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.
[Ill.u.s.tration: 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 pa.s.sed 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 ca.n.a.l 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 cloacae, 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.
_Sequelae 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 pa.s.sage 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 hyperaemia.
_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 s.p.a.ce 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 sc.r.a.ped 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 const.i.tutional 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.
#Circ.u.mscribed Abscess of Bone--"Brodie"s Abscess."#--The most important form of relapsing osteomyelitis is the circ.u.mscribed 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 ca.n.a.l 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 sh.e.l.l 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 ca.n.a.l, and a considerable increase in the girth of the bone.
[7] Alexis Thomson, _Edin. Med. Journ._, 1906.
[Ill.u.s.tration: 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.
[Ill.u.s.tration: 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 a.s.sociated 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 a.s.sume 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 dema 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 cloacae (Fig. 122).
[Ill.u.s.tration: FIG. 122.--Tubular Sequestrum resulting from Septic Osteomyelitis in Amputation Stump.]
Like other pyogenic infections, it may terminate in pyaemia, 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.
[Ill.u.s.tration: 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.