Ch XX

DISEASES OF BONE

Anatomy and physiology--Regeneration of bone--Transplantation of bone. DISEASES OF BONE--Definition of terms--Pyogenic diseases: _Acute osteomyelitis and periostitis_; _Chronic and relapsing osteomyelitis_; _Abscess of bone_--Tuberculous disease--Syphilitic disease--Hydatids; Rickets; Osteomalacia--Ostitis deformans of Paget--Osteomyelitis fibrosa--Affections of bones in diseases of the nervous system--Fragilitas ossium--Tumours and cysts of bone.

#Surgical Anatomy.#--During the period of growth, a long bone such as the tibia consists of a shaft or _diaphysis_, and two extremities or _epiphyses_. So long as growth continues there intervenes between the shaft and each of the epiphyses a disc of actively growing cartilage--_the epiphysial cartilage_; and at the junction of this cartilage with the shaft is a zone of young, vascular, spongy bone known as the _metaphysis_ or _epiphysial junction_. The shaft is a cylinder of compact bone enclosing the medullary canal, which is filled with yellow marrow. The extremities, which include the ossifying junctions, consist of spongy bone, the spaces of which are filled with red marrow. The articular aspect of the epiphysis is invested with a thick layer of hyaline cartilage, known as the _articular cartilage_, which would appear to be mainly nourished from the synovia.

The external investment--the _periosteum_--is thick and vascular during the period of growth, but becomes thin and less vascular when the skeleton has attained maturity. Except where muscles are attached it is easily separated from the bone; at the extremities it is intimately connected with the epiphysial cartilage and with the epiphysis, and at the margin of the latter it becomes continuous with the capsule of the adjacent joint. It consists of two layers, an outer fibrous and an inner cellular layer; the cells, which are called osteoblasts, are continuous with those lining the Haversian canals and the medullary cavity.

The arrangement of the _blood vessels_ determines to some extent the incidence of disease in bone. The nutrient artery, after entering the medullary canal through a special foramen in the cortex, bifurcates, and one main division runs towards each of the extremities, and terminates at the ossifying junction in a series of capillary loops projected against the epiphysial cartilage. This arrangement favours the lodgment of any organisms that may be circulating in the blood, and partly accounts for the frequency with which diseases of bacterial origin develop in the region of the ossifying junction. The diaphysis is also nourished by numerous blood vessels from the periosteum, which penetrate the cortex through the Haversian canals and anastomose with those derived from the nutrient artery. The epiphyses are nourished by a separate system of blood vessels, derived from the arteries which supply the adjacent joint. The veins of the marrow are of large calibre and are devoid of valves.

The _nerves_ enter the marrow along with the arteries, and, being derived from the sympathetic system, are probably chiefly concerned with the innervation of the blood vessels, but they are also capable of transmitting sensory impulses, as pain is a prominent feature of many bone affections.

It has long been believed that _the function of the periosteum_ is to form new bone, but this view has been questioned by Sir William Macewen, who maintains that its chief function is to limit the formation of new bone. His experimental observations appear to show that new bone is exclusively formed by the cellular elements or osteoblasts: these are found on the surface of the bone, lining the Haversian canals and in the marrow. We believe that it will avoid confusion in the study of the diseases of bone if the osteoblasts on the surface of the bone are still regarded as forming the deeper layer of the periosteum.

The formation of new bone by the osteoblasts may be _defective_ as a result of physiological conditions, such as old age and disease of a part, and defective formation is often associated with atrophy, or more strictly speaking, absorption, of the existing bone, as is well seen in the edentulous jaw and in the neck of the femur of a person advanced in years. Defective formation associated with atrophy is also illustrated in the bones of the lower limbs of persons who are unable to stand or walk, and in the distal portion of a bone which is the seat of an ununited fracture. The same combination is seen in an exaggerated degree in the bones of limbs that are paralysed; in the case of adults, atrophy of bone predominates; in children and adolescents, defective formation is the more prominent feature, and the affected bones are attenuated, smooth on the surface, and abnormally light.

On the other hand, the formation of new bone may be _exaggerated_, the osteoblasts being excited to abnormal activity by stimuli of different kinds: for example, the secretion of certain glandular organs, such as the pituitary and thyreoid; the diluted toxins of certain micro-organisms, such as the staphylococcus aureus and the spirochæte of syphilis; a condition of hyperæmia, such as that produced artificially by the application of a Bier's bandage or that which accompanies a chronic leg-ulcer.

The new bone is laid down on the surface, in the Haversian canals, or in the cancellous spaces and medullary canal, or in all three situations. The new bone on the surface sometimes takes the form of a diffuse _encrustation_ of porous or spongy bone as in secondary syphilis, sometimes as a uniform increase in the girth of the bone--_hyperostosis_, sometimes as a localised heaping up of bone or _node_, and sometimes in the form of spicules, spoken of as _osteophytes_. When the new bone is laid down in the Haversian canals, cancellous spaces and medulla, the bone becomes denser and heavier, and is said to be _sclerosed_; in extreme instances this may result in obliteration of the medullary canal. Hyperostosis and sclerosis are frequently met with in combination, a condition that is well illustrated in the femur and tibia in tertiary syphilis; if the subject of this condition is confined to bed for several months before his death, the sclerosis may be undone, and rarefaction may even proceed beyond the normal, the bone becoming lighter and richer in fat, although retaining its abnormal girth.

The _function of the epiphysial cartilage_ is to provide for the growth of the shaft in length. While all epiphysial cartilages contribute to this result, certain of them functionate more actively and for a longer period than others. Those at the knee, for example, contribute more to the length of limb than do those at the hip or ankle, and they are also the last to unite. In the upper limb the more active epiphyses are at the shoulder and wrist, and these also are the last to unite.

The activity of the epiphysial cartilage may be modified as a result of disease. In rickets, for example, the formation of new bone may take place unequally, and may go on more rapidly in one half of the disc than in the other, with the result that the axis of the shaft comes to deviate from the normal, giving rise to knock-knee or bow-knee. In bacterial diseases originating in the marrow, if the epiphysial junction is directly involved in the destructive process, its bone-forming functions may be retarded or abolished, and the subsequent growth of the bone be seriously interfered with. On the other hand, if it is not directly involved but is merely influenced by the proximity of an infective focus, its bone-forming functions may be stimulated by the diluted toxins and the growth of the bone in length exaggerated. In paralysed limbs the growth from the epiphyses is usually little short of the normal. The result of interference with growth is more injurious in the lower than in the upper limb, because, from the functional point of view, it is essential that the lower extremities should be approximately of equal length. In the forearm or leg, where there are two parallel bones, if the growth of one is arrested the continued growth of the other results in a deviation of the hand or foot to one side.

In certain diseases, such as rickets and inherited syphilis, and in developmental anomalies such as achondroplasia, _dwarfing_ of the skeleton results from defective growth of bone at the ossifying junctions. Conversely, excessive growth of bone at the ossifying junctions results in abnormal height of the skeleton or _giantism_ as a result, for example, of increased activity of the pituitary in adolescents, and in eunuchs who have been castrated in childhood or adolescence; in the latter, union of the epiphyses at the ends of the long bones is delayed beyond the usual period at which the skeleton attains maturity.

#Regeneration of Bone.#--When bone has been lost or destroyed as a result of injury or disease, it is capable of being reproduced, the extent to which regeneration takes place varying under different conditions. The chief part in the regeneration of bone is played by the osteoblasts in the adjacent marrow and in the deeper layer of the periosteum. The shaft of a long bone may be reproduced after having been destroyed by disease or removed by operation. The flat bones of the skull and the bones of the face, which are primarily developed in membrane, have little capacity of regeneration; hence, when bone has been lost or removed in these situations, there results a permanent defect.

Wounds or defects in articular cartilage are repaired by fibrous or osseous tissue derived from the subjacent cancellous spaces.

_Transplantation of Bone--Bone-grafting._--Clinical experience is conclusive that a portion of bone which has been completely detached from its surroundings--for example, a trephine circle, or a flap of bone detached with the saw, or the loose fragments in a compound fracture--may become, if replaced in position, firmly and permanently incorporated with the surrounding bone. Embedded foreign bodies, on the other hand, such as ivory pegs or decalcified bone, exhibit, on removal after a sufficient interval, evidence of having been eroded, in the shape of worm-eaten depressions and perforations, and do not become united or fused to the surrounding bone. It follows from this that the implanting of living bone is to be preferred to the implanting of dead bone or of foreign material. We believe that transplanted living bone when placed under favourable conditions survives and becomes incorporated with the bone with which it is in contact, and does not merely act as a scaffolding. We believe also that the retention of the periosteum on the graft is not essential, but, by favouring the establishment of vascular connections, it contributes to the survival of the graft and the success of the transplantation. Macewen maintains that bone grafts "take" better if broken up into small fragments; we regard this as unnecessary. Bone grafts yield better functional results when they are immovably fixed to the adjacent bone by suture, pegs, or plates. As in all grafting procedures, asepsis is essential.

Transplanted bone retains its vitality when embedded in the soft parts, but is gradually absorbed and replaced by fibrous tissue.

DISEASES OF BONE

The morbid processes met with in bone originate in the same way and lead to the same results as do similar processes in other tissues. The structural peculiarities of bone, however, and the important changes which take place in the skeleton during the period of growth, modify certain of the clinical and pathological features.

_Definition of Terms._--Any diseased process that affects the periosteum is spoken of as _periostitis_; the term _osteomyelitis_ is employed when it is located in the marrow. The term _epiphysitis_ has been applied to an inflammatory process in two distinct situations--namely, the ossifying nucleus in the epiphysis, and the ossifying junction or metaphysis between the epiphysial cartilage and the diaphysis. We shall restrict the term to inflammation in the first of these situations. Inflammation at the ossifying junction is included under the term osteomyelitis.

The term _rarefying ostitis_ is applied to any process that is attended with excessive absorption of the framework of a bone, whereby it becomes more porous or spongy than it was before, a condition known as _osteoporosis_.

The term _caries_ is employed to indicate any diseased process associated with crumbling away of the trabecular framework of a bone. It may be considered as the equivalent of ulceration or molecular destruction in the soft parts. The carious process is preceded by the formation of granulation tissue in the marrow or periosteum, which eats away and replaces the bone in contact with it. The subsequent degeneration and death of the granulation tissue under the necrotic influence of bacterial toxins results in disintegration and crumbling away of the trabecular framework of the portion of bone affected. Clinically, carious bone yields a soft grating sensation under the pressure of the probe. The macerated bone presents a rough, eroded surface.

The term _dry caries_ (_caries sicca_) is applied to that variety which is unattended with suppuration.

_Necrosis_ is the term applied to the death of a tangible portion of bone, and the dead portion when separated is called a _sequestrum_. The term _exfoliation_ is sometimes employed to indicate the separation or throwing off of a superficial sequestrum. The edges and deep surface of the sequestrum present a serrated or worm-eaten appearance due to the process of erosion by which the dead bone has been separated from the living.

BACTERIAL DISEASES

The most important diseases in this group are the pyogenic, the tuberculous, and the syphilitic.

PYOGENIC DISEASES OF BONE.--These diseases result from infection with pyogenic organisms, and two varieties or types are recognised according to whether the organisms concerned reach their seat of action by way of the blood-stream, or through an infection of the soft parts in contact with the bone.

INFECTIONS THROUGH THE BLOOD-STREAM

#Diseases caused by the Staphylococcus Aureus.#--As the majority of pyogenic diseases are due to infection with the staphylococcus aureus, these will be described first.

#Acute osteomyelitis# is a suppurative process beginning in the marrow and tending to spread to the periosteum. The disease is common in children, but is rare after the skeleton has attained maturity. Boys are affected more often than girls, in the proportion of three to one, probably because they are more liable to exposure, to injury, and to violent exertion.

_Etiology._--Staphylococci gain access to the blood-stream in various ways, it may be through the skin or through a mucous surface.

Such conditions as, for example, a blow, some extra exertion such as a long walk, or exposure to cold, as in wading, may act as localising factors.

The long bones are chiefly affected, and the commonest sites are: either end of the tibia and the lower end of the femur; the other bones of the skeleton are affected in rare instances.

_Pathology._--The disease commences and is most intense in the marrow of the ossifying junction at one end of the diaphysis; it may commence at both ends simultaneously--_bipolar osteomyelitis_; or, commencing at one end, may spread to the other.

The changes observed are those of intense engorgement of the marrow, going on to greenish-yellow purulent infiltration. Where the process is most advanced--that is, at the ossifying junction--there are evidences of absorption of the framework of the bone; the marrow spaces and Haversian canals undergo enlargement and become filled with greenish-yellow pus. This rarefaction of the spongy bone is the earliest change seen with the X-rays.

The process may remain localised to the ossifying junction, but usually spreads along the medullary canal for a varying distance, and also extends to the periosteum by way of the enlarged Haversian canals. The pus accumulates under the periosteum and lifts it up from the bone. The extent of spread in the medullary canal and beneath the periosteum is in close correspondence. The periosteum of the diaphysis is easily separated--hence the facility with which the pus spreads along the shaft; but in the region of the ossifying junction it is raised with difficulty because of its intimate connection with the epiphysial cartilage. Less frequently there is more than one collection of pus under the periosteum, each being derived from a focus of suppuration in the subjacent marrow. The pus perforates the periosteum, and makes its way to the surface by the easiest anatomical route, and discharges externally, forming one or more sinuses through which fresh infection may take place. The infection may spread to the adjacent joint, either directly through the epiphysis and articular cartilage, or along the deep layer of the periosteum and its continuation--the capsular ligament. When the epiphysis is intra-articular, as, for example, in the head of the femur, the pus when it reaches the surface of the bone necessarily erupts directly into the joint.

While the occurrence of purely periosteal suppuration is regarded as possible, we are of opinion that the embolic form of staphylococcal osteomyelitis always originates in the marrow.

The portion of the diaphysis which has sustained the action of the concentrated toxins has its vitality further impaired as a result of the stripping of the periosteum and thrombosis of the blood vessels of the marrow, so that _necrosis_ of bone is one of the most striking results of the disease, and as this takes place rapidly, that is, in a day or two, the term _acute necrosis_, formerly applied to the disease, was amply justified.

When there is marked rarefaction of the bone at the ossifying junction, the epiphysis is liable to be separated--_epiphysiolysis_. The separation usually takes place through the young bone of the ossifying junction, and the surfaces of the diaphysis and epiphysis are opposed to each other by irregular eroded surfaces bathed in pus. The separated epiphysis may be kept in place by the periosteum, but when this has been detached by the formation of pus beneath it, the epiphysis is liable to be displaced by muscular action or by some movement of the limb, or it is the diaphysis that is displaced, for example, the lower end of the diaphysis of the femur may be projected into the popliteal space.

The epiphysial cartilage usually continues its bone-forming functions, but when it has been seriously damaged or displaced, the further growth of the bone in length may be interfered with. Sometimes the separated and displaced epiphysis dies and constitutes a sequestrum.

The adjacent joint may become filled at an early stage with a serous effusion, which may be sterile. When the cocci gain access to the joint, the lesion assumes the characters of a purulent arthritis, which, from its frequency during the earlier years of life, has been called _the acute arthritis of infants_.

Separation of an epiphysis nearly always results in infection and destruction of the adjacent joint.

Osteomyelitis is rare in the bones of the carpus and tarsus, and the associated joints are usually infected from the outset. In flat bones, such as the skull, the scapula, or the ilium, suppuration usually occurs on both aspects of the bone as well as in the marrow.

_Clinical Features._--The constitutional symptoms, which are due to the associated toxæmia, vary considerably in different cases. In mild cases they may be so slight as to escape recognition. In exceptionally severe cases the patient may succumb before there are obvious signs of the localisation of the staphylococci in the bone marrow. In average cases the temperature rises rapidly with a rigor and runs an irregular course with morning remissions, there is marked general illness accompanied by headache, vomiting, and sometimes delirium.

The local manifestations are pain and tenderness in relation to one of the long bones; the pain may be so severe as to prevent sleep and to cause the child to cry out. Tenderness on pressure over the bone is the most valuable diagnostic sign. At a later stage there is an ill-defined swelling in the region of the ossifying junction, with œdema of the overlying skin and dilatation of the superficial veins.

The swelling appears earlier and is more definite in superficial bones such as the tibia, than in those more deeply placed such as the upper end of the femur. It may be less evident to the eye than to the fingers, and is best appreciated by gently stroking the bone from the middle of its shaft towards the end. The maximum thickening and tenderness usually correspond to the junction of the diaphysis with the epiphysis, and the swelling tails off gradually along the shaft. As time goes on there is redness of the skin, especially over a superficial bone, such as the tibia, the swelling becomes softer, and gives evidence of fluctuation. This stage may be reached at the end of twenty-four hours, or not for some days.

Suppuration spreads towards the surface, until, some days later, the skin sloughs and pus escapes, after which the fever usually remits and the pain and other symptoms are relieved. The pus may contain blood and droplets of fat derived from the marrow, and in some cases minute particles of bone are present also. The presence of fat and bony particles in the pus confirms the medullary origin of the suppuration.

If an incision is made, the periosteum is found to be raised from the bone; the extent of the bare bone will be found to correspond fairly accurately with the extent of the lesion in the marrow.

_Local Complications._--The adjacent joint may exhibit symptoms which vary from those of a simple effusion to those of a purulent _arthritis_. The joint symptoms may count for little in the clinical picture, or, as in the case of the hip, may so predominate as to overshadow those of the bone lesion from which they originated.

_Separation and displacement of the epiphysis_ usually reveals itself by an alteration in the attitude of the limb; it is nearly always associated with suppuration in the adjacent joint.

When _pathological fracture_ of the shaft occurs, as it may do, from some muscular effort or strain, it is attended with the usual signs of fracture.

_Dislocation_ of the adjacent joint has been chiefly observed at the hip; it may result from effusion into the joint and stretching of the ligaments, or may be the sequel of a purulent arthritis; the signs of dislocation are not so obvious as might be expected, but it is attended with an alteration in the attitude of the limb, and the displacement of the head of the bone is readily shown in a skiagram.

_General Complications._--In some cases a _multiplicity of lesions_ in the bones and joints imparts to the disease the features of pyæmia. The occurrence of endocarditis, as indicated by alterations in the heart sounds and the development of murmurs, may cause widespread infective embolism, and metastatic suppurations in the kidneys, heart-wall, and lungs, as well as in other bones and joints than those primarily affected. The secondary suppurations are liable to be overlooked unless sought for, as they are rarely attended with much pain.

In these multiple forms of osteomyelitis the toxæmic symptoms predominate; the patient is dull and listless, or he may be restless and talkative, or actually delirious. The tongue is dry and coated, the lips and teeth are covered with sordes, the motions are loose and offensive, and may be passed involuntarily. The temperature is remittent and irregular, the pulse small and rapid, and the urine may contain blood and albumen. Sometimes the skin shows erythematous and purpuric rashes, and the patient may cry out as in meningitis. The post-mortem appearances are those of pyæmia.

_Differential Diagnosis._--Acute osteomyelitis is to be diagnosed from infections of the soft parts, such as erysipelas and cellulitis, and, in the case of the tibia, from erythema nodosum. Tenderness localised to the ossifying junction is the most valuable diagnostic sign of osteomyelitis.

When there is early and pronounced general intoxication, there is likely to be confusion with other acute febrile illnesses, such as scarlet fever. In all febrile conditions in children and adolescents, the ossifying junctions of the long bones should be examined for areas of pain and tenderness.

Osteomyelitis has many features in common with acute articular rheumatism, and some authorities believe them to be different forms of the same disease (Kocher). In acute rheumatism, however, the joint symptoms predominate, there is an absence of suppuration, and the pains and temperature yield to salicylates.

The _prognosis_ varies with the type of the disease, with its location--the vertebræ, skull, pelvis, and lower jaw being specially unfavourable--with the multiplicity of the lesions, and with the development of endocarditis and internal metastases.

_Treatment._--This is carried out on the same lines as in other pyogenic infections.

In the earliest stages of the disease, the induction of hyperæmia is indicated, and should be employed until the diagnosis is definitely established, and in the meantime preparations for operation should be made. An incision is made down to and through the periosteum, and whether pus is found or not, the bone should be opened in the vicinity of the ossifying junction by means of a drill, gouge, or trephine. If pus is found, the opening in the bone is extended along the shaft as far as the periosteum has been separated, and the infected marrow is removed with the spoon. The cavity is then lightly packed with rubber dam, or, as recommended by Bier, the skin edges are brought together by sutures which are loosely tied to afford sufficient space between them for the exit of discharge, and the hyperæmic treatment is continued.

When there is widespread suppuration in the marrow, and the shaft is extensively bared of periosteum and appears likely to die, it may be resected straight away or after an interval of a day or two. Early resection of the shaft is also indicated if the opening of the medullary canal is not followed by relief of symptoms. In the leg and forearm, the unaffected bone maintains the length and contour of the limb; in the case of the femur and humerus, extension with weight and pulley along with some form of moulded gutter splint is employed with a similar object.

Amputation of the limb is reserved for grave cases, in which life is endangered by toxæmia, which is attributed to the primary lesion. It may be called for later if the limb is likely to be useless, as, for example, when the whole shaft of the bone is dead without the formation of a new case, when the epiphyses are separated and displaced, and the joints are disorganised.

Flat bones, such as the skull or ilium, must be trephined and the pus cleared out from both aspects of the bone. In the vertebræ, operative interference is usually restricted to opening and draining the associated abscess.

#Nature's Effort at Repair.#--_In cases which are left to nature_, and in which necrosis of bone has occurred, those portions of the periosteum and marrow which have retained their vitality resume their osteogenetic functions, often to an exaggerated degree. Where the periosteum has been lifted up by an accumulation of pus, or is in contact with bone that is dead, it proceeds to form new bone with great activity, so that the dead shaft becomes surrounded by a sheath or case of new bone, known as the _involucrum_ (Fig. 118). Where the periosteum has been perforated by pus making its way to the surface, there are defects or holes in the involucrum, called _cloacæ_. As these correspond more or less in position to the sinuses in the skin, in passing a probe down one of the sinuses it usually passes through a cloaca and strikes the dead bone lying in the interior. If the periosteum has been extensively destroyed, new bone may only be formed in patches, or not at all. The dead bone is separated from the living by the agency of granulation tissue with its usual complements of phagocytes and osteoclasts, so that the sequestrum presents along its margins and on its deep surface a pitted, grooved, and worm-eaten appearance, except on the periosteal aspect, which is unaltered. Ultimately the dead bone becomes loose and lies in a cavity a little larger than itself; the wall of the cavity is formed by the new case, lined with granulation tissue. The separation of the sequestrum takes place more rapidly in the spongy bone of the ossifying junction than in the compact bone of the shaft.

When foci of suppuration have been scattered up and down the medullary cavity, and the bone has died in patches, several sequestra may be included by the new case; each portion of dead bone is slowly separated, and comes to lie in a cavity lined by granulations.

Even at a distance from the actual necrosis there is formation of new bone by the marrow; the medullary canal is often obliterated, and the bone becomes heavier and denser--sclerosis; and the new bone which is deposited on the original shaft results in an increase in the girth of the bone--hyperostosis.

[Illustration: FIG. 118.--Shaft of Femur after Acute Osteomyelitis. The shaft has undergone extensive necrosis, and a shell of new bone has been formed by the periosteum.]

_Pathological fracture_ of the shaft may occur at the site of necrosis, when the new case is incapable of resisting the strain put upon it, and is most frequently met with in the shaft of the femur. Short of fracture, there may be bending or curving of the new case, and this results in deformity and shortening of the limb (Fig. 119).

The _extrusion of a sequestrum_ may occur, provided there is a cloaca large enough to allow of its escape, but the surgeon has usually to interfere by performing the operation of sequestrectomy. Displacement or partial extrusion of the dead bone may cause complications, as when a sequestrum derived from the trigone of the femur perforates the popliteal artery or the cavity of the knee-joint, or a sequestrum of the pelvis perforates the wall of the urinary bladder.

The extent to which bone which has been lost is reproduced varies in different parts of the skeleton: while the long bones, the scapula, the mandible, and other bones which are developed in cartilage are almost completely re-formed, bones which are entirely developed in membrane, such as the flat bones of the skull and the maxilla, are not reproduced.

[Illustration: FIG. 119.--Femur and Tibia showing results of Acute Osteomyelitis affecting Trigone of Femur; sequestrum partly surrounded by new case; backward displacement of lower epiphysis and implication of knee-joint.]

It may be instructive to describe _the X-ray appearances of a long bone that has passed through an attack of acute osteomyelitis_ severe enough to have caused necrosis of part of the diaphysis. The shadow of the dead bone is seen in the position of the original shaft which it represents; it is of the same shape and density as the original shaft, while its margins present an irregular contour from the erosion concerned in its separation. The sequestrum is separated from the living bone by a clear zone which corresponds to the layer of granulations lining the cavity in which it lies. This clear zone separating the shadow of the dead bone from that of the living bone by which it is surrounded is conclusive evidence of a sequestrum. The medullary canal in the vicinity of the sequestrum being obliterated, is represented by a shadow of varying density, continuous with that of the surrounding bone. The shadow of the new case or involucrum with its wavy contour is also in evidence, with its openings or cloacæ, and is mainly responsible for the increase in the diameter of the bone.

The skiagram may also show separation and displacement of the adjacent epiphysis and destruction of the articular surfaces or dislocation of the joint.

_Sequelæ of Acute Suppurative Osteomyelitis._--The commonest sequel is the presence of a sequestrum with one or more discharging sinuses; owing to the abundant formation of scar tissue these sinuses have rigid edges which are usually depressed and adherent to the bone.

_The Recognition and Removal of Sequestra._--So long as there is dead bone there will be suppuration from the granulations lining the cavity in which it lies, and a discharge of pus from the sinuses, so that the mere persistence of discharge after an attack of osteomyelitis, is presumptive evidence of the occurrence of necrosis. Where there are one or more sinuses, the passage of a probe which strikes bare bone affords corroboration of the view that the bone has perished. When the dead bone has been separated from the living, the X-rays yield the most exact information.

The traditional practice is to wait until the dead bone is entirely separated before undertaking an operation for its removal, from fear, on the one hand, of leaving portions behind which may keep up the discharge, and, on the other, of removing more bone than is necessary. This practice need not be adhered to, as by operating at an earlier stage healing is greatly hastened. If it is decided to wait for separation of the dead bone, drainage should be improved, and the infective element combated by the induction of hyperæmia.

_The operation_ for the removal of the dead bone (_sequestrectomy_) consists in opening up the periosteum and the new case sufficiently to allow of the removal of all the dead bone, including the most minute sequestra. The limb having been rendered bloodless, existing sinuses are enlarged, but if these are inconveniently situated--for example, in the centre of the popliteal space in necrosis of the femoral trigone--it is better to make a fresh wound down to the bone on that aspect of the limb which affords best access, and which entails the least injury of the soft parts. The periosteum, which is thick and easily separable, is raised from the new case with an elevator, and with the chisel or gouge enough of the new bone is taken away to allow of the removal of the sequestrum. Care must be taken not to leave behind any fragment of dead bone, as this will interfere with healing, and may determine a relapse of suppuration.

The dead bone having been removed, the lining granulations are scraped away with a spoon, and the cavity is disinfected.

There are different ways of dealing with a _bone cavity_. It may be packed with gauze (impregnated with "bipp" or with iodoform), which is changed at intervals until healing takes place from the bottom; it may be filled with a flap of bone and periosteum raised from the vicinity, or with bone grafts; or the wall of bone on one side of the cavity may be chiselled through at its base, so that it can be brought into contact with the opposite wall. The method of filling bone cavities devised by Mosetig-Moorhof, consists in disinfecting and drying the cavity by a current of hot air, and filling it with a mixture of powdered iodoform (60 parts) and oil of sesame and spermaceti (each 40 parts), which is fluid at a temperature of 112° F.; the soft parts are then brought together without drainage. As the cavity fills up with new bone the iodoform is gradually absorbed. Iodoform gives a dark shadow with the X-rays, so that the process of its absorption can be followed in skiagrams taken at intervals.

These procedures may be carried out at the same time as the sequestrum is removed, or after an interval. In all of them, asepsis is essential for success.

The _deformities_ resulting from osteomyelitis are more marked the earlier in life the disease occurs. Even under favourable conditions, and with the continuous effort at reconstruction of the bone by Nature's method, the return to normal is often far from perfect, and there usually remains a variable amount of hyperostosis and sclerosis and sometimes curving of the bone. Under less favourable conditions, the late results of osteomyelitis may be more serious. _Shortening_ is not uncommon from interference with growth at the ossifying junction. _Exaggerated growth_ in the length of a bone is rare, and has been observed chiefly in the bones of the leg. Where there are two parallel bones--as in the leg, for example--the growth of the diseased bone may be impaired, and the other continuing its normal growth becomes disproportionately long; less frequently the growth of the diseased bone is exaggerated, and it becomes the longer of the two. In either case, the longer bone becomes curved. An _obliquity_ of the bone may result when one half of the epiphysial cartilage is destroyed and the other half continues to form bone, giving rise to such deformities as knock-knee and club-hand.

Deformity may also result from vicious union of a pathological fracture, permanent displacement of an epiphysis, contracture, ankylosis, or dislocation of the adjacent joint.

#Relapsing Osteomyelitis.#--As the term indicates, the various forms of relapsing osteomyelitis date back to an antecedent attack, and their occurrence depends on the capacity of staphylococci to lie latent in the marrow.

Relapse may take place within a few months of the original attack, or not for many years. Cases are sometimes met with in which relapses recur at regular intervals for several years, the tendency, however, being for the attacks to become milder as the virulence of the organisms becomes more and more attenuated.

_Clinical Features._--Osteomyelitis in a patient over twenty-five is nearly always of the relapsing variety. In some cases the bone becomes enlarged, with pain and tenderness on pressure; in others there are the usual phenomena which attend suppuration, but the pus is slow in coming to the surface, and the constitutional symptoms are slight. The pus may escape by new channels, or one of the old sinuses may re-open. Radiograms usually furnish useful information as to the condition of the bone, both as it is altered by the original attack and by the changes that attend the relapse of the infective process.

_Treatment._--In cases of thickening of the bone with persistent and severe pain, if relief is not afforded by the repeated application of blisters, the thickened periosteum should be incised, and the bone opened up with the chisel or trephine. In cases attended with suppuration, the swelling is incised and drained, and if there is a sequestrum, it must be removed.

#Circumscribed Abscess of Bone--"Brodie's Abscess."#--The most important form of relapsing osteomyelitis is the circumscribed abscess of bone first described by Benjamin Brodie. It is usually met with in young adults, but we have met with it in patients over fifty. Several years may intervene between the original attack of osteomyelitis and the onset of symptoms of abscess.

_Morbid Anatomy._[7]--The abscess is nearly always situated in the central axis of the bone in the region of the ossifying junction, although cases are occasionally met with in which it lies nearer the middle of the shaft. In exceptional cases there is more than one abscess (Fig. 120). The tibia is the bone most commonly affected, but the lower end of the femur, or either end of the humerus, may be the seat of the abscess. In the quiescent stage the lesion is represented by a small cavity in the bone, filled with clear serum, and lined by a fibrous membrane which is engaged in forming bone. Around the cavity the bone is sclerosed, and the medullary canal is obliterated. When the infection becomes active, the contents of the cavity are transformed into a greenish-yellow pus from which the staphylococcus can be isolated, and the cavity is lined by a thin film of granulation tissue which erodes the surrounding bone and so causes the abscess to increase in size. If the erosion proceeds uniformly, the cavity is spherical or oval; if it is more active at some points than others, diverticula or tunnels are formed, and one of these may finally erupt through the shell of the bone or into an adjacent joint. Small irregular sequestra are occasionally found within the abscess cavity. In long-standing cases it is common to find extensive obliteration of the medullary canal, and a considerable increase in the girth of the bone.

[7] Alexis Thomson, _Edin. Med. Journ._, 1906.

[Illustration: FIG. 120.--Segment of Tibia resected for Brodie's Abscess. The specimen shows two separate abscesses in the centre of the shaft, the lower one quiescent, the upper one active and increasing in size.]

The size of the abscess ranges from that of a cherry to that of a walnut, but specimens in museums show that, if left to Nature, the abscess may attain much greater dimensions.

The affected bone is not only thicker and heavier than normal, but may also be curved or otherwise deformed as a result of the original attack of osteomyelitis.

The _clinical features_ are almost exclusively local. Pain, due to tension within the abscess, is the dominant symptom. At first it is vague and difficult to localise, later it is referred to the interior of the bone, and is described as "boring." It is aggravated by use of the limb, and there are often, especially during the night, exacerbations in which the pain becomes excruciating. In the early stages there are periods of days or weeks during which the symptoms abate, but as the abscess increases these become shorter, until the patient is hardly ever free from pain. Localised tenderness can almost always be elicited by percussion, or by compressing the bone between the fingers and thumb. The pain induced by the traction of muscles attached to the bone, or by the weight of the body, may interfere with the function of the limb, and in the lower extremity cause a limp in walking. The limb may be disabled from _involvement of the adjacent joint_, in which there may be an intermittent hydrops which comes and goes coincidently with exacerbations of pain; or the abscess may perforate the joint and set up an acute arthritis.

The _diagnosis_ of Brodie's abscess from other affections met with at the ends of long bones, and particularly from tuberculosis, syphilis, and new growths, is made by a consideration of the previous history, especially with reference to an antecedent attack of osteomyelitis. When the adjacent joint is implicated, the surgeon may be misled by the patient referring all the symptoms to the joint.

The X-ray picture is usually diagnostic chiefly because all the lesions which are liable to be confused with Brodie's abscess--gumma, tubercle, myeloma, chondroma, and sarcoma--give a well-marked central clear area; the sclerosis around Brodie's abscess gives a dense shadow in which the central clear area is either not seen at all or only faintly (Fig. 121).

_Treatment._--If an abscess is suspected, there should be no hesitation in exploring the interior of the bone. It is exposed by a suitable incision; the periosteum is reflected and the bone is opened up by a trephine or chisel, and the presence of an abscess may be at once indicated by the escape of pus. If, owing to the small size of the abscess or the density of the bone surrounding it, the pus is not reached by this procedure, the bone should be drilled in different directions.

[Illustration: FIG. 121.--Radiogram of Brodie's Abscess in Lower End of Tibia.]

#Other Forms of Acute Osteomyelitis.#--Among the less severe forms of osteomyelitis resulting from the action of attenuated organisms are the _serous_ variety, in which an effusion of serous fluid forms under the periosteum; and _growth fever_, in which the child complains of vague evanescent pains (growing pains), and of feeling tired and disinclined to play; there may be some rise of temperature in the evening.

Infection with the _staphylococcus albus_, the _streptococcus_, or the _pneumococcus_ also causes a mild form of osteomyelitis which may go on to suppuration.

_Necrosis without suppuration_, described by Paget under the name "quiet necrosis," is a rare disease, and would appear to be associated with an attenuated form of staphylococcal infection (Tavel). It occurs in adults, being met with up to the age of fifty or sixty, and is characterised by the insidious development of a swelling which involves a considerable extent of a long bone. The pain varies in intensity, and may be continuous or intermittent, and there is tenderness on pressure. The shaft is increased in girth as a result of its being surrounded by a new case of bone. The resemblance to sarcoma may be very close, but the swelling is not as defined as in sarcoma, nor does it ever assume the characteristic "leg of mutton" shape. In both diseases there is a tendency to pathological fracture. It is difficult also in the absence of skiagrams to differentiate the condition from syphilitic and from tuberculous disease. If the diagnosis is not established after examination with the X-rays, an exploratory incision should be made; if dead bone is found, it is removed.

In typhoid fever the bone marrow is liable to be invaded by _the typhoid bacillus_, which may set up osteomyelitis soon after its lodgment, or it may lie latent for a considerable period before doing so. The lesions may be single or multiple, they involve the marrow or the periosteum or both, and they may or may not be attended with suppuration. They are most commonly met with in the tibia and in the ribs at the costo-chondral junctions.

The bone lesions usually occur during the seventh or eighth week of the fever, but have been known to occur much later. The chief complaint is of vague pains, at first referred to several bones, later becoming localised in one; they are aggravated by movement, or by handling the bone, and are worst at night. There is redness and œdema of the overlying soft parts, and swelling with vague fluctuation, and on incision there escapes a yellow creamy pus, or a brown syrupy fluid containing the typhoid bacillus in pure culture. Necrosis is exceptional.

When the abscess develops slowly, the condition resembles tuberculous disease, from which it may be diagnosed by the history of typhoid fever, and by obtaining a positive Widal reaction.

The prognosis is favourable, but recovery is apt to be slow, and relapse is not uncommon.

It is usually sufficient to incise the periosteum, but when the disease occurs in a rib it may be necessary to resect a portion of bone.

#Pyogenic Osteomyelitis due to Spread of Infection from the Soft Parts.#--There still remain those forms of osteomyelitis which result from infection through a wound involving the bone--for example, compound fractures, gun-shot injuries, osteotomies, amputations, resections, or operations for un-united fracture. In all of these the marrow is exposed to infection by such organisms as are present in the wound. A similar form of osteomyelitis may occur apart from a wound--for example, infection may spread to the jaws from lesions of the mouth; to the skull, from lesions of the scalp or of the cranial bones themselves--such as a syphilitic gumma or a sarcoma which has fungated externally; or to the petrous temporal, from suppuration in the middle ear.

The most common is an osteomyelitis commencing in the marrow exposed in a wound infected with pyogenic organisms. In amputation stumps, fungating granulations protrude from the sawn end of the bone, and if necrosis takes place, the sequestrum is annular, affecting the cross-section of the bone at the saw-line; or tubular, extending up the shaft, and tapering off above. The periosteum is more easily detached, is thicker than normal, and is actively engaged in forming bone. In the macerated specimen, the new bone presents a characteristic coral-like appearance, and may be perforated by cloacæ (Fig. 122).

[Illustration: FIG. 122.--Tubular Sequestrum resulting from Septic Osteomyelitis in Amputation Stump.]

Like other pyogenic infections, it may terminate in pyæmia, as a result of septic phlebitis in the marrow.

The _clinical features_ of osteomyelitis in _an amputation stump_ are those of ordinary pyogenic infection; the involvement of the bone may be suspected from the clinical course, the absence of improvement from measures directed towards overcoming the sepsis in the soft parts, and the persistence of suppuration in spite of free drainage, but it is not recognised unless the bone is exposed by opening up the stump or the changes in the bone are shown by the X-rays. The first change is due to the deposit of new bone on the periosteal surface; later, there is the shadow of the sequestrum.

Healing does not take place until the sequestrum is extruded or removed by operation.

_In compound fractures_, if a fragment dies and forms a sequestrum, it is apt to be walled in by new bone; the sinuses continue to discharge until the sequestrum is removed. Even after healing has taken place, relapse is liable to occur, especially in gun-shot injuries. Months or years afterwards, the bone may become painful and tender. The symptoms may subside under rest and elevation of the limb and the application of a compress, or an abscess forms and bursts with comparatively little suffering. The contents may be clear yellow serum or watery pus; sometimes a small spicule of bone is discharged. Valuable information, both for diagnosis and treatment, is afforded by skiagrams.

[Illustration: FIG. 123.--New Periosteal Bone on surface of Femur from Amputation Stump. Osteomyelitis supervened on the amputation, and resulted in necrosis at the sawn section of the bone. (Anatomical Museum, University of Edinburgh.)]

TUBERCULOUS DISEASE

The tuberculous diseases of bone result from infection of the marrow or periosteum by tubercle bacilli conveyed through the arteries; it is exceedingly rare for tubercle to appear in bone as a primary infection, the bacilli being usually derived from some pre-existing focus in the bronchial glands or elsewhere. According to the observations of John Fraser, 60 per cent. of the cases of bone and joint tubercle in children are due to the bovine bacillus, 37 per cent. to the human variety, and in 3 per cent. both types are present.

Tuberculous disease in bone is characterised by its insidious onset and slow progress, and by the frequency with which it is associated with disease of the adjacent joint.

#Periosteal tuberculosis# is met with in the ribs, sternum, vertebral column, skull, and less frequently in the long bones of the limbs. It may originate in the periosteum, or may spread thence from the marrow, or from synovial membrane.

_In superficial bones_, such as the sternum, the formation of tuberculous granulation tissue in the deeper layer of the periosteum, and its subsequent caseation and liquefaction, is attended by the insidious development of a doughy swelling, which is not as a rule painful, although tender on pressure. While the swelling often remains quiescent for some time, it tends to increase in size, to become boggy or fluctuating, and to assume the characters of a cold abscess. The pus perforates the fibrous layer of the periosteum, invading and infecting the overlying soft parts, its spread being influenced by the anatomical arrangement of the tissues. The size of the abscess affords no indication of the extent of the bone lesion from which it originates. As the abscess reaches the surface, the skin becomes of a dusky red or livid colour, is gradually thinned out, and finally sloughs, forming a sinus. A probe passed into the sinus strikes carious bone. Small sequestra may be found embedded in the granulation tissue. The sinus persists as long as any active tubercle remains in the tissues, and is apt to form an avenue for pyogenic infection.

_In deeply seated bones_, such as the upper end of the femur, the formation of a cold abscess in the soft parts is often the first evidence of the disease.

_Diagnosis._--Before the stage of cold abscess is reached, the localised swelling is to be differentiated from a gumma, from chronic forms of staphylococcal osteomyelitis, from enlarged bursa or ganglion, from sub-periosteal lipoma, and from sarcoma. Most difficulty is met with in relation to periosteal sarcoma, which must be differentiated either by the X-ray appearances or by an exploratory incision.

_X-ray appearances in periosteal tubercle_: the surface of the cortical bone in the area of disease is roughened and irregular by erosion, and in the vicinity there may be a deposit of new bone on the surface, particularly if a sinus is present and mixed infection has occurred; in _syphilis_ the shadow of the bone is denser as a result of sclerosis, and there is usually more new bone on the surface--hyperostosis; in _periosteal sarcoma_ there is greater erosion and consequently greater irregularity in the contour of the cortical bone, and frequently there is evidence of formation of bone in the form of characteristic spicules projecting from the surface at a right angle.

The early recognition of periosteal lesions in the articular ends of bones is of importance, as the disease, if left to itself, is liable to spread to the adjacent joint.

The _treatment_ is that of tuberculous lesions in general; if conservative measures fail, the choice lies between the injection of iodoform, and removal of the infected tissues with the sharp spoon. In the ribs it is more satisfactory to remove the diseased portion of bone along with the wall of the associated abscess or sinus. If all the tubercle has been removed and there is no pyogenic infection, the wound is stitched up with the object of obtaining primary union; otherwise it is treated by the open method.

#Tuberculous Osteomyelitis.#--Tuberculous lesions in the marrow occur as isolated or as multiple foci of granulation tissue, which replace the marrow and erode the trabeculæ of bone in the vicinity (Fig. 124). The individual focus varies in size from a pea to a walnut. The changes that ensue resemble in character those in other tissues, and the extent of the destruction varies according to the way in which the tubercle bacillus and the marrow interact upon one another. The granulation tissue may undergo caseation and liquefaction, or may become encapsulated by fibrous tissue--"encysted tubercle."

[Illustration: FIG. 124.--Tuberculous Osteomyelitis of Os Magnum, excised from a boy æt. 8. Note well-defined caseous focus, with several minute foci in surrounding marrow.]

Sometimes the tuberculous granulation tissue spreads in the marrow, assuming the characters of a diffuse infiltration--diffuse tuberculous osteomyelitis. The trabecular framework of the bone undergoes erosion and absorption--rarefying ostitis--and either disappears altogether or only irregular fragments or sequestra of microscopic dimensions remain in the area affected. Less frequently the trabecular framework is added to by the formation of new bone, resulting in a remarkable degree of sclerosis, and if, following upon this, there is caseation of the tubercle and death of the affected portion of bone, there results a sequestrum often of considerable size and characteristic shape, which, because of the sclerosis and surrounding endarteritis, is exceedingly slow in separating. When the sequestrum involves an articular surface it is often wedge-shaped; in other situations it is rounded or truncated and lies in the long axis of the medullary canal (Fig. 125). Finally, the sequestrum lies loose in a cavity lined by tuberculous granulation tissue, and is readily identified in a radiogram. This type of sclerosis preceding death of the bone is highly characteristic of tuberculosis.

[Illustration: FIG. 125.--Tuberculous Disease of Child's Tibia, showing sequestrum in medullary cavity, and increase in girth from excess of new bone.]

_Clinical Features._--As a rule, it is only in superficially placed bones, such as the tibia, ulna, clavicle, mandible, or phalanges, that tuberculous disease in the marrow gives rise to signs sufficiently definite to allow of its clinical recognition. In the vertebræ, or in the bones of deeply seated joints, such as the hip or shoulder, the existence of tuberculous lesions in the marrow can only be inferred from indirect signs--such, for example, as rigidity and curvature in the case of the spine, or from the symptoms of grave and persistent joint-disease in the case of the hip or shoulder.

With few exceptions, tuberculous disease in the interior of a bone does not reveal its presence until by extension it reaches one or other of the surfaces of the bone. In the shaft of a long bone its eruption on the periosteal surface is usually followed by the formation of a cold abscess in the overlying soft parts. When situated in the articular ends of bones, the disease more often erupts in relation to the reflection of the synovial membrane or directly on the articular surface--in either case giving rise to disease of the joint (Fig. 156).

[Illustration: Fig. 126.--Diffuse Tuberculous Osteomyelitis of Right Tibia.

(Photograph lent by Sir H. J. Stiles.)]

#Diffuse Tuberculous Osteomyelitis in the shaft of a long bone# is comparatively rare, and has been observed chiefly in the tibia and the ulna in children (Fig. 126). It commences at the growing extremity of the diaphysis, and spreads along the medulla to a variable extent; it is attended by the formation of vascular and porous bone on the surface, which causes thickening of the diaphysis; this is most marked at the ossifying junction and tapers off along the shaft. The infection not only spreads along the medulla, but it invades the spongy bone surrounding this, and then the cortical bone, and is only prevented from reaching the soft parts by the new bone formed by the periosteum. The bone is replaced by granulation tissue, and disappears, or part of it may become sclerosed and in time form a sequestrum. In the macerated specimen, the sequestrum appears small in proportion to the large cavity in which it lies. All these changes are revealed in a good skiagram, which not only confirms the diagnosis, but, in many instances, demonstrates the extent of the disease, the presence or absence of a sequestrum, and the amount of new bone on the surface. Finally the periosteum gives way, and an abscess forms in the soft parts; and if left to itself ruptures externally, leaving a sinus. The most satisfactory _treatment_ is to resect sub-periosteally the diseased portion of the diaphysis.

_In cancellous bones, such as those of the tarsus_, there is a similar caseous infiltration in the marrow, and this may be attended with the formation of a sequestrum either in the interior of the bone or involving its outer shell, as shown in Fig. 127. The situation and extent of the disease are shown in X-ray photographs. After the tuberculous granulation tissue erupts through the cortex of the bone, it gives rise to a cold abscess or infects adjacent joints or tendon sheaths.

[Illustration: FIG. 127.--Advanced Tuberculous Disease in region of Ankle. The ankle-joint is ankylosed, and there is a large sequestrum in the calcaneus.

(Specimen in Anatomical Museum, University of Edinburgh.)]

If an exact diagnosis is made at an early stage of the disease--and this is often possible with the aid of X-rays--the affected bone is excised sub-periosteally or its interior is cleared out with the sharp spoon and gouge, the latter procedure being preferred in the case of the _calcaneus_ to conserve the stability of the heel. When several bones and joints are simultaneously affected, and there are sinuses with mixed infection, amputation is usually indicated, especially in adults.

#Tuberculous dactylitis# is the name applied to a diffuse form of the disease as it affects the phalanges, metacarpal or metatarsal bones. The lesion presents, on a small scale, all the anatomical changes that have been described as occurring in the medulla of the tibia or ulna, and they are easily followed in skiagrams. A periosteal type of dactylitis is also met with.

The _clinical features_ are those of a spindle-shaped swelling of a finger or toe, indolent, painless, and interfering but little with the function of the digit. Recovery may eventually occur without suppuration, but it is common to have the formation of a cold abscess, which bursts and forms one or more sinuses. It may be difficult to differentiate tuberculous dactylitis from the enlargement of the phalanges in inherited syphilis (syphilitic dactylitis), especially when the tuberculous lesion occurs in a child who is the subject of inherited syphilis.

[Illustration: FIG. 128.--Tuberculous Dactylitis.]

In the syphilitic lesion, skiagrams usually show a more abundant formation of new bone, but in many cases the doubt is only cleared up by observing the results of the tuberculin test or the effects of anti-syphilitic treatment.

Sarcoma of a phalanx or metacarpal bone may closely resemble a dactylitis both clinically and in skiagrams, but it is rare.

_Treatment._--Recovery under conservative measures is not uncommon, and the functional results are usually better than those following upon operative treatment, although in either case the affected finger is liable to be dwarfed (Fig. 129). The finger should be immobilised in a splint, and a Bier's bandage applied to the upper arm. Operative interference is indicated if a cold abscess develops, if there is a persistent sinus, or if a sequestrum has formed, a point upon which information is obtained by examination with the X-rays. When a toe is affected, amputation is the best treatment, but in the case of a finger it is rarely called for. In the case of a metacarpal or metatarsal bone, sub-periosteal resection is the procedure of choice, saving the articular ends if possible.

[Illustration: FIG. 129.--Shortening of Middle Finger of Adult, the result of Tuberculous Dactylitis in childhood.]

SYPHILITIC DISEASE

Syphilitic affections of bone may be met with at any period of the disease, but the graver forms occur in the tertiary stage of acquired and inherited syphilis. The virus is carried by the blood-stream to all parts of the skeleton, but the local development of the disease appears to be influenced by a predisposition on the part of individual bones.

Syphilitic diseases of bone are much less common in practice than those due to pyogenic and tuberculous infectious, and they show a marked predilection for the tibia, sternum, and skull. They differ from tuberculous affections in the frequency with which they attack the shafts of bones rather than the articular ends, and in the comparative rarity of joint complications.

_Evanescent periostitis_ is met with in acquired syphilis during the period of the early skin eruptions. The patient complains, especially at night, of pains over the frontal bone, ribs, sternum, tibiæ, or ulnæ. Localised tenderness is elicited on pressure, and there is slight swelling, which, however, rarely amounts to what may be described as a _periosteal node_.

In the later stages of acquired syphilis, _gummatous periostitis and osteomyelitis_ occur, and are characterised by the formation in the periosteum and marrow of circumscribed gummata or of a diffuse gummatous infiltration. The framework of the bone is rarefied in the area immediately involved, and sclerosed in the parts beyond. If the gummatous tissue degenerates and breaks down, and especially if the overlying skin is perforated and septic infection is superadded, the bone disintegrates and exhibits the condition known as _syphilitic caries_; sometimes a portion of bone has its blood supply so far interfered with that it dies--_syphilitic necrosis_. Syphilitic sequestra are heavier and denser than normal bone, because sclerosis usually precedes death of the bone. The bones especially affected by gummatous disease are: the skull, the septum of the nose, the nasal bones, palate, sternum, femur, tibia, and the bones of the forearm.

_In the bones of the skull_, gummata may form in the peri-cranium, diploë, or dura mater. An isolated gumma forms a firm elastic swelling, shading off into the surroundings. In the macerated bone there is a depression or an actual perforation of the calvaria; multiple gummata tend to fuse with one another at their margins, giving the appearance of a combination of circles: these sometimes surround an area of bone and cut it off from its blood supply (Fig. 130). If the overlying skin is destroyed and septic infection superadded, such an isolated area of bone is apt to die and furnish a sequestrum; the separation of the dead bone is extremely slow, partly from the want of vascularity in the sclerosed bone round about, and partly from the density of the sequestrum. In exceptional cases the necrosis involves the entire vertical plate of the frontal bone. Pus is formed between the bone and the dura (suppurative pachymeningitis), and this may be followed by cerebral abscess or by pyæmia. Gummatous disease in the wall of the orbit may cause displacement of the eye and paralysis of the ocular muscles.

[Illustration: FIG. 130.--Syphilitic Disease of Skull, showing a sequestrum in process of separation.]

On the inner surface of the skull, the formation of gummatous tissue may cause pressure on the brain and give rise to intense pain in the head, Jacksonian epilepsy, or paralysis, the symptoms varying with the seat and extent of the disease. The cranial nerves may be pressed upon at the base, especially at their points of exit, and this gives rise to symptoms of irritation or paralysis in the area of distribution of the nerves affected.

_In the septum of the nose, the nasal bones, and the hard palate_, gummatous disease causes ulceration, which, beginning in the mucous membrane, spreads to the bones, and being complicated with septic infection leads to caries and necrosis. In the nose, the disease is attended with stinking discharge (ozœna), the extrusion of portions of dead bone, and subsequently with deformity characterised by loss of the bridge of the nose; in the palate, it is common to have a perforation, so that the air escapes through the nose in speaking, giving to the voice a characteristic nasal tone.

_Syphilitic disease of the tibia_ may be taken as the type of the affection as it occurs _in the long bones_. Gummatous disease in the periosteum may be localised and result in the formation of a well-defined node, or the whole shaft may become the seat of an irregular nodular enlargement (Fig. 132). If the bone is macerated, it is found to be heavier and bulkier than normal; there is diffuse sclerosis with obliteration of the medullary canal, and the surface is uneven from heaping up of new bone--hyperostosis (Fig. 131). If a periosteal gumma breaks down and invades the skin, a syphilitic ulcer is formed with carious bone at the bottom. A central gumma may eat away the surrounding bone to such an extent that the shaft undergoes pathological fracture. In the rare cases in which it attacks the articular end of a long bone, gummatous disease may implicate the adjacent joint and give rise to syphilitic arthritis.

[Illustration: FIG. 131.--Syphilitic Hyperostosis and Sclerosis of Tibia, on section and on surface view.]

_Clinical Features._--There is severe boring pain--as if a gimlet were being driven into the bone. It is worst at night, preventing sleep, and has been ascribed to compression of the nerves in the narrowed Haversian canals.

The _periosteal gumma_ appears as a smooth, circumscribed swelling which is soft and elastic in the centre and firm at the margins, and shades off into the surrounding bone. The gumma may be completely absorbed or it may give place to a hard node. In some cases the gumma softens in the centre, the skin becomes adherent, thin, and red, and finally gives way. The opening in the skin persists as a sinus, or develops into a typical ulcer with irregular, crescentic margins; in either case a probe reveals the presence of carious bone or of a sequestrum. The health may be impaired as a result of mixed infection, and the absorption of toxins and waxy degeneration in the viscera may ultimately be induced.

A _central gumma_ in a long bone may not reveal its presence until it erupts through the shell and reaches the periosteal surface or invades an adjacent joint. Sometimes the first manifestation is a fracture of the bone produced by slight violence.

In radiograms the appearance of syphilitic bones is usually characteristic. When there is hyperostosis and sclerosis, the shaft appears denser and broader than normal, and the contour is uneven or wavy. When there is a central gumma, the shadow is interrupted by a rounded clear area, like that of a chondroma or myeloma, but there is sclerosis round about.

_Diagnosis._--The conditions most liable to be mistaken for syphilitic disease of bone are chronic staphylococcal osteomyelitis, tuberculosis, and sarcoma; and the diagnosis is to be made by the history and progress of the disease, the result of examination with the X-rays, and the results of specific tests and treatment.

_Treatment._--The general health is to be improved by open air, by nourishing food, and by the administration of cod-liver oil, iron, and arsenic. Anti-syphilitic remedies should be given, and if they are administered before there is any destruction of tissue, the benefit derived from them is usually marked.

Radiograms show the rapid absorption of the new bone both on the surface and in the marrow, and are of value in establishing the therapeutic diagnosis.

In certain cases, and particularly when there are destructive changes in the bone complicated with pyogenic infection, specific remedies have little effect. In cases of persistent or relapsing gummatous disease with ulceration of skin, it is often necessary to remove the diseased soft parts with the sharp spoon and scissors, and to gouge or chisel away the unhealthy bone, on the same lines as in tuberculous disease. When hyperostosis and sclerosis of the bone is attended with severe pain which does not yield to blistering, the periosteum may be incised and the sclerosed bone perforated with a drill or trephine.

#Lesions of Bone in Inherited Syphilis.#--_Craniotabes_, in which the flat bones of the skull undergo absorption in patches, was formerly regarded as syphilitic, but it is now known to result from prolonged malnutrition from any cause. _Bossing of the skull_ resulting in the formation of Parrot's nodes is also being withdrawn from the category of syphilitic affections. The lesions in infancy--epiphysitis, bossing of the skull, and craniotabes--have been referred to in the chapter on inherited syphilis.

_Epiphysitis or Syphilitic Perichondritis._--The first of these terms is misleading, because the lesion involves the ossifying junction and the shaft of the bone, and the epiphysis only indirectly. The young bone is replaced by granulation tissue, so that large clear areas are seen with the X-rays. The symptoms are referred to the joint, because it is there that the muscles are inserted and drag on the perichondrium when movement occurs; swelling is most marked in the vicinity of the joint, and it may be added to by effusion into the synovial cavity. The baby, usually under six months, is noticed to be feverish and fretful and to cry when touched. The mother discovers that the pain is caused by moving a particular limb, usually the arm, as the humerus, radius, and ulna are the bones most commonly affected; the limb, moreover, hangs useless at the side as if paralysed, and the condition was formerly described as _syphilitic pseudo-paralysis_.

The lesions met with later correspond to those of the tertiary period of the acquired disease, but as they affect bones which are still actively growing, the effects are more striking. Gummatous disease may come and go over periods of many years, with the result that the external appearance and architectural arrangement of a long bone come to be profoundly altered. In the tibia, for example, the shaft is bowed forward in a gentle curve, which is compared to the curve of a sabre--"sabre-blade" deformity (Fig. 132). The diffuse thickening all round the bone obscures the sharp margins so that the bone becomes circular in section and the anterior and mesial edges are blunted, and the comparison to a cucumber is deserved. In some cases the tibia is actually increased in length as well as in girth.

[Illustration: FIG. 132.--Sabre-blade Deformity of Left Tibia in Inherited Syphilis.

(From a photograph lent by Sir George T. Beatson.)]

The contrast between the grossly enlarged and misshapen tibia and the normal or even attenuated fibula is a striking one.

_Treatment_ is carried out on lines similar to those recommended in the acquired disease. When curving of the tibia causes disability in walking, the bone may be straightened by a cuneiform resection.

_Syphilitic dactylitis_ is met with chiefly in children. It may affect any of the fingers or toes, but is commonest in the first phalanx of the index-finger or of the thumb. Several fingers may be attacked at the same time or in succession. The lesion consists in a gummatous infiltration of the soft parts surrounding the phalanx, or a gummatous osteomyelitis, but there is practically no tendency to break down and discharge, or to the formation of a sequestrum as is so common in tuberculous dactylitis.

The finger becomes the seat of a swelling, which is more evident on the dorsal aspect, and, according to the distribution and extent of the disease, it is acorn-shaped, fusiform, or cylindrical. It is firm and elastic, and usually painless. The movements are impaired, especially if the joints are involved. In its early stages the disease is amenable to anti-syphilitic treatment, and complete recovery is the rule.

HYDATID DISEASE

This rare disease results from the lodgment of the embryos of the tænia echinoccus, which are conveyed to the marrow by the blood-stream. The cysts are small, usually about the size of a pin-head, and they are present in enormous numbers scattered throughout the marrow. The parts of the skeleton most often affected are the articular ends of the long bones, the bodies of the vertebræ, and the pelvis.

As the cysts increase in number and in size, the framework of the bone is gradually absorbed, and there result excavations or cavities. The marrow and spongy bone first disappear, the compact tissue then becomes thin, and pathological fracture may result. The bone becomes expanded, and the cysts may escape through perforations into the surrounding cellular tissue, and when thus freed from confinement may attain considerable dimensions. Suppuration from superadded pyogenic infection may be attended with extensive necrosis, and lead to disorganisation of the adjacent joint.

_Clinical Features._--The patient complains of deep-seated pains. In superficial bones, such as the tibia, there is enlargement, and it may be possible to recognise egg-shell crackling, or unequal consistence of the bone, which is hard in some parts, and doughy and elastic in others. The disease may pursue an indolent course during months or years until some complication occurs, such as suppuration or fracture. With the occurrence of suppuration the disease becomes more active, and abscesses may form in the soft parts and in the adjacent joint. In the vertebral column, hydatids give rise to angular deformity and paraplegia. In the pelvis, there is usually great enlargement of the bones, and when suppuration occurs it is apt to infect the hip-joint and to terminate fatally.

Examination with the X-rays shows the characteristic excavations of the bone caused by the cysts. The disease is liable to be mistaken for central tumour, gumma, tuberculosis, or abscess of bone.

The _treatment_ consists in thorough eradication of the parasite by operation. The bone is laid open and scraped or resected according to the extent of the disease, and the raw surfaces swabbed with 1 per cent. formalin. In advanced cases complicated with spontaneous fracture or with suppuration, amputation affords the best chance of recovery.

The lesions in the bones resulting from _actinomycosis_ and from _mycetoma_, have been described with these diseases.

CONSTITUTIONAL DISEASES ATTENDED WITH LESIONS IN THE BONES

These include rickets, scurvy-rickets, osteomalacia, ostitis deformans, osteomyelitis fibrosa, fragilitas ossium, and diseases of the nervous system.

RICKETS

Rickets or rachitis is a constitutional disease associated with disturbance of nutrition, and attended with changes in the skeleton. The disease is most common and most severe among the children of the poorer classes in large cities, who are improperly fed and are brought up in unhealthy surroundings. There is evidence that the most important factors in the causation of rickets are ill-health of the mother during pregnancy, and the administration to the child after its birth of food which is defective in animal fat, proteids, and salts of lime, or which contains these in such a form that they are not readily assimilated. The occurrence of the disease is favoured, and its features are aggravated, by imperfect oxygenation of the blood as the result of a deficiency of fresh air and sunlight, want of exercise, and by other conditions which prevail in the slums of large towns.

_Pathological Anatomy._--The most striking feature is the softness (malacia) of the bones, due to excessive absorption of osseous tissue, and the formation of an imperfectly calcified tissue at the sites of ossification. The affected bones lose their rigidity, so that they are bent under the weight of the body, by the traction of muscles, and by other mechanical forces.

The _periosteum_ is thick and vascular, and when detached carries with it plates and spicules of soft porous bone. The new bone may be so abundant that it forms a thick crust on the surface, and in the flat bones of the skull this may be heaped up in the form of bosses or ridges resembling those ascribed to inherited syphilis.

In the epiphysial cartilages and at the ossifying junctions, all the processes concerned in ossification, excepting the deposition of lime salts, occur to an exaggerated degree. The cartilage of the epiphysial disc proliferates actively and irregularly, so that it becomes softer, thicker, and wider, and gives rise to a visible swelling, best seen at the lower end of the radius and lower end of the tibia, and at the costo-chondral junctions where the series of beaded swellings is known as the "rickety rosary."

The ossifying zone is increased in depth; the marrow is abnormally vascular; and the new bone that is formed is imperfectly calcified. The result is that the bones may never attain their normal length, and they remain stunted throughout life as in rickety dwarfs (Fig. 133), or the shafts may grow unequally and come to deviate from their normal axes as in knock-knee and bow-knee.

[Illustration: FIG. 133.--Skeleton of Rickety Dwarf, known as "Bowed Joseph," leader of the Meal Riots in Edinburgh, who died in 1780.

(Anatomical Museum, University of Edinburgh.)]

These changes are well brought out in skiagrams; instead of the well-defined narrow line which represents the epiphysial cartilage, there is an ill-defined, blurred zone of considerable depth.

In the shafts of the long bones, owing to the excessive absorption of bone, the cortex becomes porous, the spongy bone is rarefied, and the bones readily bend or break under mechanical influences. When the disease is arrested, a process of repair sets in which often results in the bones becoming denser and heavier than normal. In the flat bones of the skull, the absorption may result in the entire disappearance of areas of bone, leaving a membrane which dimples like thin cardboard under the pressure of the finger--a condition known as _craniotabes_.

_Changes in the Skeleton before the Child is able to walk._--The fontanelles remain open until the end of the second year or longer, and the frontal and parietal eminences are unduly prominent. There is sometimes hydrocephalus, and the head is characteristically enlarged. The jaws are altered so that while the upper jaw is contracted into the shape of a #V#, the lower jaw is square instead of rounded in outline, and the teeth do not oppose one another. In the _thorax_, the chief feature may be the beading at the costo-chondral junctions, principally of the fifth and sixth ribs or its walls may be contracted, particularly if respiration is interfered with as a result of bronchial catarrh or adenoids. The contraction may take the form of a vertical groove on each side, or of a horizontal groove at the level of the upper end of the xiphi-sternum; when the sternum and cartilages form a projection in front, the deformity is known as "pigeon-breast."

The _spine_ may be curved backwards--_kyphosis_--throughout its whole extent or only in one part; or it may be curved to one side--_scoliosis_.

In the _limbs_, the prominent features are the deficient growth in length of the long bones, the enlargements at the epiphysial junctions, and the bending, and occasional greenstick fracture, of the shafts. The degree of enlargement of the epiphysial junctions is directly proportionate to the amount of movement to which the bone is subjected (John Thomson). The curves at this stage depend on the attitude of the child while sitting or being carried--for example, the arm bones become bent in children who paddle about the floor with the aid of their arms; and in a child who lies on its back with the lower limbs everted, the weight of the limb may lead to curvature of the neck of the femur--coxa vara. The clavicle or humerus may sustain greenstick fracture from the child being lifted by the arms; the femur, by a fall. From the extreme laxity of the ligaments, the joints can be moved beyond the normal limits, and the child is often observed to twist its limbs into abnormal attitudes.

_In Children who have walked._--In these children the most important deformities occur in the spine, pelvis, and lower extremities, and result for the most part from yielding of the softened bones under the weight of the body. Scoliosis is the usual type of spinal curvature, and in extreme cases it may lead to a pronounced form of hump-back. The pelvis may remain small (_justo-minor pelvis_), or it may be contracted in the sagittal plane (_flat pelvis_); when the bones are unusually soft, the acetabular portions are pushed inwards by the femora bearing the weight of the body, and the pelvis assumes the shape of a trefoil, as in the malacia of women. The shaft of the femur is curved forwards and laterally; the bones of the leg laterally as in bow-leg, or forwards, or forwards and laterally just above the ankle. The deformities at the knee (genu valgum, genu varum, and genu recurvatum), and at the hip (coxa vara), will be described in the volume dealing with the Extremities.

The majority of cases seen in surgical practice suffer from the deformities resulting from rickets rather than from the active disease. The examination of a large series of children at different ages shows that the deformities become less and less frequent with each year. Those who recover may ultimately show no trace of rickets, and this is especially true of children who grow at the average rate; in those, however, in whom growth is retarded, especially from the fifth to the seventh year, the deformities are apt to be permanent. It may be noted that the scoliosis due to rickets has little tendency towards recovery.

_Treatment._--The treatment of the disease consists in regulating the diet, improving the surroundings, and preventing deformity. Phosphorus in doses of 100th grain may be given dissolved in cod-liver oil, and preparations of iron and lime may be added with advantage. To avoid those postures which predispose to deformities, the child should lie as much as possible. In the well-to-do classes this is readily accomplished by the aid of a nurse and the use of a perambulator. In hospital out-patients the child is kept off its feet by the use of a light wooden splint applied to the lateral aspect of each lower extremity, and extending from the pelvis to 6 inches beyond the sole.

When deformities are already present, the treatment depends upon whether or not there is any prospect of the bone straightening naturally. Under five years of age this may, as a rule, be confidently expected; the child should be kept off its feet, and the limbs bathed and massaged. In children of five or six and upwards, the prospect of natural straightening is a diminishing one, and it is more satisfactory to correct the deformity by operation. In rickety curvature of the spine, the child should lie on a firm mattress, or, to allow of its being taken into the open air, upon a double Thomas' splint extending from the occiput to the heels; the muscles acting on the trunk should be braced up by massage and appropriate exercises.

#Late Rickets# or #Rachitis Adolescentium# is met with at any age from nine to seventeen, and is generally believed to be due to a recrudescence of rickets which had been present in childhood. The disease is not attended with any disturbance of the general health; the pathological changes are the same as in infantile rickets, but are for the most part confined to the ossifying junctions, especially those which are most active during adolescence, for example at the knee-joint. The patient is easily tired, complains of pain in the bones, and, unless care is taken, deformity is liable to ensue. There can be no doubt that adolescent rickets plays an important part in the production of the deformities which occur at or near puberty, especially knock-knee and bow-knee.

#Scurvy-Rickets# or #Infantile Scurvy#.--This disease, described by Barlow and Cheadle, is met with in infants under two years who have been brought up upon sterilised or condensed milk and other proprietary foods, and is most common in the well-to-do classes. The hæmorrhages, which are so characteristic of the disease, are usually preceded for some weeks by a cachectic condition, with listlessness and debility and disinclination for movement. Very commonly the child ceases to move one of his lower limbs--pseudo-paralysis--and screams if it is touched; a swelling is found over one of the bones, usually the femur, accompanied by exquisite tenderness; the skin is tense and shiny, and there may be some œdema. These symptoms are due to a sub-periosteal hæmorrhage, and associated with this there may be crepitus from separation of an epiphysis, rarely from fracture of the shaft of the bone. X-ray photographs show enlargement of the bone, the periosteum being raised from the shaft and new bone formed in relation to it. Hæmorrhages also occur into the skin, presenting the appearance of bruises, into the orbit and conjunctiva, and from the mucous membranes.

The _treatment_ consists in correcting the errors in diet. The infant should have a wet nurse or a plentiful supply of cow's milk in its natural state. Anti-scorbutics in the form of orange, lemon, or grape juice, and of potatoes bruised down in milk, may be given.

#Osteomalacia.#--The term osteomalacia includes a group of conditions, closely allied to rickets, in which the bones of adults become soft and yielding, so that they are unduly liable to bend or break.

One form occurs in _pregnant and puerperal women_, affecting most commonly the pelvis and lumbar vertebræ, but sometimes the entire skeleton. The lime salts are absorbed, the bones lose their rigidity and bend under the weight of the body and other mechanical influences, with the result that gross deformities are produced, particularly in the pelvis, the lumbar spine, and the hip-joints.

_Neuropathic_ forms occur in certain chronic diseases of the brain and cord; in some cases the bones lose their lime salts and bend, in others they become brittle.

_Osteomalacia associated with New Growths in the Skeleton._--When _secondary cancer_ is widely distributed throughout the skeleton, it is associated with softening of the bones, as a result of which they readily bend or break, and after death are easily cut with a knife. In the disease known as _multiple myeloma_, the interior of the ribs, sternum, and bodies of the vertebræ is occupied by a reddish gelatinous pulp, the structure of which resembles sarcoma; the bones are reduced to a mere shell, and may break on the slightest pressure; the urine contains albumose, a substance resembling albumen but coagulating at a comparatively low temperature (140° F.), and the coagulum is re-dissolved on boiling, and it is readily precipitated by hydrochloric acid (Bence-Jones).

#Ostitis Deformans--Paget's Disease of Bone.#--This rare disease was first described by Sir James Paget in 1877. In the early stages, the marrow is transformed into a vascular connective tissue; its bone-eating functions are exaggerated, and the framework of the bone becomes rarefied, so that it bends under pressure as in osteomalacia. In course of time, however, new bone is formed in great abundance; it is at first devoid of lime salts, but later becomes calcified, so that the bones regain their rigidity. This formation of new bone is much in excess of the normal, the bones become large and bulky, their surfaces rough and uneven, their texture sclerosed in parts, and the medullary canal is frequently obliterated. These changes are well brought out in X-ray photographs. The curving of the long bones, which is such a striking feature of the disease, may be associated with actual l

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