_New growths_ include the fibroma, the myxoma, the myeloma or giant-celled tumour, and various forms of sarcoma.
#Diseases of Individual Bursae.#--The _olecranon bursa_ is frequently the seat of pyogenic infection and of traumatic or trade bursitis, the latter being known as "miner"s" or "student"s elbow."
[Ill.u.s.tration: FIG. 115.--Tuberculous Disease of Sub-deltoid Bursa.
(From a photograph lent by Sir George T. Beatson.)]
The _sub-deltoid_ or _sub-acromial bursa_, which usually presents a single cavity and does not normally communicate with the shoulder-joint, is indispensable in abduction and rotation of the humerus. When the arm is abducted, the fixed lower part or floor of the bursa is carried under the acromion, and the upper part or roof is rolled up in the same direction, hence tenderness over the inflamed bursa may disappear when the arm is abducted (Dawbarn"s sign). It is liable to traumatic affections from a fall on the shoulder, pressure, or over-use of the limb. Pain, located commonly at the insertion of the deltoid, is a constant symptom and is especially annoying at night, the patient being unable to get into a comfortable position. Tenderness may be elicited over the anatomical limits of the bursa, and is usually most marked over the great tuberosity, just external to the inter-tubercular (bicipital) groove. When adhesions are present, abduction beyond 10 degrees is impossible. Demonstrable effusion is not uncommon, but is disguised by the overlying tissues. If left to himself, the patient tends to maintain the limb in the "sling position," and resists movements in the direction of abduction and rotation. In the treatment of this affection the arm should be maintained at a right angle to the body, the arm being rotated medially (Codman). When pain does not prevent it, movements of the arm and ma.s.sage are persevered with. In neglected cases, when adhesions have formed and the shoulder is fixed, it may be necessary to break down the adhesions under an anaesthetic.
The bursa is also liable to infective conditions, such as acute rheumatism, gonorrha, suppuration, or tubercle. In tuberculous disease a large fluctuating swelling may form and acquire the characters of a cold abscess (Fig. 115).
The bursa underneath the tendon of the _subscapularis_ muscle when inflamed causes alteration in the att.i.tude of the shoulder and impairment of its movements.
An advent.i.tious bursa forms over the _acromion_ process in porters and others who carry weights on the shoulder, and may be the seat of traumatic bursitis.
The bursa under the _tendon of insertion of the biceps_, when the seat of disease, is attended with pain and swelling about a finger"s breadth below the bend of the elbow; there is pain and difficulty in effecting the combined movement of flexion and supination, slight limitation of extension, and restriction of p.r.o.nation.
In the lower extremity, a large number of normal and advent.i.tious bursae are met with and may be the seat of bursitis. That over the _tuberosity of the ischium_, when enlarged as a trade disease, is known as "weaver"s" or "tailor"s bottom." It may form a fluctuating swelling of great size, projecting on the b.u.t.tock and extending down the thigh, and causing great inconvenience in sitting (Fig. 116). It sometimes contains a number of loose bodies.
There are two bursae over the _great trochanter_, one superficial to, the other beneath the aponeurosis of the gluteus maximus; the latter is not infrequently infected by tuberculous disease that has spread from the trochanter.
The bursa _between the psoas muscle and the capsule of the hip-joint_ may be the seat of tuberculous disease, and give rise to clinical features not unlike those of disease of the hip-joint. The limb is flexed, abducted and rotated out; there is a swelling in the upper part of Scarpa"s triangle, but the movements are not restricted in directions which do not entail putting the ilio-psoas muscle on the stretch.
Cartilaginous and partly ossified loose bodies may acc.u.mulate in the ilio-psoas bursa and distend it, both in a downward direction towards the hip-joint, with which it communicates, and upwards, projecting towards the abdomen.
The bursa beneath the quadriceps extensor--_subcrural bursa_--usually communicates with the knee-joint and shares in its diseases. When shut off from the joint it may suffer independently, and when distended with fluid forms a horse-shoe swelling above the patella.
In front of the patella and its ligament is the _prepatellar bursa_, which may have one, two, or three compartments, usually communicating with one another. It is the seat of the affection known as "housemaid"s knee," which is very common and is sometimes bilateral, and, less frequently, of tuberculous disease which usually originates in the patella.
[Ill.u.s.tration: FIG. 116.--Great Enlargement of the Ischial Bursa.
(Mr. Scot-Skirving"s case.)]
The bursa _between the ligamentum patellae and the tibia_ is rarely the seat of disease. When it is, there is pain and tenderness referred to the ligament, the patient is unable to extend the limb completely, the tuberosity of the tibia is apparently enlarged, and there is a fluctuating swelling on either side of the ligament, most marked in the extended position of the limb.
Of the numerous bursae in the popliteal s.p.a.ce, that _between the semi-membranosus and the medial head of the gastrocnemius_ is most frequently the seat of disease, which is usually of the nature of a simple hydrops, forming a fluctuating egg-or sausage-shaped swelling at the medial side of the popliteal s.p.a.ce. It is flaccid in the flexed, and tense in the extended position. As a rule it causes little inconvenience, and may be left alone. Otherwise it should be dissected out, and if, as is frequently the case, there is a communication with the knee-joint, this should be closed with sutures.
[Ill.u.s.tration: FIG. 117.--Gouty Disease of Bursae in a tailor. The bursal tumours were almost entirely composed of urate of soda. (Cf. Fig. 114.)]
An advent.i.tious bursa may form over the _lateral malleolus_, especially in tailors, giving rise to the condition known as "tailor"s ankle"
(Fig. 117).
The bursa _between the tendo-calcaneus (Achillis) and the upper part of the calcaneus_ may become inflamed--especially as a result of post-scarlatinal rheumatism or gonorrha. The affection is known as Achillo-bursitis. There is severe pain in the region of the insertion of the tendo-calcaneus, the movements at the ankle-joint are restricted, and the patient may be unable to walk. There is a tender swelling on either side of the tendon. When, in spite of palliative treatment, the affection persists or relapses, it is best to excise the bursa. The tendo-calcaneus is detached from the calcaneus, the bursa dissected out, and the tendon replaced. If there is a bony projection from the calcaneus, it should be shaved off with the chisel.
The bursa that is sometimes met with on the under aspect of the calcaneus--_the subcalcanean bursa_--when inflamed, gives rise to pain and tenderness in the sole of the foot. This affection may be a.s.sociated with a spinous projection from the bone, which is capable of being recognised in a skiagram. The soft parts of the heel are turned forwards as a flap, the bursa is dissected out, and the projection of bone, if present, is removed.
The enlargement of advent.i.tious bursae over the head of the first metatarsal in hallux valgus; over the tarsus, metatarsus, and digits in the different forms of club-foot; over the angular projection in Pott"s disease of the spine; over the end of the bone in amputation stumps, and over hard tumours such as chondroma and osteoma, are described elsewhere.
CHAPTER XX
DISEASES OF BONE
Anatomy and physiology--Regeneration of bone--Transplantation of bone.
DISEASES OF BONE--Definition of terms--Pyogenic diseases: _Acute osteomyelitis and periost.i.tis_; _Chronic and relapsing osteomyelitis_; _Abscess of bone_--Tuberculous disease--Syphilitic disease--Hydatids; Rickets; Osteomalacia--Ost.i.tis 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 ca.n.a.l, which is filled with yellow marrow. The extremities, which include the ossifying junctions, consist of spongy bone, the s.p.a.ces 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 ca.n.a.ls 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 ca.n.a.l 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 ca.n.a.ls 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 ca.n.a.ls 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 a.s.sociated 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 a.s.sociated with atrophy is also ill.u.s.trated 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 spirochaete of syphilis; a condition of hyperaemia, 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 ca.n.a.ls, or in the cancellous s.p.a.ces and medullary ca.n.a.l, 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 ca.n.a.ls, cancellous s.p.a.ces 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 ca.n.a.l. Hyperostosis and sclerosis are frequently met with in combination, a condition that is well ill.u.s.trated 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 r.e.t.a.r.ded 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 s.p.a.ces.
_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 _periost.i.tis_; 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 ost.i.tis_ 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_.