Sarcoidosis

Chapter 50 discusses sarcoidosis, which is a systemic disease that often involves the musculoskeletal system. The radiographic changes seen in sarcoid of the phalanges are characteristic, however, involvement of bone and other tissues may be occult or nonspecific. Tissue sampling is often required for diagnosis, especially when sarcoid resembles metastatic disease. The organ systems most commonly involved in sarcoid are the lungs, lymph nodes, skin and eyes. Radiographs are the standard first study used to evaluate symptomatic hand or foot involvement. Uncommon, palpable soft tissue lesions are best evaluated by MRI. Systemic corticosteroids are the primary treatment of active sarcoidosis.

Mixed Connective Tissue Disease

Chapter 43 discusses mixed connective tissue disease (MCTD), which is a complex disease with overlapping features of systemic sclerosis, systemic lupus erythematosus, and polymyositis. MCTD is rare and more common in women than in men, characterized by the presence of high titers of a distinctive autoantibody, called anti-U1 ribonucleoprotein (RNP). Arthritis and myositis are common features. Radiographs are standard in the initial evaluation of symptomatic extremities. Ultrasound is useful to evaluate multiple joints. MRI is especially sensitive in detection of myositis. Medical therapy is targeted to specific organ involvement and extent of disease activity. There are large variations in clinical features, response to therapy, and outcomes.

Alkaptonuria (Ochronosis)

Chapter 39 discusses alkaptonuria (ochronosis), a rare hereditary metabolic disease that leads to the deposition of homogentisic acid. Homogentisic acid accumulation causes damage to connective tissues; leads to formation of renal, urethral, and prostatic calculi; causes cardiovascular abnormalities; and causes arthropathy. Ochronotic arthropathy is the articular manifestation of alkaptonuria with the most common clinical sites of involvement being the spine, knees, and hips. Diagnosis of the disease is made by demonstration of homogentisic acid in the urine. Radiography is the standard method for detecting changes associated with alkaptonuria. CT can aid in the detection of intervertebral disc calcification.

Fracture Fixation

Chapter 27 discusses fracture fixation. Although many fractures are managed nonoperatively, others require various forms of surgical intervention. Fracture fixation can be conservative or surgical. The goal is to stabilize the fractured bone, enable fast healing, and return early mobility and function of the injured extremity. Orthopedic hardware permits stabilization of the fractured bone, expediting healing and early mobility. Percutaneous pins and wires can be used to apply traction to a fracture. External and internal fixation are used when more advanced operative intervention is required and encompass external fixator devices, pins/wires, screws, plates, and intramedullary nails/rods. Hardware is unfortunately susceptible to complication, including loosening, migration, fracture, and infection.

Radius and Ulna Trauma

Chapter 15 discusses radius and ulna trauma. Forearm fractures are common and may be isolated to the ulna or more commonly involve both bones. Fractures of the radius or ulna are usually because of direct trauma and are often displaced. Depending on their complexity, isolated fractures of the ulnar diaphysis may be treated nonoperatively or operatively whereas both bone (radius and ulna) diaphyseal fractures are typically treated operatively. Galeazzi fracture-dislocations are comprised of radial diaphyseal fractures in association with distal radioulnar joint (DRUJ) dislocation/subluxation. Monteggia fracture-dislocations are comprised of a proximal ulnar fracture in association with radial head dislocation. In type IV Monteggia injuries, there is an additional fracture of the proximal radial diaphysis. Essex-Lopresti fracture-dislocations include radial head fractures in association with DRUJ dislocation/subluxation.

Elbow Trauma

Chapter 14 discusses elbow trauma. The elbow is a hinge synovial joint that consists of the ulnohumeral, radiocapitellar, and proximal radioulnar joints. The olecranon and radial head fractures are common and may occur secondary to direct trauma or with transmitted forces from an injury such as a fall on an outstretched hand. The elbow is the second most commonly dislocated large joint of the body. Radiographs are the mainstay in the evaluation of acute injuries and treatment follow-up. CT examination is helpful in preoperative assessment of complex fractures/injuries. All elbow dislocations are initially close reduced and splinted. Further conservative versus operative treatment depends on complexity of injury.

Pigmented Villonodular Synovitis

Chapter 68 on pigmented villonodular synovitis (PVNS) reviews the clinical features, pathology, and imaging characteristics of PVNS. Epidemiology and treatment are briefly discussed. Diffuse intraarticular PVNS, localized intraarticular PVNS, and localized extraarticular PVNS, also referred to as giant cell tumor of the tendon sheath, are discussed. PVNS is considered to be a benign neoplastic disorder. Joints, tendon sheaths, and bursae may be involved. The knee is the most common location of the intraarticular form. The characteristic MRI finding is low signal intensity synovial proliferation or mass with blooming from susceptibility artifact on gradient echo images, secondary to the presence of hemosiderin.

Synovial Chondromatosis

Chapter 67 discusses synovial chondromatosis, which is a neoplastic process that can lead to a monoarticular erosive arthropathy. It is divided into primary and secondary forms, and this chapter focuses on primary synovial chondromatosis. It can occur in joints, bursae and tendon sheaths, and can be calcified or noncalcified. The knee and hip are the most commonly involved joints. Pathologically, there is subsynovial hypertrophy with cartilaginous nodules. These cartilaginous bodies can detach and may calcify and ossify. The pathophysiology, epidemiology and treatment are discussed, and the imaging features of this disease on radiographs, CT, and MRI are described.

Radiation Changes

Chapter 64 discusses radiation changes. Radiation has long been used to treat soft tissue and bone neoplasms. In many instances, radiation can cause changes in the bones and soft tissues that are recognizable on imaging studies and should not be mistaken for aggressive processes. The effects of radiation may vary based on whether the patient is skeletally mature at the time of exposure. Some patients with prior radiation exposure are at risk for developing benign and malignant neoplasms. This chapter discusses the effects of radiation on the skeletal system, noting different effects based on skeletal maturity, as well as mentioning some of the radiation-induced neoplasms.

Metastatic Disease

Chapter 63 discusses metastatic disease. Metastatic disease from carcinomas accounts for approximately 70% of malignant tumors involving the skeleton. The most common primary tumors that metastasize to bone are prostate and breast carcinomas and are termed osteotropic. Other tumors with a propensity for skeletal metastasis include lung, renal, bladder, thyroid, and lymphomas. Prostate, breast, renal cell, and lung carcinomas account for up to 80% of skeletal metastases. Patients with metastatic bone lesions may be asymptomatic or may present with localized bone pain, pathologic fracture, neurologic impingement, or an associated soft tissue mass. Imaging plays an important role in detection, diagnosis, prognosis, planning, and treatment response of metastatic bone lesions. This chapter focuses on imaging strategies to detect and characterize metastatic osseous lesions from malignant tumors.