disorders of the musculoskeletal system - lecture 31

Structural Support

Bones give the body its shape and framework. They allow us to stand, sit, and move in complex ways by maintaining structural integrity.

Bone (Osseous) Tissue

Connective tissue that provides:

- Support/protection

- Levers for muscle

- Mineral storage

Bone is well ______________ (Implication for healing?)

- blood/oxygen/nutrients: this is why we need the bone to be vascularized

vascularized

organic - extracellular matrix

Collagen fibers (~90%)- tensile strength

Ground substance (proteins and polysaccharides)- support and adhesion

inorganic salts - extracellular matrix

Calcium and phosphate

25% of bone’s volume, but half of its weight

compact bone

Outer shell

Densely packed, calcified extracellular matrix (more rigid)

Functional Unit: Osteon

Bones contain ______ compact and spongy bone in different proportions

both

Spongy Bone (trabecular, cancellous)

Inner bone

Light weight, lattice like pattern

Compressive (force absorption)

Functional Unit: Trabeculae

Trabeculae remodeled to align with ....

compressive forces

osteoprogentior cells

undifferentiated cells that differentiate into osteoblasts. found in the periosteum, endosteum, and epiphyseal growth plate of growing bones

osteoblasts

bone building cells that synthesize and secrete the organic matrix of bone. participate in calcification of the organic matrix

osteocytes

mature bone cells, for maintenance of bone matrix. play an active role in releasing calcium into blood

osteoclasts

bone chewing cells responsible for resorption (removal of bone mineral and organic matrix)

In normal bone, the remodeling cycle of resorption and formation is at __________

equilibrium

which of the following is an organic component of the bone matrix?

a. calcium

b. phosphate

c. collagen

d. magnesium

c. collagen

which statement correctly describes spongy (trabecular) bone?

a. forms the outer shell of bone

b. composed of densely packed osteons

c. also known as cortical bone

d. has a lightweight, lattice pattern

d. has a lightweight, lattice pattern

which bone cell type is responsible for bone resorption (bone chewing)

a. osteoclasts

b. osteoblasts

c. osteocytes

d. osteoprogenitor cells

a. osteoclasts

in norma;, healthy adult bone, the remodeling cycle is characterized by:

a. a constant increase in bone mass

b. an equilibrium between bone reabsorption and bone formation

c. a constant decrease in bone mass

d. no remodeling once the bone has matured

b. an equilibrium between bone reabsorption and bone formation

1. ___________ resorption of existing bone

Organic and inorganic components are removed, creating a _______-______ space in the osteon

Soluble factors (e.g. OPG) released during resorption aid in the recruitment of osteoblasts to the site

("__________")

1. Osteoclastic

2. tunnel like

3. reversal

___________ begin to deposit organic matrix (osteoid) on the wall of the osteon canal

Successive lamellae are deposited, and the canal attains relative proportions of original osteon

When they receive a signal, osteoblasts release RANKL (induces osteoclast activity)

Osteoblasts

RANKL

Receptor activator of nuclear factor kappa-Β ligand

Paracrine system that balances resorption and formation

1. _______

-- Produced by osteoblasts

-- Binds to RANK receptor and promotes activation of osteoclasts

2. ______________________

-- “Decoy” receptor to block RANKL activity to ensure balance

1. RANKL

2. Osteoprotegerin (OPG)

Dysregulation of the RANKL/OPG system plays a role in ...

pathogenesis of bone diseases

which statement best describes the role of RANKL in bone remodeling?

a. RANKL is produced by osteoclasts to inhibit osteoblasts

b. RANKL binds to the OPG receptor to stimulate bone formation

c. RANKL is produced by osteoblasts and promotes osteoclasts activation

d. RANKL acts as a decoy receptor for OPG, blocking osteoclasts

c. RANKL is produced by osteoblasts and promotes osteoclasts activation

osteoprotegrin (OPG) functions as a decoy receptor by:

a. binding to RANKL, thereby preventing osteoclast activation

b. binding to calcium to enhance bone calcification

c. stimulating osteoblasts to resorb bone

d. inhibiting collagen production in bone matrix

a. binding to RANKL, thereby preventing osteoclast activation

Cartilage

Chondrocytes & matrix

avascular - if its gone its gone

Ligaments and tendons

have a limited blood supply

(Implication for healing?)

Dense regular connective tissue

-- Inelastic collagen fibers

-- High tensile strength

tendonitis

Inflammation of a tendon where it attaches to or contacts a bone

Causes: Repetitive motion/overuse

Symptoms:

- Pain

- Tenderness

- Weakness

Treatments:

- Rest

- Occupational therapy &/or PT

Bracing and exercise

- Anti-inflammatory medications

- Surgery in severe cases (tears)

Strain

Stretching or partial tear in a muscle or muscle–tendon unit

Inflammatory response and fibrous tissue replacement at the site

Symptoms: Pain, stiffness, swelling, and local tenderness

Common sites: Lower back, neck, hamstring

Sprain

Involves ligaments or joint capsule

Due to abnormal or excessive movement of a joint

Symptoms: Pain, rapid swelling, discoloration, and limited function

Common sites: Ankle, knee (ACL), elbow

treatment for strain and sprain

Rest, Ice, Compression, and Elevation (RICE) --> Movement, Exercise, Analgesia, Treatment (MEAT)

The affected area may be immobilized until pain/swelling is reduced (24-48 hours)

Early diagnosis, treatment, and rehabilitation are essential in preventing weakening of injured area due to immobilization

compression: only at rest

Disruption in the continuity of a bone:

Causes: High compression, tension, shearing, bending, or torsion forces

which are bones best at resisting?

fractures

Further classified by:

- Open or closed

- Location

- Type or pattern of fracture line

what is an immediate concern with an open fracture?

infection

Greenstick

seen in children, partial break in bone continuity

types of fractures

fractures (2)

Pain, tenderness, swelling, loss of function, deformity of the affected part, abnormal mobility

Types of deformities (long bones)

- Angulation

- Shortening

- Rotation

X-ray confirms diagnosis, directs treatment

Treatment:

1. reduction

2. immobilization

3. preserve/restore function

which of the following best describes tendonitis?

a. inflammation of a tendon where it attaches to or contacts a bone

b. a complete rupture of a tendon

c. degeneration of joint cartilage

d. a chronic condition only seen in elderly patients

a. inflammation of a tendon where it attaches to or contacts a bone

which of the following is the best description of a sprain?

a. always leads to bone fractures

b. involves ligaments or joint capsule with pain and swelling

c. only involves muscle fibers

d. results exclusively from direct compact

b. involves ligaments or joint capsule with pain and swelling

a fracture that partially breaks the bone and is commonly seen in children is called:

a. spiral

b. oblique

c. greenstick

d. comminuted

c. greenstick

what is the immediate concern with an open (compound) fracture?

a. difficulty diagnosing the fracture on x ray

b. increased bone density

c. inability to reduce the fracture

d. possible infection due to bone exposure

d. possible infection due to bone exposure

stages of fracture healing

hematoma formation

Blood vessels in the bone and surrounding tissues bleed into and around the fragments forming a hematoma

Fibrin meshwork forms and seals the fracture site

-- Initiates healing process

fibrocartilaginous callus formation

Granulation tissue called procallus is formed

Fibroblasts invade the procallus

Fibroblasts produce soft callus bridge that connects bone fragments

Callus formed by end of 2nd or 3rd week, not strong enough for weight bearing

bony callus formation

Cartilage is ossified to form a bony callus

Formation of bone progresses toward the fracture site until a new bony sheath covers the callus

Fibrocartilage is converted to woven bone and gradually calcifies into mature bone

Begins 3 to 4 weeks after injury and continues for months later

remodeling

Dead bone is removed by osteoclasts

Compact bone replaces spongy bone

Excess material is removed and compact bone is laid to reconstruct the shaft

complication of fractures

Compartment Syndrome - complication of fracture

Increased pressure within limited space

Compromises circulation and function

-- Screen for signs

Nerve and muscle death in 8 hrs

Treatment: Relieve pressure (fasciotomy)

Wolff’s Law

a tissue adapts to the level of stress imposed upon it

-- Strengthening and weakening- depending on level of stress

What can a patient do to regain mass & function after immobilization (disuse atrophy)?

Physical and/or occupational therapy

Return to daily activities

Structured exercise

rhabdomyolysis

Direct or indirect severe muscle injury (e.g., trauma, statins, excessive alcohol) and release of myoglobin into the blood

Symptoms:

- Excessive muscle pain, muscle weakness

- Dark red or brown urine

- Serum creatine kinase and myoglobin are elevated

Complications: Acute renal failure, fatal heart rhythm disturbances, hypovolemic shock, disturbances of electrolyte balance, metabolic acidosis, hyperthermia, compartment syndrome

Overall mortality rate is ~5%

Treatments:

IV fluids

Fasciotomy

Stop drug use (if applicable)

osteomyelitis

Acute or chronic infection of the bone and marrow

Pyogenic - Staphylococcus aureus is most common cause

-- Hematogenous- Originates with infectious organisms that reach the bone through the bloodstream.

-- After open fracture, bacteria from patient’s skin run high risk of establishing colonies inside the bone

Symptoms:

- Bacteremia (chills, fever, malaise)

- Bone lesion (pain, reduced motion)

Treatment:

- Identify causative organism

- Treat organism (e.g., antibiotic)

- Rest & pain management

Possible drainage

hematogenous osteomyelitis

A: Systemic infection spreads to bone

B: Purulent exudate collects as infection spreads, shearing off perforating arteries

C: Bone necrosis; necrotic bone separates from live bone to form devascularized fragments, called sequestra

D: Catch it early, long term consequences are relatively rare (less than 1-10%) – but include increase in fracture, development of chronic or reoccurring infection

osteonecrosis

Aseptic destruction of a segment of bone due to an interruption in blood flow

Sites with poor collateral circulation (e.g., femoral head) are most commonly affected

Symptoms:

- Depend on location & severity

- Pain with activity (can progress to pain at rest)

Treatment:

- Short-term immobilization or limited weight-bearing

- Exercises

- NSAIDs

- Advanced: total joint replacement

Jaw osteonecrosis risk increases with bisphosphonate therapy

Genu Varum (bowlegs)

outward bowing of knees (>1 in.) when medial malleoli are touching.

-- May require bracing after 2 years old

Genu Valgum (knock-knees)

medial malleoli do not touch when knees touch.

- Common at age 3-4

- May require exercise, surgery as treatments if not resolved by 7 years old

Developmental Hip Dysplasia

Screening: Ortolani test

Flex/abduct hips

Should be equal, produce no click

Treatment: Pavlik harness

Congenital Clubfoot

One of the most common pediatric orthopedic conditions

•Treated by manipulation, casting, surgery

Postural scoliosis

Small curve that corrects with bending. Corrected with passive and active exercises.

Complications

•Breathing problems (in severe scoliosis)

•Low back pain.

•Lower self-esteem.

•Persistent pain if there is wear and tear of the spine bones.

•Spine or nerve damage from an uncorrected curve or spinal surgery.

•Leakage of spinal fluid.

Structural scoliosis

Fixed deformity

Congenital (vertebral development)

Neuromuscular (cerebral palsy, DMD)

Idiopathic- majority

Complications

•Breathing problems (in severe scoliosis)

•Low back pain.

•Lower self-esteem.

•Persistent pain if there is wear and tear of the spine bones.

•Spine or nerve damage from an uncorrected curve or spinal surgery.

•Leakage of spinal fluid.

thoracic vs lumbar scoliosis

Cardinal signs of scoliosis

Uneven shoulders or iliac crest

Prominent scapula on convex side of curve

Asymmetry of thoracic cage

Treatments:

- Depend on severity and likelihood to progress

- Curves 20-30°: Considered

- Curves 30-40°: Bracing

- Curves 40-45°+: Surgery

which of the following best describes hematogenous osteomyelitis?

a. infection that enters through a penetrating wound

b. infection spreading from nearby soft tissue

c. infection that originates from organisms in the bloodstream

d. infection introduced during surgery

c. infection that originates from organisms in the bloodstream

which of the following is the most common form of scoliosis?

a. congenital

b. neuromuscular

c. idiopathic

d. postural

c. idiopathic