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.