Ulna
Page 2 – Definition
| Element | Content |
|---|---|
| Structure Name | Ulna |
| Definition | The ulna is one of the two long bones of the forearm, located medially (on the side of the little finger) and forming the stable base of the forearm. It articulates with the humerus at the elbow and the radius at both proximal and distal radioulnar joints. |
| System | Musculoskeletal System – Skeletal Subsystem |
| Function | Provides structural support to the forearm, contributes to elbow joint stability, and serves as an attachment point for muscles that control forearm and hand movement. |
| Common Diseases | Fractures, dislocations, Monteggia fracture-dislocations |
| Diagnostic Methods | X-ray, CT, physical exam, orthopedic tests |
| Treatments | Casting/splinting, surgical fixation, physiotherapy |
3. Anatomy
Page 3 – Applied Anatomy and Diagnostic Approach
U-SSPCT–C Table 1: Ulna Structural Anatomy
| Category | Details |
|---|---|
| Units | – Olecranon – Coronoid process – Radial notch – Ulnar shaft – Styloid process |
| Size | Long bone, typically 26–28 cm in adult males, slightly shorter in females |
| Shape | Curved longitudinally; prismatic shaft with widened proximal and distal ends |
| Position | Medial bone of the forearm, in anatomical position (pinky side); spans from elbow to wrist |
| Character | Strong and relatively straight; dense cortical bone in shaft, cancellous bone at ends |
| Time (Development) | Ossifies from multiple centers (olecranon, shaft, and distal end); complete fusion occurs by ~18–20 years |
| Connections | |
| – Arterial Supply | – Ulnar artery – Interosseous arteries |
| – Venous Drainage | – Basilic vein – Cephalic vein (via perforating branches) – Deep venous network |
| – Lymphatic Drainage | – Superficial and deep lymphatics to epitrochlear and axillary nodes |
| – Nerve Supply | – No direct innervation of bone – Surrounding structures innervated by ulnar, radial, and median nerves |
| – Joints | – Elbow (humeroulnar joint) – Proximal radioulnar joint – Distal radioulnar joint |
| – Ligaments | – Ulnar collateral ligament – Annular ligament – Triangular fibrocartilage complex (TFCC) |
| – Tendons | – Triceps brachii (olecranon) – Flexor carpi ulnaris – Extensor carpi ulnaris – Pronator quadratus |
Imaging Modalities
| Modality | Primary Use | When/Why Used |
|---|---|---|
| X-ray | Initial assessment of trauma or deformity | Suspected fracture or dislocation |
| CT | High-resolution bone detail | Complex fractures or surgical planning |
| MRI | Soft tissue and ligament evaluation | TFCC injury, tendon avulsion |
| Ultrasound | Dynamic soft tissue assessment | Tendon integrity, synovial swelling |
| Bone Scan | Evaluate metabolic activity | Suspected stress fractures or tumors |
Laboratory Tests
| Test | Purpose | When/Why Used |
|---|---|---|
| Serum Calcium/Phosphate | Bone metabolism | Assess systemic bone disease |
| Alkaline Phosphatase | Bone turnover | Suspect metabolic bone conditions |
| CBC, CRP, ESR | Inflammatory or infectious markers | Osteomyelitis or post-trauma infection |
Other Diagnostic Tools
| Tool | Use | Indication |
|---|---|---|
| Physical Exam | Assess pain, range of motion, instability | Trauma, overuse injury |
| Orthopedic Provocative Tests | Evaluate joint or ligament integrity | TFCC injury, instability |
| Arthroscopy | Direct visualization of joint | TFCC repair, intra-articular assessment |
4. Disease and Diagnosis
Page 4 – Clinical Diagnosis
1. Pathology by TCV Disease Categories (IINMTM)
| Category | Examples |
|---|---|
| Inflammatory | Rheumatoid arthritis affecting distal radioulnar joint |
| Infectious | Osteomyelitis, septic arthritis |
| Neoplastic – Benign | Osteochondroma, enchondroma |
| Neoplastic – Malignant (Primary) | Ewing’s sarcoma, osteosarcoma |
| Neoplastic – Metastatic | Rare; lung, prostate, breast metastases |
| Mechanical | Overuse syndromes, ulnar impaction syndrome |
| Traumatic | Ulna shaft fracture, Monteggia fracture, nightstick fracture |
| Metabolic | Osteomalacia, hyperparathyroidism-related bone disease |
| Circulatory | Avascular necrosis (rare in ulna) |
| Inherited | Osteogenesis imperfecta, hereditary multiple exostoses |
| Infiltrative | Sarcoidosis (rare bone involvement) |
| Idiopathic | Ulnar variance syndromes |
| Iatrogenic | Post-surgical complications, nerve entrapment post-casting |
| Functional | None specific |
| Psychiatric | Not applicable |
2. Clinical Signs and Symptoms
| Symptom | Meaning/Implication |
|---|---|
| Pain over ulna | Trauma, inflammation, or overuse |
| Swelling or deformity | Fracture or dislocation |
| Limited range of motion | Joint involvement or fracture |
| Numbness/tingling | Ulnar nerve compression |
| Weak grip | Tendon/ligament injury or nerve dysfunction |
3. Imaging Modalities
| Modality | Primary Use | When/Why Used |
|---|---|---|
| X-ray | Fracture/dislocation | Initial trauma workup |
| CT | Bone reconstruction | Pre-op planning |
| MRI | Ligament/Tendon pathology | TFCC or soft tissue assessment |
| Ultrasound | Tendon tracking | Dynamic tests for extensor/flexor function |
4. Laboratory Tests
| Test | Purpose | When/Why Used |
|---|---|---|
| CBC, ESR, CRP | Infection/inflammation markers | Suspected osteomyelitis |
| Calcium, PTH | Bone metabolism | Fragility fracture or bone turnover concern |
5. Other Diagnostic Tools
| Tool | Use | Indication |
|---|---|---|
| Physical examination | Pain, mobility, deformity | All clinical evaluations |
| Arthroscopy | Intra-articular visualization | TFCC tear or DRUJ instability |
5. History and Culture
Page 5 – History, Culture, and Art (Updated)
1. History of Anatomy
| Aspect | Details |
|---|---|
| Early Discovery | The ulna was described in ancient medical texts by Greek physicians like Galen. It was recognized as one of two bones in the forearm by early anatomists. |
| Renaissance Advancements | Andreas Vesalius included detailed depictions of the ulna in De Humani Corporis Fabrica (1543), improving understanding of its articulations and muscular attachments. |
| Modern Refinement | The anatomical terminology and classification of fractures (e.g., Monteggia fracture) evolved in the 19th and 20th centuries with contributions from Giovanni Battista Monteggia and orthopedic pioneers. |
2. History of Physiology
| Aspect | Details |
|---|---|
| Static vs Dynamic Role | In early biomechanics, the ulna was understood as the stabilizing “axis” during rotation, while the radius performed the dynamic movement. |
| Joint Mechanics | Studies of elbow biomechanics clarified the ulna’s role in hinge motion, contributing to modern prosthetic design and reconstructive surgery. |
| Forearm Stability | The ulna’s interaction with interosseous membrane and TFCC has been key in understanding stability during rotation and load transfer. |
3. History of Diagnosis
| Aspect | Details |
|---|---|
| Palpation Techniques | In pre-radiologic eras, diagnosis of ulna fractures was based on swelling, deformity, and pain localization through tactile assessment. |
| Eponymous Injuries | The “nightstick fracture” was historically noted among soldiers and civilians who suffered forearm trauma while shielding themselves. |
| Orthopedic Milestones | The recognition of combined ulna fractures with radial head dislocations (Monteggia) advanced trauma classification in the 19th century. |
4. History of Imaging
| Aspect | Details |
|---|---|
| Early Radiographs | Shortly after Roentgen’s discovery, the ulna became one of the first bones to be radiographed due to its superficial and accessible location. |
| Advanced Imaging | CT and MRI revolutionized the assessment of complex fractures and associated ligamentous injuries (e.g., TFCC tears). |
| Dynamic Techniques | Ultrasound introduced the ability to assess tendon movement and real-time joint function in ulnar pathology. |
5. History of Laboratory Testing
| Aspect | Details |
|---|---|
| Infection Monitoring | ESR and CRP became standard for evaluating osteomyelitis in open fractures of the ulna. |
| Bone Turnover | Alkaline phosphatase and vitamin D levels became tools to investigate fracture healing delays or metabolic bone disorders affecting the ulna. |
| Genetic Testing | Rare inherited conditions like osteogenesis imperfecta or multiple hereditary exostoses involving the ulna now use genetic screening. |
6. History of Therapies
| Aspect | Details |
|---|---|
| Ancient Splinting | The Egyptians and Greeks used wood and linen wraps to immobilize forearm fractures, including the ulna. |
| Evolution of Fixation | Metal plates and intramedullary rods began replacing plaster and wood in the 20th century, improving healing alignment. |
| Functional Bracing | Introduced in the mid-20th century, this allowed early motion while maintaining fracture stability in selected ulna injuries. |
7. Cultural Meaning
| Culture/Context | Symbolism or Role |
|---|---|
| Martial Symbolism | The ulna is historically linked to defense, as it was commonly fractured while shielding the face or body—thus known as the “nightstick” bone. |
| Forensic Anthropology | Ulna fractures may suggest patterns of assault or self-defense, contributing to legal investigations. |
| Linguistics | “Ulna” derives from Latin ulna, meaning “forearm” or “elbow,” also used metaphorically to describe closeness (e.g., “within one’s ulna” = embraced). |
8. Artistic Representations
| Art/Artist | Interpretation |
|---|---|
| Leonardo da Vinci | Studied the ulna in dynamic poses, emphasizing muscle attachments and joint motion in anatomical sketches. |
| Frank Netter | Illustrated detailed renderings of the ulna in orthopedic and surgical contexts, contributing to modern medical visualization. |
| Forensic and Trauma Art | The ulna is often shown fractured in artwork depicting defense mechanisms, such as shields or martial combat. |
9. Notable Figures
| Figure | Contribution |
|---|---|
| Giovanni Battista Monteggia | Described the ulna fracture and radial head dislocation combination known today as the Monteggia fracture. |
| Sir John Charnley | Innovator in orthopedic implants and techniques, including internal fixation methods applied to forearm fractures. |
| Robert Salter | Advanced the understanding of epiphyseal injuries, including growth plate considerations in pediatric ulna trauma. |
10. Quotes
| Quote | Source / Context |
|---|---|
| “The hand is where the mind meets the world—but it is the forearm that gets it there.” | Anonymous orthopedic aphorism |
| “Within one’s ulna lies the strength to block, not to strike.” | Modern reinterpretation of ancient defensive wisdom |
| “Bones may heal, but they never forget the story of impact.” |
7. MCQ's
Page 6 – MCQs
Basic Science MCQ 1
Which structure articulates with the olecranon of the ulna to form the elbow joint?
A. Capitulum
B. Trochlea
C. Radial head
D. Coronoid process
Correct Answer Table
| Correct Answer | Explanation |
|---|---|
| B. Trochlea | The trochlea of the humerus articulates with the trochlear notch of the ulna (which includes the olecranon and coronoid process) to form the humeroulnar part of the elbow joint. |
Incorrect Answer Table
| Option | Why Incorrect |
|---|---|
| A | Capitulum articulates with the radial head, not the ulna. |
| C | Radial head articulates with the capitulum, not olecranon. |
| D | Coronoid process is part of the ulna itself, not a separate articulating structure. |
Basic Science MCQ 2
The ulna primarily functions as which of the following in forearm rotation?
A. Axis of rotation
B. Prime mover
C. Flexor tendon insertion site
D. Distal rotation stabilizer
Correct Answer Table
| Correct Answer | Explanation |
|---|---|
| A. Axis of rotation | The ulna acts as the stabilizing axis during pronation and supination, while the radius rotates around it. |
Incorrect Answer Table
| Option | Why Incorrect |
|---|---|
| B | Muscles—not bones—act as movers. |
| C | Primarily the radius and metacarpals serve this function. |
| D | The ulna’s role is more global than limited to the distal aspect. |
Clinical MCQ 1
A 35-year-old man sustains an isolated midshaft ulna fracture while defending himself. This injury is commonly referred to as:
A. Colles’ fracture
B. Galeazzi fracture
C. Nightstick fracture
D. Smith’s fracture
Correct Answer Table
| Correct Answer | Explanation |
|---|---|
| C. Nightstick fracture | This term refers to an isolated ulna shaft fracture typically seen when the arm is raised to block a blow. |
Incorrect Answer Table
| Option | Why Incorrect |
|---|---|
| A | Colles’ fracture involves distal radius, not ulna. |
| B | Galeazzi involves radius fracture + distal radioulnar dislocation. |
| D | Smith’s is a reverse Colles’ fracture of distal radius. |
Clinical MCQ 2
In a Monteggia fracture-dislocation, which bone is fractured and which joint is dislocated?
A. Radius; elbow joint
B. Ulna; distal radioulnar joint
C. Ulna; proximal radioulnar joint
D. Radius; proximal radioulnar joint
Correct Answer Table
| Correct Answer | Explanation |
|---|---|
| C. Ulna; proximal radioulnar joint | Monteggia injury involves a proximal ulna fracture with radial head dislocation at the proximal radioulnar joint. |
Incorrect Answer Table
| Option | Why Incorrect |
|---|---|
| A | Radial fracture with elbow dislocation is not typical of Monteggia. |
| B | Distal radioulnar involvement occurs in Galeazzi, not Monteggia. |
| D | Radius is not typically fractured in Monteggia. |
Radiologic MCQ 1
Which imaging modality is most useful for evaluating complex ulna fractures?
A. X-ray
B. CT
C. MRI
D. Ultrasound
Correct Answer Table
| Correct Answer | Explanation |
|---|---|
| B. CT | CT provides high-resolution bone detail and is preferred for evaluating complex or comminuted ulna fractures. |
Incorrect Answer Table
| Option | Why Incorrect |
|---|---|
| A | X-rays are useful initially but limited in complexity. |
| C | MRI is better for soft tissues. |
| D | Ultrasound is limited for bone visualization. |
Radiologic MCQ 2
What radiologic feature is expected in a healed ulna shaft fracture?
A. Osteolysis
B. Periosteal reaction
C. Subchondral cysts
D. Lytic lesion with rim enhancement
Correct Answer Table
| Correct Answer | Explanation |
|---|---|
| B. Periosteal reaction | Healing fractures often show periosteal new bone formation along the cortex. |
Incorrect Answer Table
| Option | Why Incorrect |
|---|---|
| A | Suggests destruction, not healing. |
| C | Seen in arthritis, not fracture healing. |
| D | Suggests neoplasm or abscess, not fracture. |
Radiologic MCQ 3
An MRI of the distal ulna reveals fluid and partial discontinuity of the TFCC. What does this suggest?
A. Olecranon bursitis
B. Ulnar impaction syndrome
C. TFCC tear
D. Extensor carpi ulnaris rupture
Correct Answer Table
| Correct Answer | Explanation |
|---|---|
| C. TFCC tear | MRI is sensitive for detecting tears and fluid signal in the TFCC, a stabilizing structure of the distal ulna. |
Incorrect Answer Table
| Option | Why Incorrect |
|---|---|
| A | Olecranon bursitis occurs proximally. |
| B | Ulnar impaction affects lunate, not TFCC directly. |
| D | ECU rupture would show tendon discontinuity, not TFCC findings. |
8. Memory Image
Page 7 – Memory Image
| Title | Metaphor of the Shield – The Ulna |
|---|---|
| Caption | The image shows a defensive warrior with a long curved shield strapped to his forearm, guarding against incoming strikes. The shield is shaped like the ulna and bears attachments for muscular bands and a hinge at the elbow, representing articulation and support. Behind him, the rotating radius swings like a blade – together forming the coordinated duo of forearm function. |
| Interpretation | The ulna is the protective, stabilizing backbone of the forearm – a shield for the warrior. It is built to absorb force, connect with the elbow, and guide motion. Its strength lies in its steadfastness, while its function is complemented by the mobile, rotating radius. |