MSK Flashcards
Osteomyelitis. Sickle cell disease predisposes to x infection.
Salmonella infection
x% of mycobacterial osteomyelitis cases involve the spine (x disease).
Forty percent of mycobacterial osteomyelitis cases involve the spine (Pott disease)
Infarction of bone and marrow is relatively common. It can be limited to the medullary cavity or involve both the medulla and cortex.
x and x are the two most common causes, but many other conditions also predispose to osteonecrosis, including …
Fractures and corticosteroid administration
alcohol abuse, bisphosphonate therapy, connective tissue disease, chronic pancreatitis, Gaucher disease, pregnancy, radiation therapy, sickle cell crisis, tumors, and dysbarism (e.g., decompression sickness).
Osteomyelitis denotes inflammation of x, virtually always secondary to infection.
bone and marrow
Soft tissue abscesses may also form after periosteal rupture, and these can channel to the skin as draining sinuses. Dead bone, or x, can crumble and release fragments into the sinus tract.
As the inflammatory process evolves, chronic inflammatory cells recruited during the first week release cytokines that stimulate bone resorption, fibrous tissue ingrowth, and peripheral deposition of reactive bone. This new bone can form a living shell, or x, around the devitalized, infected bone
sequestrum
involucrum
The location of bone infections is influenced by the osseous vascular circulation, which varies with age.
In neonates, x vessels penetrate the growth plate, resulting in frequent infection of the x.
In older children, involvement of the x is typical.
The x are more commonly involved in adults, after growth plate closure, in which merger of metaphyseal and epiphyseal vessels provides a route for bacterial spread.
metaphyseal, metaphysis, epiphysis, or both
metaphysis
epiphyses and subchondral regions
Septic arthritis
In neonates, contiguous spread from underlying epiphyseal osteomyelitis is relatively common.
x arthritis predominates in children younger than 2 years of age.
x is the main causative agent in older children and adults, while x is prevalent during late adolescence and young adulthood.
Individuals with sickle cell disease are prone to x infection at any age.
H. influenzae
S. aureus
gonococcus
Salmonella
Proliferative x affecting small vessels with a surrounding plasma cell–rich infiltrate is characteristic of all stages of syphilis
endarteritis
Manifestations of syphilis
Spondyloarthropathies are a heterogeneous group of disorders unified by the following features:
- Absence of rheumatoid factor
- Pathologic changes in the ligamentous attachments (i.e.entheses) rather than synovium
- Sacroiliac joint involvement
- Association with HLA-B27
- Bony proliferation leading to ankylosis
x is a heterogeneous group of disorders of unknown cause that present with arthritis before 16 years of age and persist for at least 6 weeks
Juvenile idiopathic arthritis (JIA)
Comparative Features of Osteoarthritis and Rheumatoid Arthritis
The lesions of x stem from degeneration of the articular cartilage and disordered repair.
OA
Osteopenia refers to decreased bone mass; osteoporosis is defined as osteopenia that is severe enough to significantly increase the risk of fracture.
Radiographically, osteoporosis is considered bone mass at least x standard deviations below mean peak bone mass in young adults.
Osteopenia is x standard deviations below the mean
2.5
1 to 2.5
Categories of Generalized Osteoporosis
Osteomalacia and rickets are manifestations of impaired x
The hallmark of osteoporosis is x
mineralization of bone matrix.
histologically normal bone that is decreased in quantity.
Most examples of undermineralized matrix result from abnormal vitamin D metabolism or vitamin D deficiency
Rickets refers to the disorder in children, in whom it interferes with the deposition of bone in the growth plates. Osteomalacia is the adult counterpart, in which bone formed during remodeling is undermineralized and predisposed to fractures.
Hyperparathyroidism causes increased
bone resorption.
Parathyroid hormone (PTH) has a central role in calcium homeostasis through the following effects:
- Activation of osteoclasts, increasing bone resorption and calcium mobilization. PTH mediates the effect indirectly by increasing RANKL expression on osteoblasts.
- Increasing calcium resorption by the renal tubules
- Increasing urinary phosphate excretion
- Increasing synthesis of active vitamin D, 1,25 (OH)2-D, by the kidneys, thereby enhancing intestinal calcium absorption and mobilizing bone calcium by inducing RANKL expression on osteoblasts
Symptomatic, untreated primary hyperparathyroidism manifests with three interrelated skeletal abnormalities:
osteoporosis, brown tumors, and osteitis fibrosa cystica
The term renal osteodystrophy describes the collective skeletal changes that occur in chronic renal disease, including those associated with dialysis.
The manifestations include many of the entities described earlier including
(1) osteopenia/osteoporosis, (2) osteomalacia, (3) secondary hyperparathyroidism, and (4) growth retardation
Classification of Gout
Only about 10% of individuals with hyperuricemia develop gout. Other factors linked to disease include the following:
- Age of the individual and duration of the hyperuricemia, as gout usually appears after 20 to 30 years of hyperuricemia
- Male sex
- Genetic predisposition, including X-linked HGPRT abnormalities and primary gout, which has a multigenic pattern of inheritance
- Alcohol consumption
- Obesity
- Drugs (e.g., thiazides) that reduce urate excretion
Paget disease is a disorder marked by
increased, but disordered and structurally unsound, bone mass
Classification of Major Nonhematopoietic Primary Bone Tumors
By definition, osteoid osteomas are less than x in diameter. They are most common in x and have a predilection for the appendicular skeleton, with about 50% involving the cortex of the x. A thick rim of reactive cortical bone may be the only radiographic clue. Despite their small size, osteoid osteomas present with severe nocturnal pain that is probably caused by prostaglandin E 2 (PGE2 ) produced by the proliferating osteoblasts and is relieved by aspirin and other NSAIDs.
Osteoblastomas are larger than x, typically involve the posterior spine (laminae and pedicles), cause pain that is unresponsive to aspirin, and do not induce reactive cortical bone.
?differences in treatment
2 cm
young men in their teens and 20s
femur or tibia
2 cm
Osteoid osteoma can be treated by radiofrequency ablation, but osteoblastoma usually requires curettage or en bloc excision.
The age distribution of osteosarcoma is x
bimodal, with 75% occurring before 20 years of age.
A smaller peak occurs in older adults, in whom it is frequently associated with predisposing conditions such as Paget disease, bone infarcts, and prior radiation (sometimes called secondary osteosarcomas)
- RB mutations are present in up to 70% of sporadic osteosarcomas; germline RB mutations confer a 1000-fold increased risk of osteosarcoma.
- TP53 is mutated in the germline of individuals with Li-Fraumeni syndrome, who have a greatly increased incidence of osteosarcoma.
Osteosarcoma
Although any bone can be involved, tumors usually arise in the x
metaphyseal region of the long bones; almost 50% are near the knee in the distal femur or proximal tibia
Giant cell tumors are treated by x, but x recur locally. Although up to 4% metastasize to the lungs, these can regress spontaneously and are seldom fatal.
The RANKL inhibitor denosumab has shown promise as an adjuvant therapy.
curettage
40% to 60%
Fibrous dysplasia
Clinical patterns …
The lesions arise during skeletal d ment and appear in several distinctive but sometimes overlapping clinical patterns:
- Monostotic: involvement of a single bone
- Polyostotic: involvement of multiple bones
- Mazabraud syndrome: fibrous dysplasia (usually polyostotic) and soft tissue myxomas
- McCune-Albright syndrome: polyostotic disease, associated with café-au-lait skin pigmentations and endocrine abnormalities, especially precocious puberty
Rhabdomyosarcoma is a malignant mesenchymal tumor with skeletal muscle differentiation.
Four subtypes are recognized:
alveolar (20%), embryonal (50%), pleomorphic (20%), and spindle cell/sclerosing (10%). Alveolar and embryonal subtypes of rhabdomyosarcoma are the most common soft tissue sarcoms a of childhood and adolescence, usually appearing before 20 years of age.
, are the most common sarcomas of adulthood.
Liposarcomas, malignant tumors of adipose tissue
Lipoma, a benign tumor of fat, is the most common soft tissue tumor in adults.
Clinical Features of Soft Tissue Tumors
Chondroblastoma histology
Nodules of mature cartilage surrounded by highly cellular tissue
Chicken wire calcification (calcs surrounding chondroblasts; pathognomonic
