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Musculoskeletal Pathophysiology Notes

Definitions of Fractures

  • Fracture: Break in the continuity of bone when force exceeds the tensile or compressive strength of the bone.

Classifications of Fractures:

  • Complete: Bone is broken all the way through.
  • Incomplete: Bone is damaged but still in one piece.
    • Closed/Simple: Skin is intact.
    • Open/Compound: Skin is broken.
  • Comminuted: Bone breaks into more than two fragments.
  • Linear: Fracture runs parallel to the long axis of the bone.
  • Oblique: Shaft of the bone is slanted.
  • Spiral: Fracture encircles the bone.
  • Transverse: Occurs straight across the bone.
  • Greenstick: Perforates one cortex and splinters spongy bone (like a tree branch).
  • Torus: Cortex buckles but does not break.
  • Bowing: Longitudinal force applied to a bone (common in children: radius/ulna, tibia/fibula).
  • Pathologic: Break occurs at a site of preexisting abnormality (tumor, osteoporosis, infection).
  • Stress Fractures: Caused by fatigue and insufficiency, often seen in athletes.

Pathophysiology of Bone Fracture

  • Bone fractures can damage surrounding tissue, periosteum, and blood vessels in the cortex and marrow.
  • Bone heals with normal tissue rather than scar tissue, occurring in several phases:
    • Inflammatory Phase: Bone tissue destruction triggers inflammation and hematoma formation. Lasts 3-4 days.
    • Repair Phase: Capillary ingrowth and fibroblasts transform hematoma into granulation tissue. Osteoblasts synthesize collagen and matrix to form callus. Lasts several days.
    • Remodeling Phase: Unnecessary callus is resorbed and trabeculae are formed, bone can withstand normal stresses. This can last months to years.

Complications of Bone Healing:

  • Nonunion: Failure of bone ends to grow together, results in a pseudarthrosis.
  • Delayed Union: Healing does not occur until 8-9 months after fracture.
  • Malunion: Bone heals in a nonanatomic position.

Support Structure Injuries

  • Dislocation: Temporary displacement of bone from its joint.
  • Subluxation: Partial loss of contact between bones at the joint.

Clinical Manifestations:

  • Pain, swelling, limitation of motion, and joint deformity.

Strain and Sprain:

  • Strain: Tear or injury to a tendon, often from a sudden, forced motion. Local muscle damage, with potential regeneration within 6 weeks.
  • Sprain: Tear or injury to a ligament.
  • Avulsion: Complete separation of tendon or ligament from its attachment.

Pathophysiology:

  • Inflammatory exudate forms between torn ends, granulation tissue grows, and collagen formation begins after 3-4 days.

Epicondylitis, Tendinopathy, and Bursitis:

  • Tendinitis: Inflammation of a tendon.
  • Tendinosis: Degeneration of collagen fibers causing pain.
  • Bursitis: Inflammation of the bursa, often due to trauma or infection (e.g., septic bursitis).

Myositis Ossificans:

  • Inflammation of muscular tissue with calcification, often a complication of local muscle injury.
  • Seen in various populations including equestrians and infantry soldiers.

Rhabdomyolysis:

  • Life-threatening condition due to severe muscle trauma leading to muscle cell loss.
  • Classic triad of symptoms includes muscle pain, weakness, and dark urine (from myoglobin).

Compartment Syndrome:

  • Occurs with fractures and leads to compromised blood flow due to venous pressure, causing ischemia and edema.
  • Clinical manifestations include the 5 P's: Pain, Paresthesia, Pallor, Pulselessness, and Paralysis (late sign).

Osteoporosis:

  • Characterized by porous bone and decreased bone mass/density.
  • Distinction between primary vs. secondary osteoporosis (related to specific conditions or factors).
  • Pathophysiology involves hormone levels, activity levels, and vitamin deficiencies affecting bone density.

Osteomalacia:

  • Vitamin D deficiency leading to inadequate or delayed mineralization of bones resulting in soft bones.

Paget Disease:

  • Increased metabolic activity in bone leading to excessive resorption and formation, typically affecting the axial skeleton.

Osteomyelitis:

  • Infection of bone often caused by staphylococcus, can be exogenous or endogenous.

Bone Tumors:

  • Can originate from different types of cells. Malignant tumors illustrate increased nuclear-cytoplasmic ratio and irregular borders.

Osteosarcoma:

  • Common in adolescents/young adults and associated with pain and swelling. Predominantly affects long bones.

Chondrosarcoma:

  • Produces cartilage, commonly seen in middle-aged adults, characterized by pain and swelling.

Fibrosarcoma:

  • Composed of malignant fibroblasts, often metastasizes to the lungs.

Arthropathies:

  • Osteoarthritis: Age-related degenerative joint disease characterized by cartilage loss and bone spur formation.
  • Symptoms include pain, stiffness, and joint deformity.
  • Rheumatoid Arthritis: An autoimmune disorder causing inflammation in the synovial membrane leading to joint damage. Symptoms of systemic inflammation often present.

Ankylosing Spondylitis:

  • Chronic inflammatory disorder primarily affecting the spine, eventually leading to joint fusion.
  • Symptoms include low back pain and stiffness.

Gout:

  • Metabolic disorder related to high uric acid levels and the crystallization of uric acid in joints.
  • Clinical stages: asymptomatic hyperuricemia, acute gouty arthritis, tophaceous gout (with visible tophi).

Muscle Conditions:

  • Fibromyalgia: Chronic pain condition with various symptoms including fatigue and tender points.
  • Chronic Fatigue Syndrome: Debilitating fatigue with multiple physical and mental symptoms.
  • Disuse Atrophy: Reduction in muscle cell size due to inactivity, often resulting from casting or immobility.