CHAPTER II

INJURIES OF JOINTS

SURGICAL ANATOMY--INJURIES: _Contusions_; _Wounds_; _Sprains_; _Dislocations_--TRAUMATIC DISLOCATIONS: _Causes_: _Varieties_; _Clinical features_; _Treatment_--Compound dislocations--Old-standing dislocations.

#Surgical Anatomy.#--The function of a joint is to permit of the movement of one bone upon another. The articular surfaces are covered with a thin layer of hyaline cartilage, and are retained in apposition by the tension of ligaments and of the muscles surrounding the joint. The articular capsule (capsular ligament) is directly continuous with the periosteum, and is lined by a synovial layer, which at the line of attachment of the capsule is reflected on to the bone as far as the articular cartilage. The synovial layer invests intra-articular ligaments, and is projected into the interior of the joint in the form of loose folds wherever the articulating surfaces are not in immediate contact. The surface of the synovial layer is covered with minute processes or villi, which in diseased conditions may become hypertrophied. The synovia owes its lubricating property to mucin, derived from the solution of the endothelial cells on the free surface of the synovial layer. The opposing surfaces of a joint being always in accurate contact, the so-called cavity is only a potential one. If fluid is poured out into the joint, the synovial layer and the capsule are put upon the stretch, causing discomfort or actual pain, which is partly relieved by slightly flexing the joint. If the distension persists, the ligaments become elongated and the joint unstable.

The common origin of bone, cartilage, periosteum, and synovial layer from one parent tissue of the embryo, accords with the readiness with which any one of these tissues may be converted into another under traumatic or pathological influences; and how in ligaments and in synovial membrane foci of hyaline cartilage may form and, after increasing in size, undergo ossification.

Joints derive an abundant blood supply through the articular arteries. The lymphatics, which take origin in the synovial layer, pass to efferent vessels which run in the intermuscular and other connective-tissue planes of the limb. The nerve supply is derived chiefly from the nerves distributed to the muscles acting on the joint and to the skin over it.

#Sources of Joint Strength.#--The capacity of a joint to resist dislocation depends upon (1) the shape of its osseous elements; (2) the strength and arrangement of its ligaments; (3) the support it receives from muscles or tendons placed in relation to it; and (4) the relative stability of adjacent structures. While all these factors contribute to the strength of a given joint, one or other of them usually predominates, so that certain joints are osseously strong, others are ligamentously strong, while a few depend chiefly upon adjacent muscles for their stability.

The hip and elbows are the best examples of joints deriving their strength mainly from the architectural arrangement of the constituent bones. These joints are dislocated only by extreme degrees of violence, and not infrequently--especially in the elbow--portions of the bones are fractured before the articular surfaces are separated.

The knee, the wrist, the carpal, the tarsal, and the clavicular joints depend for their stability almost entirely on the strength of their ligaments. These joints are rarely dislocated, but as the main incidence of the violence falls on the ligaments they are frequently sprained.

The shoulder is the typical example of a joint depending for its security chiefly upon the muscles and tendons passing over it, and hence the frequency with which it is dislocated when the muscles are taken unawares. At the same time the great mobility of the scapula and clavicle materially increases the stability of the shoulder-joint. The tendons passing in relation to the knee, ankle, and wrist add to the stability of these joints.

The proximity of an easily fractured bone also contributes to prevent dislocation of certain joints--for example, fracture of the clavicle prevents an impinging force expending itself on the shoulder-joint; and the frequency of Colles' fracture of the radius, and of Pott's fracture of the fibula, doubtless accounts to some extent for the rarity of dislocation of the wrist and ankle-joints respectively. The immunity from dislocation which the joints of young subjects enjoy is partly due to the ease with which an adjacent epiphysis is separated.

The mechanical axiom that "what is gained in movement is lost in stability" applies to joints, those which have the widest range of movement being the most frequently dislocated.

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The injuries to which a joint is liable are Contusions, Wounds, Sprains, and Dislocations.

#Contusions of Joints.#--Contusion is the mildest form of injury to a joint. Whether the violence is transmitted from a distance, as in contusion of the hip from a fall on the feet, or acts more directly, as in a fall on the great trochanter, the bones are violently driven against one another, and the force expends itself on their articular surfaces. The articular cartilages and the underlying spongy bone, as well as the synovial lining, are bruised, and there is an effusion of blood and serous fluid into the joint and surrounding tissues.

The most prominent _clinical features_ are swelling and discoloration. The swelling, especially in superficially placed joints, is an early and marked symptom, and is mainly due to the effusion of blood into the joint (_haemarthrosis_). In deeply placed joints, discoloration may not appear on the surface for some days, especially if the violence has been indirect. The joint is kept in the flexed position, and is painful only when moved. In haemophilic subjects, considerable effusion of blood into a joint may follow the most trivial injury.

A slight degree of serous effusion into the joint (_hydrarthrosis_) often persists for some time, and tuberculous affections of joints not infrequently date from a contusion.

The _treatment_ is the same as for sprains (p. 36).

#Wounds of Joints.#--The importance of accidental wounds of joints--such, for example, as result from a stab with a penknife or the spike of a railing--lies in the fact that they are liable to be followed by infection of the synovial cavity. The infection may involve only the synovial layer (_septic synovitis_), or may spread to all the elements of the joint (_septic arthritis_). These conditions are described with diseases of joints.

Penetration of the joint may sometimes be recognised by the escape of synovia from the wound, or the synovial layer or articular cartilage may be exposed. When doubt exists, the wound should be enlarged. The use of the probe is to be avoided, on account of the risk of carrying infective material from the track of the wound into the joint.

Penetrating wounds of joints are treated on the same lines as compound fractures. If the penetrating instrument is to be regarded as infected,--as, for example, when the spoke of a motor bicycle is driven through the upper pouch of the knee,--the injury is to be looked upon as serious and capable of endangering the function of the joint, loss of the limb, or even life itself. Reliance is chiefly laid on primary excision of the edges and track of the wound, and other measures employed in the treatment of gun-shot wounds. While the wound in the synovialis and capsule is sutured, that in the soft parts is left open. If drainage is employed, the tube extends down to the opening in the synovialis, but not into the joint itself. If sepsis supervenes, the joint is opened and irrigated by Carrel's method. Some form of splint and a Bier's bandage are valuable adjuncts. The final recourse is to amputation.

#Gun-shot injuries# of joints vary in severity from a mere puncture of the synovial layer by a chip of shell to complete shattering of the articular surfaces. Between these extremes are cases in which the capsular and synovial layer are extensively lacerated without involvement of the bones, and others in which the bones are implicated without serious damage being done to ligaments or synovial layer--for example, by a bullet passing through and through the cancellated part of one of the constituent bones, or by a fissure extending into the articular surface.

In all degrees the great risk is from septic infection, which may be assumed to be present in all but the last-named variety.

The _treatment_ consists in immediately cleansing the wound by excising grossly damaged tissue and removing any foreign body that may have lodged; disinfecting the exposed part of the joint cavity with eusol, "bipp," or other antiseptic, and closing the wound or establishing drainage, according to circumstances. The joint is then immobilised till the wound has healed, after which massage and movement are commenced. When the bones are shattered or when sepsis gets the upper hand and disorganises the joint, amputation is called for.

#Sprains.#--A sprain results from a stretching or twisting form of violence which causes the joint to move beyond its physiological limits, or in some direction for which it is not structurally adapted. The main incidence of the force therefore falls upon the ligaments, which are suddenly stretched or torn. The synovial layer also is torn, and the joint becomes filled with blood and synovial fluid.

Muscles and tendons passing over the joint are stretched or torn, and their sheaths filled with serous effusion. It is not uncommon for portions of bone to be torn off at the site of attachment of strong ligamentous bands or tendons, constituting a "sprain fracture"; or for intra-articular cartilages to be torn and displaced, as in the knee.

_Clinical Features._--The injury is accompanied by intense sickening pain, and this may persist for a considerable time. At first it is aggravated by moving the joint, but if the movement is continued it tends to pass off. The particular ligaments involved may be recognised by the tenderness which is elicited on making pressure over them, or by putting them on the stretch. In this way a sprain may often be diagnosed from a fracture in which the maximum tenderness is over the injury to the bone.

The effusion of blood and synovia into the joint and into the tissues around gives rise to swelling and discoloration, and the fluid effused into tendon sheaths often produces a peculiar creaking sensation, which may be mistaken for the crepitus of fracture. In sprains, the bony points about the joint retain their normal relations to one another, and this usually enables these injuries to be diagnosed from dislocations. When the swelling is great, it is often necessary to have recourse to the Roentgen rays to make certain that there is no fracture or dislocation. The special features and complications of sprains of the knee are discussed with other injuries of that joint.

_Repair of Sprains._--Blood and synovia are absorbed and torn structures become reunited, but in this process adhesions may form inside the joint and in the surrounding tendon sheaths and interfere with the movement of the joint.

_Prognosis._--Stiffness, lasting for a longer or shorter time, follows most sprains, but may be largely prevented by proper treatment. In old and rheumatic persons, changes of the nature of arthritis deformans are liable to supervene, interfering greatly with movement. While suppuration is rare, tuberculous disease is alleged to have resulted from a sprain.

_Treatment._--If seen immediately after the accident, firm pressure should be applied by means of an elastic bandage over a thick layer of cotton wool, to prevent bleeding and effusion of synovia. Later the best treatment is by massage and movement. In the ankle, for example, massage should be commenced at once, the part being gently stroked upwards. If the massage is light enough there is no pain, it is actually soothing. The rubbing is continued for from fifteen to twenty minutes, and the patient is encouraged to move the toes and ankle; a moderately firm elastic bandage is then applied. The massage is repeated once or twice a day, the sittings lasting for about fifteen minutes. The patient should be encouraged to move the joint from the first, beginning with the movements that put least strain upon the damaged ligaments, and gradually increasing the range. In the course of a few days he is encouraged to walk or cycle, or otherwise to use the joint without subjecting it to strain, or to a repetition of the movement that caused the accident. Alternate hot and cold douching, or hot-air baths, followed by massage, are also useful. Complete rest and prolonged immobilisation are to be condemned.

TRAUMATIC DISLOCATIONS

A dislocation or luxation is a persistent displacement of the opposing ends of the bones forming a joint. We are here concerned only with such dislocations as immediately follow upon injury. Those that are congenital or that result from disease will be studied later.

_Causes._--The majority of dislocations are the result of _indirect_ violence, the more movable bone acting as a lever, on a fulcrum furnished by the natural check to movement in the form of ligament, bone, or muscle. It is in this way that most dislocations of the shoulder, hip, and elbow are produced.

At the moment the violence is applied, the muscles are relaxed or otherwise taken at a disadvantage, so that the joint is for the time being deprived of their support. The joint is moved beyond its physiological range, and the end of one of the bones being brought to bear upon the capsule, tears it, and passes through the rent thus made. The muscles then contract reflexly, and pull the head of the bone into an unnatural position outside the capsule. The position assumed will depend upon such factors as the direction of the force, the structure of the joint, the position of the limb at the time of the accident, and the relative strength of the different groups of muscles acting upon the bone which is displaced.

Violence applied _directly_ to the joint is a much less frequent cause of dislocation. In this way, however, the knee-joint may be dislocated, one bone being driven past the other--for example, by a kick from a horse; or the acromio-clavicular joint by a blow on the shoulder.

_Muscular contraction_ is not often the sole cause of dislocation, although, as has been mentioned, it plays an important role in the production of the majority of these injuries. The shoulder, mandible, and patella are, however, not infrequently displaced by muscular action alone. Acrobats sometimes acquire the power of dislocating certain joints by voluntary contraction of their muscles.

_Age and Sex._--Dislocations occur most frequently in adult males, doubtless on account of the nature of their occupations and recreations. In children the epiphyses are separated, and in old people the bones are broken by such forms of violence as cause dislocation in the middle-aged.

Muscular debility and undue laxness of ligaments resulting from disease or previous dislocation are also predisposing factors.

_Clinical Varieties._--The separation between the bones may be _complete_ or _partial_. When partial, portions of the articular surfaces remain in apposition, and the injury is known as a _sub-luxation_. Like fractures, dislocations may be _simple_ or _compound_, the latter being specially dangerous on account of the risk of infection. When seen within a few days of its occurrence, a dislocation is looked upon as _recent_; but when several weeks or months have elapsed, it is spoken of as an _old-standing_ dislocation. The latter will be described later.

Dislocations, like fractures, may be _complicated_ by injuries to large blood vessels or nerve-trunks, by injuries to internal organs, or by a wound of the soft tissues which does not communicate with the joint. Further, a fracture may coexist with a dislocation--a most important complication.

_Clinical Features._--The most characteristic signs of dislocation are _preternatural rigidity_, or want of movement where movement should naturally take place; _mobility in abnormal directions_; and _deformity_, the part being "out of drawing" as compared with the uninjured side (Fig. 18). The bony landmarks lose their normal relationship to one another; and the deformity is characteristic, and is common to all examples of the same dislocation.

Although any of the subsidiary signs may occur in lesions other than dislocations, due weight must be given to them in making a diagnosis. _Loss of function_ is complete as a rule. _Pain_ is much more intense than in fracture, usually because the displaced bone presses upon nerve-trunks, and from the same cause there is often numbness and partial paralysis of the limb beyond. _Swelling_ of the soft parts due to effused blood is usually less marked in dislocation than in fracture, but is often sufficiently great to interfere with diagnostic manipulations. The displaced bone, and sometimes the empty socket, may be palpable. _Discoloration_ is usually later of appearing than in fractures. _Alteration in the length_ of the injured limb--usually in the direction of shortening--is a common feature; while girth measurements usually show an increase. A peculiar soft _grating_ or _creaking sensation_ is often felt on attempting to move the joint; this is due to cartilaginous or ligamentous structures rubbing on one another, and must not be mistaken for the crepitus of fracture. In the majority of cases, although not in all, after reduction has been effected, the bones retain their proper relations without external support, a point in which a dislocation differs from a fracture. A careful investigation of the kind of force which produced the injury, particularly as regards its intensity and direction of action, may aid in the diagnosis. The diagnosis can always be verified by the use of the Roentgen rays, and this should be had recourse to whenever possible, as a fracture may be shown that otherwise would escape recognition.

_Prognosis._--After having once been dislocated, a joint is seldom as strong as it was formerly, although for all practical purposes the limb may be as useful as ever. Some degree of stiffness, of limited movement, or of muscular weakness, and occasional arthritic changes and a liability to re-dislocation, are the commonest sequelae. Prolonged immobilisation is liable to lead to stiffness by permitting of the formation of adhesions; while too early movement tends to produce a laxity of the ligaments which favours re-displacement from slight causes.

_Treatment._--Reduction should be attempted at the earliest possible moment. Every hour of delay increases the difficulty. The guiding principle is to cause the displaced bone to re-enter its socket by the same route as that by which it left it--that is, through the existing rent in the capsule. This is done by carrying out certain manipulations which depend upon the anatomical arrangement of the parts, and which vary, not only with different joints, but also with different varieties of dislocation of the same joint. In general terms it may be said that the main impediments to reduction are: the contraction of the muscles acting upon the displaced bone; the entanglement of the bone among tendons or ligamentous bands which fix it in its abnormal position; and the rent in the capsule being small or valvular, so that it forms an obstacle to the bone reentering the socket.

Muscular contraction is best overcome by the administration of a general anaesthetic, and in all but the simplest cases this should be given to ensure accurate and painless reduction. Failing this, however, the muscles may be wearied out by the surgeon making steady and prolonged traction on the limb, while an assistant makes counter-extension on the proximal segment of the joint. Advantage may also be taken of such muscular relaxation as occurs when the patient is already faint, or when his attention is diverted from the injured part, to carry out the manipulations necessary to restore the bone to its normal position.

The appropriate manoeuvres for disengaging the head of the bone from tendons, ligaments, or bony processes with which it may be entangled, will be suggested by a consideration of the anatomy of the particular joint involved, and will be described with individual dislocations.

In reducing a dislocation, no amount of physical force will compensate for a want of anatomical knowledge. All tugging, twisting, or wrenching movements are to be avoided, as they are liable to cause damage to blood vessels, nerves, or other soft parts, or even--and especially in old people--to fracture one of the bones concerned.

After reduction, great benefit is gained by the systematic use of _massage_ and movement. Before any restraining apparatus is applied the whole region should be gently stroked in a centrifugal direction for fifteen or twenty minutes; and this is to be repeated daily, each sitting lasting for about twenty minutes. From the first day onward, movement of the joint is carried out in every direction, except that which tends to bring the head of the bone against the injured part of the capsule; and the patient is encouraged to move the joint as early as possible. The appropriate apparatus and the period during which it should be worn will be considered with the individual dislocations.

_Operation in Simple Dislocations._--In a limited number of cases, even with the aid of an anaesthetic, reduction by manipulation is found to be impossible. Resort must then be had to operation, which is a comparatively safe and satisfactory proceeding, although often difficult. It may happen in rare instances that the undoing of the displacement is only possible after the removal of a portion of one or other of the bones.

#Compound Dislocations.#--Compound dislocations are usually the result of extreme violence produced by machinery or railway accidents, or by a fall from a height. In the majority of cases they are complicated by fracture of one or more of the constituent bones of the joint, as well as by laceration of muscles, tendons, and blood vessels. In the region of the ankle, wrist, and joints of the thumb, however, compound dislocation is sometimes met with uncomplicated by other lesions. The great risk is infection, which may result in serious impairment of the usefulness of the joint or even in its complete destruction, results towards which the concomitant injuries materially contribute. In many instances where infection has occurred, ankylosis is the best result that can be hoped for.

_Treatment._--As a rule, the first question that arises is whether amputation is necessary or not, and the considerations that determine this point are the same as in compound fractures (p. 26). If an attempt is to be made to save the limb, the treatment is the same as in compound fracture (p. 25).

#Dislocation complicated by Fracture.#--In certain dislocations the separation of small portions of bones or of epiphyses is of common occurrence--for example, fracture of the tip of the coronoid process in dislocation of the elbow backwards, and chipping off of a portion of the edge of the acetabulum in dislocation of the hip.

The most important example of a fracture complicating a dislocation is fracture of the surgical neck of the humerus coexisting with dislocation of the shoulder. Here the difficulty of diagnosis is greatly increased, and the treatment of both injuries requires to be modified. The dislocation must be reduced--by operation if necessary--before the fracture is treated, and in many cases it is advisable to secure the fragments of the broken bone by pegs, or plates, to admit of movement being commenced early, and so to prevent stiffness of the joint.

#Old-standing Dislocations.#--When, from want of recognition--and, curiously enough, a dislocation is much more liable to be overlooked than would have been thought possible--or from unsuccessful treatment, a dislocation is left unreduced, changes take place in and around the joint which render reduction increasingly difficult or impossible. The rent in the capsule closes upon the neck of the bone, and fibrous adhesions form between muscles, tendons, and other structures that have been torn. The articular cartilage of the head, being no longer in contact with an opposing cartilage, tends in time to be converted into fibrous tissue, and may become adherent to other fibrous structures in its vicinity. By pressing on adjacent structures it may form for itself a new socket of dense fibrous tissue which in time becomes lined with a secreting membrane. When the displaced head lies against a bone, the continuous pressure produces a new osseous socket, from the margins of which osteophytic outgrowths may spring, and as the surrounding fibrous tissue becomes condensed and forms a strong capsule, a new joint results. The occurrence of these changes in the direction of a new ball-and-socket joint is largely dependent on the behaviour of the patient: a vigorous man, anxious to recover the use of the limb, will employ it with a degree of determination and indifference to pain that could not be expected in a sensitive elderly female. The most perfect example of a new ball-and-socket joint, following upon an unreduced dislocation at the hip, that has come under our observation, was in a hunting dog, given one of us by an Australian pupil, who testified that the animal was as fleet with the new joint as it had been with the original one. Meanwhile the cartilage of the original socket is converted into fibrous tissue, which may come to fill up the cavity. Changes resembling those of arthritis deformans may occur. The large blood vessels and nerves in the vicinity may be pressed upon or stretched by the displaced bone, or may be implicated in fibrous adhesions. In course of time they become lengthened or shortened in accordance with the altered attitude of the limb.

In many cases the new joint is remarkably mobile and useful; but in others, pain, limited movement, and atrophy of muscles render it comparatively useless, and surgical intervention is called for.

_Treatment._--It is always a difficult problem to determine the date after which it is inadvisable to attempt reduction by manipulation in an old dislocation and no rules can be laid down which will cover all cases. Rather must each case be decided on its own merits, due consideration being had to the risks that attend this line of treatment. The chief of these are: rupture of a large blood vessel or nerve that has formed adhesions with the displaced bone, or has become shortened in adaptation to the altered shape or length of the limb; tearing of muscles or tendons, or even of skin; fracture of the bone, especially in old people; and separation of epiphyses in the young.

Before carrying out the manipulations appropriate to the particular dislocation, all adhesions must first be broken down; and during the proceedings no undue force is to be employed. The first attempt at reduction may fail, and yet subsequent efforts, at intervals of a few days, may ultimately prove successful; the vigorous traction and twisting of the soft parts, matted together as they are by scar-tissue, causes reactive changes in the vessels and tissues which render them more liable to yield on subsequent attempts at reduction. In old people, and where there is an absence of suffering from pressure on nerves or vessels, it may be wiser to leave the dislocation unreduced, and strive rather by massage and movement to obtain a useful variety of false joint. If the conditions are otherwise, it may be better to improve the function of the limb by an _open operation_. Tight ligaments and other structures are divided, and the socket is cleared out. If reduction is still impossible, a partial excision may be performed and a flap of fascia lata introduced to prevent ankylosis (arthroplasty). In the case of the hip, the dislocation may be left alone and the femur divided below the trochanter, especially if there is pronounced flexion.

#Habitual or recurrent dislocation# is almost exclusively met with in the shoulder, and will be described with the injuries of that joint.

#Pathological Dislocations.#--Joints may become dislocated in the course of certain diseases. These pathological dislocations fall into different groups: (1) those due to gradual stretching of the capsular and other ligaments weakened by inflammatory and suppurative processes, such as sometimes follow on typhoid, scarlet fever, or diphtheria, and in pyaemia; (2) those due to destructive changes in the ligaments and bones--typically seen in tuberculous arthritis, in arthritis deformans, in Charcot's disease, and in nerve lesions, _e.g._ dislocation of the hip in spastic conditions, such as Little's disease; (3) those associated with deformed attitudes of the limb; (4) those due to changes in the articular surfaces, _e.g._ the phalanges in arthritis deformans. These will be considered with the conditions which give rise to them.

#Congenital Dislocations.#--Congenital dislocations are believed to be the result of abnormal or arrested development _in utero_, and are to be distinguished from dislocations occurring during birth, which are essentially traumatic in origin. They will be described along with the Deformities of the Extremities.