RADIOGRAPHY- SKELETAL SYSTEM PATHOLOGY

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Aseptic Necrosis Cystic and sclerotic degeneration caused by injury, not infection. A disease of growing children and adolescents, but it also occurs at a high rate in elderly persons. Certain portions of the growing skeleton are at increased risk and undergo infarction more often than others. The carpal bones are especially vulnerable because of their complex blood supply. In elderly persons, the most important site of aseptic necrosis is the head of the femur.

Compound fracture also known as an open fracture as the overlying skin is disrupted. Although it is a clinical distinction, the radiographic demonstration of bone clearly protruding through the skin and the presence of air and soft tissues about the fracture site on radiographs obtained immediately after the injury are highly suggestive of an open fracture. Since the bone has penetrated the skin, this type of fracture leaves an open route for bacteria to enter from outside the body which may lead to infection.

Gout a disorder in which an increase in the blood level of uric acid leads to the deposition of uric acid crystals in the joints, cartilage and kidneys. In gouty arthritis, sodium urate crystals are deposited in the soft tissues of the joints. Gout most often affects the joints of the feet, most commonly at the base of the great toe. The crystals irritate and erode the cartilage, causing inflammation, swelling, and acute pain. Eventually, the crystals destroy all of the joint tissues.

Greenstick fracture an incomplete fracture with the opposite cortex intact. Greenstick fractures are found almost exclusively in infants and children under the age of ten because of the softness of their cancellous bone. The Torus fracture is a greenstick fracture in which the cortex bulges outward, usually in the metaphysis producing only a slight irregularity.

Impacted fracture a fracture in which one of the fragments is driven into the cancellous bone of another fragment. A common type of fracture of the humerus and femoral head.

Intertrochanteric fracture a fracture of the proximal femur located in the metaphyseal bone in the region between the greater and lesser trochanters. A Richard’s hip pinning procedure is done in the OR to fixate this type of fracture.

Osteomalacia refers to insufficient mineralization of the adult skeleton. The lack of a balance between osteoid formation and mineralization influencing bone quality results in either excessive osteoid formation or, more frequently, insufficient mineralization. Proper calcification of osteoid requires that adequate amounts of calcium and phosphorus be available at the mineralization sites. In osteomalacia, failure of calcium and phosphorus deposition in bone matrix may be attributable to an inadequate intake of, or to a failure of absorption of, calcium, phosphorus, or vitamin D. Vitamin D is necessary for intestinal absorption of calcium and phosphorus and may have a direct effect on bone. At times, the level of vitamin D is sufficient but is not used because of resistance to the action of the vitamin at end organs, such as the kidneys. Other non-nutritional causes of osteomalacia include chronic kidney failure and certain renal diseases in which calcium is lost to the urine and then bone breaks down as the body attempts to maintain a normal calcium level in the blood.

Paget’s disease (osteitis deformans) is one of the most common chronic metabolic diseases of the skeleton. Destruction of bone, followed by a reparative process, results in weakened, deformed, and thickened bony structures that tend to fracture easily. The disease, seen most commonly during middle life, affects men twice as often as women and has been reported to occur in about 3% of all persons older than 40 years of age. Although the destructive phase often predominates initially, there is more frequently a combination of destruction and repair in the pelvis and weight-bearing bones of the lower extremities. In its destructive phase, radiographically, it appears as areas of sharply demarcated lucencies. The reparative process may begin early and may be the prominent feature, often involving multiple bones. The radiographic appearance during this reparative process is mottled, and “cotton-wool” like. Paget’s disease affects particularly the pelvis, femurs, skull, tibias, vertebrae, clavicles, and ribs. The radionuclide bone scan is the most efficient method to visualize multicentric lesions.

Rheumatoid arthritis is a chronic systemic disease of unknown cause that appears primarily as a non-infectious inflammatory arthritis of the small joints of the hands and feet. Women are affected about three times more frequently than men, and the average age of onset in adults is 40 years. There is usually symmetric involvement of multiple joints, and the disease often progresses proximally toward the trunk until practically every joint in the body is involved. Rheumatoid arthritis begins as an inflammation of the synovial membrane. The excessive exudate, a result of the inflammation, causes proliferation of the synovium. The resulting mass of thickened granulation tissue causes erosion of the articular cartilage and underlying bony cortex, fibrous scarring, and even the development of ankylosis. The erosion occurs because the inflammatory cells produce lytic enzymes. A combination of the fusion of joint surfaces and an inflammatory laxity of ligaments leads to the development of crippling deformities in the end stage of the disease.

Scoliosis An abnormal lateral and rotational curvature of the spine. The lateral curves are usually convex to the right in the thoracic region and to the left in the lumbar region. There may be a secondary curve developed as compensation to the primary curve. Up to 80% of all scolioses are idiopathic and do not usually become visually apparent until adolescence, affecting females more frequently than males. The 20% of known causes are congenitally malformed vertebrae, chronic sciatica, paralysis of muscles on one side of the vertebral column, poor posture, or one leg being shorter than the other.

Spondylolysis refers to a cleft in the pars interarticularis that is situated between the superior and inferior articular processes of a vertebra in the area of the lamina. Occurring in about 5% of the population, these clefts are usually bilateral, most commonly involve the fifth lumbar vertebra, and predispose to the forward displacement of one vertebra on the other that may cause chronic back pain. Spondylolysis is the term for a defect in the pars interarticularis without displacement; if displacement occurs, the condition is called spondylolisthesis. It appears radiographically as a “collar” or “broken neck” on the “Scotty dog” and is demonstrated on an oblique projection of the lumbar spine.

Smith’s fracture a reverse “Colles’ fracture” with displacement toward the palmar aspect of the hand. A direct blow or fall with the wrist in hyperflexion is the usual mechanism of injury.

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