Section 2: Musculoskeletal Disorders and Related Conditions
What is Degenerative Disc Disease (DDD)?
Degenerative Disc Disease (DDD) is a common musculoskeletal condition characterized by the gradual deterioration of the intervertebral discs, which serve as cushions and allow flexibility between the vertebrae. Over time, aging or repetitive mechanical stress causes these discs to lose hydration and elasticity, impairing their shock-absorbing capability. This degeneration can lead to vertebral misalignment and an increased risk of spinal nerve compression, causing radiculopathy—a condition associated with nerve root pain. When DDD affects the lumbar or sacral regions, it may compress the sciatic nerve, resulting in sciatica. Sciatica manifests as pain radiating along one or both legs, often accompanied by numbness or weakness (Huether & McCance, 2020).
What is Paget’s Disease of Bone?
Paget’s Disease of Bone is a chronic disorder marked by abnormal and accelerated bone remodeling, where bone resorption outpaces formation. This imbalance results in structurally weak, brittle, and deformed bone tissue. Many individuals remain asymptomatic until the disease is incidentally discovered through imaging. During active phases, increased osteoclastic activity causes excessive calcium release into the bloodstream, sometimes leading to hypercalcemia. Clinical manifestations include localized bone pain, deformities, and neurological symptoms arising from nerve compression due to bone enlargement (Porter et al., 2021).
How Do Stress Fractures Develop and Where Are They Commonly Located?
Stress fractures occur when repetitive mechanical loading overwhelms the bone’s ability to repair itself. This condition is common in athletes and military personnel who undergo rigorous physical activity without adequate rest. Patients typically report localized pain that worsens with activity and eases during rest.
| Causes | Risk Factors | Common Sites |
|---|---|---|
| Repetitive impact loading | Vitamin D deficiency, overtraining, poor nutrition | Tibia, metatarsals, femur |
What Are Rickets and Osteomalacia?
Rickets and osteomalacia are disorders related to defective bone mineralization, primarily caused by vitamin D deficiency.
Rickets affects children, leading to soft, weak bones and skeletal deformities such as bowed legs and delayed growth. Symptoms include bone pain, craniotabes (soft skull bones), and abdominal protrusion. Other causes include malabsorption syndromes and insufficient sunlight exposure.
Osteomalacia affects adults and involves inadequate mineralization of mature bone, resulting in bone pain, muscle weakness, and increased fracture risk with minimal trauma (McCance & Huether, 2020).
What is Compartment Syndrome and How is it Diagnosed?
Compartment Syndrome arises when increased pressure within a closed muscle compartment impairs blood flow and nerve function. If untreated, this condition can lead to tissue necrosis and permanent disability.
Clinical Signs (6 P’s):
Pain disproportionate to injury
Paresthesia (tingling)
Pallor (paleness)
Pulselessness (absent pulse)
Poikilothermia (cool temperature)
Paralysis (a late and severe sign)
| Causes | Complications | Diagnostic Criteria |
|---|---|---|
| Crush injuries, fractures, burns, tight casts or dressings | Tissue necrosis, gangrene, rhabdomyolysis, nerve injury | Compartment pressure >30 mmHg, CT, MRI, CBC |
Emergency intervention with fasciotomy or removal of constrictive dressings is critical. Severe cases may necessitate amputation.
What is Rhabdomyolysis and Its Classic Presentation?
Rhabdomyolysis is characterized by the breakdown of skeletal muscle fibers, releasing intracellular contents such as myoglobin and creatine kinase into the bloodstream. Excess myoglobin can block kidney tubules, leading to acute renal failure.
Classic Triad of Symptoms:
Muscle pain (myalgia)
Muscle weakness
Dark, tea-colored urine (myoglobinuria)
Prompt intravenous hydration and electrolyte correction are essential to prevent kidney damage.
What is a Sequestrum?
A sequestrum is a segment of necrotic bone that separates from healthy bone, often due to infection or trauma. Surgical removal of the sequestrum (debridement) is necessary to facilitate healing and prevent chronic osteomyelitis (Smeltzer et al., 2020).
What are Deep Vein Thrombosis (DVT) and Pulmonary Embolism (PE), and How Are They Diagnosed?
Patients undergoing orthopedic surgery or immobilization are at increased risk for DVT and PE, conditions linked to venous stasis and vessel injury.
| Condition | Key Features | Diagnostic Tests |
|---|---|---|
| DVT | Swelling, tenderness, warmth, palpable cord | D-dimer test, Doppler ultrasound, coagulation profile |
| PE | Shortness of breath, chest pain, cyanosis, rapid breathing, hemoptysis | CT pulmonary angiogram, V/Q scan |
Preventive strategies include early mobilization, compression stockings, and anticoagulant therapy.
What is Fat Embolism Syndrome (FES), and How is It Diagnosed?
FES occurs when fat droplets from bone marrow enter the bloodstream following fractures, blocking pulmonary or cerebral vessels. This results in respiratory distress and neurological symptoms.
| Diagnostic Criteria for FES | Major Criteria | Minor Criteria |
|---|---|---|
| Requires 1 major + ≥4 minor + fat macroglobulinemia | Respiratory failure, cerebral symptoms, petechial rash | Tachycardia, fever, retinal petechiae, renal dysfunction, jaundice, anemia, thrombocytopenia, elevated ESR |
Management involves immediate fluid resuscitation with normal saline or lactated Ringer’s solution to maintain circulation and aid emboli clearance.
What is Avascular Necrosis (AVN)?
AVN results from disrupted blood supply to bone tissue, causing bone death, structural collapse, and joint dysfunction. Commonly affected bones include the femoral head, scaphoid, and talus. Symptoms include localized pain, weakness, and limited joint movement. MRI or bone scans confirm diagnosis. Treatment ranges from core decompression to surgical excision of necrotic bone.
How Are Delayed Healing Fractures Classified?
| Term | Definition | Clinical Implications |
|---|---|---|
| Delayed Union | Prolonged healing time | Persistent pain, reduced function |
| Malunion | Healing with improper alignment | Bone deformity, impaired function |
| Nonunion | Failure of bone ends to unite | Requires surgical repair |
What Are the Consequences of Prolonged Immobility?
Extended immobilization negatively impacts multiple body systems:
| System | Possible Complications |
|---|---|
| Skin | Pressure ulcers, infections |
| Gastrointestinal | Constipation due to decreased motility |
| Muscular | Atrophy and weakness |
| Skeletal | Osteoporosis, decreased bone density |
| Cardiovascular | Venous stasis, thrombosis |
| Urinary | Urinary stasis, kidney stones |
| Respiratory | Pneumonia, atelectasis |
| Psychological | Depression, social isolation |
Section 3: The Nervous System (Overview)
What Are the Types of Stroke and Their Characteristics?
Strokes are classified based on the underlying mechanism of cerebral ischemia:
| Type | Pathophysiology | Clinical Notes |
|---|---|---|
| Ischemic Stroke | Artery blockage by thrombus or embolus | Most common (~85% of strokes) |
| Thrombotic Stroke | Local clot formation from atherosclerosis | Develops gradually |
| Embolic Stroke | Clot travels from heart or artery to brain | Sudden onset |
| Hemorrhagic Stroke | Arterial rupture causing intracranial bleeding | High mortality (~15%) |
The ischemic penumbra is the surrounding brain tissue at risk but salvageable with prompt reperfusion (Grossman & Porth, 2021).
What are Neuropathies and Related Disorders?
Peripheral neuropathy involves damage to peripheral nerves, resulting in sensory loss, weakness, and pain.
| Type | Mechanism | Examples/Causes |
|---|---|---|
| Demyelinating | Myelin sheath destruction | Guillain-Barré Syndrome |
| Axonal Degeneration | Axonal damage | Diabetes mellitus, toxins |
Common causes include diabetes, chronic alcohol use, and neurotoxic medications.
Myasthenia Gravis is an autoimmune disorder targeting acetylcholine receptors at the neuromuscular junction, causing fluctuating muscle weakness. Symptoms include eyelid drooping (ptosis), double vision (diplopia), and worsening weakness with activity.
Meniere’s Disease results from fluid imbalance in the inner ear, producing vertigo, tinnitus, and progressive hearing loss.
How to Differentiate Cerebrovascular and Neurological Conditions?
| Condition | Definition | Key Differentiator |
|---|---|---|
| Aneurysm | Cerebral artery dilation | Risk of rupture causing hemorrhage |
| Hemorrhage | Active bleeding in brain tissue | Often caused by hypertension |
| Hematoma | Localized blood collection | Can cause brain compression symptoms |
| Epidural Hematoma | Bleeding between skull and dura mater | Linked to temporal bone fracture and arterial rupture |
Section 4: Cardiovascular and Hematologic Disorders
What is the Role of the Cardiovascular System?
The cardiovascular system forms a closed circuit responsible for transporting oxygen, nutrients, hormones, and waste products throughout the body. It relies on coordinated cardiac electrical activity, vascular integrity, and sufficient blood volume. Dysfunction in any of these components may lead to diseases such as hypertension, atherosclerosis, or heart failure (Huether & McCance, 2020).
How is Hypertension Classified and What Are Its Risk Factors?
| Classification | Systolic (mmHg) | Diastolic (mmHg) |
|---|---|---|
| Normal | <120 | <80 |
| Elevated | 120–129 | <80 |
| Stage 1 Hypertension | 130–139 | 80–89 |
| Stage 2 Hypertension | ≥140 | ≥90 |
| Hypertensive Crisis | ≥180 | ≥120 |
Risk factors include genetics, obesity, high salt and alcohol intake, chronic stress, diabetes, and hyperlipidemia.
What Are the Pathophysiology and Complications of Hypertension?
Chronic hypertension damages the vascular endothelium, increases arterial stiffness, and elevates peripheral resistance. These changes can cause left ventricular hypertrophy (LVH) and elevate the risk of stroke, myocardial infarction, kidney disease, and hypertensive retinopathy.
What Is Atherosclerosis and Its Risk Factors?
Atherosclerosis is a progressive condition where lipid plaques accumulate inside arteries, narrowing vessels and impairing blood flow. Plaque rupture can cause thrombosis or embolism.
| Pathogenesis Steps |
|---|
| Endothelial injury (due to hypertension, smoking, diabetes) → LDL infiltration → inflammation and foam cell formation → fibrous cap and calcification → plaque rupture → thrombus formation |
Risk factors include dyslipidemia, hypertension, diabetes, smoking, obesity, and sedentary lifestyle.
| Plaque Type | Characteristics | Clinical Presentation |
|---|---|---|
| Stable Plaque | Thick fibrous cap, gradual narrowing | Predictable angina |
| Unstable Plaque | Thin cap, prone to rupture | Myocardial infarction, stroke |
What is Coronary Artery Disease (CAD) and How Does Angina Present?
| Type of Angina | Description | Trigger | Relief |
|---|---|---|---|
| Stable Angina | Predictable chest pain with exertion | Physical/emotional stress | Rest or nitroglycerin |
| Unstable Angina | Chest pain at rest or minimal exertion | Plaque rupture, thrombosis | Emergency treatment needed |
| Prinzmetal (Variant) | Vasospasm of coronary arteries | Cold, stress, drugs | Calcium channel blockers |
What Are the Clinical Features and Management of Myocardial Infarction (MI)?
MI occurs due to complete blockage of coronary arteries, causing heart muscle death.
Clinical Features:
Severe chest pain, possibly radiating to jaw, shoulder, or arm
Diaphoresis, shortness of breath, nausea, anxiety
ECG changes such as ST elevation or depression and Q waves
Elevated cardiac enzymes including troponin and CK-MB
Complications:
Heart failure, arrhythmias, cardiogenic shock, pericarditis
Treatment:
MONA protocol (Morphine, Oxygen, Nitrates, Aspirin)
Reperfusion therapy (thrombolytics, percutaneous coronary intervention)
Long-term medications (beta-blockers, ACE inhibitors, statins)
What Are the Types of Heart Failure and Their Symptoms?
| Type | Pathophysiology | Key Symptoms |
|---|---|---|
| Left-Sided HF | Left ventricle fails to eject blood causing pulmonary congestion | Dyspnea, orthopnea, crackles, cough |
| Right-Sided HF | Right ventricle failure due to pulmonary hypertension or LV failure | Peripheral edema, ascites, hepatomegaly |
| Systolic HF | Decreased ejection fraction (<40%) | Fatigue, poor contractility |
| Diastolic HF | Impaired ventricular relaxation | Preserved EF, pulmonary congestion |
What Are Peripheral Arterial Disease (PAD) and Its Management?
PAD involves arterial narrowing in the limbs, usually due to atherosclerosis, resulting in impaired blood flow.
Clinical Manifestations:
Intermittent claudication: leg pain during exertion relieved by rest
Pallor, cold limbs, weak pulses
Ulcers or gangrene in advanced disease
| Diagnostic Tests | Purpose |
|---|---|
| Ankle-Brachial Index (ABI) | <0.9 indicates PAD |
| Doppler Ultrasound | Detects blood flow obstruction |
| Angiography | Visualizes arterial blockages |
Management:
Smoking cessation, exercise therapy
Antiplatelet drugs (aspirin, clopidogrel)
Statins for cholesterol control
Surgical interventions (angioplasty, bypass)
What is Deep Vein Thrombosis (DVT), Its Causes, Signs, and Management?
DVT is the formation of clots in deep veins, primarily in the legs.
Virchow’s Triad of Causes:
Venous stasis (immobility, prolonged travel)
Endothelial injury (trauma, surgery)
Hypercoagulability (cancer, pregnancy)
Signs:
Swelling, pain, redness, warmth over affected vein
Tenderness and positive Homan’s sign (pain on dorsiflexion)
Complications: Pulmonary embolism (PE), chronic venous insufficiency
Management:
Anticoagulants (heparin, warfarin, DOACs)
Early mobilization
Compression stockings
Inferior vena cava filters (for recurrent PE)
What Are Common Hematologic Disorders?
| Disorder | Cause | Key Features |
|---|---|---|
| Iron-Deficiency Anemia | Blood loss, poor diet | Microcytic, hypochromic RBCs, fatigue |
| Megaloblastic Anemia | B12 or folate deficiency | Large RBCs, glossitis, neurological symptoms |
| Hemolytic Anemia | Premature RBC destruction | Jaundice, splenomegaly |
| Aplastic Anemia | Bone marrow failure | Pancytopenia, infections, bleeding |
Treatment varies depending on the cause and may include supplements, injections, or transfusions.
Polycythemia involves excess red blood cells leading to thickened blood and thrombosis risk.
| Type | Mechanism | Example |
|---|---|---|
| Primary | Myeloproliferative disorder (JAK2 mutation) | Polycythemia vera |
| Secondary | Increased erythropoietin | Chronic hypoxia (COPD, high altitude) |
Symptoms include ruddy complexion, headaches, and dizziness. Treatment may involve phlebotomy or myelosuppressive drugs.
Disseminated Intravascular Coagulation (DIC) is characterized by simultaneous excessive clotting and bleeding, often triggered by sepsis, trauma, or malignancy.
Lab Findings:
Low platelet count and fibrinogen
Elevated PT, aPTT, and D-dimer
Presence of schistocytes in blood smear
Management focuses on treating the underlying cause and supportive care, including blood product replacement.
References
Grossman, S., & Porth, C. M. (2021). Porth’s Pathophysiology: Concepts of Altered Health States (10th ed.). Wolters Kluwer.
Huether, S. E., & McCance, K. L. (2020). Understanding Pathophysiology (7th ed.). Elsevier.
McCance, K. L., & Huether, S. E. (2020). Pathophysiology: The Biologic Basis for Disease in Adults and Children (8th ed.). Elsevier.
Porter, R. S., Kaplan, J. L., & Homeier, B. P. (2021). The Merck Manual of Diagnosis and Therapy (20th ed.). Merck Research Laboratories.
Smeltzer, S. C., Bare, B. G., Hinkle, J. L., & Cheever, K. H. (2020). Brunner & Suddarth’s Textbook of Medical-Surgical Nursing (15th ed.). Wolters Kluwer.