Lacerations

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, f Localised portions of tissue are displaced by the impact of the blunt force, which sets up traction forces and causes tearing of the tissues. Displacement of tissues occurs most commonly when soft tissues 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 anvii for the skin and underlying tissues to be pinned against. In lacerations of 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 of the skin 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 tissues, the injury is a/contused-laceration' or 'bruised-tear'. If the blunt force produces extensive bruising and laceration of deeper tissues, it is called "crushing" injury. The force may be produced by some moving weapon or object or by a fall.

Types : (1) Split Lacerations : 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. such as the ground or a blunt instrument.

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 tissues are scanty, may produce a wound which by linear splitting of the tissues, may look like incised wound. The sites are the scalp, eyebrows, cheek bones, lower jaw, iliac crest, perineum, and shin. A wound produced by a fall on the knee or elbow with the limb flexed, and by a broken glass or sharp stone also simulates incised wound.

(2) Stretch Lacerations : Overstretching of

the skin, if it is fixed, will cause laceration. There

is localised pressure with pull which increases until

tearing occurs and produces 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, arid also

when sudden deformity of a bone occurs after

fracture, making it compound.

(3) Avulsion : An avulsion is a laceration

produced 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 produce

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 skin may

show extensive abrasions from the rotating factional

effect of the tyre, but one portion is still in continuity

Fig. (8-4). Laceration of scalp (star-shaped).

Fig. (8-5). Crush injury leg caused by run over accident

Fig. (8-6). Avulsion caused by running over of the wheel of automobile. The skin is torn away in a flap due to the grinding action of the wheel.with adjacent skin. Internally, organs can be avulsed or torn off in part or completely from their attachments.

In lacerations produced by shearing forces, 4he skin may not show signs of injury, but the underlying soft tissue is avulsed from the underlying fascia or connective tissue, 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.

(4) Tears : 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.

This is another form of overstretching.

(5) Cut Lacerations : 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'produce 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 everted, exposing the hair follicles in the depths. In an impact over the scalp, external laceration may not occur due tc 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 laceration, lacerations 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}

Characters : (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 of lacerations, at angles diverging from the main laceration 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 of tissues at the bottom of the wound bridging across the margin. Tissue bridges consist of nerves, blood vessels and elastic and connective tissue fibres as they are stronger. (4) Hair bulbs are crushed. (5) Hair and epidermal tags may be driven deeply into the wound. (6) Haemorrhage 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. A laceration is usually curved; the convexity of the curve points towards the direction of application of force, (a) A blunt round end may cause stellate laceration, (b) A blunt object with an edge, such as hammer head, may cause crescentic laceration (patterned laceration), (c) Long, thin objects, such as pipes, tend to produce linear lacerations, while objects with flat surfaces produce irregular, ragged, or Y-shaped lacerations. (10) Gaping is seen due to the pull of elastic and muscular tissues. (II) 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 bevelled. If the impact was produced by an object with a downward course, the lower margin of the wound is likely to be more bruised and undermined than the upper.

Ante-mortem lacerations show bruising of margins, vital reaction, eversion, and gaping of the margins.

Complications : (!) The laceration may cause severe or even fatal bleeding. Multiple lacerations, involving only the skin and subcutaneous tissue, each causing some haemorrhage, may combine to cause shock and death. (2) Infection. (3) If it is located where skin stretches or is wrinkled, e.g. over joints, repeated and continued oozing of tissue fluids and blood may cause irritation, pain and dysfunction. (4) Pulmonary or systemic fat embolism may occur due to crushing of subcutaneous tissue.

Medico-legal Importance : (1) The type of laceration 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, unco¬ordinated 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 the laceration. 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 laceration 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.

INCISED WOUNDS j An incised wound" (cut, slash, slice) is a clean cut through the tissues, (usually the skin and subcutaneous tissues, including blood vessels), caused by sharp-edged instrument, which is longer than it is deep. It is produced by the pressure and friction against the tissue, by an object having a sharp-cutting edge, such as knife, razor, scalpel, sword, etc. In this, the force is delivered over a very narrow area, corresponding with the cutting edge of the blades,

Causes: (1) Striking the body with the edge of sharp-cutting weapon, (2) by drawing the weapon, and (3) by using the weapon like a saw in which case there may be more than one cut in the skin at the beginning of the wound which merge into one at the end.

A curved weapon like a sickle, produces a stab from the pointed end, and incised wound from the blade, sometimes with an intervening intact skin. When the skin becomes folded under the cutting edge of the weapon, a single movement of a sharp weapon may produce a series of incised wounds, separated one from another by bridges of normal skin.

Characters : (j)Margins : The edges are clean-cut, welI-definealmcr~TrsTfally everted. The edges may be inverted, if a thin layer of muscle fibres is adherent to the skin as in the scrotum. The edges are free from contusions and abrasions. A dull irregular-edged or nicked cutting edge may produce a wound with irregular, contused, and/or abraded margins, as the wound is caused more by the pressure applied by the weapon than by the cutting edge. The depth of the wound will not show bridging.

(2) Width : The width is greater than the

edge of the weapon causing it, due to retraction of

the divided tissues. Shaking of the blade tends to

make the wound wider than the weapon.

(3) Length :^The length is greater than its

width and depth, and has no relation to the cutting

edge of the weapon, for it may be drawn to any

distance. When the skin becomes folded under the

cutting edge of the weapon, a single movement of

the weapon may produce a series of incised wounds

separated one from another by bridges of normal

skin.

(4) Shape: It is usually spindle-shaped due

to greater retraction of the edges in the centre.

Gaping is greater if the underlying muscle fibres

have been cut transversely or obliquely, and less

when cut longitudinally. The wound may take

zig-zag course if the skin is loosely attached as in

axillary fold, because the skin is pushed in front of

the blade before it is cut. If the blade is curved,

the edges will be crescentic. If the surface is

convex, the straight-bladed weapon may also produce

a crescentic wound.

Haemorrhage; As the vessels are cut cleanly, the haemorrhage is mor£: If the artery is completely cut, the bleeding ^vill be more. Spurting of blood occurs if an artery is cut.

CX6) Direction: Incised wounds are deeper at the beginning, because more pressure is exerted on the knife at this point. This is known as the head of the wound. Towards the end of the cut the wound becomes increasingly shallow, till finally as the knife leaves the tissues the skin alone is cut. This is known as the tailing of the wound, and indicates the direction in which the cut was made. (7) Bevelling cut : If the blade of weapon enters obligtieiyrTfie"tissues will be visible at one margin, and the other margin will be undermined, and if the blade is nearly horizontal, a flap wound is caused. Bevelling can be produced by sharp weapon only. It is usually homicidal and may indicate the relative position of the assailant and the victim,

yn Age of Incised Wound : In an uncomplicated

wound, healing occurs as follows: Fresh: Haematoma

formation. 12 hours: The edges are red, swollen

and adherent with blood and lymph; leucocytic

infiltration. 24 hours : A continuous layer of

, endothelial cells covers the surface; overlying this

a crust or scab of dried clot is seen.

Histopathology: Few minutes: Dilatation of

capillaries and margination and emigration of

neutrophils, reactive changes in the tissue histiocytes

and swelling of the vascular endolhelium. 12 hours:

Reactive changes occur in the fibroblasts at the site

of injury within few hours, monocytes appear in the

exudate. IS hours: Monocytes begin to undergo

mitotic division. 24 hours: Epithelium begins to

grow at the edges. Vascular buds begin to form.

72 hours: Vascularised granulation tissue is formed.

4 to 5 days: New fibrils are formed. One week:

Scar formation in small wounds.

The above changes are considerably modified if infection of the wound occurs.

Wounds by Glass : Wounds produced by glass are lacerated, but can resemble incised and stab wounds. If a sharp-pointed piece of glass enters by its point, the wound has a stab-like appearance. Margins of the wound will almost always show tiny side cuts due to irregularities of the glass. Particles of glass may be found in the wound.

(_Medico-legal Importance: (1) They indicate the nature of weapon (sharp-edged). (2) They give an idea about the direction of the force. (3) The age of the injury can be determined: (4) Position and. character of wounds may indicate mode of production, i.e., suicide, accident, homicide. ^

Table (8-4). Difference between suicidal and homicidal cut-throat wounds