APPLICATION OF METAL PLATES, SCREWS,WIRE,ETC,

ACROSS FRACTURE SITE

LANE PLATE

METAL SCREW

WIRE

INTRAMEDULLARY FIXATION AT FRACTURE SITE BY OPEN

REDUCTION

(BONE GRAFT)

5. Various open operative techniques in which the bone fragments are lined under direct vision and transfixed or immobilized by various special devices or bone grafts.

These various methods of immobilization and general mechanisms for fixation are illustrated in Figure 3-11.

Fixation Devices. These devices are highly variable and different in many institutions. Some of them are shown in Figure 3-12.

It is important that the metal or alloy employed be relatively inert within the bone, since electrolysis within the bone must be avoided. This is recognized radiographically in the healing fracture by a lucent zone which surrounds the metallic fixation device.

In addition to those metallic devices illustrated, wire encircling methods may also be employed. 1n the adult, wires may be left in situ without concern. In the adolescent, their removal is indicated, since with the normal growth and the thickness of the bone, the wires will break or become embedded within the bone.

Bone Grafts. In the utilization of bone grafts, the following orthopedic principles have been demonstrated.

Osteogenesis occurs in bone grafts regardless of the integrity of the periosteum and endosteum, but is facilitated when the periosteum and endosteum are left intact.

There is an intimate fusion of the graft to the host bone even after 30 days.Although vascularity within grafts can be demonstrated, they may have large areas of necrosis.When stability at the site of a graft is needed through internal fixation,.it is desirable to use

a solid graft of compact bone, a metal plate, or both.Since cancellous bone generally undergoes less necrosis than compact bone, the use of

cancellouschip grafts around a fracture site is desirable, even when a metal plate is used.Necrotic areas in bone grafts are gradually replaced by "creeping substitution" made

possible through the ingrowth of adjacent cellular and vascular elements After a fresh bone graft transplantation the first roentgenographic evidence detectable is

usually a minimal bone callus surrounding the graft while the adjoining zone becomes atrophic. Later on, the transplant gradually becomes less dense because of the resorption of the dead bony tissues. The transplant itself does not become revascularized and remain alive. Ordinarily, the autoplastic transplant of calcific bony tissue dies along with the osteocytes contained therein. But meanwhile it still fills its mechanical function for a certain period of time. Only the osteoblasts and osteoclasts in the periosteum and endosteum of the graft remain alive; these proliferate and form new bony tissue, which replaces the original graft area by "creeping substitution."

figure 3-13. Representative hip prostheses (A), knee prostheses (8), and upper limb prostheses (C)

figure 3-12. A B, and C, Representative metallic orthopedic fixation devices. More complete identification charts are available 'am surgical supply companies.

re 3-13. Representative hip prostheses (A), knee prostheses (8), and upper limb prostheses (C)

Prostheses

Joint replacement was first used in 1891. During the following 60 years various types and methods were employed, most of which failed. In the past 30 years, the use of joint replacements has become more widespread with an increasing success rate. In 1981, approximately 130,000 total joint replacements (80,000 hips, 40,000 knees, and 10,000 mis-cellaneous) were performed in the United States. Of total hip replacements, approximately 60 per cent were in patients older than 65 years and another 25 per cent were in patients between 55 and 64. The commonest indications for total hip replacement are osteoarthritis, fracture dislocation, rheumatoid arthritis, aseptic necrosis, and revision of previous hip surgery.`

Joint replacement may be (a) partial (e.g., Austin Moore femoral head replacement) or (b) total (Fig. 3-13A, B, and C).

Materials used in prostheses are metal and polyethylene, which may be used either alone or in combination. Cement (methyl methacrylate) is used in many cases.

COMPLICATIONS OF PROSTHESES

Dislocation. The incidence of dislocation in total joint replacement ranges between 1 and 4 per cent (Figs. 3-14 and 3-15).

Loosening of the Prosthesis and Infection (Weissman, 1981, 1983). Loosening and/or infection should be suspected if any of the following occurs:

· The cement bone lucency measures 2 mm or more (Fig. 3-16).· There is progressive widening of the cement, bone lucency on sequential films.· Widening of the metal-cement lucency.,,-';

· Migration of prosthetic components lucency; 3-17). Various lining techniques (Weissman, 1981) have been proposed for prosthetic devices in order to help determine loosening or displacement; unfortunately, reference lines must be established by experience with different prostheses (Weissman, 1981; Jackson) (Fig. 3-18).

· Cement fracture.· Periosteal reaction (Fig. 3-16).· Motion of the components on stress views or fluoroscopy.· Bone destruction in the region of the prosthesis (Fig. 3-19).

Prosthesis Fracture. This may be associated with bone fracture or result from metal fatigue (Fig. 3-20).Bone Fracture. Bone fractures may follow acute trauma and usually occur near the tip of the

prosthesis. Stress fractures occurring either near or far from the prosthesis have been

described with increasing frequency. For example, pubic rami fractures with total hip

replacement or Austin Moore

Figure 3-14. Dislocation of total hip prosthesis and intrapelvic extrusion of methacrylate. Note loosening of intrafemoral component with its cephalad shift from femoral shaft

Figure 3-16. Knee prosthesis with loosening of the tibial component. Note wide lucent zone between the cement and the bone (open arrows); a periosteal reaction is present laterally (solid arrow)

prosthesis (Halle) and Malkin; McElfresh and Covcnny) and patellar fractures with total knee replacement (Scott et al) have been reported.

Heterotopic Bone Formation (Fig. 3-21). Radiographic demonstration of heterotopic bone formation is seen in up to 40 per cent of patients. How(wer, less than 2 per cent have functional limitation.

Extrusion of Cement. Methyl methacrylate may Ire extruded outside the bone (intrapelvic [Fig. 3-22]

Figure 3-15. Dislocation of femoral head prosthesis from prosthetic acetabular cup

Figure 3-17. Hip prosthesis with fragmentation and lateral migration of the acetabular component

figure 3-18. Reference lines for evaluating the position of total hip replacements. The ischial 1.6,ffosty line (ITL) and the midline (MID) are shown. The acehilmlor angle (curved arrow] is measured between the ITL and ij line through the long axis of the acetabular marker wire. Differences in limb length can be assessed by comparing the dislance (D) from the top of the lesser trochanter to the ITL on each side when the femora are Identically positioned. (From Weissman BNW: Radiographic evaluation of total joint replacement. In Kelley WN et at

(eds.):loxtbook of Rheumatology. Philadelphia, W. 8 Saunders Co.. 1981.)

of extraosseous around joints) and may cause damage to adjacent nerves or vessels. Extrusion of cement within the joint space may result in later failure of the prosthesis owing to the abrasive character of the methyl methacrylate (Tailor et at).

Other Complications. Associated with surgery and postsurgery but not specific for joint replacement are the complications of intraoperative death, thromboembolic disease, urologic infection, and pulmonary infection.

Figure 3-19. Hip prosthesis (Austin-Moore) with bone destruction around the shaft

Figure 3-20. Fracture of intramedullary rod at site of refracture through femur

figure 3-29. Heterotopic new bone formation on supert spect of hip joint.

figure 3-22. Intrapelvic extrusion of methyl methacrylate

Radionuclide imaging and arthrography as well 3 subtraction arthrography are considered imporint adjuncts in demonstrating loosening as well as then causes of painful total joint prostheses (Get-tan et al). With scintigraphy, increased activity in to acetabular and/or femoral shaft regions after the sixth postoperative month is considered significant of loosening and/or infection.

Congenital and Hereditary Abnormalities of the Skeletal System: Changes in Size and Shape and Diminished Density

Introduction

The subject of congenital and hereditary abnormalities has become exceedingly complex and extends far beyond the scope of this text. Inborn errors of metabolism are more and more being identified as specific metabolic disorders, which in turn may be related to genetic mutations or chromosomal aberrations.

This chapter is included so that students may formulate a systematic approach to these problems from the radiologic standpoint, and so that they may utilize the outlined material as a framework around which they may build a concept of the complexity of the field and its detailed parts.

In this chapter we shall consider those congenital and hereditary abnormalities associated with changes in size and shape and diminished density, reserving the discussion of changes in increased density for Chapter 7.

We shall consider the problem of hereditary and congenital disorders under two main categories:(1) the chondrodysplasias detectable at birth and(2) those that become manifest after approximately one year of life or even later in adolescence or adulthood.

The principal chondrodysplasias detectable at birth may further be subdivided into those disorders that are incompatible with life and those that are compatible with life and may go on for some time.

Although there are lethal types among those entities that we shall categorize as compatible with life, the main diseases considered incompatible with life are the following:

1. Thanatophoric dwarfism (Fig. 4-1)2. Achondrogenesis (Fig. 4-2)In some classifications, additional entities are included (Greenfield). They are the

following:

3. Osteogenesis imperfecta congenita, which is included later in our discussion of collagen disease

4. Asphyxiating thoracic dystrophy, included by us in the abnormalities that are compatible with life

5. Diastrophic dwarfism of Lamy-Maroteaux, also included by us under abnormalities compatible with life

6. Hypophosphatasia of a lethal type7. Achondroplasia of a homozygous type8. Unclassified lethal bone dysplasias

In examination of these many disorders, those detectable at birth and compatible

with life, those detectable at birth and incompatible with life, and those that become manifest in later years, we find that there are five major areas of the skeletal system that come into consideration. It is most convenient, therefore, to describe all of these entities in terms of the following five major categories:

· Involvement of the extremities· Involvement of the head, either because of bony involvement of the calvaria or

face or because of mental retardation, which may bring , the patient to the attention of the physician

· Spinal involvement· Involvement of the thorax, with attention especially to the ribs, clavicles,

sternum, and associated congenital heart disease· Involvement of the pelvisIn certain instances; there is involvement of all five of these major areas; in others

there may be involvement of only four or even three. In still others there is paramount involvement of either two or one.

The European Society for Pediatric . Radiology and the National Foundation—March of Dimes has recommended a nomenclature, revised in 1977, for

Figure 4-1. Thanatophoric dwarf. A, Anteroposterior view. B, Lateral view. See text for description

figure 4-2. Achondrogenesis. Findings in this stillborn infant include edematous soft tissue, especially about the head, extreme lack of ossification of the vertebral colu sh rt. ened

these so-called "constitutional" diseases of bone, in which the term "dwarfism" is no longer utilized and is replaced by other terms, such as dysplasia. This international nomenclature identifies defects of growth of tubular bones and/or spine; disorganized development of cartilage and fibrous components of the skeleton; abnormalities of density of cortical diaphyseal structure and/or metaphyseal mottling; dysostoses with cranial and facial involvement; dysostoses with predominant axial involvement; dysostoses with predominant involvement of extremities; idiopathic osteolyses; chromosomal aberrations; and primary metabolic abnormalities involving calcium and/or phosphorus, complex carbohydrates, lipids, nucleic acids, amino acids and metals.

It is our purpose in this text to be as objective as possible at all times in approaching radiologic diagnostic problems, and this classification serves this end only in part; therefore, our own approach to this problem has been considered more helpful and advisable.

Principal ChondrodysplasiasDetectable at Birth (Tables 4-1 through 4-8)CHONDRODYSPLASIA INCOMPATIBLE WITH LIFE (Table 4--1)

The principal chondrodysplasias incompatible with life in the newborn are hypophosphatasia (to be discussed with entities compatible with life, since those types arising beyond the neonatal period may permit survival even to adulthood); thanatophoric dwarfism (Fig. 4-1); and achondrogenesis (Fig. 4-2).

Thanatophoric Dwarfism (Fig. 4-1A and B; Keatset al). This type of dwarfism involves all five skeletal areas enumerated above. The skull has a shortened base, and there is a prominence of the frontal bone with depression of the root of the nose. Its shape resembles that of a "cloverleaf." The trunk appears long, largely because the extremities are so short and bowed. The thorax appears long and narrow, and the ribs are markedly shortened with a spatula-like widening near the costochondral junctions. The lower extremities are especially involved. The tubular bones also are very short and bowed. The metaphyses are irregular and cupped. The vertebrae are flattened (platyspondyly), with a reduction of the interpedicular distances of the last lumbar vertebrae. In this respect as well as

figure 4-2. Achondrogenesis. Findings in this stillborn infant include edematous soft tissue, especially about the head, extreme lack of ossification of the vertebral colu sh rt. ened

others there is a close resemblance to achondroplasia. In the pelvis, the iliac wings appear small and square, with a narrow slitlike sacrosciatic notch. It is the extreme flatness of the vertebral bodies with excessive widening of the intervertebral spaces that to some extent distinguishes this entity from achondroplasia.

Table 4-1. PRINCIPAL CHONDRODYSPLASIASDETECTABLE AT BIRTH AND INCOMPATIBLE WITH LIFE"

Thanatrophoric Dwarfism Achondrogenesis

Clinical Features Severe micromelic Severe micromelic Narrowness of the dwarfism thorax

RadiologicFeaturesExtremities Short, bowed (especially

lower) Metaphyses irregular and

cuppedThorax Narrowness, but long trunk Ribs shortVertebrae Platyspondyly Reduction of

interpedicular distances of lower lumbar

Pelvis Iliac wings small and square Narrow sacrosciatic notch

Skull Shortened base Prominent frontal bone and depressed nose "Cloverleaf"

Miscellaneous Depressed nasal bridge

InheritanceMutation

Miccomelic, stout, and deformed Metaphyses flare

Short, clubbed ribs at costochondral junction

Severe dwarfism Defects in ossification, especially vertebrae

Hypoplastic

Large headBasilar hypoplasia Frontal bossingSmall faceNormal jaw Ossification retardedAutosomal recessive

Unlike achondroplasia, which is transmitted as an autosomal dominant hereditary trait, with ominous genetic implications, this type of dwarfism is a mutation per se, apparently without hereditary influence.

Achondrogenesis (Fig. 4-2). Achondrogenesisdemonstrates a close resemblance to the thanatophoric dwarf, with the following exceptions.

Spine. The interpedicular distances of the cervical and lumbar region are not narrowed but normal in width. There is a greater defect in the ossification of the vertebrae as well.

The ossification of the spine is so impaired that at times it appears that the cervical and lumbar spine lack ossification and have poorly outlined margins (Fig. 4-2).

Pelvis. There is only rudimentary ossification of the bones of the pelvis.Extremities. The metaphyses of the markedly shortened extremities show a greater degree offlaring. The marked widening and lack of bowing of the metaphyses of the humeri and femora are important differential points, with short periosteal spicules of bone apparently projecting from the ends.

Table 4-4. SUMMARY OF MUCOPOLYSACCHARIDOSES (MPS)

Major Features1. Defective enzymatic activity —

incompletely degraded glycosaminoglycons

2. Coarse facies; short stature; skeletal oysplasia in the main

3. Hepatosplenomegaly4. Corneal clouding5. Cardiac valve infiltration

Historical TermsCalled "gargoylism"

- Later: lipochondrodystrophyLater: Hunter, Hurler, MorquioLater: mucopolysaccharidoses:

dermatan; heparan; keratanRadiographic Features (dysostosis multiplex), which change with age

Skeleton: OsteoporoticSkull., Colvaria thick; J-shaped Sella turcica Thorax: Oar-shaped ribsSpine: Vertebrae: flat, anterior beakingPelvis: Flared ilia; dysplastic acetabula

Extremities: Short; defective claphyseal modeling; metaphyses and epiphyses irregular

MPS-I-H (in addition to above):Stiff jointsThorax deformed

Aortic and mitral valves incompetent

MPS-I-S (differs from basic in following)Relatively normal height, intelligence, and

life spanCorneal cloudingDigital rigidityAortic incompetenceCarpal tunnel syndromeRadiographic changes minor

MPS-II (Hunter's syndrome)Severe type usually dies before adolescence Mild type — middle age Hands clawedNo corneal clouding Deafness Is common

MPS-III-A and B (Sanfilippo)Profound mental retardation Death early in adulthood Stature normalRadiographic changes mild

MPS-IV (Morquio) (less common than I and 11) Joints are laxFacies normalIntellect unimpairedCorneal clouding and deafness lateCardiac valves involved — deathOdontoid hypoplastic — atlanto-axial subluxation Severe radiographic features

MPS-VI (Maroteaux-Lamy) - H in radiographic features

Table 4-5. PRINCIPAL CHONDRODYSPLASIAS DETECTABLE AT BIRTH AND COMPATIBLE WITH LIFE: SPINE NORMAL;OTHER MAJOR AREAS AFFECTED

Chondroectodermal Asphyxiating Thoracic Dysplasia

Dysplasia (Ellis-van Creveld SyndromeClinical Feature,, Polydactyly

Ectodermal abnormalities Cardiac

malformation Short stature

Narrowness of the thorax Shortness of the limbs Metaphyses irregular

Radiologic FeaturesExtremities Polydactyly

Metaphyseal notchingPeripheral shortening of tubular bones Lateral defect in epiphysis of tibia leading to peakingGenu valgum, hypoplastic patellaThird cuneiforms often

absent in feet Thorax NarrowClavicles horizontalElongatedRibs short with paddle ends

Vertebrae Normal spinePelvis Horizontal acetabular roof

with lateral spur projectingHypoplastic ilia—trident

Skull Poorly developed but appears normalTeeth dysiolostic

hortness of limbs: exostoses PolydoctylyEpiphyses cone-shapedNarrowness and asphyxiation Shortened ribs with paddle ends

Similar to Ellis-Van Creveld syndromeHydrocephalus occasionally

Miscellaneous

Inheritance

Ectodermal abnormalitiesCardiac malformation in

one-third of casesAutosomal recessiveFusion major carpals

inheritanceEctodermal abnormalitiesCardiac malformation in one-third of

cases

of these long bones, imparting to them a "hairbrush" pattern. Moreover, the other tubular bones appear shorter and wider than in the thanatophoric dwarf.

Skull. There are ossification defects in the calvaria, with a large head, basilar hypoplasia, andI P

frontal bossing. Although the mandible would appear to be normal in its development, the other bones of the face appear to have a retarded ossification.

CHONDRODYSPLASIA DETECTABLE AT BIRTH AND COMPATIBLE WITH LIFE

These disorders may be subdivided into five separate categories, as indicated in Tables 4-2 through 4-6.

In Table 4-2, all five of the major skeletal areas are affected. The entities to be described are (1) Larsen's syndrome; (2) achondroplasia (Fig. 4-3); (3) chondrodysplasia punctata (Fig. 4-4); (4) spondyloepiphyseal dysplasia (congenital) (Fig. 4-5); (5)

Table 4-6. PRINCIPAL CHONDRODYSPLASIAS DETECTABLE AT BIRTH AND COMPATIBLE WITH LIFE: SKULL NORMAL; OTHER MAJOR AREAS AFFECTED*

Metatropic Dwarfism

Clinical Features Micromelic dwarfism KyphoscoliosisRadiologicFeatures

Extremities Micromelia Widened ("trumpet-like") metaphyses Long, thin fingers

Thorax Long and narrowVertebrae Kyphoscoliosis

Reduction in height of vertebral bodiesAnterior wedging

Pelvis Hypoplastic iliaDeformed femoral epiphyses

Skull NormalMiscellaneous Flexion contracturesInheritance Autosomal recessive

Table 4-7. PRINCIPAL CHONDRODYSPLASIASDETECTABLE AT BIRTH AND COMPATIBLE WITH LIFE:

THORAX AND SKULL NORMAL; OTHER MAJOR AREASABNORMAL*

Metaphyseal or Spondyloepiphyseal Pseudoachondro Dysplasia or Dysostosis

Clinical Cartilage dysplasia ofFeatures metaphysic, pelvis and spine occasionally

Variable disorderRadiologicFeatures

Extremities Long bones short Metaphyseal cupping and thick Epiphyses irregular Brachydactyly Severe arthritis

Thorax Ribs normal with Rib ends may be full round chest cupped

Vertebrae Rounded bodies Rounded bodies No loss in height Sometimes secondary

? Slight beaking ossification centers fragmentedPelvisIliac crests flared Coxa vara, resorption of femoral necks, hypoplasiaSkull Normal base and Underdeveloped

odontoid base but normal Normal face otherwiseM i s c e l l a n e o u s J a n s e n ' s d i s e a s e i n infancy may be fatalInheritance Autosom al recessive

some of the mucopolysaccharidoses (Figs. 4-6 and 4-7; and (6) hypophosphatasia (Fig. 4-8).

Larsen's Syndrome. Larsen's syndrome is present at birth and is characterized especially by a flat facial appearance and joint dislocations.

Extremities. With regard to the extremities and apart from the joint dislocations especially prevalent in the knees, hips, and elbows, the fingers tend to appear cylindrical.

Spine. In the spine there is an abnormal curvature and usually segmentation, to the extent that there may be cord compression and death as a result.

Pelvis. In the pelvis the most prominent finding is the hip dislocation.Skull. In the skull, apart from the flatness in the appearance of the fades there would

appear to be a craniofacial disproportionism and occasionally a hydrocephalus.Thorax. In the thorax the costochondrat cartilages are very lax. These patients very

frequentlyhave a largyneal malformation, which may lead to asphyxiation and death.

Achondroplasia (Fig. 4-3)

Extremities. This dwarfism is characterized by a marked shortening and thickening of the tubular bones, with the proximal bones being more affected. Although three types of achondroplasia have been recognized (hypoplastic, hyperplastic, and malacic), it is the hypoplastic variety that is most common. Here too the bone ends appear splayed, with a metaphyseal cupping. Although the cortex and meiulla are readily differentiated, the thickening of he tubular bones gives them a "square" appearnce. If the individual lives sufficiently long, the piphyses, when they appear, are normal but invainate the metaphyses. The hands assume a tridentype deformity.

The fingers appear to have the same length, nd it is the separation of the ring and middle finger that imparts to the hand its trident appearance. In the forearms and the legs, the ulna is disproportionately shorter than the radius and the tibia is shorter than the fibula, respectively.

Spine. As in the case of the thanatophoric dwarf, the vertebrae appear flattened (platyspondyly), but unlike achondrogenesis, there is a reduction of the lumbar interpediculate distances and there is a thoracolumbar kyphosis.

Pelvis. Here the iliac bones have a squared appearance and the sacrosciatic notch is markedly acute, so that it appears "slitlike." There are usually flexion contractures of the hips.

Skull. The skull appears hydrocephalic; the face, small with a prognathism. The base of the skull is short and has an acute angle. The foramen magnum is usually constricted, and there is a frontal bone bossing. The nasal bridge is depressed, as is the case in the thanatophoric 'devarf.

Thorax. The patient is "flat" chested, and the ribs are oar or paddle shaped, with thin necks relative to the body of the ribs.

This bone dysplasia is a defect in enchondral bone formation carried as a dominant autosomal defect. Approximately 90 per cent of cases are sporadic, although occasionally a familial history is elicited.

Chondrodysplasia Punctata (Fig. 4-4). This disorder (also called chondroangiopathia calcificans congenita) presents two types: an autosomal dominant form, in which a normal life span may be anticipated (Conrad-Hilnermann's disease) and an autosomal recessi4e form, which affects the proximal portions of the extremities greatest (rhizomelic).

Extremities. The disease is readily recognized by the stippled appearance of both the primary and secondary centers of ossification, even of the carpal and tarsal bones, which is due

to a collagen deficiency (Fig. 4-4A through E).Spine. The stippling of the bones is most apparent in the vertebrae, where a vertical cleft in

the bodies of the vertebrae may also be apparent. A platyspondyly and slight gibbus scoliosis are usually recognized.

Pelvis. In the pelvis the iliac crests appear stippled also, with dislocation of the hips bilaterally.

Skull. Although the head may appear normal, it is usually large, and there is an increased distance between the orbits (hypertelorism). In the face a saddle nose and malarhypoplasia are apparent. Cataracts are common even though they may be asymmetrical.

Thorax. Even the anterior ribs and sternum have a stippled appearance, although the ribs may be normal in length but have a "paddlelike" appearance.

Ichthysosis of the skin is also apparent.

Spondyloepiphyseal Dysplasia congenita (Fig. 4-5). Another disorder of a somewhat similar type is spondyloepiphyseal dysplasia congenital.

Extremities. Here too dwarfism with a marked shortness of the trunk is apparent. There is a delay in the ossification of the extremities with marked irregularity of the epiphyses. The diaphyses tend to be narrow, and a brachydactyly is also frequent. A valgus deformity of the knees is also noted.

Spine. There is a platyspondyly with hypoplasia and an anterior tonguelike protrusion at T12 and Ll levels. The odontoid process tends to be hypo-plastic.Pelvis. The bases of the iliac wings are broad, with an increased depth of the acetabuli and a tendency to protrusio acetabuli. There is also a tendency to coxa vera deformity and associated contractures.

Thorax. The ribs are normal in length, but the chest is barrel shaped, with a pectus carinatum.

Skull. The base of the skull is flattened, forming a platybasia, and the calvaria may be enlarged. There is a saddle-nose deformity. There is often a marked prominence of the eyes, cleft palate, and detachment of the retinae, but no corneal clouding has been noted.

There is an amosomal dominance of this chondrodysplasia. It must be differentiated from spondyloepiphyseal dysplasia tarda, which is not manifest at birth and will be described subsequently.

Mucopolysaccharidoses. The mucopolysaccharidoses (Figs. 4-6 and 4-7) may also fall into this category of chondrodysplasias, in which the thorax, extremities, spine, pelvis, and skull may all be affected. Actually, some forms of this disorder demonstrate greater involvement radiologically than others. As indicated in Table 4-3, there are at least seven of these entities that have been dembnstrated on the basis of enzymal defects, and they may be differentiated on the basis of the abnormal compound stored and excreted. As wilt .be shown, the mucopolysaccharidoses and the mucolipidoses show somewhat similar roentgen appearances and often cannot be differentiated on the basis of the radio-logic examination alone.

Those with the most prominant radiologic findings are Hurler's syndrome (Fig. 4-6) (gargoylism Hurler-Pfaundler syndrome), Hunter's syndrome, and Morquio's disease (Fig. 4-7).

Skull. In general, with these disorders there is a scaphocephaly and macrocephaly of the skull. The Sella turcica tends to be "shoe shaped" (Fig: "A). The calvaria are thickened and the base of the skull flattened, producing a platybasia. The skull may be enlarged, and the nose may have a "saddle" appearance.

Extremities. The hands are quite characteristic, with a tapering of the metacarpals toward the wrist, producing a pyramidal appearance. The radius and ulna are also tapered distally.

In the long tubular bones, apart from the hands, there is a shortening, epiphyseal dysplasia,

and metaphyseal widening, and in the knee there is a lack of normal modeling of the shaft and slanting of the proximal tibial growth plate so that a germ valgus deformity is produced (Fig 4-7F).

Thorax. The ribs are quite characteristic with a narrowing neck and distal broadening resembling an oar or "caveman's club."

Spine. The vertebrae, especially in the lower thoracic and upper lumbar regions, appear hypo-plastic with a "tonguelike" defect anteriorly.

Pelvis (Fig. 4-6E). There is a stenosis above the acetabulum at the iliac base and in the proximal femoral necks. The capital femoral epiphyses also appear dysplastic. A coxa valga deformity is noted.

Specific Syndromes. Among the mucopolysaccharidoses, a precise diagnosis usually requires a knowledge of the pattern of genetic transmission nd biochemical data, including the characterization of the mucopolysaccharide that is increased in the urine.

Although Hurler's syndrome very closely resembles Morquic's syndrome, the best differentiation is probably obtained in the spine. In Hurler's syndrome the ovoid vertebral bodies are ipferiorly beaked; in Morquio's syndrome, the beaking is central. Moreover, the acetabular irregularities are much more pronounced in Morquio's syndrome (Fig. 4-7).

Hurler's Syndrome (MPS-1). Apart from the skeletal changes noted above, there are certain distinctive features in Hurler's syndrome: mental retardation, deafness, dwarfism, corneal opacities, hepatosplenomegaly, cardiomegaly, and cardiac murmurs.

Hunter's Syndrome (MPS-18..This syndrome occurs only in males and hence is X-linked. In general the skeletal and autosomal findings are somewhat milder than in Hurler's syndrome, although two forms of this disease are known to exist, one of which is much more severe than the other.

Sanfidippo Syndrome (MPS-111). This syndrome demonstrates somatic changes that tend to be much milder, whereas the neurologic abnormalities are quite severe. These include mental retardation and motor hyperactivity. Here, too, two clinically indistinguishable but biochemically different forms are recognized. The most diagnostic findings radiologicatty are found in the hands, pelvis, and spine.

Morquio's Syndrome (MPS-IV,- Fig. 4-7). This syn-

drome resembles Hurler's disease, with dwarfism, facial deformity, corneal opacities, deafness, and skeletal changes, except that usually there is a central beaking of the vertebral bodies instead of the inferior beaking that is characteristic of Hurler's. The appearance of the hands, pelvis, and other tubular bones as well as the ribs shows the errors of bone modeling characteristics of Hurler's.

Scheie's Syndrome (MPS 1-5). Originally MPS-V, Scheie's syndrome is characterized by peripheral clouding of the cornea, but here mentality is normal. The appearance of the hands, ribs, and skull resembles the other diseases in this MPS category closely, but the abnormality is perhaps less marked, and generally the radiologic features are less striking.

Maroteaux-Lamy Syndrome (MPS-VI). This syndrome is likewise a mucopolysaccharidosis, but it usually does not become evident until about 2 years of age, with the usual lumbar kyphosis, pectus carinatum, genu valgus, hepatosplenomegaly, and abnormal facies. Intelligence is usually normal, but corneal opacification is noted. The radiographic findings are otherwise very similar but perhaps somewhat less marked than those noted above.

P-Glucuronidase Deficiency (MPS-V11). This deficiency is also characterized by growth retardation, hepatosplenomegaly, and mental retardation and often by pneumonia.

Other mucopolysaccharidose-like disorders have been noted by some investigators, but

their correct classification has been disputed.

Mucolipidosis. As noted previously, the mucopolysaccharidoses and the mucolipidoses are ra-diologically extremely difficult, if not impossible, to differentiate. In the mild form of mucolipidosis I there are usually no neurologic or eye changes, whereas in some severe varieties there is marked mental retardation and neurologic degeneration with hepatosplenomegaly. The radiologic skeletal findings are very often the same as those described for the mucopolysaccharidoses.

In mucolipidosis II there is likewise a marked similarity with Hurler's syndrome, but there is no excretion of mucopolysaccharides in the urine. Moreover, there is a high association of congenital dislocation of the hip in this disorder.

Mucolipidosis III has also been known as pseudo-Hurler polydystrophy. The radiographic ab-normalities are similar to those of Hurler's syndrome but are of variable severity, and there is a normal urinary excretion of mucopolysaccharides.

- There are other mucolipidosis-like disorders representing biochemical storage abnormalities virtually identical radiologically to those already described.

Hypophosphatasia (Fig. 4-8). There is both a lethal and a tarda autosomal recessive type of infantile hypophosphatasia. In the lethal form, present at birth, there is usually an associated respiratory distress and intracranial hemorrhage leading to the very rapid death of the infant. Characteristically the serum alkaline phosphatase levels are low, and there is increased phosphoethanolamine in the urine. The bones of the calvaria do not appear to be ossified. The tubular bones are markedly shortened and likewise irregularly ossified- The metaphyses strongly suggest vitamin D-type rickets with poor ossification of the ribs, flat bones, and vertebrae.

Even in the tarda form, death usually occurs by the first year of life from cardiorespiratory failure and increased intracranial pressure. If the infant does survive, the appearance strongly suggests acquired rickets with a defective gait, mental retardation, dental anomalies, joint pain, and increased bone fragility. As noted previously, there is an absent or low serum alkaline phosphatase, hypercalcemia, and a high excretion of phosphoethanolamine in the urine. If the patient survives, the cranial vault is ossified late and the metaphyseal ossification defects in the tubular bones are strongly suggestive of rickets.

An entity that may be confused with rickets and hypophosphatasia is metaphyseal chondrodysplasia. Although several types of this disorder have been described, the Jansen type is an autosomal dominant disorder found in infancy or childhood, with short limbs, prominent skull and face, and relatively immobile joints. Hypercalcemia is found in the blood, and metaphyseal cupping and marked irregularity reminiscent of findings in rickets or hype rpa rathyroidism are seen. Cranial ossification is usually defective, and there are metaphyseal irregularities in the tubular bones. There is a tendency to Association with Hirschsprung's disease with an aganglionic colon.

The spine is affected somewhat unusually. The vertebrae appear to be either normal or increased in height, with an increase in the lumbosacral angle and a normal skull. Other varieties of metaphyseal dysostoses are present with immunologic defects, intestinal disorders, and ectodermal dysplasia.

Table 4-8. PRINCIPAL CHONDRODYSPLASIAS.DETECTABLE AT BIRTH AND COMPATIBLE WITH LIFE:

THORAX, SPINE, SKULL, AND PELVIS NORMAL; EXTREMITIESABNORMAL*

M e s o m e l i cD w a r f i s m

(Forearms andT i b i a e S h o r t )

(Dyschondrosteosisdoes not Diastrophic

belong--not Dwarfismdwarfed) (Lamy-Maroteaux)

Clinical Micromelia with Micromelic drawfismFeatures selective Club foot

involvement of Cleft palatethe forearm and Deformity of theleg external ear (at 1 or

2 months of age)Hitch-hiker's thumbShort phalanges

Radiologic FeaturesExtremities Micromelia Micromelia

selectively Club foot (cuboid feetinvolving and hands)forearm and leg Changes in epiphyses Incurvation of and metaphysesradius Epiphyses appear

Aplasia of fibula lateJoint luxationsShort, flared massive tubular bones Epiphyses irregular around knee; short femoral necks

Thorax NormalVertebrae Scoliosis but vertebrae normalPelvis NormalSkull Mandible Cleft palate

hypoplastic Deformed external earNormal skull otherwise

Miscellaneous Micromelic(a) Nievergelt(b) Longer*(c) Acromesomelic(d) Other types

Inheritance Autosomal Autosomal recessive

Figure 4-3. Achondroplasia. A, Forearm, B, Lower extremities. C, Hands of an infant. D, Pelvis and femurs

Gambar 4-3 Lanjutan. E, Lateral view of spine and thorax. F, Anteroposterior view of lower thoracic and lumbar spine. Note dimin ished interpediculate distance in lower lumbar (spinal stenosis). (See text for description.) (Courtesy of Dr. J. O. Johnston.)