x-rAY- SKELETAL SYSTEM PATHOLOGY

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Achondroplasia; The most common inherited disorder affecting the skeletal system which results in bone deformity and dwarfism. It results from diminished proliferation of cartilage in the growth plate (decreased enchondral bone formation). This autosomal dominant condition does not affect membranous bone formation and does not skip generations. Individuals with this gene have about a 50% chance of transmitting it to their children. Because of a disturbance in endochondral bone formation, the cartilage located in the epiphyses of the long bones does not convert to bone in the normal manner, impairing the longitudinal growth of the bones. An adult with achondroplasia is usually no more than 4 feet in height, with lower extremities usually less than half the normal length. The individual has short limbs, which contrast with the nearly normal length of the trunk. Other characteristic physical features include a large head with frontal bulging, saddle nose, a prognathous (jutting) jaw, and prominent buttocks that give the false impression of lumbar lordosis, and a narrowing of the foramen magnum within the skull causing neural compression. Typical radiographic findings include progressive narrowing of the interpedicular distances from above downward, the opposite of normal, and scalloping of the posterior margins of the lumbar vertebral bodies. The decreased enchondral bone formation may make the long bones appear short and thick with a widened metaphysis (Erlenmeyer flask deformity). In some instances sonography may be used for prenatal diagnosis of achondroplasia. CT is beneficial in demonstrating the degree of spinal narrowing caused by spondylosis and the changes in the vertebral column.  Bone age radiographic studies may be used to help monitor patients with growth hormone (GH) deficiency. Occasionally, orthopedic surgery may be necessary in management of complications associated with achondroplasia.

Closed Fracture (formerly referred to as a simple fracture) is one in which the skin is not penetrated, thus reducing the chance of infection.

Complete fracture  a fracture that results in discontinuity between two or more fragments.

Developmental Dysplasia of the Hip also known as Congenital hip dysplasia, results from incomplete acetabulum formation caused by physiologic and mechanical factors. Physiologically the fetus is exposed to increased hormone levels during delivery. Mechanically, as the fetus grows and occupies more space, the amount of amniotic fluid decreases, placing gentle pressure on the infant. Hip dysplasia is more common in females. Upon pediatric assessment of the hip, when the leg is flexed and abducted, the hip may “pop” out of joint and a “click” is felt or heard. The tendons and ligaments responsible for proper femoral head alignment are affected. Because the acetabulum does not completely form, the head of the femur is displaced superiorly and posteriorly. DDH can be unilateral or bilateral. Sonography may be used to diagnose this anomaly early in life through visualization of the cartilaginous structures of the hip. Conventional hip radiographs are often difficult to interpret in the neonate. This anomaly should be treated early with immobilization through casting or splinting the affected hip to allow the acetabulum to grow and form a normal joint. Left untreated, uneven limb length, hip muscle weakness, and an uneven gait can result.

Incomplete Fracture only part of the bony structure gives way, with little or no displacement. A common example is the greenstick fracture, or a torus fracture, (commonly referred to as a buckle fracture). Incomplete fractures may also occur in demineralized bone, such as occurs with osteoporosis. The bone in question breaks only part of the way through, resulting in a sharp angular deformity without displacement.

Lordosis Forward curvature of the lumbar spine. Poor posture or disease may cause the lumbar curve to be abnormally accentuated—a condition known as “sway back,”. This condition is frequently seen during pregnancy as the woman adjusts to changes in her center of gravity. It may also be secondary to traumatic injury or a degenerative process of the vertebral bodies.

March fracture A fracture that occurs at a site of maximal strain on a bone, usually connected with some unaccustomed activity (also known as a stress, or insufficiency fracture). Stress (fatigue) fractures are the result of repeated stresses to a bone that would not be injured by isolated forces of the same magnitude. The type of stress fracture and the site where it occurs vary with the activity. Regardless of location, the activities resulting in stress fractures are usually strenuous. Stress fractures frequently occur in soldiers during basic training (“march” fracture). The most common sites are the shafts of the second and third metatarsals, the calcaneus, the proximal and distal shafts of the tibia. The earliest pathologic process in a stress fracture is osteoclastic resorption, followed by the development of periosteal callus in an attempt to repair and strengthen the bone. Radionuclide bone scans can demonstrate a stress fracture before it can be detected on plain radiographs. MRI, used only for cases with indeterminate radiographic findings, is highly sensitive for detecting stress fractures. In some cases, MRI has higher specificity than radionuclide bone scans.

Osteoma Is a less frequent benign growth most commonly located in the skull. These lesions are composed of very dense, well-circumscribed, normal bone tissue, and are rarely larger than 2 cm in diameter. They usually project into the orbits, paranasal sinuses or mandible. They are generally slow-growing tumors of little significance unless they cause obstruction, impinge on the brain or eye, or interfere with the oral cavity. Diagnosis of these tumors may be incidental on radiographs taken because of the pain produced by bone expansion.

Pathologic fracture occurs in bone at an area of weakness caused by such processes as tumor, infection, or metabolic bone disease. Pathologic fractures are those occurring in bone that has been weakened by a preexisting condition. The most common underlying process is metastatic malignancy or multiple myeloma. In children, developmental diseases, such as osteogenesis imperfecta or osteopetrosis, or nutritional deficiencies (rickets, scurvy) may result in pathologic fractures. Pathologic fractures also may occur when there is a benign cause of weakened bone, such as simple bone cyst, enchondroma, aneurysmal bone cyst, and fibrous dysplasia. Metabolic disorders causing a diffuse loss of bone substance (osteoporosis, osteomalacia, hyperparathyroidism) also make the skeleton more susceptible to injury. Clinically, pathologic fractures arise from minor trauma that would not affect normal bone. Radiographically the fracture crosses an area of abnormal thinning, expansion, or bone destruction. The most common sites of pathologic fractures are the spine, femur, and humerus, areas in which metastatic disease is most common. CT or MRI scanning may detect a subtle change in the abnormal bone that is obscured by an abnormal lytic area or by sclerotic changes on plain radiographs.

Patients with suspected pathologic fractures must be handled with extreme care lest the radiographer cause either further injury to the bone in question or an additional pathologic fracture in another area. Often, pathologic fractures may be the first indication of the presence of pathology.

Spondylolisthesis a forward displacement of a vertebra over a lower segment due to a congenital defect or fracture in the pars interarticularis, usually of the fifth lumbar over the sacrum or the fourth lumbar over the fifth. Radiographically demonstrated on a plain lateral projection of the lower lumbar spine.

Subluxation  a partial dislocation, often occurring with a fracture. The ankle and vertebral column, especially the cervical spine, are common sites of subluxations.

Supracondylar Fracture A transverse fracture above the condyles of the humerus or femur. Elbow injuries in children may result in a fracture of the distal end of the humerus, above the level of the epicondyles (60% of all elbow fractures in children.) The distal fragment and its soft tissues are pulled posteriorly by the triceps muscle. This posterior displacement effectively ‘bowstrings’ the brachial artery over the irregular proximal fracture fragment. In children, this is a relatively devastating injury: the muscles of the anterior compartment of the forearm are rendered ischemic and form severe contractions, significantly reducing the function of the anterior compartment and flexor muscles

Trimalleolar Fracture involves the medial and posterior lip of the tibia and the lateral malleolus of the fibula, and usually represents fracture dislocations.

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