Lacerations are tears or splits of skin, mucous membranes, muscle or internal organs produced by application of blunt force to broad area of the body, which crushed or stretched tissues beyond the limits of their elasticity.
They are also called tears or ruptures. Localized portions of tissue are displaced by the impact of the blunt force, which sets up traction forces and causes tearing.
Displacement of tissues occurs most commonly when soft ones are crushed against bone, e.g. scalp, shins, shoulders and face. Unless great force is used, most lacerations require a firm base to act as an anvil for the skin and underlying tissues to be pinned against.
In soft areas, such as buttock, thigh, calf, abdomen, upper arm, etc., the lacerating agent is either a projecting point or edge, or a completely blunt object is pulled obliquely against the tension until it tears.
They are caused by blows from blunt objects, by falls on hard surfaces, by machinery, traffic accidents, etc. If the force produces bleeding into adjacent ones, the injury is a ‘contused-laceration’ or ‘bruised-tear’.
If the margins are abraded, it is called “abraded” or “scraped tear”. If the blunt force produces extensive bruising of deeper nerves, it is called “crushing” injury. The force may be produced by some moving weapon or object or by a fall.
Splitting occurs by crushing of the skin between two hard objects. Scalp lacerations occur due to the tissues being crushed between skull and some hard object.
Incised-like or Incised-looking Wounds: Lacerations produced without excessive skin crushing may have relatively sharp margins. Blunt force on areas where the skin is close to bone, and the subcutaneous ones are scanty, may cause a wound which by linear splitting of the tissues (as it is easily stretched during impact), may look like incised wound.
The sites are the scalp, eyebrows, cheek bones, lower jaw, iliac crest, perineum, and shin. A wound caused by a fall on the knee or elbow with the limb flexed, and by a broken glass or sharp stone also simulates incised wound.
Overstretching of the skin, if it is fixed, will cause laceration. There is localised pressure with pull which increases until tearing occurs and causes a flap of skin, which is peeled off the underlying bone or deep fascia.
This is seen in the running over by a motor vehicle, and the flap may indicate the direction of the vehicle. They can occur from kicking, and also when sudden deformity of a bone occurs after fracture, making it compound.
An avulsion is caused by sufficient force (shearing force) delivered at an acute angle to detach (tear off) a portion of a traumatised surface or viscus from its attachments.
The shearing and grinding force by a weight, such as lorry wheel passing over a limb may cause separation of the skin from the underlying tissues (avulsion) over a relatively large area. This is called “flaying”.
The underlying muscles are crushed, and the bones may be fractured. The separated one may show extensive abrasions from the rotating frictional effect of the tyre, but one portion is still in continuity with adjacent skin. Internally, organs can be avulsed or torn off in part or completely from their attachments.
In lacerations produced by shearing forces, the skin may not show signs of injury, but the underlying soft tissue is avulsed from the underlying fascia or connective, producing a pocket which may be filled with blood.
This is seen usually on the back of the thighs of pedestrians struck by motor vehicles. In a case of extreme avulsion, an extremity or even the head can be torn off the body.
Tearing of the skin and tissues can occur from impact by or against irregular or semi- sharp objects, such as door handle of a car. It may be caused by blows by broken glass, or fall over a rough projected object. A tear is deeper at the starting point than at the termination. This is another form of overstretching.
Cut lacerations may be produced by a heavy sharp-edged instrument.
The object causing a lacerated wound crushes and stretches a broad area of skin, which then splits in the centre. The edges are irregular and rough, because of the crushing and tearing nature of the blunt trauma.
Frequently, the skin, at the margins is abraded due to the flatter portion of the striking object rubbing against the skin as it is indented by the forceful blow. The margins are contused due to the bleeding into the tissues caused by trauma.
A single blow with a blunt weapon may cause more than one lacerated wound, e.g., a single blow over the side of the head may produce lacerated wounds over the parietal prominence, ear and the lower jaw.
If a blunt object, e.g., a bottle strikes the skin surface, the edge at the point of impact will be sharp and turned inwards, whereas the other edge may be averted, exposing the hair follicles in the depths.
In an impact over the scalp, external laceration may not occur due to the hair, but inner layers of scalp may be lacerated. If the instrument is padded or has a broad striking surface, severe fractures of the skull may occur without external one. Those of the internal organs may be caused by :
(1) direct injury of the viscera by fragments of fractured bone,
(2) development of traction shears or strain shears in the viscera,
(3) stretching of the visceral attachments, and
(4) hydrostatic forces.
(1) Margins are irregular, ragged and uneven, and their ends are pointed or blunt, and they too show minute tears in the margins. The edges of lacerations, especially over a bony area, e.g., skull are undermined due to the crushing and tearing force of the impact. Tearing at the ends, at angles diverging from the main one itself, so-called swallow tails, are frequently noted.
(2) Bruising is seen either in the skin or the subcutaneous tissues around the wound. If the force is exerted by an object with a downward course, the lower margin of the wound is likely to be bruised more and undermined than the upper.
(3) Deeper tissues are unevenly divided with tags at the bottom of the wound bridging across the margin. Bridging fibers consist of nerves, blood vessels and elastic and connective fibers.
(4) Hair bulbs are crushed.
(5) Hair and epidermal tags may be driven deeply into the wound.
(6) Hemorrhage is less because the arteries are crushed and torn across irregularly, and thus retract and the blood clots readily, except in wounds of the scalp, where the temporal arteries bleed freely as they are firmly bound and unable to contract.
(7) Foreign matter may be found in the wound.
(8) Depth varies according to the thickness of the soft parts at the site of the injury and degree of force applied.
(9) The shape and size may not correspond with the weapon or object which produced it. It is usually curved; the convexity of the curve points towards the direction of application of force.
- A blunt round end may cause stellate laceration.
- A blunt object with an edge, such as hammer head, may cause crescentic laceration (patterned).
- Long, thin objects, such as pipes, tend to produce linear lacerations, while objects with flat surfaces produce irregular, ragged, or Y shaped.
(10) If the impact is from an angle, the skin on side of wound opposite to direction of motion is usually torn free or undermined for a variable distance. The other side, i.e. the side from which the blow was delivered, will be abraded and beveled. Gaping is seen due to the pull of elastic and muscular tissues.
Age determination is difficult unless there are clear signs of healing, such as granulation tissue, fibroblast in growth, or organizing infiltrate. Antemortem lacerations show bruising, eversion, gaping and blood-staining of margins, greater bleeding and vital reaction.
(1) Laceration of an internal organ may cause severe or even fatal bleeding. Temporal arteries may bleed freely as they are firmly bound and unable to contract. Multiple lacerations, involving only the skin and subcutaneous one, each causing some hemorrhage, may combine to cause shock and death.
(3) If it is located where skin stretches or is wrinkled, e.g. over joints, repeated and continued oozing of fluids and blood may cause irritation, pain and dysfunction.
(4) Pulmonary or systemic fat embolism may occur due to crushing of subcutaneous tissue.
(1) The type of it may indicate the cause of the injury and the shape of the blunt weapon.
(2) Foreign bodies found in the wound may indicate the circumstances in which the crime has been committed.
(3) The age of the injury can be determined.
CIRCUMSTANCES OF INJURIES
Violent, uncoordinated muscular contractions can produce disruptive tissue stresses which produce fractures, and lacerations of tendons and muscles. Internal forces and hydrostatic pressure created by convulsions can cause mural lacerations in hollow viscera.
Suicidal lacerations are usually situated on the exposed parts of the body, and mostly on the same side. In the case of a fall on the head, the abraded scalp surface will be circular and completely surrounds it.
A blow with a blunt, narrow object, such as the edge of an angle iron or a crowbar will produce a linear tear with finely abraded margins. Homicidal wounds are usually seen on the head.
Combinations of Abrasions, Contusions and Lacerations : Abrasions, contusions and lacerations are frequently seen together or as integral parts of one another. The same object may cause a contusion with one blow, a one with second, and an abrasion with a third.
Sometimes, all three types of injury may result from a single blow. Sometimes, an imprint may result from an object, and it may be difficult to determine whether the imprint is primarily an abrasion or a contusion.
Punching, i.e. blows with the clenched fist will produce abrasions and contusions; it may occur over bony prominences. Punches on the face may split the lips, fracture the teeth, nose, jaw or maxilla and produce black eye.
Kicking and stamping injuries are caused by a foot which is either swung or moved downwards (compression) with some force. They will produce abrasions, contusions and sometimes lacerations, which are more severe than punching.
The feet may be used to stamp down on the recumbent body, causing deep injuries to abdominal organs and fractures of ribs and sternum. The pattern of the footwear may be imprinted on to the skin.