Roentgen interpretation; a manual for students and practitioners

Front matter

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ROENTGEN INTERPRETATIOX

A MANUAL

CHAPTER I. CHAPTER n

AnATOMIC.U. V.IEIATIOXS AND DE^"ELOPilEXT 26

CHAPTER in.

Feactitres an'd Dislocations 33

CH.\PTER IV.

BoxE Pathology 50

CHAPTER y.

Skull 83

CHAPTER VI.

CHAPTER VII.

The Chest Ill

CHAPTER VIII.

CHAPTER IX.

EOENTGEN INTERPRETATION.

Introduction

It cannot be too strongly emphasized in the begmning that roentgen images are shadowgraphs; that they are the record of the varying opacities through which a bundle of rays has passed; and that they are subject to the possibilit}' of erroneous deductions consequent upon the fact that they are shadows. Objects are visible when they differ in density from their surroundings. The outline of the heart is distinct against the air-filled lung about it while the uterus of similar density is lost in the shadow of the pelvis.

Furthermore, the roentgenogram is a projection on a flat surface of everything in every plane between the plate and the tube's target. It must not be forgotten that in addition to the patient this includes opaque objects upon the filters, the clothing of the patient and the envelope of the plate. The shadow of a rounded bone with ridges on opposite sides will appear on the plate as a flat image with the ridges lying side by side. It is therefore essential for the roentgenologist to have a thorough knowledge of the projected appearance of anatomical structures, so that he may be able to visualize from a flat plate the relative depth of objects seen upon it. The study of stereoscopic plates is of great value in this connection.

Another source of possible error lies in the fact that we commonly employ divergent rays. Parallel rays are seldom made use of in roentgenology except in determinations of the size of the heart. Ordinarily plates are produced by a tube which is relatively close to the plate; therefore we are using divergent rsiys, and the images of objects in their path will be distorted according to their position with reference to the plate. Objects in contact with the plate give an image of actual size and are sharply outlined. As they recede from it their outline becomes more hazy and their size increases. When a wide field of illumination is employed the central rays are practically parallel, but at the margins of the field they strike 2 .

18 INTRODUCTION

obliquely, giving a markedly distorted image. It is customary, therefore, to limit the rays as much as possible to the central bundle by the use of diaphragms and to place the area under observation as closely as possible to the plate. There is an additional advantage to be gained in the employment of small diaphragms because the plates are brighter. Anything in the path of the rays gives off secondary radiation and scatters the primary beam just as light is scattered by fog. This secondary and scattered radiation tends to obscure the image cast by the primary rays, therefore the area of tissue exposed to the rays should be as limited as possible.

One view is an isolated observation and is perhaps less to be relied upon than a single observation in any field of medicine. As far as possible, plates should always be secured in planes at right angles to each other, and often additional plates at various angles will establish a diagnosis which would otherwise be impossible. This is particularly important in studies of the skull, spine and the neighborhood of joints.

In conclusion, there are several axioms which form the basis for successful roentgen interpretation:

1. Do not attempt to include e^'ery thing on one plate; several small ones are always preferable.

2. Do not make a diagnosis before everything possible has been done; thoroughness is essential.

3. Be familiar with the projected appearance of normal structures.

4. Use routine positions for all examinations as far as possible.

5. Do not give opinions on poor plates.

In order to avoid confusion in the use of the terms "increased" and "diminished" density, it should be understood that when they occur in this text they apply to the tissues of the patient. These expressions may be employed to designate the thickness of the silver deposit on the roentgenogram — the actual density in the image of the emulsion — which necessaril}' is reciprocal to the density of the patient. So, in this book, "increased density" means the loss of transparency to the rays and light areas on the roentgenogram. Diminished density means increased radiability and darkening of the plate. Most of the illustrations are positives of the original roentgen negatives and therefore their values are the opposites of those in the plates.

CHAPTER I.

CONFUSING SHADOWS AND ARTEFACTS.

There are many shadows in normal plates which ma}' cause errors in interpretation. Their significance is obvious when they have once been recognized, but the beginner is prone to attach undue importance to them, particularly when they occur in regions to which his attention has been directed by the clinical picture. In case of doubt it is always wise to take plates of the corresponding parts or to compare them with other plates of the same region in other individuals.

Lines Mistaken for Fractures.^ — The most common error here occurs with the epiphyseal lines, which appear as a definite break in the continuity of the bones. It is therefore essential for the roentgenologist to have a complete knowledge of the time of appearance of the, various centers of ossification, the location of epiphyseal lines and the approximate age at which they disappear.

When one bone overlaps another or the edge of a muscle bundle crosses a bone there may be a thin, sharply drawn black line which at times resembles a fracture. This appearance is often noticed in the trans^'erse process of the lumbar ^-ertebrse where the inner margin of the psoas muscle crosses them.

A third possibility of error is furnished by the markings due to bloodvessels which are particularly evident in the skull where the course of the middle meningeal artery appears as a tortuous groove behind the coronal suture and is more or less sharply outlined. The venous channels in the diploe of the skull provide another s;et of dark lines, irregular in their course and indefinite in outline.^ In the long bones there is ordinarily a definite groove where the nutrient artery enters the shaft, which may be mistaken for a fracture when seen in profile, as, for example, in the phalanges of the hands and feet. It is well, therefore, to be familiar with the anatomy of these vessels.

An accurate knowledge of the location and appearance of the sutures of the skull will prevent their misinterpretation, a common

20 CONFUSING SHADOWS AND ARTEFACTS

error particularly with the parietomastoid, which is often called a fracture of the base.

The characteristics of a fracture line which are usually sufficient to identify it are that it is a dense black with sharply cut margins; its course is usually irregular and, particularly in the skull, at variance with that of the bloodvessel markings.

Roughening of the Margins of Bones Mistaken for Periostitis. — Frequently there is a thin plate of boiie extenduig out on the intermuscular septum, as, for example, between the tibia and fibula, or radius and ulna, which seen in profile is quite suggestive of periosteal proliferation, and one must be careful to differentiate this condition from a true periostitis.

A similar process is liable to occur at the attachment of tendons, such as the tendo Achillis, the triceps, along the margin of the iliac crests, along the linea aspera of the femur and about the external occipital protuberances of the skull. There is very commonly a roughening and slight proliferation along the margins of the phalanges of the hands, which is without significance. The flange behind the intercostal groove on the inferior margin of the ribs posteriorly is often exaggerated and suggests a periostitis. The tibial tubercle may be somewhat widened and its lateral margin projected outside the outer border of the tibia a short distance below the head; it is frequently mistaken for a localized proliferation of periosteum. There is normally a variable amount of roughening on the inferior margin of the pubes and ischial tuberosities.

A true periostitis consists of more or less extensive deposit of new bone upon a normal appearing cortex. This deposit may be laid down in multiple thin lamellae, giving it a delicately stratified structure, which is a form frequently seen in lues; or it may be a low irregular fringe, as seen in some forms of osteomyelitis.

Calcifications. — Calcium salts cast a dense shadow wherever they occur. They have an extensive distribution in the body outside of the bony structures. Cartilage is perhaps the tissue in which calcium salts are most prone to be deposited. This is seen in the costal cartilages, where the deposit usually occurs upon the surface of the cartilage in the form of irregular plaques appearing in the chest, spine, gall-bladder and kidney plates. These shadows are without significance and their nature is, as a rule, easily determined.

Calcification also occurs in the same manner in the cartilages of the larynx and is easily recognizable in lateral views of the neck. In anteroposterior views of this region, however, they are projected

CALCIFICATIONS 21

in the region of the lateral masses of the cervical vertebrse and have been mistaken for hypertrophic changes in the spine or calcified vertebral arteries.

Another common seat of calcification is old tuberculous foci, examples of which are the irregular masses in bronchial glands, the characteristic agglomerations of small masses which produce the irregular mulberry-like shadows typical of tuberculous glands, which

Fig 1 . — Calcified retroperitoneal gland suggesting gall-stones.

are frequently found in the neck and throughout the mesentery in the abdomen. They are usually multiple. Small, rounded, dense masses sometimes occur scattered throughout the spleen and may occur anywhere beneath the peritoneum as the end-result of localized tuberculous processes. An extensive calcification is sometimes encountered in tuberculous kidneys. Extensive sheets of calcification are sometimes seen in the pleura and very rarely in the pericardium following tuberculous infection.

22 CONFUSING SHADOWS AND ARTEFACTS

The calcification which occurs in arterial walls as a result of arteriosclerosis is a familiar picture. It may be found in the course of any of the arteries, and is sometimes extensive and striking. The age of the patient must always be taken into consideration in estimating its proper significance. When it occurs in a young patient it is most commonly the result of lues. These changes in the internal iliac arteries may be mistaken for stone in the ureter.

Calcification appears in veins most frequently in the form of small, rounded, dense masses, so-called phleboliths, seen in the pelvis and in the region of the ischial spines; they represent small calcified thrombi on the distal side of the valves, and must not be mistaken for ureteral stones. Rarely, calcification similar to that seen in arteriosclerosis may be evident in old varicose veins.

Extensive calcification may occur in hematomata; this is most commonly seen about the elbow and in the quadriceps extensor. It may develop rather suddenly several weeks after an injury and present an appearance on the plate which resembles periosteal sarcoma.

Definite irregular deposits of calcium salts may be found about foreign bodies, such as silk sutures, and the cysts of parasites. Coming under this head may be mentioned calcified pineal glands which are fairly common and the rare cases of calcification within a dead fetus.

Calcification is fairly common in tumor masses whose blood supply has been obliterated, of which an ordinary example is that seen in uterine fibroids. It is encountered also in other slow-growing and benign tumors of the connective-tissue group, such as fibromata and lipomata. It occurs in certain slowly growing scirrhous carcinomata and has been noted in some tumors in the pancreas and gall-bladder as well as in glandular metastases. Angiomata may contain round cyst-like masses of varying size, representing calcified thrombi, and endotheliomata frequently contain irregular dense areas, as, for example, in psammomata in the skull.

Ovaries are sometimes the site of calcification, in which case they appear as flat oval masses resembling glands in the lateral portions of the pelvis.

Mention must also be made of the fact that infarcts of any of the viscera may subsequently calcify. Another rare condition is the so-called calcareous metastasis in which in extreme resorption of bone from extensive caries, malignant disease, etc., a widespread deposit of calcium salts may occur in the cartilages, mucous membranes of the mouth, stomach and arteries.

AREAS OF INCREASED DENSITY IN SPONGY BONE 23

Areas of Increased Density in Spongy Bone. — Small round areas of condensation are sometimes seen in cancellous bone. There is no disturbance in the normal structure of the bone about them, and their significance has been a matter of considerable speculation. They may represent old healed areas of infection or some localized

Fig.

-Foreign body in soft tissues. (Metallic injection.)

disturbance in the growth of the bone. At any rate, they have no pathological importance. They may occur near the ends of long bones in the carpus, tarsus or within any of the flat bones. The transverse dense lines, often multiple, which occur along the medullary canal toward the end of the long bones, are the result of disturbances of growth which occurred at the time when the epiphyseal line was

24 CONFUSING SHADOWS AND ARTEFACTS

at that point; they may be hkened to the growth of rings In the trunk of a tree.

Warts and Fibromata on the Skin. — Any area of skin which presses heavily on the plate will be recorded as a spot of increased density, common examples of which are outlines of the buttocks of a thin individual in a plate of the entire pelvis, the breasts of women in anteroposterior plates of the chest or the ears in lateral skull plates.

Fig. 3. — Gas gangrene.

In the same way warts and fibromata appear as rounded areas of increased density, which when they occur in the kidney and gall-bladder regions may strongly suggest calculi. A characteristic which may help to identify them is that they ha^'e extremely sharp margins because of the fact that they are in contact with the plate. The presence of fibromata should always be noted in the patient's record.

DEFECTIVE PLATES 25

Metallic Salts. — Dense shadows of the metalHc salts may be seen where there are bismuth or barium residues in the sinus which has been injected or in portions of the gastro-intestinal tract; where zinc or mercurial ointments are present on the skin, or iodin which in any form casts a shadow of particular density. The presence of iodin upon the skin or within the soft tissues as a result of intramuscular injection is quite striking (Fig. 3). Air or gas in the soft tissues also gives a characteristic picture.

Gas in the Intestinal Tract. — Accumulations of gas, particularly in the colon where it overlies the spine, the wings of the ilia or sacrum, arc; sometimes mistaken for areas of rarefaction in the bone. Careful inspection will reveal the presence of normal bone structure in the doubtful area or the patient may be reexamined.

Defective Plates. — Plates may show irregular light or dark areas as a result of defects of manufacture, or fogging by light or a;-rays. One particularly troublesome defect is the occurrence of localized thin spots in the emulsion which give shadows light in color resembling those of stones. Irregular patterns of increased or diminished density occasionally result from uneA'en immersion of the plate in the developer; these are very sharply marked and have long curved outlines. Finger marks appear on plates as light or dark spots, depending upon the substance present on the finger at the time of impression; their presence is always an indication of faulty darkroom technic.

BIBLIOGRAPHY.

Wells, H. Gideon: Metastatic calcification, Arch. Int. Med., 1915, xv, p. 574.

Hetherington, .1. P.: Causes of apparent and real mistakes in ar-ray diagnosis. Railway Surg. Jour., 1915-16, xxii, p. 223.

Pirie, A. H.: Interpretation of a;-ray negatives, British Med. .Jour., 1910, part 2, p. 584.

Jones, R., and Morgan, D.: On osseous foi-mations in muscles due to injury, Arch. Roent. Ray, 1904-5, ix, p. 245, and 190.5-6, x, pp. 10, 46, 72, 100, 199, 249, 275, .304.

Outerbridge, G. W.: Non-teratomatous bone formation in the human ovary. Am. .Jour. Med. Sc, 1916, cli, 868.

Klotz, Oskar: Obsolete miliary tubercles of the spleen. Am. Jour. Med. Sc, 1917, clxxx, p. 786.

Chapter II. Anatomical Variations And Development

Anatomical variations in bone structure may occur anywhere in the skeleton and are of considerable importance aside from their interest as curiosities, for they are commonly points of lowered resistance. A strain or injury which would be without effect on a normally constructed individual may give rise to severe and stubborn symptoms when such anomalies are present. This is particularly true of variations in the spine.

Skull. — The skull may show partial absence of bones or variation in the width of sutures, of which extreme examples are acephalic monsters. Thin areas appearing as holes are occasionally seen in the frontal and parietal regions and along the sagittal suture. The sinuses and mastoids are subject to wide variation, from complete absence to enormous size. Cases have been observed in which the mastoids communicated with the sphenoid sinus anteriorly and with each other posteriorly.

Vertebrae. — A most common anomaly in the spinal column is the presence of extra bodies, e. g., six lumbar or thirteen thoracic segments, or of extra portions of bodies which take the form of a triangular wedge which may bear an extra rib when it occurs in the thoracic region.

Another frequent finding is the failure of union of the posterior ring. All degrees of this condition are seen from bifid spinous processes to complete spina bifida.

There may be increase of length or size of the transverse processes, particularly in the last cervical and last lumbar vertebrae. There are all gradations found up to partial or complete fusion of the process with the sacrum, or so-called sacralization. These enlarged processes give rise to symptoms whenever, on account of size or position, they cause pressure on nerve trunks or impinge on neighboring bones. On the other hand, the processes of the first lumbar are often short and have accessory ribs attached; these may be mistaken for fractures.

VERTEBR.^

Fig. 4. — Congenital abnormality. Wedge-shaped vertebra.

P;q_ 5_ — Enlarged sacralized transverse process on fifth lumbar vertebra.

28 ANATOMICAL VARIATIONS AND DEVELOPMENT

While spinous processes are ordinarily arranged in a straight Hne, slight lateral deviations of individual processes may occur without pathological significance. Unusually long or thick spinous processes may impinge on one another, especially in the lumbar spine in cases of exaggerated lumbar curve.

There is a considerable variation in the plane of the articular facets at the lumbosacral junction. Normally these articular surfaces are approximately transverse, but one or both may be rotated so that the plane of the articulation between them is anteroposterior. These are a potential source of symptoms in the lower back because they permit of various degrees of forward dislocation of the fifth lumbar vertebra upon the sacrum.

Fig. 6. — Double cervical ribs.

Ribs. — One anomaly has already been mentioned; that is, the occurrence of extra ribs which may appear in the lower cervical or upper lumbar regions or attached to extra bodies. These cervical ribs may be of sufficient length to articulate with the sternum or be attached to the first rib. They are usually longer than they appear on the plate, due to foreshortening of their shadow. On the

VARIATIONS OF THE TARSUS 29

other hand, one or more ribs may be absent, or partially so, or adjacent ribs may be fused. A mild form of this latter condition is frequently seen near the sternal end, where a rib may flare considerably before its attachment to the costal cartilage, and this enlargement may or may not be perforated.

Scapulae. — These bones vary considerably in thickness and holes may occur in the thin regions, especially in old people; in the same way unusually prominent grooves may simulate fractures. There is a condition known as congenital elevation of the scapula (Sprengel's deformity) , in which a partially developed scapula is found high up toward the neck. In cases of obstetrical paralysis there may be an imperfect development of the lower half of the scapula.

Fig. 7. — Congenital abnormality of the scapulge.

Variations of the Carpus. — Perhaps the most important anomaly here is the divided scaphoid, which is to be differentiated from a fracture of the scaphoid. The margins of the halves are more rounded and smooth and the space separating them is not quite so black as in the case of fracture. The semilunar and the radial sesamoid of the thumb may be similarly divided. Small extra bones may be found, of which the most common is the styloid; this develops from an extra center of ossification lying between the trapezoid, the magnum and the third metacarpal.

Variations of the Tarsus. — The astragalus bears a backward prolongation of variable length which often exists as a separate bone, the trigonum; when present it must be differentiated from a fracture of a long process. The next in order of importance is the tibiale externum, a small detached bone which sometimes occurs at the

30 ANATOMICAL YARIATIOXS AND DEVELOPMENT

posterior end of the scaphoid on the inner side of the foot. The peroneum in the tendon of the peroneiis longus overlying the cuboid may be subdivided.

The small separate center of ossification on the outer side of the posterior end of the fifth metatarsal may persist into adult life as a small bone called the vesalianum.

Divided sesamoids in the tendons of the flexor hallucis brevis beneath the head of the first metatarsal are fairly common. They must be carefully dift'erentiated from fracture of single sesamoids, which are extremely rare.

The subject of variations in the hands and feet is exhaustively treated by Dwight.

Other Bony Variations. — In e\'ery roentgenological practice one may encounter cases of partial or complete absence of long bones, particularly the fibula, radius and phalanges. On the other hand, supernumerary bones, usually extra fingers or toes, may also be seen. Fusion of bones may be looked for occasionally; this is most frequently found between the radius and the ulna. Adjacent carpal and tarsal bones may be united, and there is an hereditary anomaly in which the first and second phalanges of one or more digits may coalesce with obliteration of the interphalangeal joint. Atavistic variations may occur, as, for example, the hooked supracondylar process occasionally found on the inner margin of the humerus above the elbow.

Ossification. — Variability is also evident in the time of appearance of centers of ossification. The following table taken from Rotch and Morris's Anatomy gives figures which can be relied upon as a working average.

Age of Age of

appearance. fusion.

Ribs: Epiphyses for head and tubercle 15 2-3

Clavicle: Small epiphysis of the sternal end 18 25

Humerus: Head 8 mos. 20

Greater tuberosity 3 20

I^esser tuberositj' 4 20

(All fuse at six years and join the shaft at twenty years).

Capitellum 1 17

Internal epicondyle 5 18

Trochlea 10 17

External epicondyle 12 17

(The capitellum, ti'oclilea and external epicondyle join as a mass at seventeen and the internal epicondyle at eighteen j'ears.)

Radms: Head 5 17

Lower epiphysis 2 20

Ulna: Olecranon 10 17

Lower epiphysis 4 18

OSSIFICATION 31

Age of Age of

,^ ,~v^ appearance, fusion.

Carpus: (IrTthe order of appearance.)

Magnum 1

Cuneiform . .."^y $-■- . 2 to 3

Semilunar . ■. ' \ '; . 4 to 5

Trapezium 5

Scaphoid . .' 5 to 6

Trapezoid . .' • 6 to 8

Pisiform . . . .' 12

Metacarpals: Epiphyses 3 20

Phalanges: Epiphyses 3 18

Peh-is: (Pubis and ischium unite at eight years; the acetabulum closes at sixteen years.)

Epiphyses for 0 0

Crest of ilium, "I

Ischial tuberosity, I 15 20

Anterior inferior iliac spine, f

Tubercle of pubes, J

Femur: Head 1 19

Greater trochanter 4 18

Lesser trochanter 13 17

Lower epiphysis 8 mos. 20

Fibula: Upper epiphysis -. . . . 4 24

Lower epiphysis 2 20

Tibia: Upper epiphysis 9 mos. 22

Lower epiphysis 2 18

Tarsus: (In order of appearance.) ,. ,_^^

Epiphysis of calcis . ^ 10

Astragalus . . f—^'*'^ 7 mos.

Cuboid 9 mos.

External cuneiform 1

Internal cuneiform 3

Middle cuneiform 3

Scaphoid 4

Metatarsals: Epiphyses 3 to 8 20

Phalanges: Epiphyses 4 to 7 18

Sesamoids of flexor hallucis brevis: 5

Vertebrae: Ossification is from three primary centers, one for the body and one for each lateral mass. The nucleus for the Ijody is often bilobed, A\'ith a partial plane of cleavage in the vertical or horizontal diameter. The laminse unite during the first year. Five secondary centers described in the anatomies — namely, thin plates on the upper and lower surfaces of the body and the tips of the mammillary tubercle, transverse and spinous processes — appear at the age of fifteen to twenty years and unite at twenty-five. The fifth lumbar vertebra is an exception in that it ossifies from five centers, one for the body, one on each side from which is developed the superior articular process, pedicle and transverse process, and one on each .side which subsequently form the inferior articular process, lamina and spinous process.

It is well to bear in mind that epiphyses which appear last are the first to unite and that the nutrient foramen is directed toward them; that ossification begins earliest in the epiphyses bearing the largest relative proportion to the shaft (except the fibula); that when an epiphysis ossifies from several centers, they fuse together before uniting with the shaft.

32 ANATOMICAL VARIATIONS AND DEVELOPMENT

Thomas Morgan Rotch has called attention to the fact that the time of appearance of the carpal centers is the best index we have of the actual development of an individual.

Delayed Union or Failure of Union. — Variations in the normal process of the union of epiphyses are of great importance as a factor in the production of deformities. For example, failure of development of a center in the lateral masses of the fifth lumbar may result in scoliosis. Abnormal fusing of the lower epiphysis of the radius produces the malformation known as Madelung's deformity, in which the plane of the radiocarpal articulation is rotated inward and backward.

Delayed union may be an evidence of retarded mental or physical development, of which a common example is cretinism; of infections, prominent among which is lues; or of injury.

BIBLIOGRAPHy.

Milne, James A.: Congenital absence of the radii, British Med. Jour., 1915, ii, p. 821.

Piersol, George A.: Congenital perforations of the parietal bones, Univ. Peinia. Med. Bull., 1902, xv, p. 203.

Skillei'n, P. G.: Congenital perforations of the parietal bones, Ann. Surg., 1914, ix, p. 807.

Adams: Relation of anomalies of lumbar and sacral spine to lordosis. Am. Jour. Orthop. Surg., 1915, xii, p. 45.

Hodgson, F. G. : Congenital deformities of the vertebrae and I'ibs, Am. Jour. Orthop. Surg., 1916, xiv, p. 34.

Case, J. T. : Anacephaly successfully diagnosed before birth, Surg., Gynec. and Obst., 1917, xxiv, p. 312.

Boorstein, S. W. : Symmetrical congenital malformation of extremities, Ann. Surg., 1916, Ixiii, p. 192.

Rugh: Sprengel's deformity, Tr. Philadelphia Acad. Surg., 1915, xvii, p. 62.

Albers-Schonberg : A skeletal anomaly, the supracondylar process. Am. Jour. Roent., 1916, iii, p. 182.

Geist, E. S.: Supernumerary bones of the foot, Am. Jour. Orthop. Surg., 1914-15, xii, p. 403.

Ruh, H. O.: Acrocephalosyndactylism, Am. Jour. Dis. Children, 1916, xi, p. 281.

Schueller, A.: Peculiar cranial defects in young individuals. Am. Jour. Roent., 1916, iii, p. 497.

Ashhurst, A. P. C: Congenital absence of the fibula, Ann. Surg., 1916.

Peckham, F. E.: Congenital elevation of the scapula, British Med. Surg. Jour., 1916, clxxiv, p. 315.

Dwight, T. : Closure of cranial sutures as a sign of age, British Med. Surg. Jour., 1890, cxxii, p. 389.

Hartung, A.: Congenital anomalies and variations of the bony skeleton, Am. Jour. Roent., 1916, iii, p. 430.

Dunlop: Adolescent tibial tubercle, Am. Jour. Orthop. Surg., 1912-13, ix, p. 313.

Goldwaite,'J., and Painter, C. F. : Congenital elevation of shoulder, Tr. Am. Orthop. Assn., xix, p. 302.

Barnes, N. P.: The sesamoids of the flexor brevis hallucis. New Yoi'k Med. Jour., 1915, cu, p. 940. Tr. Am. Therap. Soc, 1915, p. 59.

Clark, D. A.: Sacralization of lumbar vertebra, Canadian Med. Assn., Jour. 1916, vi, p. 914.

Pryor, J. W. : Ossifications of the bones of the hand, Bull. Univ. Kentucky, viii, No. 11, November, 1916. Reviewed in Am. Jour. Roent., 1916, iii, p. 416.

Sever, J. W.: Obstetrical paralysis, Am. Jour. Orthop. Surg., 1916, xvi, p. 456.

Chapter III. Fractures And Dislocations

FRACTURES.

It is most important for a roentgenologist to have a thorough knowledge of roentgen anatomy and of the surgical pathology of wound and fracture repair. Gross fractures are, of course^ obvious, but in a doubtful case the diagnosis may depend entirely upon the breadth of his anatomical and surgical experience. He should at least know that the more accurately a fracture is reduced the sooner will function be restored and the smaller the callus which results ; that calcification begins in callus in from two to four weeks and is usually complete in six; that at first callus may show very little evidence of lime deposit when there is no displacement of fragments; and that an extensive comminution or a malposition of fragments should be accompanied by a large, thoroughly calcified callus.

The prognosis of fractures involving joints should always be guarded because of the fact that there is no means of estimating from the roentgen examination how much damage has occurred to the soft tissues or what eiTect their repair will have on function. The possibility of organization and calcification in extensive hematomata which may follow injuries to the supporting structures should always be remembered.