FRA CTURE S Causes.A fracture is defined as a sudden and violent solution in the continuity of a bone. The immediate causes of a fracture are external violence, some severe force acting from with out, or extreme muscular action. The force acting from without may be direct, the fracture occurring at the point of impact, or it may be indirect, in which case the bone is fractured at some distance from the point of impact. The force in this instance has been applied in the long axis of the bone, which is bent beyond its limits of elasticity. It is broken by a twist or bending, and the fracture is oblique or spiral. In fracture by extreme muscular action the bone is broken by a tearing or traction. This is the case in fracture of one or more of the dorsal or lumbar vertebrre seen in broken back, when a horse struggles when cast in the stall or in hobbles.
Classification. — Fractures are classified as simple, compound, and complicated. A simple fracture is one in which there is no communica tion between the broken bone and external air, and there is no injury to the important struc tures in the neighbourhood. A compound or open fracture is one in which such a com munication exists. This opening furnishes means for the entrance of pyogenic organisms, and adds greatly to the gravity of the injury. It may not be immediate, occurring later from within by the protrusion of some of the frac tured parts through the soft structures, or from without by sloughing of the bruised or dead structures surrounding the fracture. A com plicated fracture is one that is associated with injury to muscles, blood-vessels, joints, or other structures in the neighbourhood. The fractured bone may sever important blood-vessels and nerves. The force causing the fracture may also cause a dislocation of the joint, and the fracture may extend into it.
Types of Fracture. A fracture may be a simple fissure or depression, seen occasionally in fractures of the bones of the face. The fracture may be sub-periosteal when the bone is com pletely broken across, but the periosteum re mains intact and prevents displacement of the fractured parts. These fractures are not rare in the tibia of the horse. The fracture may be transverse when due to direct violence, or oblique when the force has been indirect. The fracture is impacted when one fragment is wedged into the substance of the other. A fracture may also occur in which there is no displacement. The bone may be completely broken across, yct the ends remain in apposition. Such fractures, occasionally seen in the pelvis of the horse, are extremely difficult to diagnose.
Displacement of Fractures.The displacement in a fracture is determined by the direction of the force of injury. It is increased by the con traction of the muscles, and the weight of the limb, when that part of the body is fractured. Transverse fractures with serrated edges are less liable to displacement than oblique ones with smooth surfaces.
Symptoms of a Fracture. The main symptom of a fracture is loss of function, the injured bone is less capable of bearing weight or acting as a lever. In the case of one of the bones of a limb, there is lameness, acute pain, swelling, unnatural mobility, and deformity of the part when com pared with the normal side. Crepitus is the name applied to the peculiar grating sound which sometimes may be both heard and felt when the fractured ends or surfaces are moved the one against the other. The finding of the above symptoms would be sufficient to diagnose a fracture, but the absence of one or more of them would not be sufficient to negative its existence. A horse has occasionally been taken to work with a fracture of the tibia, the lameness at the time being so slight as to be considered of no importance until the fractured bone protruded through the skin. Again, an impacted fracture, or one in which there is no displacement, may exist without any crepitus or increased mobility of the part. When there is little or no displace ment deformity may also be absent. Crepitus may be absent in fractures with great displace. went, if soft tissues intervene between the fractured parts, or where the broken pieces are drawn apart by the traction of the muscles, as in a fracture of the external angle of the ilium, or point of the elbow. Swelling may be absent in certain fractures. In some fractures of the tibia in the horse, without displacement, the swelling in the early stages is so slight as to be overlooked owing to the resisting character of the periosteum, and strong fascia covering this bone. In examining for fracture it is necessary to be on guard against what is termed"false crepitus,"a grating sound, not easily described, heard in deep masses of muscles in which blood has been extravasated, or in which subcutaneous emphysema exists. The swelling in a fracture, except in the case mentioned, comes on rapidly, and is due to displacement of the parts, and effusion of blood into the surrounding tissues. It is always greater in cases due to direct violence, the result of the contusion.
It will be gathered from the above that it is sometimes impossible to secure positive proof that a fracture is present, while on the other hand it is impossible to deny that one is absent.
Treatment of Fractures. The treatment of a simple fracture consists of reduction, co aptation, and immobilization. Reduction and co-aptation are brought about by manual dexterity. The fracture is then retained in position by the application of splints made of metal or wood. Other substances are also used for this purpose, such as pitch, starch, and plaster of Paris in the form of bandages. Plastic materials, as mill-board, leather, and poroplastio felt, are also used, and found more satisfactory in certain fractures.
Splints are not always easy to keep in posi tion in animals. When used they should be light, simple, and as free from specialization as possible. In many fractures adhesive bandages
or some of the plastic materials will be found more satisfactory than splints. On the other hand, fractures are met with in which it is not possible to apply splints or other retaining materials with any benefit. When it is decided to treat such fractures, it must be on expectant lines with rest and time.
When applying splints, adhesive bandages, or plastic material, all prominences must be speci ally padded with either tow or cotton-wool, and all hollows filled with the same material, so that the pressure may be equally distributed on the surrounding parts, and support provided against displacement, due to the weight of the limb, muscular action, or the movements of the patient. The parts should be carefully ex amined daily for the first few days to ascertain that the restraining material and bandages are not too tight and are not interfering with the local circulation.
Treatment of Compound Fractures.If it is decided to treat a compound fracture, a similar procedure is followed for obtaining immobiliza tion. An attempt should be made to render and keep the wound free from sepsis. Before the retaining appliances are applied the wound must, if necessary, be enlarged, and destroyed soft tissues and all loose pieces of bone be removed. The parts should then be disinfected with pure carbolic acid and the opening packed with suitable antiseptic or sterilized material. A window must be left in the splints and bandages for further dressing.
Repair of Simple Fractures.In repair of a simple fracture the blood-clot from the torn vessels of the periosteum and the marrow becomes permeated with leucocytes and fibroblasts. A granulation tissue is formed which does not differ from that found in the repair of other tissues except that the fibroblasts, being from cells that normally form bone, become osteo blasts, and proceed to form that material, so that this new fibrous tissue becomes converted into bone. In some instances, especially when the immobilization is not complete, an inter mediate stage of cartilage is formed. The newly formed bone is at first arranged in small masses, which, uniting together, form a network of spongy bone. This reparative material of granulation tissue in the process of conversion into bone is called the callus. The external callus surrounds the fragments in a long bone, a similar mass occupying the medullary canal is called the internal callus, while the continuity of the compact bone is maintained by the inter mediate callus. Small detached portions of bone may become absorbed or incorporated in the callus, helping to bridge the divided parts. In three or four weeks union is complete; the new bone is soft and spongy, but at the end of six weeks it has become sufficiently dense, in young animals, for splints and other retaining appliances to be dispensed with.
In a compound fracture, provided there is no infection, the process of repair is the same. Should infection occur detached fragments of bone die, a constant discharge of pus is kept up, and when union does take place the succeeding callus is excessive, so much so that it may interfere with the function of the part. When repair is complete the ensheathing as well as the internal callus reduce in size with age, but in the lower animals are very rarely entirely absorbed. The term"vicious union"or"mal-union"is applied to a fracture when its repair is so faulty, owing to excess of callus or overlapping of the fragments, as to cause deformity or loss of function in the part as a weight bearer or as a lever for progression. In certain fractures there may be no attempt at repair by an ensheathing callus. In these cases of non-union the tissue between the fragments may be fibrous, or the fragments themselves may become covered with cartilage surrounded by a capsule forming a false joint. Non-united fractures in the lower animals are nearly always due to local causes. The most frequent are faulty apposition, the presence of muscle, tendon, or fibrous tissue between the fragments.
Prognosis in Fractures.In arriving at a prognosis many considerations must be kept in view, the age and species of the animal, the service expected of it, and the time and cost of treatment. Whether the animal is kept for the purpose of work, breeding, or fattening will also have to be taken into account. The difficulties in reducing and immobilizing fractures in large animals are obvious. It is also obvious that fractures are less grave and more amenable to treatment in small animals, especially if they are young. The chances of success in treating fractures in small ruminants and dogs is much greater than in the case of horses and cattle.
In certain fractures in some of the large animals, the bony union with time and rest to the part may be complete, but it will be dis covered that the callus is so excessive, or the deformity so great, leading to severe and per manent lameness, that the animal is incapable of performing what is required of it. The ensheathing callus is increased and excessive in a comminuted fracture, in any fracture not kept immobile, or in one in which there is im perfect reduction or apposition of the parts. This excessive callus may interfere with the normal movement of the joint, and remain a source of permanent lameness after complete repair of the fracture. Other causes of lame ness may be adhesions of some of the soft structures to the callus, or the pressure of the bony material on a nerve.