Bone Conditions Flashcards
Describe a greenstick fracture
Incomplete, extends partway thro width of bone following bending stress;
bone fails on tension side; compression side intact (compare to torus fracture)
Describe Torus (buckle) fracture
Axial force applied to immature bone = cortex buckles on compression (concave) side + fractures
Tension (convex) side remains solid (intact)
What is Achondroplasia
Failure of longitudinal bone growth (endochondral ossification) = short limbs
Membraneous unaffected (large head relative to limbs)
Most common cause of short-limbed dwarfism
How does achondroplasia occur
Constitutive activation of fibroblast growth factor receptor (FGFR3) inhibits chondrocyte proliferation
>85% of mutations sporadic (AD, homozygosity lethal)
Risk factor for achondroplasia
Increased paternal age
What is osteoporosis
Trabecular (spongy) and cortical bone lose mass despite normal bone mineralization and lab values (serum Ca, phosphate)
How does osteoporosis occur
Increased bone resorption (increased osteoclast # and activity) related to decreased estrogen levels and old age
Name causes of secondary osteoporosis
Drugs (eg, steroids, alcohol, anticonvulsants, anticoagulants, thyroid replacement therapy) or other conditions (eg, hyperparathyroidism, hyperthyroidism, multiple myeloma, malabsorption syndromes, anorexia)
How is osteoporosis diagnosed
Bone mineral density measurement by DEXA at the lumbar spine, total hip, and femoral neck, with a T-score of ≤ −2.5/by a fragility fracture (eg, fall from standing height, minimal trauma) at hip or vertebrae
Prophylaxis for osteoporosis
Regular weight-bearing exercise and adequate Ca2+ and vitamin D intake throughout adulthood
Tx for osteoporosis
Bisphosphonates, teriparatide, SERMs, rarely calcitonin; denosumab (monoclonal antibody against RANKL)
What can osteoporosis lead to
Vertebral compression fractures (acute back pain, loss of height, kyphosis
Can also present w fractures of femoral neck, distal radius (Colles)
Define osteopetrosis
Failure of normal bone resorption due to defective osteoclasts = thickened, dense bones that are prone to fracture
Mutation that occurs in osteopetrosis and its result
(E.g carbonic anhydrase II) impairs ability of osteoclast to generate acidic env needed for bone resorption
Overgrowth of cortical bone fills marrow space = pancytopenia, extramedullary hematopoiesis
Can result in cranial nerve impingement, palsies due to narrowed foramina
X-ray in osteopetrosis
Diffuse symmetric sclerosis (bone-in-bone, “stone bone”)
Tx of osteopetrosis
Bone marrow transplant is potentially curative as osteoclasts are derived from monocytes
Define osteomalacia + cause
Defective mineralization of osteoid (osteomalacia) or cartilaginous growth plates (rickets, only in children)
Commonly due to Vitamin D deficiency
X-rays in osteomalacia/rickets
Osteomalacia: osteopenia, pseudofractures
Rickets: epiphyseal widening, metaphyseal cupping/fraying
Presentation of rickets
Children have pathologic bow legs (genu varum), beadlike costochondral junctions (rachitic rosary), craniotabes (soft skull)
Describe the pathophysiology of osteomalacia/rickets
Decreased vitamin D = Decreased serum calcium = increased PTH secretion and decreased serum phosphate
Hyperactivity of osteoblasts = increased ALP
Define osteitis deformans
Aka Paget disease
Common, localized disorder of bone remodeling caused by increased osteoclast activity followed by increased osteoblast activity = poor quality bone
*Serum Ca, phosphate, PTH are normal
*Increased ALP
Describe the findings of osteitis deformans
Mosaic pattern of woven and lamellar bone (osteocytes within lacunae in chaotic juxtapositions)
Long bone chalk-stick fractures
Hat size can be increased due to skull thickening
Hearing loss from skull deformity
What can Paget disease result in
Increased blood flow from increased AV shunts may cause high-output heart failure
Increased risk of osteosarcoma
Describe the stages of Paget disease
Early destructive (lytic): osteoclasts
Intermediate (mixed): osteoclasts/blasts
Late (sclerotic/blastic): Osteoblasts
May enter quiescent phase
Tx of Paget
Bisphosphonates
Define AVN of bone + where its most common and why
Infarction of bone and marrow, usually very painful
Most common site is femoral head (watershed zone) bc insufficiency of medial circumflex femoral artery
Causes of AVN of bone
“CASTS Bend LEGS”
glucoCorticoids, chronic Alcohol use, Sickle cell disease, Trauma, SLE, “the Bends” (caisson/decompression disease), LEgg-Calve-Perthes, Gaucher, Slipped capital femoral epiphysis
What lab findings are found in osteoporosis
Decreased bone mass
Lab values normal
Lab findings (Ca, PO, ALP, PTH) in osteopetrosis
normal/decreased serum Ca
Dense, brittle bones (Ca decreased in severe, malignant disease)
Lab findings (Ca, PO, ALP, PTH) in Paget
Increased ALP
Abnormal “mosaic” bone architecture
Lab findings (Ca, PO, ALP, PTH) in osteitis fibrosa cystica (primary hyperparathyroidism)
Increased serum Ca, ALP, PTH
Decreased phosphate
“Brown tumors” due to fibrous replacement of bone, subperiosteal thinning
Idiopathic or parathyroid hyperplasia, adenoma, carcinoma
Lab findings (Ca, PO, ALP, PTH) in osteitis fibrosa cystica (secondary hyperparathyroidism)
Increased phosphate, ALP, PTH
Decreased serum Ca
Often as compensation for CKD (decreased phosphate excretion and production of activated vitamin D)
Lab findings (Ca, PO, ALP, PTH) in osteomalacia/rickets
Decreased serum Ca, phosphate
Increased ALP, PTH
Soft bones; vitamin D deficiency also causes 2° hyperparathyroidism
Lab findings (Ca, PO, ALP, PTH) in hypervitaminosis D
Inc serum Ca, phosphate
Decreased PTH
Caused by oversupplementation or granulomatous disease (eg, sarcoidosis)
Describe the type of tumour, location of osteochondroma
Most common benign tumour in males <25
Found in metaphysis of long bones
Characteristics of osteochondroma
Lateral bony projection of growth plate (continuous with marrow space) covered by cartilaginous cap
Rarely transforms to chondrosarcoma
Describe the type of tumour, location of osteoma
Benign, in middle age
Found in surface of facial bones
Characteristics of osteoma
Associated w Gardner syndrome
Describe the type of tumour, location of osteoid osteoma
In adult males < 25
Found in cortex of long bones
Characteristics of osteoid osteoma
Presents as bone pain (worse at night) that is relieved by NSAIDs
Bony mass (< 2 cm) with radiolucent osteoid core
Describe the type of tumour, location of chondroma
Benign tumour of cartilage found in medulla of small bones of hand and feet
Describe the type of tumour, location of giant cell tumor
Benign tumour found in 20-40 year olds
In epiphysis of long bones (often knee region)
Characteristics of giant cell tumour
Locally aggressive benign tumor
Neoplastic mononuclear cells that express RANKL and reactive multinucleated giant (osteoclastlike) cells. “Osteoclastoma”
“Soap bubble” appearance on x-ray
