Skeletal System

Axial Skeleton 80 bones

Appendicular Skeleton 126 bones

Bony composition Compact bone: outer portion Medullary canal- inner portion made of cancellous bone. Bone marrow is located within medullary canal ad it is interspaced with trabeculae. Trabeculae: web like bony structure. Can be seen on a properly exposed radiograph. Diploe: cancellous bone located within the skull. Red bone marrow: found in normal adult bones of the trunk. At 20 years of age the majority is replaced by yellow bone marrow which is primarily fat. Osteoblasts: bone forming cells that line the medullary canal and are interspaced throughout the peristeum. Responsible for bone growth and thickening, ossification and regeneration. Osteoclasts: break down bone to enlarge the medullary canal and allow for bone growth.

Endochondral Ossification Diaphysis: refers to the shaft portion of the long bones. Primary site of ossification. Epiphysis: expanded end portion and it’s the secondary site of ossification. Metaphysis: growth zone between the epiphysis and diaphysis. Diaphysis: refers to the shaft portion of the long bones. Primary site of ossification. Epiphysis: expanded end portion and it’s the secondary site of ossification. Metaphysis: growth zone between the epiphysis and diaphysis. There is a growth plate between the metaphysis and epiphysis made of cartilage. Appears radiolucent until child grows and it calcifies. Peristoeum: fibrous membrane that encloses all the bone except the joint surfaces. The more physical stress the bone is under the more thickly the compact bone becomes.

Congenital and Hereditary Diseases

Osteogenesis Imperfecta Often called brittle bone disease Hereditary or congenital Serious disease Bone cortex is thin and porous, and trabeculae are thin, delicate and widely separated X-ray demonstrates various fractures in various stages of healing and general decrease in bone mass Deficient formation of osseous tissue, skin , slcera, inner ear and teeth. 2 Main groups: 1) Congenita- present at birth and there are multiple fractures at birth. Limb deformities and dwarfism that may lead to death. 2) Tarda- fractures may not appear until some years after birth and then generally stop once adulthood is reached. They often have hearing disorder that persists called otoslcerosis. Otosclerosis is abnormal connective tissue around auditory ossicles.

Osteogeneis Imperfecta

Achondroplasia Most common inherited disorder of the skeletal system Results in bone deformity & dwarfism Normal trunk size & shortened extremities Usually no more than 4ft tall Clinical manifestation: Lumbar lordosis, bowed legs, bulky forehead with hypoplasia narrowing of foramen magnum causing neural compression Achondroplasia Most common inherited skeletal disorder. Results in bone deformity and dwarfism. Does not skip generations and 50% of passing it to children. Cartilage on epiphysis of the long bones does not convert to bone; impairs longitudinal growth of the bones. Normal trunk size and shortened extremities. Usually no taller than 4 ft. Other symptoms include extreme l-spine lordosis, bowed legs, bulky forehead, and narrowing of the foramen magnum.

Achondroplasia

Osteopetrosis Bones are abnormally heavy and compact but brittle All bones are affected by most changes occur in long bones of extremities, vertebrae, pelvis and base of skull X-rays demonstrate increase in thickness and density of bony cortex. Increase in the # and size of trabeculae, reduction of the marrow space Increase in bone density and defective bone contour. Bones are heavy and compact but brittle. All bone are affected but primarily the bones of the extremities, vertebrae, pelvis and base of the skull. Radiographs show increase density and thickness of bony cortex as well as an increase in the number and size of trabeculae with reduction of bone marrow space.

Osteopetrosis

Scoliosis Lateral curvature of the spine Does not usually become visible until adolescents Affects girl more Lateral curvature of the spine. Convex to the RT on the t-spine and convex to the LT on the l-spine. 80% are idiopathic Can generate complications such as cardiopulmonary complications, degenerative spinal arthritis, fatigue, joint dysfunction syndromes. Non-structural scoliosis-results from uneven leg length or postural changes due to chronic pain elsewhere in the body.

Scoliosis

Rotoscoliosis

Transitional Vertebra Often called Lumbar Ribs Takes on characteristics of both vertebrae on each side of a major division of the spine 1st lumbar may have a rib At C7 there may be a cervical rib

Cervical Ribs & Lumbar Ribs AT C7 it can exert pressure on brachial nerve plexus or subclavian artery requiring removal.

Anencephaly Congenital abnormality Brain and cranial vault do not form Results in death shortly after birth Can be diagnosed with US before they are born

Anencephaly

Inflammatory Diseases

Rheumatoid Arthritis Chronic autoimmune that may fluctuate in severity Overgrowth of the synovial tissues X-ray shows soft tissue swelling & osteoporosis of affected bone. Bone erosion & decalcification 7 criteria for diagnosis of RA Morning stiffness in and around the joints Simultaneous soft tissue swelling or fluid of at least 3 joint areas lasting for at least 6 weeks and observed by and MD Arthritis hand joints-at least one area swollen in a PIP, MCP or wrist joint for at least 6 weeks. Rheumatoid nodules or lumps of tissue Abnormal amounts of serum RF Symmetric arthritic- simultaneous involvement of the same joint areas on both sides of the body for at least weeks. Radiographic changes demonstrating bone erosion and decalcification

Rheumatoid Arthritis Occurs in 30-40 years and affects women 3x’s more than men. As the disease progresses cortical erosion with joint space narrowing occurs b because of overgrowth of synovial tissue in the articualr spaces. This damage makes joint unstable and leads to deformity caused by displacement of bones. Can result in subluxation and dislocation eventually leads to fusing. Sometimes surgical intervention is needed to correct these pathologies. synovium excision dislocation correction joint reconstruction joint replacements

Osteoarthritis Most common form of arthritis Articular cartilage degenerates & gradually is worn away exposing underlying bone Ostephytes & bone spurs are on x-rays Osteoarthritis Affects men/women equally. Asymptomatic until 50’s. Generally affects the LG weight bearing joints such as the hip and knee Loss of cartilage appears as joint narrowing. Overgrowth of cartilage occurs in the peripheral surfaces of the joint and calcifies- bone spurs. The bone spurs or osteophytes are what distinguish one arthritis from the other. NSAIDS and exercise are the best treatment.

Osteoarthritis

Osteomyelitis Infection of the bone & bone marrow Symptoms & signs include fever, heat in the affected area, & dull pain X-rays demonstrate loss of bone calcium and soft tissue swelling Osteomyelitis Pathogenic microorganisms spread via the bloodstream. (hematogenous) Contiguous infetions- burns, sinus disease, peridontal infection, soft tissue infection and peripheral vascular disease. NUC med and MRI are better for imaging this pathology.

Osteomyelitis

Ankylosing Spondylitis Progressive form of arthritis affecting the spine X-ray shows bilateral narrowing & fuzziness of the SI joints Calcification of the bones of the spine with ossification of the vertebral ligaments Ankylosing Spondylitis Progressive type of arthritis mainly affecting the spine. Usually affects men 20-40 years old. Symptoms: low back pain at night, morning stiffness, weight loss, low grade fever, fatigue and anemia. Early radiographic signs include narrowing and fuzziness of SI joints. Eventually there are no SI joints and disease progresses up the spine. Disk space calcifies and bone of the spine fuses. Treated with NSAIDS, exercise and postural training.

Ankylosing Spondylitis

Is an inherited metabolic disorder in which excessive amounts of uric acid is produced & deposited in the joint and adjacent bone Bone changes include erosion & overhanging edges Gout Inherited metabolic disorder in which uric acid is deposited into the joint and adjacent bone. Occurs more frequently in men and most commonly in the metatarsalphalangeal joints of the great toe. The crystallization causes an inflammatory action. Treatment includes medications to promote excretion of uric acid or to inhibit the production of uric acid.

Gout

Spondylolisthesis Slipping of the body of the vertebra Symptoms are similar to those of a herniated disk Refers to the anterior slipping of the body of the vertebra. Symptoms are similar to those of a slipped disk. 90% occur at L5-S1, best detected on a lateral projection.

Spondylolisthesis

Osteochondroma Benign bone tumor Affects women more than men Asymptomatic Excessive bone growth Cortex of osteochondroma blends in with normal bone and growth protrudes up & away from nearest joint Most common benign bone tumor Affects men 3x’s more than women. Arises in the metaphysis. Most commonly involves lower femur and upper tibia. Cortex blends with normal bone, growth protrudes upward and away form the nearest joint and most commonly in the knee. Many times it is asymptomatic until trauma occurs.

Osteochondroma

Osteosarcoma Most common primary malignancy of the skeleton Highly aggressive and most often occurs in the bone marrow X-ray appears as a sunray or sunburst Osteosarcoma Most frequently found in the metahysis of the long bones and 50% affect knees. 75% of patients are under 20 years Most commonly in bone marrow and it is highly aggressive.

Osteosarcoma

Bone Cyst Idiopathitic disease and is not a true neoplasm Consists of numerous blood filled arterivenous communications Most common treatment is surgical removal Bone Cyst Generally occurs in the metaphysis of long bones in patients under 20 years. Slow growing. Symptoms include pain and swelling at the site of cyst. Cystic growth causes thinning of the bony cortex that is apparent radiographically. It is a well-circumscribed lesion associated with soft tissue extension and peristeal bulging.

Bone Cyst

MRI Superior contrast resolution for soft tissue detail Modality of choice for soft tissue tumor Extremely useful in eval of joints MRi detects a larger number of musculoskeletal subtleties with higher resolution imaging Bone marrow imaging is better than nuc med scans for subtle abnormalities

CT Can be performed quickly & noninvasively Defines extent of fractures and dislocations Superior to MRI for cortical bone and visualization of bony detail Gives better bone detail than plain x-ray Has been largely replaced by MRI for soft tissue

Nuclear Medicine Has advantage over CT & MRI because it can scan the whole body at one time Can show if an injury is old or new Still the standard for examination of metastatic processes because it demonstrates metabolic reaction of bone to the disease process Is more sensitive than comparative radiographic studies