Page 2 – Definition
| Component | Content |
|---|---|
| Definition | The humerus is the long bone of the upper arm that spans from the shoulder to the elbow, forming a structural and functional bridge between the pectoral girdle and the forearm. It plays a critical role in limb mobility, leverage, and force transmission. |
| Structure | Long bone with proximal head, shaft, and distal condyles; articulates with scapula proximally and radius/ulna distally. |
| Function | Supports upper limb movement and load-bearing; enables arm lifting, rotation, and flexion-extension. |
| Common Diseases | 1. Fractures (e.g., surgical neck, shaft) 2. Osteosarcoma 3. Osteomyelitis |
| Diagnosis | Clinical examination (pain, deformity), X-ray, CT/MRI for complex trauma or tumors. |
| Treatment | Immobilization, surgical fixation, antibiotics (infection), chemotherapy (malignancy). |
3. Anatomy
Page 3 – Applied Anatomy and Diagnostic Approach
Table 1 – U-SSPCT–C (Including Fully Expanded Connections)
| Category | Details |
|---|---|
| Units | – Head – Anatomical neck – Surgical neck – Greater tubercle – Lesser tubercle – Shaft – Deltoid tuberosity – Radial groove – Medial epicondyle – Lateral epicondyle – Capitulum – Trochlea – Olecranon fossa |
| Size | Average length ~30 cm in adults; varies with individual height and sex. |
| Shape | Long cylindrical shaft with expanded proximal and distal ends; rounded head; hourglass-like distal end with articular surfaces. |
| Position | Located in the upper limb; extends from shoulder to elbow; lies in the anterior compartment of the arm. |
| Character | Dense cortical bone with central medullary canal; highly vascularized; mechanical strength suited for load bearing and leverage. |
| Time (Development & Aging) | – Primary ossification center in shaft appears during fetal life (~8th week). – Secondary centers (head, tubercles, condyles) appear at birth to puberty. – Epiphyseal fusion completed by ~18 years. – Susceptible to osteoporotic fractures in elderly. |
| ConnectionS | |
|---|---|
| Arterial Supply | – Anterior circumflex humeral artery – Posterior circumflex humeral artery – Deep brachial (profunda brachii) artery |
| Venous Drainage | – Brachial veins – Cephalic vein – Basilic vein |
| Lymphatic Drainage | – Drains primarily into axillary lymph nodes |
| Nerve Supply | – Axillary nerve (around surgical neck) – Radial nerve (courses along radial/spiral groove) – Musculocutaneous nerve (pierces coracobrachialis, anterior compartment) – Median and ulnar nerves (pass anterior to distal humerus) |
| Joints | – Glenohumeral joint (proximal) – Elbow joint (distal: humeroulnar and humeroradial articulations) |
| Ligaments | – Glenohumeral ligaments (superior, middle, inferior) – Coracohumeral ligament – Annular ligament (stabilizes proximal radioulnar joint) |
| Tendons | – Rotator cuff insertions: supraspinatus, infraspinatus, subscapularis – Long head of biceps brachii (originates from supraglenoid tubercle, passes through bicipital groove) |
4. Disease and Diagnosis
Page 4 – Clinical Diagnosis
1. Pathology by TCV Category
| Category | Examples Relevant to Humerus |
|---|---|
| Inflammatory/Immune | Rheumatoid arthritis affecting the shoulder or elbow joints |
| Infection | Osteomyelitis (e.g., hematogenous spread in children) |
| Neoplasm – Benign | Enchondroma, bone cyst |
| Neoplasm – Malignant (Primary) | Osteosarcoma, Ewing sarcoma |
| Neoplasm – Malignant (Metastatic) | Breast, lung, prostate cancer mets |
| Mechanical | Rotator cuff impingement leading to proximal humeral degeneration |
| Trauma | Fractures: surgical neck, shaft, supracondylar region (common in children) |
| Metabolic | Osteoporosis → pathologic fractures |
| Circulatory | Avascular necrosis post-fracture (especially humeral head) |
| Inherited | Osteogenesis imperfecta → brittle bones |
| Infiltrative | Sarcoidosis (rarely with osseous involvement) |
| Idiopathic | Idiopathic humeral head necrosis |
| Iatrogenic | Nerve damage during shoulder surgery or fracture repair |
| Functional | Brachial plexus compression from poor posture affecting humeral function |
| Psychiatric | Not directly applicable |
2. Clinical Signs and Symptoms
| Symptom | Meaning/Implication |
|---|---|
| Arm pain | Trauma, infection, tumor, arthritis |
| Swelling | Fracture, inflammation, tumor |
| Limited mobility | Fracture, dislocation, tendon injury |
| Numbness or weakness | Nerve injury (e.g., radial nerve palsy with midshaft fractures) |
| Deformity | Fracture displacement or dislocation |
3. Imaging Modalities
| Modality | Primary Use | When/Why Used |
|---|---|---|
| X-ray | Initial evaluation of trauma or deformity | Detects fractures, dislocations, tumors |
| CT Scan | Complex fractures or tumor evaluation | 3D reconstruction, surgical planning |
| MRI | Soft tissue evaluation | Assess rotator cuff, marrow lesions, tumors |
| Bone Scan | Metastasis, occult lesions | Evaluates bone turnover/activity |
| Ultrasound | Dynamic tendon/muscle imaging | Tendon tears, effusions near shoulder |
4. Laboratory Tests
| Test | Purpose | When/Why Used |
|---|---|---|
| CBC | Detects infection/inflammation | Suspected osteomyelitis |
| ESR/CRP | Inflammatory markers | Assess osteomyelitis or arthritis |
| Alkaline phosphatase | Bone activity marker | Bone tumors or healing fractures |
| Calcium/phosphate | Bone metabolism | Metabolic bone disease |
| Biopsy | Definitive diagnosis of tumors | Histopathological confirmation |
5. Other Diagnostic Tools
| Tool | Use | Indication |
|---|---|---|
| Electromyography (EMG) | Assesses nerve injury | Radial or axillary nerve palsy |
| Joint aspiration | Rule out infection | Septic arthritis of shoulder or elbow |
| Range-of-motion testing | Functional assessment | Post-injury rehab or arthritis evaluation |
5. History and Culture
Page 5 – History, Culture, and Art (Humerus)
1. History of Anatomy
| Topic | Details |
|---|---|
| Classical Foundations | The humerus was first described anatomically by Galen and later corrected by Vesalius, who depicted it in De Humani Corporis Fabrica (1543). |
| Evolution of Understanding | Early anatomists mistook the articulation mechanics of the humerus; Vesalius’ correction set the foundation for modern musculoskeletal anatomy. |
| Anatomical Nomenclature | The term “humerus” comes from Latin umerus, originally meaning shoulder or upper arm, highlighting its proximal location. |
2. History of Physiology
| Topic | Details |
|---|---|
| Arm Mechanics | 19th and early 20th-century physiologists studied the biomechanics of the upper limb, emphasizing the leverage and rotation enabled by the humerus. |
| Muscle Dynamics | Research into deltoid and rotator cuff functions focused on their origin and insertion on the humerus to explain shoulder and arm movement. |
| Nerve-Motor Control | The radial and axillary nerve courses along the humerus became central to understanding upper limb motor function. |
3. History of Diagnosis
| Topic | Details |
|---|---|
| Palpation and Percussion | In ancient and medieval medicine, humeral fractures were diagnosed by deformity, crepitus, and swelling without imaging. |
| Functional Testing | Arm abduction weakness and wrist drop became key diagnostic signs linked to humeral fractures and nerve injury. |
| 20th Century Advancements | Introduction of systematic clinical exams and correlation with radiographs allowed accurate localization of fracture types. |
4. History of Imaging
| Topic | Details |
|---|---|
| Early Radiography | Following Roentgen’s discovery (1895), the humerus was among the first bones to be imaged due to its superficial location and fracture prevalence. |
| CT and 3D Imaging | CT revolutionized trauma assessment, especially in comminuted or intra-articular fractures of the proximal or distal humerus. |
| MRI in Musculoskeletal Disease | MRI enabled detailed soft tissue evaluation—rotator cuff pathology, marrow edema, and tumors within the humerus. |
5. History of Laboratory Testing
| Topic | Details |
|---|---|
| Infections | Blood cultures, ESR, and CRP became standard in evaluating osteomyelitis of long bones including the humerus. |
| Tumor Evaluation | Alkaline phosphatase levels used to assess bone-forming tumors like osteosarcoma affecting the humerus. |
| Modern Biomarkers | Research continues into bone metabolism markers to monitor fracture healing or cancer recurrence. |
6. History of Therapies
| Topic | Details |
|---|---|
| Splints and Braces | Ancient Egyptians and Greeks used wooden splints for humeral fractures, preceding plaster and fiberglass casts. |
| Surgical Fixation | 20th-century orthopedic innovations introduced intramedullary nails, locking plates, and dynamic compression screws. |
| Arthroplasty | Shoulder arthroplasty now includes proximal humeral replacement for complex fractures, especially in elderly or osteoporotic patients. |
| Nerve Repair | Microsurgical techniques evolved to repair radial nerve injuries from humeral trauma. |
7. Cultural Meaning
| Topic | Details |
|---|---|
| Symbol of Strength | The humerus, as the main arm bone, is symbolically tied to strength, power, and combat ability—seen in both classical and modern iconography. |
| Arm as Extension of Will | Philosophically, the arm (and by extension the humerus) represents human agency—used to build, strike, protect, or create. |
| Ritual Significance | In some tribal cultures, long bones like the humerus were used in rituals, as trophies of war, or as tools. |
8. Artistic Representations
| Artwork | Details |
|---|---|
| Michelangelo’s David | The detailed representation of humeral contours in David’s flexed right arm highlights classical anatomical precision. |
| Vesalius’ Anatomical Plates | Early accurate drawings of the humerus, including cross-sections and articulations, from the Renaissance. |
| Leonardo da Vinci | His anatomical sketches include detailed studies of the upper limb, showing the humerus and its muscular attachments. |
| Modern Medical Art | Cross-sectional and digital reconstructions of the humerus used in patient education and surgical planning. |
9. Notable Figures
| Person | Contribution |
|---|---|
| Andreas Vesalius | Corrected Galenic errors about the humerus; introduced precise visual anatomy. |
| Sir John Charnley | Advanced orthopedic surgical techniques influencing humeral fracture fixation. |
| Robert Danis | Pioneered internal fixation of long bone fractures, including humeral shaft repair. |
| Paul Grammont | Developed reverse shoulder prosthesis affecting humeral component design. |
10. Quotes
| Quote | Attribution |
|---|---|
| “The humerus is not just a bone—it’s the bridge between strength and intention.” | Ashley Davidoff MD |
| “The arm is the tool of tools.” | Aristotle |
| “Bones are the silent witnesses to the life we’ve lived.” | Anonymous orthopedic proverb |
7. MCQ's
Page 6 – MCQs
Basic Science MCQ 1
Which nerve is most at risk in a midshaft humeral fracture?
A. Median nerve
B. Ulnar nerve
C. Radial nerve
D. Musculocutaneous nerve
Correct Answer and Explanation
| Answer | Explanation |
|---|---|
| Radial nerve | Travels in the spiral groove of the humerus and is commonly injured in midshaft fractures. |
Incorrect Answers
| Option | Reason Incorrect |
|---|---|
| Median nerve | Runs anteriorly; not associated with midshaft region. |
| Ulnar nerve | Passes near medial epicondyle, not shaft. |
| Musculocutaneous nerve | Travels anteriorly through coracobrachialis; less likely involved. |
Basic Science MCQ 2
What is the primary ossification center of the humerus?
A. Greater tubercle
B. Diaphysis
C. Capitulum
D. Olecranon
Correct Answer and Explanation
| Answer | Explanation |
|---|---|
| Diaphysis | The primary ossification center in long bones begins in the shaft (diaphysis). |
Incorrect Answers
| Option | Reason Incorrect |
|---|---|
| Greater tubercle | Secondary center. |
| Capitulum | Secondary ossification center. |
| Olecranon | Part of ulna, not humerus. |
Clinical MCQ 1
An elderly woman falls and sustains a surgical neck fracture. Which complication is most likely?
A. Ulnar nerve palsy
B. Radial artery damage
C. Axillary nerve injury
D. Median nerve injury
Correct Answer and Explanation
| Answer | Explanation |
|---|---|
| Axillary nerve injury | Wraps around surgical neck of humerus; vulnerable in such fractures. |
Incorrect Answers
| Option | Reason Incorrect |
|---|---|
| Ulnar nerve palsy | Affects elbow area. |
| Radial artery damage | Not related to humeral fractures. |
| Median nerve injury | Less associated with proximal humerus trauma. |
Clinical MCQ 2
What clinical sign suggests radial nerve palsy in humeral fracture?
A. Claw hand
B. Foot drop
C. Wrist drop
D. Ape hand
Correct Answer and Explanation
| Answer | Explanation |
|---|---|
| Wrist drop | Classic sign of radial nerve dysfunction affecting wrist extensors. |
Incorrect Answers
| Option | Reason Incorrect |
|---|---|
| Claw hand | Ulnar nerve lesion. |
| Foot drop | Peroneal nerve injury. |
| Ape hand | Median nerve lesion. |
Radiologic MCQ 1
What imaging modality is most useful for detecting occult humeral fractures?
A. X-ray
B. Ultrasound
C. MRI
D. Bone densitometry
Correct Answer and Explanation
| Answer | Explanation |
|---|---|
| MRI | Detects marrow edema and occult fractures not seen on X-ray. |
Incorrect Answers
| Option | Reason Incorrect |
|---|---|
| X-ray | May miss nondisplaced fractures. |
| Ultrasound | Poor bone detail. |
| Bone densitometry | Assesses bone density, not fractures. |
Radiologic MCQ 2
Which finding is seen in X-ray of humeral shaft fracture?
A. Joint effusion
B. Fat pad sign
C. Cortical disruption
D. Increased joint space
Correct Answer and Explanation
| Answer | Explanation |
|---|---|
| Cortical disruption | Hallmark of diaphyseal fractures. |
Incorrect Answers
| Option | Reason Incorrect |
|---|---|
| Joint effusion | Soft tissue sign, not fracture-specific. |
| Fat pad sign | More relevant to elbow. |
| Increased joint space | Not typically seen with humeral fractures. |
Radiologic MCQ 3
Which view best evaluates a suspected proximal humerus fracture?
A. AP pelvis
B. Lateral neck
C. Axillary shoulder
D. Oblique knee
Correct Answer and Explanation
| Answer | Explanation |
|---|---|
| Axillary shoulder | Provides orthogonal view to AP shoulder; critical for proximal humeral fractures. |
Incorrect Answers
| Option | Reason Incorrect |
|---|---|
| AP pelvis | Irrelevant region. |
| Lateral neck | Cervical spine view. |
| Oblique knee | Unrelated to shoulder trauma. |
8. Memory Image
Page 7 – Memory Image
| Title | Metaphorical Representation of the Humerus |
|---|---|
| Image Caption | Artistic rendering of a column-like structure bridging two architectural towers, symbolizing the humerus as a load-bearing bridge between shoulder and elbow. Cables represent nerves and vessels spiraling around the shaft.
Courtesy: Ashley Davidoff MD, TheCommonVein.com (Image ID: 140547.humerus) |
| Symbol | Meaning |
|---|---|
| Column bridge | Strength and support of humerus |
| Shoulder and elbow towers | Articulating joints |
| Spiral cables | Nerve and vessel paths |
| Broken section | Fracture risk zone (e.g., surgical neck) |