unit xii musculoskeletal functionbbf07

7/31/2019 Unit XII Musculoskeletal FunctionBBF07

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Unit XII

MUSCULOSKELETAL FUNCTION


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Structure and Function of

Skeletal System Framework for attachment of muscles, tendons,

and ligaments

Protects and maintains soft tissues in properposition Provides stability for body Maintains bodys shape

Storage reservoir for calcium Contains hematopoietic connective tissue to form

blood cells


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Cartilage

Firm but flexible connective tissue consisting of cells and intercellular fibers embedded inamorphous gel-like material; smooth, resilientsurface and weight-bearing

Essential for growth before and after birth Postnatal, cartilage plays a role in growth of long

bones and persists as articular cartilage Elastic(ear),hyaline(most abundant,epiphysealplates), fibrocartilage(intervertebral discs)


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BoneIntercellular matrix impregnated with inorganic

calcium salts Organic matter 1/3 Inorganic salts 2/3

Can take up lead andantibiotics

Cancellous(spongy)

Compact(cortical)


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Osteogenic Cells Found in periosteum,

endosteum, epiphysealplate of growing bone

Active during normalgrowth, during fracturehealing, replacement of worn-out bone tissue

Both periosteum andendosteum contribute togrowth and remodeling of bone and are necessary forrepair


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Bone Cells Osteoblasts

Bone building cells are responsible for formation of bone matrix

Two stages include ossification and calcification

Secrete alkaline phosphatase Osteocytes

Mature bone cells actively involved in maintaining thebony matrix

Osteoclasts Responsible for the resorption of bone matrix and

release of calcium and phosphate from bone


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Bone Growth and Remodeling

Growth in diameter occurs in concentric rings Long bones are provide with specializes structure

called epiphyseal growth plate

As long bones grow, deeper layers of cartilagecells in growth plate multiply and enlarge, pushingthe articular cartilage farther away from themetaphysis and diaphysis of the bone

Allows for bone growth without changing shapeof bone or disrupting articular cartilage Cells in growth plate stop dividing at puberty at

which time the epiphysis and metaphysis fuse


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Hormonal Control of Bone

Formation and Metabolism PTH prevents serum calcium

levels from falling below andphosphate levels from rising

above physiologic conditions Calciotonin lowers blood

calcium levels by inhibitingrelease of Ca from bone to ECF

Vitamin D-actually steroidhormones increases intestinalabsorption of Ca and promotesaction of PTH


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Classification of Bones Long(arm), short(ankle),

flat(skull), irregular(jaw) Bone marrow occupies medullary

cavity of long bones andcancellous bone in vertebrae, ribs,sternum and pelvis; compositionvaries with age and site

Red bone marrow containsdeveloping RBC, graduallyreplaced with . . .

Yellow bone marrow composedof adipose tissues

Red persists in vertebrae, ribs,sternum and ilia


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Tendons, ligaments and joints Tendons connect muscles to bone; can appear as

cordlike structures or as flattened sheets calledaponeuroses

Ligaments connect moveable bones of joints Articulations-areas where two or more bones

meet. Prefix arthro means joint Synarthroses lack joint cavity; move little-skull,

rib, symphysis pubis Diarthroses-diarthrodial or synovial joints are

freely moveable Synovium secretes synovial fluid to act as

lubricant


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Diarthroidial Joints

Little movement,sacroiliac

Hinge, interphalangeal Many planes-hip Frequently affected by

rheumatic disorders

Articular cartilage ishyaline and healsslowly(diffusion)


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Blood supply,innervation, and

bursae Blood supply to synovial membrane rich healingand repair rapid and complete; innervated only byautonomic fibers, relatively free of pain fibers

local anesthesia As a rule, each joint of an extremity in innervated

by all the peripheral nerves that cross thearticulation referral of pain from one joint to

another Synovial membrane can form closed sacs that are

not part of joint-bursae. Prevents friction ontendon. Bunion is inflamed bursa of

metatarsophalaneal joint of great toe


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Injury and Trauma

Contusion - skin intact, ecchymotic Hematoma - large area of local hemorrhage Laceration - skin torn, continuity disrupted

Strain- stretching injury to muscle ormusculotendinous unit from mechanicaloverloading

Sprain abnormal or excessive movement of joint

with disruption to ligaments Formation of new collagen within 4-5 days, may

have original strength within 7 weeks, danger atdisruption in healing


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Injury and Trauma

Dislocations-loss of articulation of the bone endsin the joint capsule caused by displacement orseparation(congenital, pathological as well)

Shoulder permits a wide range of motion, a factorthat makes the joint relatively unstable; supportand movement of shoulder joint relies heavily onsupport of four relatively small muscle-tendongroups collectively know as the rotator cuff

Rotator cuff impingement tendonitis and tears arecommon among athletes


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Rotator cuff injury

Commonly injuredduring repetitive

movements that carryarm above shoulder-pitchers, swimmers,weight lifters

Partial-non surgical Full thickness-surgical


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Knee Injuries Subject to abnormal twisting

and compression Menisci are C-shaped plates of

fibrocartilage superimposed on

condyles of tibia and femur;stabilize, lubricate and load bear Cruciate ligament secures femur

to tibia in crossed position.Controls flexion and lateral

rotation. ACL is weaker-ofteninjured. Immediately disabling

Patellar subluxation anddislocation


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Hip Injuries

Ball/socket joint in which femoral head articulatesdeeply in acetabulum; vascular anatomy of

femoral head is critical - viability of femoral headmay lead to avascualar necrosis. Fractures

Major public health problem; falls most common cause Categorized by location; 90% are femoral neck and

intertrochanteric fractures Location important to blood flow


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Fractures

Sudden injury Fatigue or stress Pathological (10-15% of patients with

metastatic disease Classified according to location, type, and

direction or pattern of fracture line (seefigure 42-5)


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HEMATOMAFORMATION

Hematoma facilitatesthe formation of thefibrin meshwork that

seals off fracture siteand serves as aframework for theinflux of

inflammatory cells,fibroblasts, and newcapillary buds.


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FIBROCARTILAGINOUS CALLUS FORMATION

Formation of granulationtissue called procallus.Fibroblasts from theperiosteum, endosteumand red bone marrowproliferate and invadeprocallus. Fibroblastsproduce afibrocartilaginous soft

callus bridge that connectsbone fragments.

NO WEIGHT BEARING YET


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BONY CALLUS FORMATION

Fibrocartilaginouscartilage converted tobony callus. Newlyformed osteoblasts firstdeposit bone on outersurface of bone and thenmove toward fracturesite. Begins 3-4 weeks

after injury.

USUALLY SAFE TO REMOVE CAST


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Factors Affecting Bone Healing

Increased cellularity and vascularity in childsperiosteum improves healing

Fracture displacement, edema, arterial occlusion Type of bone, cancellous bone heals faster Degree of immobilization achieved Infection, malignancy, bone necrosis Amount of bone loss Age, nutrition, meds, diseases Malunion, delayed union, nonunion


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Complications of fractures and

other musculoskeletal injuries Compartment syndrome Tissue compromise from pressure in the

muscle compartment Hallmark symptom is pain out of proportion

to the original injury Five Ps


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Fat Embolism

FES refers to a constellation of clinicalmanifestations resulting from fat droplets in smallblood vessels of lung or other organs after a longbone fracture or other major trauma. Releasedfrom bone marrow or adipose tissue at fracture siteinto venous system; rare

Respiratory failure, cerebral dysfunction and skinpetechiae(does not blanch); symptoms within afew hours to 3-4 days. Initial findings subtlechange in behavior and disorientation

Stabilize fractures early


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Osteomyelitis

Acute or chronic infection Direct contamination, seeding

through bloodstream(hematogenous),vascular insufficiency

Staphylococcus most common-produces a collagen binding adhesionmolecule allowing it to adhere toconnective tissue elements of boneand ability to internalize and survive

in osteoblasts making themicroorganism resistant to antibiotics

Sequestrum-infected dead boneseparated from living bone


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Osteonecrosis

Death of bone segment caused by interruption of blood supply to marrow, medullary bone, orcortex; proximal femur, distal femur and proximalhumerus

Common complicating disorder of sickle celldisease, steroid therapy(5-25%), and hip surgery

Results from ischemia but mechanisms vary;steroids unclear may increase intraosseouspressure with vascular compression, sickle cellthrombosis


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Neoplasms Benign include osteoma,

chrondroma, osteochrondroma, andgiant cell

Osteosarcoma-peak during teens,bones with maximum growthvelocity;localized pain and swelling

Ewings sarcoma Metastatic-skeletal metastases are

most common malignancy of

osseous tissue:spine, femur, pelvis,ribs, sternum, humerus, skull

Breast, lung, prostate , kidney andthyroid are most common. 50% of bone must be destroyed beforelesion is visible on plain radiograph


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Metabolic Bone Disease

Bone integrity depends on a process of boneresorption and formation or bone remodelingwhich is continuous thru life

25% of cancellous bone replaced each year and3% or compact bone; proceeds in cycles that cantake 4 months

Osteoclasts resorb old bone and osteoblasts formnew bone

Mechanical stress, extracellular calcium andphosphate levels and hormones, local growthfactors and cytokines influence

RANK ligand may play role as chemicalmessenger


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Osteoporosis Classified as primary(postmenapausal women or elderly) or

secondary(endocrine or genetic disorder) Enhanced bone resorption relative to bone formation; varies

with age, sex, nutritional status and genetic predisposition Maximal bone mass achieved at 30; loss is 1%/year in

menopausal women; AA less prone than caucasians/Asians Greatest losses occur in areas containing abundant cancellous

bone such as spine and femoral neck Alcohol is a direct inhibitor of osteoblasts and may also

inhibit calcium absorption. Prolonged use of medication that increases calcium excretion

such as antacids and anticonvulsants Premature and low birth weight infants at risk Female athletes- poor nutrition, amenorrhea, estrogen lack


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Osteoporosis

Changes occur in the diaphysis and metaphysis of thebone; diameter of bone enlarges causing the outersupporting cortex to thin; resembles porcelain vase

First manifestations are pain accompanied by skeletalfractures-vertebral compression, hip, pelvis, humerus

Fractures represent end stage of disease Wedging and collapse of vertebrae causes height loss

and kyphosis(hump)

Monitor with bone mass density studies Prevention and early detection critical:Regular

exercise and 1500 mg calcium in post menopausalwomen


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Rheumatoid Arthritis Systemic inflammatory disease that attacks joints by

producing proliferative synovitis that leads todestruction of articular cartilage and underlying bone

0.3-1.5% of population; women 2-3X Cause not established; genetic predisposition and

immunologically mediated Pathogenesis is an aberrant immune response that leads

to synovial inflammation and destruction of jointarchitecture

May be initiated by activation of CD+4 helper T cells,release of cytokines and antibody formation

70-80% have rheumatoid factor (RF) autoantibody

Joint and extra-articular manifestations


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Systemic Lupus Erythematosus

Chronic inflammatory disease affecting any organsystem 1 in 2000, higher incidence in females, AA, Latins, and

Asians

Cause unknown but characterized by formation of autoantibodies and immune complexes; B cellhyperactivity and increased antibodies against self

Genetic, hormonal, immunologic andenvironmental(drug induced such as hydralazine andprocainamide)

Great imitator: musculoskeletal, skin, cardiovascular,lungs, kidneys, CNS, RBC and platelets

ANA testing with history and exam


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Osteoarthritis(OA)

-Formerly DJD; most prevalentform and leading cause of disability and pain in elderly

-Primary or secondary-Progressive loss of articularcartilage and synovitis resultfrom inflammation causedwhen cartilage attempts torepair itself -Creates osteophytes or spurswhich cause joint pain,stiffness, and loss of motion


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Pathogenesis of OA Resides in the homeostatic mechanism that maintains

the articular cartilage Plays two roles: (1) smooth weight bearing surface

and (2) transmits the load down to the bonedissipating mechanical stress

Composition and mechanical properties of cartilageare changed

Chemical messengers such as cytokines stimulate

production and release of proteases that aredestructive to joint structure, more injury results andrepair mechanism is inadequate; portions becomecompletely eroded and synovial membrane

inflammation


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Ankylosing Spondylitis, Gout,and Osteomalacia will not be

covered on the exam

unit xii musculoskeletal functionbbf07

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