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Osteoporosis

Metabolic disorders of the skeleton affect bone as a tissue, so that all bones are involved histologically, although radiologic features are not always evident. Such diseases can be caused by genetic, endocrine, nutritional, or biochemical disorders. Osteoporosis is the most common metabolic bone disease. It is a quantitative abnormality of bone (“too little bone”), in contrast to rickets and osteomalacia, which are qualitative abnormalities of bone…

Myelofibrosis

Etiology Myelofibrosis is a chronic myeloproliferative disorder characterized by bone marrow fibrosis and the development of extramedullary hematopoiesis. Myelofibrosis can occur as a primary disease entity (also termed idiopathic myelofibrosis or agnogenic myeloid metaplasia ) or can occur secondary to diffuse bony metastatic disease, infections (e.g., tuberculosis and fungal infections), sarcoidosis, myeloma, and lymphoma. The etiology of primary myelofibrosis is unknown, but an increased incidence of…

Thalassemia

Etiology In 1925, Cooley and Lee described a series of patients suffering from severe anemia associated with splenomegaly and bone abnormalities. The name thalassemia , after fusion of the Greek words thalassa meaning “sea” and aima meaning “blood,” underlined the Mediterranean origin of the patients who were first described. Thalassemia is not a single disease but rather a group of diseases related to an inherited abnormality…

Sickle Cell Anemia

Etiology Sickle cell anemia, first described in a 20-year-old dental student from Grenada by Herrick in 1910, is the most common single-gene disorder in African Americans. Dr. Linus Pauling and his team identified the cause of SCA as a single substitution in the gene encoding of the β-hemoglobin (Hb) chain (valine substituted for glutamic acid). An individual with two abnormal chromosomes was designated as Hb SS…

Hemophilia and Related Disorders

Etiology Of all causes of hemophilia, types A and B are most associated with intraosseous and intraarticular bleeding. Hemophilia A (classic hemophilia) results from a deficiency of factor VIII. Hemophilia B (Christmas disease) is due to a functional deficiency of plasma thromboplastin component (factor IX). These disorders are both X linked and, therefore, manifest clinically in men but are carried by women. Prevalence and Epidemiology Classic…

Ischemic Bone Lesions

Ischemic bone lesions cover a wide spectrum of conditions with variable clinical and imaging findings in which oxygen delivery to the bone and marrow cells is impaired at least to some degree. Epiphyseal ischemic lesions have been more extensively investigated because of their clinical importance. MRI has definitely contributed to the detection and in-depth knowledge of the natural history of epiphyseal osteonecrosis. Etiology Ischemic bone lesions…

General Principles of MRI of the Bone Marrow

This chapter addresses general concepts on MRI of the bone marrow, with emphasis on common normal and abnormal marrow patterns. MRI plays a key role in marrow imaging because of its high sensitivity for detecting focal or diffuse alterations in marrow content. MRI of the bone marrow is also performed for other purposes, including medullary lesion characterization, disease staging, prognosis, and monitoring of treatment response. MRI…

Atypical Infections

Mycobacterial Infection In the 1950s, the atypical mycobacteria were recognized as human pathogens. They are morphologically similar to Mycobacterium tuberculosis but have different colonial characteristics. Because there is no evidence of human-to-human transmission, the atypical mycobacteria do not pose public health hazards. Etiology The mycobacterial organisms known to cause musculoskeletal system infections in humans are M. avium intracellulare–M. avium complex (found in soil, water, swine, cattle,…

HIV Infection and AIDS

Human immunodeficiency virus (HIV) infection is almost universally fatal if left untreated, leading to and being the etiologic agent of the acquired immunodeficiency syndrome (AIDS). The HIV epidemic is prevalent worldwide and is constantly evolving, being influenced by geographic, socioeconomic, and antiretroviral treatment–related factors. The Centers for Disease Control and Prevention (CDC) has published the current case definition criteria, which include three different categories of clinical…

Pediatric Infections

Introduction Musculoskeletal infections in children are relatively common occurrences. However, in the pediatric population, such infections may produce nonspecific clinical signs and symptoms and can occur in the absence of clinically apparent features, such as swelling and erythema. This diagnostic challenge is further compounded by the potential inability for a young child to assist in localizing a symptomatic region. Prompt recognition of bone and joint infectious…

Diabetic Pedal Infection

Introduction Etiology Although hematogenous spread is the most common cause of osteomyelitis in most other areas of the body, contiguous spread and direct implantation are the most common in the foot and ankle. Direct implantation can occur from puncture wounds or deep lacerations, open fractures, and surgery or injection procedures. The vast majority of osteomyelitis involving the foot and ankle in diabetic patients, however, occurs through…

Spinal Infection

Spinal Infection Etiology Spinal infection is a multicausal disease. The three most common are hematogenous spread, direct spread, and direct inoculation, which is usually iatrogenic. Arterial hematogenous spread can be due to an infectious focus anywhere in the body. This can be responsible for pyogenic and nonpyogenic infections and is the most common source of infection. It was previously believed that hematogenous spread can occur through…

Appendicular Infection

Osteomyelitis is infection of bone or bone marrow. It is usually caused by bacterial infection, less frequently by viruses and fungi and, rarely, parasites. It is subdivided into acute, subacute, and chronic stages, depending on the clinical presentation, which, in essence, reflects the interaction between the causative organism and the host's response ( Fig. 65-1 ). Despite the tremendous advancement in the imaging of bone infection,…

Soft Tissue Infection: Cellulitis, Pyomyositis, Abscess, Septic Arthritis

Infections of the soft tissues range clinically from indolent, low-grade conditions to fulminant disease that may be life-threatening within a matter of hours. A wide range of organisms can produce an infection, although there are common culprits. Clinical confusion may occur because the presentation may mimic tumor or degenerative disease and vice versa. Infection should always be in the mind of those involved in the diagnosis…

Noninflammatory Intraarticular Pathology

Pigmented Villonodular Synovitis Introduction Etiology Pigmented villonodular synovitis (PVNS) is a benign proliferative synovial disorder that can occur in a diffuse or localized form and in both intraarticular and extraarticular locations. Although PVNS typically occurs diffusely within a joint, nodular forms exist and, when present, are commonly referred to as localized nodular synovitis. Extra-articular PVNS can involve tendon sheaths or bursae. Localized nodular synovitis of tendon…

Neuropathic Osteoarthropathy

Neuropathy results from functional abnormalities or structural insults to the axons (sensory, motor, or combined), the myelin, or both. The insensate neuropathic joint is liable to arthrosis, fractures, alignment deformities, abnormal function, ulcer, and infection. Predilection for skeletal location is influenced by whether the insult is central or peripheral and the degree to which sensory, motor, and/or autonomic function is insulted. Because diabetic pedal neuroarthropathy (Charcot…

Crystal-Related Arthritis

A number of crystals are associated with joint disease ( Fig. 61-1 ). The major culprits are calcium pyrophosphate dihydrate (CPPD) and hydroxyapatite (HA), a basic calcium phosphate (BCP). The focus in this chapter is on the disorders associated with crystal deposition in and around joints, except for true gout, which is discussed in Chapter 60 . Open full size image FIGURE 61–1 Example of crystals…

Gout

Etiology Gout is a disease with manifestations relating directly from the deposition of monosodium urate monohydrate crystals or uric acid from hyperuricemic body fluids. In humans, urate is a nonmetabolized byproduct of purine metabolism and is excreted via the kidneys (two thirds) and gastrointestinal tract (one third). The development of gout is related to both polygenic inheritance (specifically, the inability of one's kidneys to increase urate…

Diffuse Idiopathic Skeletal Hyperostosis and Ossification of the Posterior Longitudinal Ligament

Diffuse idiopathic skeletal hyperostosis (DISH), a term proposed by Resnick is the widely accepted name describing a common disorder affecting mostly elderly persons and characterized by increased bone formation at multiple sites in the spine and peripheral skeleton. Although the radiographic changes of DISH may be florid, clinical symptoms are often mild or absent, therefore the importance of the imaging appearance in establishing this diagnosis. Ossification…

Ochronosis

Etiology Ochronosis is the bluish-black discoloration that can be seen in connective tissues of patients with alkaptonuria, a rare disorder caused by the absence of homogentisic acid (HGA) oxidase. The absence of this enzyme causes a buildup of HGA in connective tissues, including the sclera, cornea, articular cartilage, intervertebral disks, tendons, and ligaments. The accumulated HGA is polymerized and oxidized, causing the characteristic pigmentation of the…