Traction or tear of the upper trunk of the brachial plexus (C5 and C6 roots); follows blow to shoulder or trauma during delivery. Findings: limb hangs by side (paralysis of abductors), medially rotated (paralysis of lateral rotators), forearm is pronated (loss of biceps). - Waiter’s tip
Klumpke’s palsy and thoracic outlet syndrome
An embryologic or childbirth defect affecting inferior trunk of brachial plexus (C8,TI ); a cervical rib can compress subclavian artery and inferior trunk, resulting in thoracic outlet syndrome: 1. Atrophy of the thenar and hypothenar eminences 2. Atrophy of the interosseous muscles 3. Sensory deficits on the medial side of the forearm and hand 4. Disappearance of the radial pulse upon moving the head to IL side
Distal ulnar nerve lesion → loss of medial lumbrical function ; 4th and 5th digits are clawed ("Pope's blessing").
Distal median nerve lesion (after branch containing C5- C7 branches off to feed forearm flexors) → loss of lateral lumbrical function; 2nd and 3rd digits are clawed.
Proximal median nerve lesion → loss of opponens pollicis muscle function→ unopposable thumb (inability to abduct thumb), hence "ape hand."
Klumpke’s total claw
Lesion of lower trunk (C8, Tl ) of brachial plexus → loss of function of all lumbricals; forearm finger flexors (fed by part of median nerve with C5-C7) and finger extensors (fed by radial nerve)are unopposed → clawing of all digits
Radial nerve actions
innervation of the Brachioradialis, Extensors of the wrist and fingers, Supinator, and Triceps
Degenerative injury -repeated use leads to tiny tears in tendons and muscles. May be inflammatory-e.g., lateral epicondylitis (tennis elbow), medial epicondylitis (golf elbow).
where the actins link together
Middle of the myosins
contains M line (Where the myosins are)
contains the Z line
1.Action potentIal depolarization opens voltage-gated Ca2+ → neurotransmItter release. 2. PostsynaptIc ligand binding→ muscle cell depolarization in motor end plate. 3. Depolarization travels along muscle cell and down the T·tubule. 4. Depolarization of voltage-sensitive dihydropyridine receptor, coupled to ryanodine receptor on SR, induces a Ca2+ release from (calcium-induced calcium release). 5 Released Ca2+ binds to troponin C, moving tropomyosin out of the myosin-binding groove on actin filaments. 6. Myosin releases bound ADP and is displaced on the actin filament (power stroke). Contraction results in H- and I-band shortening, but the A band remains the same length (A band is Always the same length, HIZ shrinkage).
Type 1 muscle
Slow twitch; red fibers due to ↑ mitochondria and myoglobin concentration (↑ oxidative phosphorylation ) → sustained contraction.
Type 2 muscle
Fast twitch; white fibers due to ↓ mitochondria and myoglobin concentration (↑anaerobic glycolysis); weight training results in hypertrophy of fast-twitch muscle fibers
Longitudinal bone growth . Cartilaginous model of bone is first made by chondrocytes. Osteoclasts and osteoblasts later replace with woven bone and remodel to lamellar bone
Flat bone growth (skull ,facial bones, and axial skeleton). Woven bone formed directly without cartilage Later remodeled to lamellar bone
Source of osteoblasts
mesenchymal stem cells in periosteum
Failure of longitudinal bone growth → short limb. Membranous ossification is affected → large sized head. Constitutive activation of fibroblast growth factor receptor (FGFR3) actually inhibits chondrocyte proliferation. > 85% of mutations occur sporadically and are associated with advanced paternal age, but the condition also demonstrates autosomal-dominant inheritance. Common cause of dwarfism. Normal Iife span and fertility . No treatment
Disease (Hypercortisol), Drugs (Heparin), Hypogonadism (Hypopituitarism), Malnutrition (Anorexia), Space travel
Reduction of primarily trabecular (spongy) bone mass in spite of normal bone mineralization
Type I osteoperosis
Postmenopausal; ↑ bone resorption due to ↓ estrogen levels. Estrogen replacement is controversial as prophylaxis (side effects).
Type II Osteoperosis
senile - affects men and women > 70 y
Vertebral crush fractures: acute back pain, loss of height, kyphosis (dowager’s hump), Femoral neck fracture (distal radius fractures)
exercise and Vit D and calcium ingestion before age 30, stop smoking
estrogen and/or calcitonin; bisphosphonates or pulsatile PTH for severe cases - glucocorticoids are contraindicated
Failure of normal bone resorption → thickened, dense bones that are prone to fracture. Bone defect is due to abnormal function of osteoclasts. Serum calcium, phosphate. and alkaline phosphatase (ALP) are normal. ↓ marrow space leads to anemia, thrombocytopenia, infection. Genetic deficlency of carbonic anhydrase II X-rays show "Erlenmeyer flask" bone that flare out. Can result in cranial nerve (visual and hearing loss) - impingement and palsies due to narrowed foramina.
Defective mineralization/calcifcation of osteoid→ soft bones. Vit D deficiency In adults → ↓ calcium levels → ↑ secretion of PTH, ↓ in serum phosphate. Reversible when vitD is replaced. Vit D deficiency in chIldhood causes rickets.
Osteitis fibrosa cystica
Caused by hyperparathyroidism. Characterized by "brown tumors" (cystic spaces lined by osteoclasts, filled with fibrous stroma and sometimes blood). High serum calcium, low serum phosphorus, and high ALP. - Commonly involves the jaw.
Paget’s disease (osteitis deformans)
Abnormal bone architecture caused by ↑ in both osteoblastic and osteoclastic activity. Possibly viral in origin (paramyxovirus is suspected). Serum calcium, phosphorus, and PTH levels are normal. ↑↑ ALP - Mosaic bone pattern; long bone chalk-stick fractures, ↑ blood flow from ↑ arteriovenous shunts may cause high-output heart failure. Ca lead to osteogenic sarcoma.
Paget’s disease clinical findings
Bone Pain, Headaches, Hearing loss, ↑ Hat Size
Paget’s disease treatment
Paget’s disease diagnosis
Thickened bone radiograph w/shaggy areas of radiolucency,↑ ALP, Normal Ca and Phos
Lab values in Osteoperosis
All normal levels - ↓ bone mass
Lab values in osteopetrosis
all normal serum levels, thickened dense bones
Lab values in osteomalacia/rickets
↓ serum Ca2+, ↓ Phosphate, normal ALP, ↑PTH, soft bones
Lab values in osteitis fibrosa cystica
↑ serum Ca, ↓ phosphate, ↑APL, ↑ PTH, brown tumors
Lab values in paget’s disease
↑ ALP, normal labs otherwise - abnormal bone architecture
Polyostotic fibrous dysplasia
Bone is replaced by fibroblast , collagen, and Irregular bony trabeculae. Affects many bones.
form of polyostotic fibrous dysplasia characterized by multiple unilateral bone Iesions associated with endocrine abnormalities (precocIous puberty) and unilateral pigmented skin lesions (cafe-a u-lait spots/ “coast of Maine" spots)
Most common bone tumor
Metastasis (breast most common primary site)
Treatment of primary bone tumor
Associated with Gardner's syndrome (FAP). New piece of bone grows on another piece of bone, often in the skull, facial bones
Interlacing trabeculae of woven bone surrounded by osteoblasts. < 2 cm and found in proximal tibia and femur. Most common in men <25 y
Osteoid osteoma sx
severe pain, typically at night, relieved by aspirin, round lucency(nidus) on radiograph, CT scan - xray not diagnostic
same morphologically as osteoid osteoma but larger and found in vertebral column
Giant cell tumor (osteoclastoma)
Occurs most commonly at epiphyseal end of long bones. Peak incidence 20-40 years of age. Locally aggressive benign tumor often around the distal femur, proximal tibial region (knee). Characteristic "double bubble" or "soap bubble" appearance on x-ray. Spindle-shaped cells with multinucleated giant cells. . . Pain, limited ROM
Most common benign bone tumor. Mature bone with cartilaginous cap. Usually in men < 25 years of age. Commonly originates from long metaphysis. Malignant transformation to chondrosarcoma is rare - typically in shoulder, knee
Benign cartilaginous neoplasm found intramedullary bone. Usually distal extremities (vs. Chondrosarcoma ) = cartilage cyst in bone marrow. . Small bones, 20-50yr. Many of these = risk for chondrosarcoma
2nd most common primary malignant tumor of bone (after multiple myeloma). Peak incidence in men 10- 20 years of age. Commonly found in metaphysis of long bones,often around distal femur, proximal tibial region (knee). Predisposing factor include Paget's disease of bone, bone infarcts, radiation, and familial retinoblastoma. . Codman's triangle or sunburst pattern (from elevation of periosteum) on x-ray. Poor prognosis, Mets to lungs
Anaplastic small blue cell malignanl tumor. Most common in boys < 15. Extremely aggressive with early mets, but responsive to chemotherapy. Characteristic "onion-skin" appearance in bone ("going out for eWing and onion rings). Commonly appears in diaphyis of long bone, pelvis, scapula, and ribs. 11: 2. Translocation. 11+ 22 = 33 (PalTi ck Ewing's Jersey number).
MalIgnant cartilaginous tumor. Most common in men 30-60. Usually in pelvis, spine, scapula, humerus, tibia, or femur. May be from osteochondroma. Expansile glistening mass within the medullary cavity
#1 primary malignant bone tumor
Bone tumors in epiphysis
Giant cell tumor (osteoclastoma)
Bone tumors in metaphysis
Bone tumors in diaphysis
Osteoid osteoma, Ewing’s sarcoma
Bone tumors intramedullary
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