Step 1 - MSK 1

denniskwinn's version from 2015-04-25 16:10


NerveCause of injuryMotor deficitSensory deficitSign
Axillary (C5,C6)Fractured surgical neck of humerus, dislocation of humeral headArm abduction at shoulderover deltoid muscleflattened deltoid
Radial (C5-C8)Fracture at midshat of humerus; “Saturday night palsy” (extended compression of axilla by back of chair or crutchesWrist extension, finger extension at MCP joints, supination, thumb extension and abductionPosterior arm and dorsal hand and dorsal thumbwrist drop
Median (C6-C8,T1) Proximal lesion: fracture of supracondylar humeruslateral finger flexion, wrist flexionDorsal and palmar aspects of lateral 3.5 fingers, thenar eminenceApe hand
Median (C6-C8,T1) Distal lesionCarpal tunnel syndrome; dislocated lunateOpposition of thumbDorsal and palmar aspects of lateral 3.5 fingersUlnar deviation of wrist upon wrist flexion
Ulnar (C8,T1) proximal lesionFracture of medial epicondyle of humerusMedial finger flexion, wrist flexionMedial 1.5 fingers, hypothenar eminenceRadial deviation of wrist upon flexion
Ulnar (C8, T1) Distal lesionFracture of hook of hamate (falling onto outstretched hand)Abduction and adduction of fingers (interossei), Adduction of thumb, Extension of 4th and 5th fingers (lumbricals)Medial 1.5 fingers, hypothenar eminenceulnar claw hand (when asked to straighten fingers) - Pope’s blessing/ hand of benediction
Musculocutaneous (C5-C7)Upper trunk compressionFlexion of arm at elbowLateral forearm


NerveCause of InjuryMotor DeficitSensory Deficit
ObturatorAnterior hip dislocationThigh adductionMedial thigh
FemoralPelvic fractureThigh flexion and leg extensionAnterior thigh and medial leg
Common peronealPelvic fractureThigh flexion and leg extensionAnterolateral leg and dorsal aspect of foot
TibialKnee TraumaFoot inversion and plantarflexion; toe flexionsole of foot
Superior glutealPosterior hip dislocation or poliothigh abduction (positive trendelenburg sign)
Inferior glutealPosterior hip dislocationCan’t jump, climb stairs, or rise from seated position


Question Answer
Draw 368, 374, 378, 387, 388
Epidermis layers out to inCorneum, Lucidium, Granulosum, Spinosum, Basalis
Zona occludens tight junction - prevents diffusion across paracellular space; composed of claudins and occludins
Zona adherens (intermediate junction) surrounds perimeter just below zona occludens; cadherins connect to actin (CADherins are Ca dependent ADhesion molecules)
Macula adherens (desmosome) small. discrete sites of attachment; cadherins, connect to intermediate filaments
Gap junction allows adjacent cells to communicate-electric and metab functions
Hemidesmosomeconnects cell to underlying extracellular matrix, has integrins that binds laminin to basement membrane
Unhappy triad knee injuryclipping from the lateral side - damage to MCL, ACL and lateral (not medial) meniscus.
Pudendal nerve block (to relieve pain of pregnancy) location ischial spine.
Appendix location 2/3 of the way from the umbilicus to the anterior superior Iliac spine= McBurney's point
Lumbar puncture locationiliac crest.
Rotator cuff muscles Supraspinatus (abduction) , Infraspinatus (lateral rotation) , Teres minor (lateral rotatoin, adduction) , Subscapularis (medial rotation, adduct)
Shoulder dermatomeC4
Lateral upper arm to lateral elbow dermatomeC5
Lateral forearm to index finger dermatomeC6
Middle finger and palm dermatomeC7
Medial hand/palm dermatomeC8
Medial writs to mid upper arm dermatomeT1
Medial upper arm dermatomeT2
Palm inner thumb, finger 2,3 innervationmedian
Back of lateral hand, outer thumb innervationradial
Medial hand finger 4.5 and 5ulnar nerve
Lesion of upper trunk of brachial plexusErbs palsy
Lesion of Lower trunk of brachial plexusKlumpke’s palsy
Long thoracic nerve lesionswinged scapula
Axillary nerve lesiondeltoid paralysis
Posterior cord lesionwrist drop
Radial nerve lesionSaturday night palsy (wrist drop, flexor posturing)
Musculocutaneous nerveDifficulty flexing elbow, variable sensory loss
Median nerve lesionThumb function problem
Ulnar lesionPope’s blessing claw hand when told to straigthen fingers
Causes of mononeuropathyCompression, trauma, diabetes, vasculitis, radiation, inflammation (e.g VZV)
Erb-Duchenne palsyTraction 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 syndromeAn 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
Ulnar clawDistal ulnar nerve lesion → loss of medial lumbrical function ; 4th and 5th digits are clawed ("Pope's blessing").
Median clawDistal 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.
Ape HandProximal median nerve lesion → loss of opponens pollicis muscle function→ unopposable thumb (inability to abduct thumb), hence "ape hand."
Klumpke’s total clawLesion 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 actionsinnervation of the Brachioradialis, Extensors of the wrist and fingers, Supinator, and Triceps
Thenar musclesOpponens pollicis, Abductor pollicis brevis, Flexor pollicis brevis.
Hypothenar muscles Opponens digiti minimi, Abductor digiti minimi, Flexor digiti minimi.
Dorsal interosseous musclesabduct the fingers .
Palmar interosseous musclesadduct the fingers.
Lumbrical musclesflex at the MP joint
Repetitive elbow traumaDegenerative injury -repeated use leads to tiny tears in tendons and muscles. May be inflammatory-e.g., lateral epicondylitis (tennis elbow), medial epicondylitis (golf elbow).
Z linewhere the actins link together
M lineMiddle of the myosins
H zonecontains M line (Where the myosins are)
I bandcontains the Z line
Muscle contraction1.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 muscleSlow 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


Question Answer
Endochondral ossificationLongitudinal bone growth . Cartilaginous model of bone is first made by chondrocytes. Osteoclasts and osteoblasts later replace with woven bone and remodel to lamellar bone
Membranous ossificationFlat bone growth (skull ,facial bones, and axial skeleton). Woven bone formed directly without cartilage Later remodeled to lamellar bone
Source of osteoblastsmesenchymal stem cells in periosteum
AchondroplasiaFailure 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
Secondary osteoperosisDisease (Hypercortisol), Drugs (Heparin), Hypogonadism (Hypopituitarism), Malnutrition (Anorexia), Space travel
OsteoperosisReduction of primarily trabecular (spongy) bone mass in spite of normal bone mineralization
Type I osteoperosisPostmenopausal; ↑ bone resorption due to ↓ estrogen levels. Estrogen replacement is controversial as prophylaxis (side effects).
Type II Osteoperosissenile - affects men and women > 70 y
Osteoperosis signsVertebral crush fractures: acute back pain, loss of height, kyphosis (dowager’s hump), Femoral neck fracture (distal radius fractures)
Osteoperosis prophylaxis exercise and Vit D and calcium ingestion before age 30, stop smoking
Osteoperosis treatmentestrogen and/or calcitonin; bisphosphonates or pulsatile PTH for severe cases - glucocorticoids are contraindicated
OsteopetrosisFailure 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.
Osteomalacia/ricketsDefective 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 cysticaCaused 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 findingsBone Pain, Headaches, Hearing loss, ↑ Hat Size
Paget’s disease treatmentBisphosphonates, Calcitonin
Paget’s disease diagnosisThickened bone radiograph w/shaggy areas of radiolucency,↑ ALP, Normal Ca and Phos
Lab values in OsteoperosisAll normal levels - ↓ bone mass
Lab values in osteopetrosisall 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 dysplasiaBone is replaced by fibroblast , collagen, and Irregular bony trabeculae. Affects many bones.
McCune-Albright syndrome 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 tumorMetastasis (breast most common primary site)
Treatment of primary bone tumorsurgery mostly
OsteomaAssociated with Gardner's syndrome (FAP). New piece of bone grows on another piece of bone, often in the skull, facial bones
Osteoid osteomaInterlacing trabeculae of woven bone surrounded by osteoblasts. < 2 cm and found in proximal tibia and femur. Most common in men <25 y
Osteoid osteoma sxsevere pain, typically at night, relieved by aspirin, round lucency(nidus) on radiograph, CT scan - xray not diagnostic
Osteoblastomasame 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
OsteochondromaMost 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
EnchondromaBenign 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
Osteosarcoma2nd 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
Ewings sarcomaAnaplastic 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).
ChondrosarcomaMalIgnant 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 tumormultiple myeloma
Bone tumors in epiphysisGiant cell tumor (osteoclastoma)
Bone tumors in metaphysisOsteochondroma, Osteosarcoma
Bone tumors in diaphysisOsteoid osteoma, Ewing’s sarcoma
Bone tumors intramedullaryEnchondroma, Chondrosarcoma