-posterior view. The second image is the same ankle x-rayed from the side, and is called a lateral view.
A dislocated ankle is a true medical emergency as the foot will quickly lose all blood supply and die if not quickly relocated.
JOINTS
There are three types of joints:
- Fibrous. Little movement is possible. Examples of these are the joints that connect the bones of the skull.
- Cartilaginous. These joints are also fairly immobile, for example, the junction of the ribs and sternum.
- Synovial. These include ALL limb joints, and are of great importance in describing combat injuries. In general, two bones are joined by a capsule which surrounds the joint cavity, and the joint is reinforced by ligaments, either on the outside or inside of the joint.
Generally, the more movement required of a joint, the more inherently unstable it is and therefore prone to dislocation, e.g. the shoulder joint.
MUCOUS and SEROUS MEMBRANES
- A mucous membrane is the lining of an internal body surface that communicates with the exterior, e.g. tongue
- A serous membrane lines a closed body cavity, e.g. lining of the lungs.
BLOOD VESSELS (see also under PHYSIOLOGY below)
There are three kinds of blood vessel:
- Arteries. These take blood from the heart to the tissues and have a thin lining of muscle.
- Veins. These take blood to the heart but do not have any muscle in their walls. Veins contain a series of one-way valves to prevent back-flow.
- Capillaries. These are the smallest of the blood vessels, and directly supply tissues such as muscle.
WOUNDS
For the purposes of close combat, a wound is defined as damage to any part of the body by the application of mechanical force. Injury occurs when the force applied is greater than the ability of the tissues to absorb a particular force.
Force is directly related to the mass of the weapon and is related by the square of its speed (a leg stamp at 3 feet per second is 9 times more powerful than a leg stamp at 1 foot per second). This is important not only in blunt injury but also to ballistics and stab wounds. F=1/2m x v2, or force is equal to half the mass of an object multiplied by its velocity squared. Force is measured in Newtons per metre squared, a Newton being equivalent to 10 kilograms. When future articles describe force required to cause injury, units will be in N.m2
The area over which the force is applied is important. A strike from the face of a cricket bat is going to be much less damaging than a strike from the edge of the cricket bat. This also is important when considering stab wounds as all the force is concentrated into the extremely small knife tip.
As mentioned in the section on bone, there are 5 types of force that are considered when applied to living tissue (compression, transverse loading, torsion, bending and shearing). The damage as a result of these forces depends on the target. For example, a compressive force as applied by a slap to the ear may not even bruise the ear but could rupture the eardrum. Transfer of energy is important. If the object (for example a bullet) comes to a halt in the body, then all its energy has been transferred. If the object passes through the body then its energy has not been completely transferred. It is preferable to have a bullet pass straight through you than to bounce around or fragment inside you as in the latter case, all the energy has been transferred, leading to massive internal damage
In combat, for example during milling, it is preferable to reduce the speed of the oncoming force and at the same time minimize contact. In this instance the punch arrives with less speed as your head and arms are already moving in the same direction, and the energy of the punch is spread out over a longer time frame.
CLASSIFICATION OF WOUNDS
Wounds can be classified into 4 types:
- ABRASIONS (grazes, scratches)
- CONTUSIONS (bruises)
- LACERATIONS (cuts or tears)
- INCISIONS (cuts, slashes, stabs)
A bruise is visible beneath the skin surface whereas a contusion can be anywhere in the body, for example the heart. One kind of bruise relevant to forensics is that formed when an implement such as a rod is struck against the body. The resultant bruise looks like railway lines or tram tracks as the edges of the rod drag the skin downwards tearing the blood vessels. Most kicking injuries cause severe bruising and can rupture internal organs, for example a bronco kick to the chest or abdomen. Kicking can also cause fractures, and the face is particularly vulnerable.
Lacerations are different from incisions as the wound is caused by tearing rather than slicing. Much force is needed especially to areas where there is nothing to push the tissues against e.g. abdomen as opposed to the shins.
An incised wound is can be caused by sharp implements such as razors, scalpels, glass and the Maori patu, and results in the clean division of skin. The following photograph demonstrates an incised wound in a young male caused by stepping on broken glass. He lost about 500mls of blood after the accident, and the tendons were also severed subsequently requiring surgery. Note the clean division of skin.
Broken glass can in fact possess a sharper cutting surface than a surgical scalpel, the significance of which becomes evident in bar brawls. A wound caused by a slashing motion is much less likely to be fatal than a stab wound because not all the energy is transferred, and as the wound is likely to be superficial, haemorrhage can be controlled.
PHYSIOLOGY
Blood loss is an important topic in combat. It will be useful to briefly cover some basic physiologic concepts.
The function of the heart is to circulate blood. The volume of blood in the human male is roughly 75mls/kg and for a female about 65mls/kg. This means the circulating blood volume of a man weighing 80kg is 80 x 75 = 6000mls or 6 litres.
When there is damage to arteries, veins, capillaries or the heart, the result is blood loss. This is also called haemorrhage, and prompts a response by the body to minimize and prevent further blood loss by setting into motion a complex clotting cascade. This is called haemostasis (“stopping of haemorrhage”).
Haemorrhage of a significant amount of blood can lead to shock. Shock is a serious clinical condition that is caused by circulatory collapse and leads to tissues receiving inadequate blood supply. Blood loss will lead to a loss of volume, and so is termed hypovolaemia (hypo = low). Hypovolaemia can lead to hypotension, or low blood pressure. Blood loss of greater than 50% (or 3 litres for an 80kg man in our example above) will most likely be fatal. Increasing hypotension leads to an increase in the risk and a reduction in time to death. In Afghanistan, US soldiers killed usually bled to death in 5 to 10 minutes, although in some cases it took several hours.
In the field, it is important to minimize or stop haemorrhage. In the tactical environment i.e. war combat, 80% of deaths caused by massive haemorrhage are in the torso, where control of bleeding is nearly impossible, the remaining 20% of deaths being from injuries to sites such as the neck and limbs where control of bleeding by pressure is possible. In recent conflicts, haemorrhage from limbs continues to account for one tenth of ALL deaths.
Death in the setting of haemorrhage occurs as a result of under supply of blood (hypoperfusion) to vital organs, especially the brain.
SUMMARY
Hopefully by now the reader is familiar with basic anatomical terms and knows how to describe fractures and wounds. Additionally, the reader should understand basic cardiac physiology relevant to close combat. Subsequent articles will employ this knowledge, and readers can refer back to this article as required. Next issue’s article will cover injuries to the foot.
REFERENCES
- Knight’s Forensic Pathology, 3rd edition, Oxford University Press
- Last’s Anatomy, Regional and Applied, 10th edition, Churchill Livingston
