☻Affections of bone

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AFFECTIONS OF THE BONE

I-BONE NECROSIS, AVASCULAR BONE NECROSIS, OR CYST

Definition: -

It is septic or aseptic necrosis of piece of bone. Septic necrosis occurs in some cases of sequestra or osteomyelitis, while aseptic necrosis occurs as a result of trauma, irradiation, or infarcts, and sometimes it is idiopathic

II-INFLAMMATION (OSTEOMYELITIS)

Definition: -

Osteomyelitis is inflammation as a result of pyogenic organism of the cortex and marrow components of bone. Osteosis (necrosis) may occur in certain types of fracture and the affected bone piece is called sequestrum.

Causes: -

Bacterial infection is the main cause; however, fungal infection may cause osteomylitis. Sources of invasion are:

1-Open traumatic injuries

2-Prolonged surgical procedure in the bone

3-Extension from adjacent tissue

4-Systemic illness (bacteremia)

5-Synthetic implant

Clinical Signs: -

Osteomyelitis is divided into acute and chronic forms

1-Acute Osteomyelitis

1-Local signs include swelling, pain and excessive tissue warmth

2-Lameness is detected in most cases

3-A serosanguineous to purulent discharge is seen at seat of traumatic wound or at the surgical site.

4-Depression and anorexia with persistent fever are detected

2-Chronic Osteomyelitis

1-Signs of pain at affected site

2-Presence of multiple drainage tracts (sinuses)

3-Persistent lameness and muscle atrophy

Diagnosis: -

1-Case history and clinical signs

2-Hematological test may reveal leucositosis or anemia

3-Radiographic examination may reveal soft tissue swelling at the first two days then bone lysis, irregular periosteal reaction and loose implants develop later on. A sequestrum may be seen as bone density tissue mass surrounded by a zone of radiolucency and sclerotic reactive bone.

Treatment: -

1-Long term antibiotic therapy for 4-6 weeks

2-Surgical management of the wound which include removal of sequestrum, necrotic soft tissue and loose implants. Also, lavage and drainage of abscessed tissue and re-stabilization of fracture.

III-FRACTURE

Definition: -

Fracture is a partial or complete disruption or break down of bone continuity

Classification: -

I-ACCORDING TO DEGREE OF DAMAGE

1-Incomplete fracture

2-Complete fracture

1-Incomplete Fracture

It is a type of fracture that doesn't extend throughout the full thickness of the bone

A-Green stick fracture: -

It is a type of fracture affects long bones of young animals especially those suffer from rickets. The increased pressure over the convex surface of the affected bone predisposes to fracture and the injured bone looks like bent green stick.

Characteristics:

1-Affected bone has convex fractured surface and concave surface

2-It affects young animals only

B-Fissure cracks or fissure lines: -

The fissures are formed in one cortex of the bone and are covered by an intact periosteum.

Characteristics:

  1. Presence of single or multiple fractures lines that are parallel or not, of different directions (transverse, longitudinal, or oblique)
  2. It causes no bone displacement

C-Splint fracture (Splinter): -

It affects flat or long bone, as a result of direct violence as  gun fire.

Characteristics:

  1. The bone still intact and the hole of the gun fire sometimes have cracks around it.
  2. Piece of bone separated from the main bone

D-Deferred incomplete fracture: -

It occurs as a result of neglecting incomplete fracture for a long period. Separation of fractured fragments occurs considerable period after the accident as a result of violence or concussion.

E-Star fracture: -

It is a type of incomplete fracture characterized by radiation of fracture lines from a central point giving star shape appearance.

2-Complete Fracture

Complete fracture denotes complete disruption of bone continuity and the bone fragments may undergo displacement.

II-ACCORDING TO FRACTURE LINE

Fracture line is subdivided according to:

1-Number of fracture line

2-Site of fracture line

3-Direction of fracture line

1-According to Number of Fracture Lines

A-Single line fracture: -

It is a fracture that divides the bone into two pieces

B-Double fracture: -

It is a fracture that divides the bone into three pieces due to presence of two fractures in the affected bone

C-Multiple fracture (Comminuted): -

It is a fracture type where the bone is divided into more than two pieces with presence of more than one fracture line

2-According to Site of Fracture Line

A-According to the location of fracture line on the bone: -

Fracture can be classified into epiphyseal, metaphyseal, or diaphyseal

B-According to the name of the fractured piece of bone: -

Fracture can be classified into condylar, supracondylar, articular, trochanteric, or inter condylar

3-According to the Direction of Fracture Line

A-Longitudinal: -                                        

Usually it affects short bones               

B-Transverse: -

Usually it affects long bones

C-Oblique: -

The fracture line exist in an angle with the longitudinal direction of the bone

D-Spiral fracture: -

The fracture line passes through spiral pass around the long axis of the bone

III-ACCORDING TO FRACTURED FRAGMENTS

1-According to Displacement of Fractured Fragments

2-According to Stability of Fractured Fragment

1-According to Displacement of Fractured Fragments

A-Overlapped fracture (Riding or over-riding): -

It is a fracture in which the two fragments overlap each other and presented side by side and it can be observed in case of oblique fracture leading to shortening of the bone

B-Angled or angulated fracture: -

It is a fracture characterized by angle formation between the two bone fragments, and this causes deformity of the shape of affected bone

C-Lateral fracture: -

It is a fracture type in which the two edges of the fractured bone exist lateral to each other

D-Spiral fracture (Torsion): -

It is a fracture type characterized by rotation of one bone fragment around its long axis

E-Wedged or impacted fracture: -

It is a fracture characterized by displacement with impaction of one fractured fragment into the other fragment like wedge. The affected bone undergoes shortening.

F-Depressed fracture: -

It is a traumatic fracture of flat bone over a cavity leading to displacement of a disc of bone into this cavity, like frontal bone.

G-Compressed fracture: -

It is a fracture with shortening and thickening of the bone as those affecting vertebrae

H-Distracted fracture (Avulsion): -

Fracture characterized by wide separation of the bone fragments due to pulling action of ligament or tendon

I-Dentate fracture: -

It is a fracture type that is characterized by presence of toothed interlocked two ends of the fractured bone

2-According to Stability of Fracture Fragment

A-Stable fracture: -

It is a fracture characterized by interlocking of the fractured fragments after reduction and they resists shortening forces, and the only fixation required in such fracture is to prevent angular deformity (like transverse fractures).

B-Unstable fracture: -

It is an oblique or comminuted fracture as the fragments don't interlock after reduction an there is no resistance to shortening accordingly the fixation is needed to maintain the length and to prevent rotation.

IV-ACCORDING TO COMPLICATIONS

1-Simple fracture

It is pure bone fracture with no complications or wounds of the skin

2-Compound fracture

It is fracture with skin injury (wound)

3-Complicated fracture

It is fracture associated with injury to nerve (like radial paralysis), artery or vein, opening of a joint, or opening of a body cavity (like chest)

Causes of fracture:  -

I-PREDISPOSING CAUSES

1-Anatomical

The superficially located bones are more susceptible to trauma and fracture

2-Age

The incidence of fracture is higher in young and senile animals

3-Sex

During sexual intercourse, females are more susceptible to pelvic fracture, while males are more susceptible to fracture of hind limb

4-Nutritional

Low calcium and phosphorus, high vitamin A, high fluorine, and high carbohydrate with obesity are all predisposing causes to osteoporosis and fracture

5-Hormonal

Hyperthyroidism increases blood Ca and P and reduces them in bone, while low estrogen level in females predisposes them to osteoporosis (human)

6-Aim of Animal Use

Galloping, jumping, and drafting horses are more susceptible to fracture than show horses

7-Nature of Land

Fracture is less frequent on soft land and its incidence increases on slippery or hard lands

8-Animal Temper

Fracture is less frequent in calm animals and more frequent in vicious animals

9-Animal condition and diseases

Cancer or chronic depilating diseases predispose to fracture 

II-EXITING CAUSE

1-Extrinsic forces

A-Direct violence: -

Like falling from high places, car accidents, or violent beating of an animal with strong stick

B-Indirect violence: -

The site of trauma is far from the site of fracture as falling on leg with fracture of the back (compression) or pelvic bones, or when twisting of hand causes fracture of shoulder bones

2-Intrinsic forces

A-Severe muscular traction during racing

Severe traction of muscle may exert enough stress on one or more bones causes its fracture

Symptoms: -

I-LOCAL SIGNS

1-Dysfunction

Dysfunction is most commonly exemplified by lameness. In the orthopedic examination the focal site of the lameness must be found and the diagnosis pursued. Dysfunction may also include paralysis with spinal fracture, unconsciousness accompanied by cranial fracture, or masticatory dysfunction with mandibular fracture.

Impairment or loss of function is a constant sign of complete fracture and is the result of pain or loss of mechanical support. Only in cases of incomplete or impacted fracture may some weight be borne by the bone.

2-Pain

Pain over the site of fracture is common. In incomplete fractures this may be the only clinical indication. Direct tenderness can be misleading, since it may be due to a contusion or other soft tissue damage caused by a blow. Indirect tenderness is a more accurate sign of fracture. It is produced by pressure in the long axis of the bone exerted at its two extremities. If there is a break in the continuity of the shaft, such pressure will cause pain at the fracture site that is quite distinct from the pain of injured soft tissue parts. If an animal is examined during the state of local tissue shock, that is, within 20 to 30 minutes after the accident, pain may not be a conspicuous sign.

3-Local Swelling

Examination of the area around a fracture may demonstrate swelling, hematoma, contusion, or laceration if the fracture is open. Often because of extreme swelling, the examiner will be unable to palpate crepitation. Local swelling, although present in many other conditions, is one of the most constant signs of a fracture. Immediately after injury the swelling may be sharply outlined as a result of bleeding from the bone and the soft parts. An indistinctly outlined swelling that occurs later is caused by edematous infiltration. Generally the swelling increases for 24 to 48 hours then gradually subsides (particularly under treatment). When applying bandages and splints immediately following fracture, it is important to bear in mind that swelling will subside.

4-Abnormal Posture or Limb Positioning

Abnormalities of positioning, when of acute onset associated with trauma, usually reflect a fracture. Deformity, a deviation from the normal anatomical structure, may be caused by displacement of the bony framework as in a fracture or dislocation, but it may also be caused by changes in configuration due to a neoplasm. The displacement of bone fragments that produces deformity in a fracture may be angular, longitudinal, or rotational.

Longitudinal displacements may cause shortening, referred to as overriding, or may result in separation of the fragments; termed distraction (e.g., fractures of the olecranon). In most cases the primary displacement is determined by the direction and force of an injury and is maintained and often increased by the contraction of muscles. If in doubt about positioning, comparison with the opposite limb or side of the body part is advised.

5-Crepitus

Crepitus is a sign of fracture that is considered pathognomonic. Bony crepitus is the gritting sensation transmitted to the palpating fingers by the contact of the broken bone ends on each other. There are other forms of crepitus (pseudo-crepitus) such as occurs in some cases of arthritis, partial luxations of the patella, or luxation of the coxofemoral joint.

The absence of crepitus does not necessarily indicate the absence of a fracture. The interposition of a piece of soft tissue between the fragments will prevent crepitus. It is also absent when the ends of the bones are so far apart that they cannot be brought into contact, or when they are impacted.

Crepitation should be elicited with the utmost precaution because of the danger of causing further damage to bony fragments and surrounding soft tissue. Vigorous palpation, which may turn a routine closed fracture into a contaminated open one, should be avoided.

6-Abnormal Mobility

A false point of motion is also pathognomonic. It occurs if there is a complete fracture of the shaft of a long bone; it does not occur in an incomplete or impacted fracture.

Mobility near a joint may be difficult to differentiate from normal or abnormal mobility of the joint itself. In order to avoid additional trauma, the same precaution should be taken in eliciting this symptom as in eliciting crepitus.

7-Radiographic Picture

Fracture, either diagnosed or suspected, should be documented by radiography. At least two views including the joints above and below the fracture are needed. Fracture of joints or special anatomical locations may require additional radiographs or special positioning. Radiographs should be read on a well illuminated flat surface. If questions about anatomical structures exist, the opposite limb or side of the body may be radiographed for comparison. The specific radiographic signs of fracture include those listed below: A break in the continuity of a bone; A line of radiolucency when the fragments are distracted; A line of radiopacity when the fragments are compressed or superimposed.

II-SYSTEMIC SIGNS

Although all of the above signs do not always occur in all fractures, combinations of these signs are always present. As time elapses between the time of the trauma and the time of treatment, symptoms change in accordance with the changes at the fracture site. Miscellaneous signs associated with fracture include the following:

1-Fever

Elevated temperatures are seen routinely 24 to 48 hours following a fracture and reflect the response to breakdown of the hematoma.

2-Anemia

Medullary arteries are high pressure vessels, and significant hemorrhage can occur with fracture. Large dogs may lose 200 ml to 300 ml of blood into the hematoma. Animals with multiple bone fractures can lose this amount of blood into each hematoma.

3-Shock

Hypovolemic shock can readily occur with severe fracture or concomitant vascular lacerations. Shock may lead to death following severe blood loss into a fracture site.

4-Nerve Injury

Depending on the location of the fracture or its severity, peripheral nerves can be involved.

5-Necrosis or Gangrene

In instances of fracture and simultaneous vascular laceration or occlusion, necrosis of distal extremities may occur. This usually occurs several days following fracture.

6-Fat in synovial fluid

This sign may indicate presence of an articular fracture; however, any trauma to a joint may result in fat in the synovial fluid. If fat is found and the animal remains lame, further studies may be needed to pursue the diagnosis of fracture.

Diagnosis: -

1-History

2-Clinical examination (local symptoms and crepitation)

3-Radiography for small animals or appendages of large animals

Healing of fracture: -

I-PATHOLOGIC CLASSIFICATION

1-Soft callous

1-Stage of hematoma (1-3 days)                        

2-Stage of tissue granulation (5 days)

3-Stage of ostoid tissue formation (5-7 days)

2-Hard callous

1-Stage of consolidation (3- 5 weeks)                

2-Stage of osseous tissue formation (6 months)

3-Stage of remodeling

II-CLINICAL CLASSIFICATION

1-Temporary Callous

2-Soft Callous               

Bleeding occurs during fracture with accumulation of inflammatory exudates leading to swelling. The fluid is reabsorbed, and blood under goes clotting with fibrin net formation. Later on angioblasts and fibroblasts appear for granulation tissue formation from the periphery toward the center. This process is associated with condrogenic changes (formation of cartilage) and ostoid tissue formation by osteoblasts with calcium deposition.

3-Hard Callous

It starts with consolidation and characterized by calcium deposition under control of blood calcium level, and gypsona can be removed 3-5 weeks later. Osseous tissue formation and remodeling occur during this stage with union of the bone fragments, conversion of ostoid tissue to osseous tissue, and formation of haversian system (it lasts 6 months). Osteoclasts lyses the external and internal callous with precipitation of calcium form outer to inner parts of the intra-fragmental callous.

Factors Affecting Healing

1-Age

The younger the age the faster the healing (2-3 weeks in young and 3-5 weeks in old animals)

2-Individual variation

Certain individuals show faster healing of fractures than others of the same species and breed and this might be related to the general health condition of that individual

3-Nutrition

Qualitative or quantitative reduction in food ingredients prolongs healing time. Low dietary levels of calcium, phosphorus, or vitamin D predisposes to delayed healing of the fracture.

4-Cause

Traumatic injuries are characterized by temporary hematoma followed by rapid healing, while infection of fracture site causes destruction of the granulation tissue with prolongation of healing time.

5-Site of fracture

Epiphyseal fracture of spongy bone heals faster than fracture of compact bone

6-Shape of fracture

Single smooth fracture is better than multiple fragmented fracture

Treatment of fracture: -

I-Supportive treatment

II-Definitive treatment

III-Restoration of normal muscles, tendons, and joints function

I-PRIMARY (SUPPORTIVE) TREATMENT

1-Prevention of shock due to pain by analgesics

2-Prevention of further damage due to movement

A-Reduction

B-Fixation

3-Prevention of change of simple fracture to compound due to movement

II-SECONDARY (DEFINITIVE) TREATMENT

The basic principles of fracture treatment are reduction, Fixation and restoration of the function.

A-Reduction of Fractured Bone to Approximate Normal Position

Reduction means correction of displaced fractured ends of bone into normal alignment and position

Types of reduction: -

1-Closed Reduction

It is performed with the skin closed (intact skin). These steps should be done after good straining of the animal with application of epidural analgesia (in hind limb fracture) or under effect of general anesthesia. The aim of anesthesia is to relieve pain, and induction of muscular relaxation. Later on extension (traction) of the lower fragment and counter extension of the upper fragment by an assistant should be done to bring the bone fragments in one level. Finally X-ray should be done to ensure the normal positioning of bone fragments.

2-Open Reduction

The fracture site is exposed surgically and reduction is performed under direct vision

Open reduction is indicated in the following cases:

1-When soft tissue is interposed between fractured ends

2-Late unreducable or untreated fractures

3-Articular fractures

4-Growth plate fractures

5-Avultion fractures

6-When internal fixation is needed

B-Fixation & Immobilization Till Complete Union of Bone

The bone fragments and the joints upper and lower to the fractured bone should be fixed till complete union of fracture

Types of fixation:

1-External Fixation

This method is usually used in association with closed reduction, especially for transverse fractures. The joints located dorsal and ventral to the fracture should be fixed, and sometimes all the limb is fixed.

Advantages: -

1-Cheap and easy method

2-It doesn’t need high experience or complicated equipment

3-There is no possibility of infection

Disadvantages: -

1-Pressure necrosis

2-Joint problems and stiffness, and muscular atrophy due to prolonged fixation

A-Ordinary splints or coaptation splints: -

Splints must be light weight, malleable, sufficiently rigid to support the weight of the animal, ends are rounded and guarded by pad of cotton   and has length greater than the distance between the two joints, like metal, wood, leather, or even cartoon in birds or pets. At least two splints (medial and lateral) are needed for proper fixation.

Application: -

The joints above and below the fracture should be involved and fixed, and sometimes the entire limb is fixed. Enough cotton padding should be applied to avoid direct pressure on skin and subsequent necrosis and gangrene, and to make the animal more comfortable, but very thick padding decreases the fixation.

Cotton should be inserted between claws or fingers, and should be at levels beyond the splint. Splints are applied medial and lateral to the limb then a gauze tapping should be applied over the splints.

B-Coaptation casts: -

Example of casts is the Gypsona or plaster of paris bandage. Other types of casts are plastic or fiberglass casts and they are stronger and not affected by moisture but they have no pores leading to heat stasis and sweat stasis with final maceration of the skin.

Advantages: -

1-Cheap

2-Easily applied

3-Has no local complications

Disadvantages: -

1-Affected by moisture

2-It needs long time to reach its maximum hardness (24 hours)

Application: -

Application of bandage by padding with cotton and tapping with gauze as mentioned before, and then the gypsona is applied and left for 30 mins to undergo hardening

Postoperative care: -

The cast should be observed for cracking, presence of discharge (color), odor, and swelling

C-Thomas tube: -

 

It is a metal tube of two rings (upper wide with a diameter 1 inch more than the thigh, and lower narrow), and two lateral splints longer than the limb. A modified Thomas tube with bent side splints is used for the hind limb.

D-External skeletal pin fixation (percutaneous pin fixation): -

This method is a mixture of external and internal methods of fixation. It is suitable fixation method for compound or infected fractures, and it is not applied directly on bone, and the bone itself is fixed externally without incising the skin by using pins that pass per-cutaneous from bone cortex to the opposite cortex and the pins are fixed outside by frame. The pins should be sterile, and of non-corrosive or ionized substances like stainless steel, platen, or cobalt nickel. The purpose of an external skeletal fixation frame is to immobilize the fracture so that healing can take place.

Types of external fixation device: -

i-Half pins: The pins pass through the skin once

ii-Full pins: The pins pass through the skin twice

However all fixation pins should pass through two bone cortices

i-Half-pins: -

Although adequate in most small animal fractures, they are the weakest and least stable method of external skeletal fixation. Full-pin fixation or through-and-through pinning with connecting bars on both sides of the fracture increases the strength of the fixation approximately fourfold. To ensure correct placement of the pins when using a half-pins splint, the proximal and distal pins are positioned as far away from the fracture site as possible, and the middle pins (near the fracture site) should be positioned as close to the fracture site as possible as determined by the quality of the soft tissues and the bone itself. The stability of the half- and full-pins devices is related to the pin diameter that penetrates the bone and the distance from the bone that the connecting bar is applied; the larger the pin diameter (up to approximately 30% of the diameter of the bone), the stronger the fixation. The greater the distance the connecting bars are applied away from the bone, the less rigid the fixation becomes.

ii-Full-pins: -

Splinting with connecting bars on both sides of the leg. The ultimate strength of the external fixation device can be influenced by the number of pins in each fracture fragment. There seems to be an increase in stability up when including four pins in each fragment.

In all situations, the most proximal and distal pins are the most highly stressed. Again, when using full-pin splinting, it is important to place the pins as far from and as near to the fracture as possible. If the bones are sufficiently long, three or four may be used in each fracture fragment.

Advantages: -

1-No joint fixation thus it avoids complications the affect joint and muscles

2-No hindrance of circulation

Disadvantages: -

1-High incidence of infection

2-Possibility of traumatization of the frame

Application: -

Under aseptic condition, the pins are driven per- cutaneously into muscles, periosteum, and the two cortexes of the bone. It is better to drive the pins in two different angels for better fixation.

2-Internal Fixation

Direct fixation applied to the bone itself

Advantages: -

1-Better method because it fixes the bone itself without involvement of the joint

2-It produces accurate reduction as the skin and muscles are opened

3-It has no circulatory hindrance or pressure atrophy

Disadvantages: -

1-High incidence of infection and inflammation, and destruction of bone marrow

2-Pressure of the splint on bone

Used materials: -

1-From clinical point of view it should be of high strength, non-corrosive, not rusting, and not ionizing

2-From economic point of view it should be cheap like stainless steel (it is the best), ceramic, nickel, or cobalt

A-Extra-medullary: -

i-Screw pin fixation or Lag screw: -

Indications:-

Fractured extremities, head of bone, neck, or condoyless

Technique: -

1-Control of the animal

2-General anesthesia and aseptic precautions

3-Open reduction of fractured bone

4-Drilling of bone fragments and screw pining through the entire thickness of the fractured fragments

5-Closure of wound in layers

6-Removal of the pin after complete healing

ii-Circular wiring or bone suturing: -

Full circlage wiring can be performed in the dog by large heavy-gauge wire of 18- or 20- gauge diameter and some method of adequately molding the wire to the bone. This technique has come to be used as a definitive method of fracture fixation in small animals and seems not to pull apart as one might suspect. The other technique is to use heavy- gauge wire and twist the wire in a fashion that allows the wire to tighten over the cortex. With this technique a wire twister or pair of pliers may be used.

Full circlage wires can be used in long oblique fractures, spiral fractures, or in fractures that have longitudinal cracks. The wires are used most easily in mid-diaphyseal locations where the diameter of the bone is most constant.

Hemicirclage wiring has been advocated by many in combination with intra-medullary Steinmann pinning. In this technique a large 18- or 20-gauge wire is used to hold fracture fragments or cracks together. The wire is effective in reinforcing longitudinal cracks in the cortex and often in preventing rotation and overriding of oblique fracture fragments.

The wire is passed through a small hole in one fracture fragment, passes across the fracture site, and comes out through a small hole in the opposite fracture fragment. The wire is twisted together in the same manner as described in full circlage wiring and may or may not be bent over in place, depending on its application.

Sometimes the wire is also placed around the intra-medullary device so that the pin is incorporated with the wire in bone-fracture fixation. Many patterns and applications of hemicirclage wiring have been reported in the veterinary literature. They are a definite adjunct in any fracture that is handled with the single Steinmann pin when rotation of the fragments is a possibility or if overriding of the fracture is a complication.

Technique: -

1-Control of the animal

2-General anesthesia and aseptic precautions

3-Open reduction of fractured bone

4-Drilling of bone fragments with suturing of fragments with simple interrupted wiring by stainless steel wire

5-Closure of wound in layers

6-Removal of wire after complete healing

iii-Bone plating: -

This method can be applied by using metal plate that has the same bone convexity and fixed with 4-6 screw pins

Indication: -

Diaphysial fracture of long bones

Disadvantages: -

1-Exposure of large area of the bone and tissue that predisposes to infection

2-The plate is applied directly on the bone that predisposes to necrosis

Technique:

1-Control and general anesthesia

2-Aseptic technique guide

3-Open reduction of the bone fragments, exposure, and fixation by plate and pins

4-Closure of the wound in layers

B-Intra-medullary pinning: -

Fixation is made here through the medullary cavity of the bone. It can be applied to diaphyseal fractures of long bones but metaphyseal fractures are treated by screw pins

Advantages: -

1-Proper reduction and fixation of the bone fragments

2-Joint, muscles, and blood supply not affected

Disadvantages: -

1-Bone marrow destruction

2-Higher probability of infection and osteomyelitis

Types of pins:-

1-Steinman pin that is straight and round in cross section with pointed end and considered as the best type of pins. Intra-medullary pinning with a single Steinmann pin may be indicated in fractures throughout the length of a long bone. It is best for transverse and short oblique fractures of the middle third of long bones. It can be applied in conjunction with cerclage and hemicerclage wiring. Single or multiple Steinmann pins together with cerclage and hemicerclage wiring may be adapted for all types of fracture fixation. The Steinmann pin is the most commonly used intra-medullary device in veterinary medicine and because it is placed in the medullary cavity, it resists bending in all directions. Its strength is related to its diameter, and its ability to restrict motion of the fracture fragment is related to its contact with the surrounding bony cortex. A small diameter intra-medullary pin in a large medullary cavity has been shown to producing non-unions. Complications of intra-medullary pinning with Steinmann pins can often be traced to mechanical factors such as pin migration, or bending. Since the medullary cavities of most bones in the dog vary widely in diameter, the Steinmann pin is usually used in three-point fixation. It is anchored at the point of introduction, has contact with the fractured surfaces and/or the isthmus of the medullary canal, and is impacted into the distal cancellous bone. In general, when an intra-medullary Steinmann pin is placed alone for reduction and stability of a fractured long bone, it should contact as much of the medullary cortex as possible in order to provide some torsional stability. If intra-medullary fixation does not present adequate stability against rotation, either multiple pinning, cerclage wiring, hemicerclage wiring, or external fixation must be used in conjunction with the pinning. Intramedullary devices provide no longitudinal support; the fracture fixation is dependent upon the stability of the fracture fragments themselves. Therefore, when comminution or cracks exist, there is a definite possibility for further collapse and telescoping of the fracture fragments over the Steinmann pin.

2-Kuntscher nails (V and "cloverleaf" shaped) that is straight and V-shape in cross section. Kuntscher nailing is indicated for middle third, transverse, or short oblique fractures of the humerus, tibia, and femur when no longitudinal cracks or fissures of the bony cortex are present. The Kuntscher nail is designed to stabilize the bony fragments by filling the marrow cavity and contacting as much of the cortical bony surface as possible. In humans this contact surface is increased by intra-medullary reaming. In the dog, intra-medullary reaming is contraindicated because the cortices are relatively thin and the diameter of the marrow cavity changes markedly throughout the length of the diaphysis. Therefore, in the dog the Kuntscher nail is usually used as a three-point fixation device. The initial point of fixation is the penetration of the nail through the proximal portion of the bone. The nail is then stabilized in the central portion of the fracture site, usually at the area of the isthmus of the marrow cavity, and distally is anchored in the cancellous portion of the bone of the distal diaphysis. The concept of the triangular or cloverleaf shape of the Kuntscher nail allows contact to be made along the marrow cavity in at least these three places. This is the one advantage of the Kuntscher nail over a firm-fitting round intra-medullary pin of the Steinmann type. The Kuntscher nail allows point contact on the inner medullary surface of the cortex, which will help prevent rotation of the bone fragments. The nail itself is a relatively weak appliance when subjected to torsional forces. The fact that it never breaks in canine application is due to that large torsional forces are not usually present or that the nail does not fit tightly enough in the medullary cavity to prevent bony rotation.

3-Rush nail that has curvature along its axis and it is bent near its wide end. Rush pins indicated when used in pairs for fractures of the distal humerus and distal femur or fractures of the central third of the diaphysis of both the humerus and femur in dogs. They can be inserted individually, but this technique has not been popularly embraced in veterinary surgery. Steinmann pins are usually preferred than single Rush pins. The Rush pin is a specially tempered, round intra-medullary device that is supposed to be quite springy. It has a hooked end that is used to drive and seat the pin into the bone and a tapered end that should bounce off the inner cortex of the bone as it is inserted so that it fits snugly against the inner wall of the medullary cavity. It is through the elastic bending of this intra-medullary pin that the rigid fixation is accomplished. Since each pin usually gives two points of fixation, Rush pins are most commonly used in pairs. It is important that the pins themselves bend elastically during their insertion, rather than cause a change in the axis of the bone.

Indications: -

Fractured long bones, but can't be used for comminuted fractures, multiple fractures, infected fractured, or metaphyseal fractures

Technique: -

1-Control and general anesthesia

2-Aseptic technique guide

3-Open reduction of the bone fragments

4-Insertion of the pin along the bone through medulla, and the excess length is removed by saw, or the pin is inserted in retrograde manner

Bone grafting

It can be used when there is no union of bone fragments or for comminuted fractures

I-AUTOGENOUS BONE GRAFTING

A piece of spongy bone is removed for healthy bone of an individual, fragmented, and transplanted to the fracture site of the same individual, it means that tissue transferred from one person or animal from one portion of the body to another.

II-ISOGRAFTING

The isograft is material that is taken from one individual and transplanted into another genetically identical individual, such as an identical twin. In this case the donor and the recipient must have the same genotype.

III-ALLOGRAFTING (Homograft)

The allograft (formerly called a homograft) is tissue that is transferred from one individual to another individual of the same species.

IV-XENOGRAFTING (formerly known as a heterograft):

It is tissue that is taken from one individual and transferred to another individual of a different species.

Treatment of Compound Fractures

The principle here is to treat the fracture and the wound as soon as possible with control of infection. Fixation, internal and direct skeletal fixations have no problem for the wound, while external fixation interferes with monitoring of the wound, so 8-Figure gypsona should be applied to leave a window for wound monitoring. The wound is treated as usual through the window in the gypsona.

III-RESTORATION of NORMAL Ms, TENDs & Js FNCTION

Gradual exercise should be performed after union of the fracture to preserve the normal function of the joint, the muscle and the tendons.

Complications of Fracture treatment

1-Pressure necrosis, muscular atrophy, and joint stiffness due to pressure of the fractured fragments

2-Damage of artery or vein due to movement of splint

3-Improper reduction and fixation

1-Gangrene

It occurs due to direct pressure of splint on skin or tissue, impairment of circulation, or thrombi of the main blood supply. Signs of gangrene appear 24-48 hours later on in the form of local signs (Bad odor, swelling, and greenish discharge) and systemic reaction (fever and anorexia)

Treatment should be applied as soon as possible by removal of splint and application of hot antiseptic fomentations to enhance circulation, but if gangrene appeared, amputation will be the main treatment.

2-Faulty callous formation

It can be prevented by proper fixation

3-Failed callous formation

It ensues due to low calcium level, infection, improper fixation

4-False joint formation

It occurs due to soft tissue between the two fragments with outer fibrous connective tissue connecting the two fragments. Fibrocartilage may be formed beside the soft tissue, it can be treated by removal of fibrous connective tissue, soft tissue, and cartilage, refresh the bone surfaces by scraping, then make proper fixation

Conclusion: -

1-Fractures of the vertebral column, scapula and pelvic bones can’t be treated

2-Fractures of the shaft of femur and humorous can be treated by intra-medullary bone pining, bone plating, or direct skeletal fixation in young animals

3-Fractures of the extremities of femur and humorous can be treated by internal fixation by screw pin

4-Fractures of extremity of radius, ulna, tibia, and fibula can be treated by screw pining, internal fixation, or external fixation (Thomus or modified Thomus)

5-Fractures of shaft of radius, ulna, tibia, and fibula can be treated by intra-medullary bone pining, direct skeletal fixation, splint and cast, or external fixation (Thomus or modified Thomus)

6-Carpus, tarsus and downward can be treated by cast or splint

7-Skull and flat bones can be treated by suturing; inter-alveolar wiring pf check teeth, bone plating, direct skeletal fixation for ramus; and wiring, bone pinning, or screw pining for fractures of mandibular body

Non-union and delayed union of fracture

Healing of fracture takes place in a certain time. When this period is passed without union this condition judged as delayed union. With time, the delay union fracture might heal or progress to non-union, at this condition, healing will not take place.

Delay or Non-union of fracture occurs as a result of

1-Wide separation                                              

2-Incarceration of soft tissue between fragments

3-Some diseases (rickets or osteomalasia)        

4-Infection or osteomylitis

5-Inadequate stabilization

6-Poor vascularity