Hematologic Bone Diseases

Chapter 11

Hematologic Bone Diseases

Gary D. Schultz

AVASCULAR NECROSIS

HEMOCHROMATOSIS

HEMOPHILIA

HEREDITARY SPHEROCYTOSIS

LEUKEMIA

SICKLE CELL ANEMIA

THALASSEMIA

Vascular conditions affecting bone may manifest through alterations in blood supply or changes in skeletal architecture caused by abnormal activation of the hematopoietic potential within bone marrow. Unfortunately, the slow metabolic rate of bone significantly delays visualization of quantitative, qualitative, and morphologic changes in the skeleton on low-tech imaging. Advanced imaging techniques such as radionuclide scintigraphy (bone scan) and magnetic resonance imaging (MRI) are capable of demonstrating early changes in bone metabolic rate and microarchitecture.1 The limited number of skeletal responses to hematologic alterations often impairs a physician’s ability to render a specific diagnosis based on plain film alone. In general, vascular conditions of the skeleton have a chronic history of development and nonspecific radiographic findings. Consequently, all radiographic clues must be correlated with historic and laboratory findings. Typically the clinical findings suggest the correct diagnosis long before plain film radiographs are useful.

Avascular Necrosis

Background

Avascular necrosis is the most common hematologic condition affecting the skeleton. Pathologically, this condition is simply bone death resulting from inadequate blood supply. Avascular necrosis is more likely to develop in locations where the blood supply to bone is tenuous or little collateral circulation is present. Many conditions and disorders may be responsible for interrupting blood supply to a segment of bone.11,36

Conditions known to cause avascular necrosis include trauma, alcoholism, infections, medications (including corticosteroids, bisphosphonates, and highly active antiretroviral therapy), dysbaric trauma, marrow infiltration disorders, hypercoagulability states, autoimmune diseases, and idiopathic etiology.4,27,31 These causes may be divided into three categories: (a) conditions resulting in external blood vessel compression near or within the bone, (b) disorders resulting in blood vessel occlusion because of thickening of the vessel wall, and (c) disorders resulting in blood vessel blockage from a thromboembolic process (Box 11-1).12

Box 11-1   Causes of Skeletal Ischemic Necrosis

External Vessel Compression

• Trauma or surgery

• Steroid administration

• Idiopathic

• Regional infection

• Neuropathic joint

• Gaucher disease

• Hyperlipidemia

Vessel Wall Disorders

• Systemic lupus erythematosus

• Polyarteritis nodosa

• Giant cell arteritis

• Radiation therapy

Thromboembolic Disorders

• Alcoholism

• Arteriosclerosis

• Steroid administration

• Thromboembolic syndrome

• Diabetes

• Trauma

• Sickle cell disease

For conditions resulting in external blood vessel compression, the mechanism is either marrow edema causing compression of the vessel in an enclosed region or excessive packing of the marrow through the deposition of abnormal tissue or material (e.g., fat in steroid administration or hyperlipidemia).16,22,47 Box 11-2 lists, in descending order of frequency, the common causes of ischemic necrosis in children and adults.

Box 11-2   Most Frequent Causes of Ischemic Necrosis

Children

• Idiopathic origin

• Trauma

• Infection

Adults

• Drugs and other substances (steroids, alcohol, immunosuppressants)

• Trauma

• Inflammatory arthritis

• Metabolic conditions (diabetes, Cushing syndrome, pregnancy)

Bone ischemia may have several presentations. Infarction affecting a focal segment of the articular surface is termed osteochondritis dissecans in the growing skeleton. This defect may occur in adults and children, and more frequently affects weight-bearing bones at their articular surfaces.19 The lateral aspect of the medial femoral condyle is the most common location of the infarction, followed by the talar dome. Trauma is believed to be the precipitating mechanism, although patients often report no history of trauma. There is evidence to suggest that transient “bone marrow edema syndrome (BMES)” precipitates compression of susceptible vascular structures, occluding the vessels and creating osteonecrosis. 37

The term medullary bone infarction is used to describe ischemic necrosis localized to the medullary portion of a long bone. This type of bony infarction generally is not of primary therapeutic interest because it causes no significant symptoms and is sufficiently distant enough from articular surfaces that it results in no alterations in osseous shape or integrity. Although the finding itself is of no therapeutic importance, medullary bone infarctions are associated with metabolic conditions, such as alcoholism, diabetes, and chronic renal disease, all of which should be ruled out in its presence.

An infarction affecting the entire epiphysis of a skeletally immature long bone is termed epiphyseal ischemic necrosis. The proximal femur is by far the most common location for this event.29 When the proximal femur is affected, the condition is sometimes termed Legg-Calvé-Perthes disease (Box 11-3) in the child or Chandler disease in the adult. Early diagnosis of Legg-Calvé-Perthes disease is important in prevention of postischemic deformity and functional impairment.28 Most cases of Legg-Calvé-Perthes disease have an idiopathic origin, although slipped femoral capital epiphysis, trauma, developmental dysplasia of the hip, and other pathologies also are associated with this condition.

Box 11-3   Legg-Calvé-Perthes Disease

Background

• Idiopathic osteonecrosis of the proximal femoral capital epiphysis in children

• Trauma, endocrine abnormality, and infection implicated as possible causes

• More common among boys, whites, and those between 3 and 5 years of age

Imaging

• Bilateral in approximately 15% of patients

• MRI and bone scans more sensitive to early disease than plain film radiographs

• Bone scans cold during avascular phase and hot during revascularization phase

• MRI scans revealing replacement of normal marrow by necrosis

• Plain film findings of capsular distention, a small fragmented epiphysis, osteosclerosis (snowcap sign), subchondral collapse (crescent sign), radiolucent defect of the lateral margin of the involved epiphysis (Cage sign), curved radiodense cortical line at the base of the femoral neck representing the margin of the deformed femoral head (sagging rope sign), and growth deformity leading to a wide, short femoral neck with an enlarged (coxa magna), flattened (coxa plana) femoral head (mushroom) deformity

Clinical

• Slowly evolving painless limp with limited abduction and internal rotation

• Clinical outcome worse if weight-bearing area of bone involved

• Osteoarthritis secondary to incongruent articular surfaces representing a significant complication

• Treatment options of avoidance of full weight-bearing, bracing, and possible surgical realignment

Although ischemia of any segment of a bone is possible, some locations are more likely to be affected because of their vascular supply (Table 11-1). An avascular etiology has been ruled out for some epiphyseal conditions previously attributed to an avascular origin (Table 11-2, Fig. 11-1).

TABLE 11-1

COMMON LOCATIONS FOR ISCHEMIC NECROSIS

Location Disorder
Metatarsal head Freiberg disease
Tarsal navicular Köhler bone disease
Talus Diaz disease
Patella (secondary Sinding-Larsen-Johansson ossification center) disease
Medial femoral condyle Spontaneous osteonecrosis of the knee (SONK)
Femoral head (child) Legg-Calvé-Perthes disease
Phalanges of hand Thiemann disease
Metacarpal head Mauclaire disease
Carpal lunate Kienböck disease
Carpal scaphoid Preiser disease
Capitellum of the humerus Panner disease
Humeral head Hass disease
Vertebral body Kümmel disease

TABLE 11-2

EPIPHYSEAL CONDITIONS UNRELATED TO AVASCULAR NECROSIS

Condition Etiology Description
Blount disease (tibia vara) Trauma Local growth alteration of the medial portion of the proximal tibial epiphysis; infantile and adolescent presentation; depressed medial metaphysis of the tibia with an osseous overgrowth noted; shortening of involved leg; usually a tibia vara deformity
Osgood-Schlatter disease Trauma Altered appearance of the tibial tuberosity occurring mostly between the ages of 11 and 15 years; more common among boys and girls who participate in sports such as soccer and weight lifting; fragmentation and soft-tissue swelling of the tibial tuberosity evident on radiographs; pain and tenderness over the region; tibial tuberosity possibly fragmented as a normal variant and distinguishable from Osgood-Schlatter disease by lack of pain and soft-tissue swelling
Scheuermann disease* Trauma Posttraumatic defect of vertebral endplate maturation first seen during adolescence with three or more levels of wedged vertebrae, narrowed anterior disc space, multiple Schmorl nodes, and vertebral endplate irregularity; middle and lower thoracic spine are the usual locations; back pain is common; more severe kyphosis possibly necessitates bracing or, in a few cases, surgery to arrest or partially correct the resulting deformity
Sever phenomenon Variation in ossification Irregularity and fragmentation of the secondary ossification center of the calcaneus; generally considered a normal variant and unrelated to any heel pain in the adolescent
Sinding-Larsen-Johansson disease Trauma Fragmented appearance of the lower pole of the patella, most commonly occurring between 10 and 14 years of age; soft-tissue swelling and tenderness common and exacerbated by activity

*See Chapter 8.

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FIG 11-1 Nontraumatic presentation of an angled deformity of the medial aspect of the proximal tibia with resulting varus deformity of the knee joint in this patient with Blount disease.

The histologic changes in bone necrosis are essentially the same, regardless of location. Pathologically, absence of a blood supply results in bone death within 48 hours; a predictable sequence of events then ensues: inflammatory reaction to the dead bone, neovascular infiltration into the dead segment of bone, resorption of dead bone and deposition of new bone, and remodeling of the resultant bone.30 This process may take 1 to 8 years to complete.

Imaging Findings

Osteochondritis Dissecans.

Osteochondritis dissecans (focal subarticular infarction) generally first manifests radiographically, the plain film demonstrating a subarticular lucent defect accompanied by a free-floating fragment of bone that formerly filled the defect. The defect is characteristically smooth and regular with varying degrees of marginal sclerosis corresponding roughly to the shape of the fragment (Fig. 11-2). The fragment may be displaced from the parent bone defect, or remain in in situ. The marginal sclerosis around the defect is most pronounced at the margin of the defect, fading gradually into the subchondral bone peripherally (Fig. 11-3). These findings assist in differentiation of focal subchondral infarction from an acute intraarticular fracture. Intraarticular swelling is often noted, but its severity varies considerably (Figs. 11-4 and 11-5).

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FIG 11-2 A to C, Osteochondritis dissecans. A, Lateral view of the knee with slight degree of noticable irregularity of the posterior margin of the condyle. B, Anteroposterior view of the knee with the leg extended reveals irregularity of the medial condyle (arrows). C, Unlike the lateral and closed joint view, this open joint view of the knee demonstrated a marked defect of the articular cortex of the medial condyle consistent with necrosis. As exhibited here, the open joint view of the knee is necessary to observe the posterior articular margin of the condyles.
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FIG 11-3 Osteochondritis dissecans of the ankle. Note the in situ osseous fragment at the superomedial aspect of the talar dome (arrow). From Deltoff MN, Kogon PL: The portable skeletal x-ray library, St. Louis, 1998, Mosby.
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FIG 11-4 Osteochondritis dissecans appearing as a focal hyperintense defect on (A) coronal T2-weighted and (B) oblique T1-weighted sequences (arrows). Osteochondritis dissecans is a traumatic defect of the articular surface, common to the dome of the talus, particularly on the medial side. It is suggested clinically by persistent symptoms after an ankle strain. Courtesy Robert Rowell, Davenport, IA.
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FIG 11-5 A small defect is noted at the top of the reading left femoral head, consistent with osteochondritis dissecans (arrow).

 

Medullary Bone Infarction.

Plain film radiographs are not capable of demonstrating the acute manifestations of a medullary bone infarction. MRI and scintigraphy are demonstrative of the pathology within days of its occurrence. Weeks to months later, after resolution and revascularization, the infarction is usually visible radiographically as discontinuous, longitudinally oriented, and wavy or serpiginous calcific opacities lying centrally in the medullary cavity (Figs. 11-6 to 11-8). The infarction does not result in periosteal reaction, alteration in the cortical thickness, or expansion of the external architecture of the affected bone. Differentiating a medullary bone infarction from a benign enchondroma of bone can be impossible on plain film images. However, definitive differentiation generally is unnecessary because both conditions are benign.

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FIG 11-6 A and B, Irregular patchy sclerosis of a medullary bone infarction.
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FIG 11-7 Subtle serpiginous calcifications in a medullary bone infarction.
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FIG 11-8 Medullary bone infarct of the proximal tibia (arrowheads) with accompanying necrosis of the medial femoral condyle (crossed arrow) and signs of degeneration of the medal joint compartment (arrow).

Epiphyseal Necrosis.

Avascular Phase.

From both therapeutic and prognostic standpoints, epiphyseal necrosis is a significantly more important condition than medullary bone infarction. During the avascular phase of epiphyseal necrosis, plain film radiographic skeletal changes are absent (Fig. 11-9).24 Intraarticular effusion may be visible, but the degree of effusion varies, making it an unreliable indicator of the condition.

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FIG 11-9 A, Normal plain films in a patient with a painful hip. B, Plain films 3 months later demonstrating increased radiodensity and a mottled appearance of the femoral head. These are typical signs of avascular necrosis of the femoral head.

Changes in marrow signal can be identified with MRI, which is the most sensitive imaging modality for the detection of early bone infarction.5 MRI demonstrates loss in the epiphyseal marrow signal, particularly on T1-weighted images, even in the earliest phases of the disease (Fig. 11-10).10,18,46

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FIG 11-10 Avascular necrosis of the patient’s left (reading right) hip with severe secondary osteoarthritis on a coronal T1-weighted MRI scan. From Firooznia H et al: MRI and CT of the musculoskeletal system, St. Louis, 1992, Mosby.

Early epiphyseal infarction also can be detected by radionuclide scintigraphy, which demonstrates focal photopenia affecting the avascular segment. An ill-defined zone of increased radionuclide uptake is present in the region surrounding the avascular segment, presumably resulting from reactive synovitis and hyperemia (Fig. 11-11).9

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FIG 11-11 Images of a 52-year-old man who has right hip pain and is receiving steroids for systemic lupus erythematosus. A, A technetium (99mTc) pyrophosphate bone scintigram shows increased uptake in the right hip (arrow) and a normal left hip. B, A coronal T1-weighted MRI shows obvious avascular necrosis on the right and subtle characteristic avascular necrosis changes on the left. Core biopsies confirmed bilateral avascular necrosis. C, Axial T1-weighted MRI. D, Axial T2-weighted MRI. Fluid is shown (arrows) in the right iliopsoas bursa. Iliopsoas bursitis may accompany avascular necrosis and cause a variety of symptoms. From Firooznia H et al: MRI and CT of the musculoskeletal system, St. Louis, 1992, Mosby.
Inflammatory Phase.

As the avascular phase gives way to the inflammatory response, plain films may demonstrate periarticular osteopenia affecting all but the involved segment of bone. This may create the visual illusion of sclerosis of the avascular segment. This subtle finding, like so many other early plain film signs is not an entirely reliable indicator of necrosis. (Fig. 11-12). The inflammatory phase may persist for weeks.

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FIG 11-12 Anteroposterior projection of the pelvis demonstrating a small radiodense epiphysis on the reading right. These changes indicate ischemic necrosis of the epiphysis (Legg-Calvé-Perthes disease) in this child.

During this time, gross architectural changes to the dead bone begin to develop. The stricken bone softens and may collapse under the stresses of normal use. With this collapse, the involved articular surface becomes deformed (Figs. 11-13 and 11-14). Subchondral fractures that interrupt the cartilaginous cap of the bone allow joint fluid to intrude into the subchondral ischemic bone. This fluid intrusion may produce a subchondral lucency defect in the subchondral bone paralleling the subchondral cortical surface. This arciform lucency is known as the “crescent sign” on plain films (Fig. 11-15). The crescent sign is considered the most reliable early plain film sign of epiphyseal infarction.24 Larger regions of bony collapse may develop, appearing as semilunar radiolucent defects extending from the articular cortex. The defects have been likened to configuration of a bite mark, known as the “bite sign.” The Gage sign is a variation of the bite sign and is visualized as a radiolucent defect of bone (often shaped as a V) appearing at the lateral margin of the involved epiphysis. As this series of gross architectural changes occurs, the healing response begins. Articular collapse is common (see Fig. 11-20).

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FIG 11-13 Avascular necrosis. A, The first radiograph of this 32-year-old woman appears normal. B, However, 1 year later, clear signs of necrosis are evident by the increased radiodensity of the femoral head and the flattened appearance of the femoral head’s articular cortex (arrow).
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FIG 11-14 A and B,

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Feb 16, 2016 | Posted by in RESPIRATORY IMAGING | Comments Off on Hematologic Bone Diseases
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