Detailed Notes on Elbow Anatomy and Related Injuries

1. Define Key Terms

• Fracture: A break in the continuity of a bone, which can vary in severity from simple (a clean break) to complex (multiple fragments, potentially involving joint surfaces). Fractures can be classified as closed (skin intact) or open (skin broken, exposing the bone). The treatment and recovery for fractures depend on the type, location, and severity of the fracture, often involving immobilization or surgery.

• Radial Pulse: The palpable pulsation of the radial artery felt at the wrist, providing an indicator of blood flow to the hand. Absence of the pulse can signify vascular compromise due to trauma, and assessing it is vital in emergency scenarios to avoid complications.

• Nerve Damage: Injury to a nerve can result in loss of sensation, such as numbness and tingling, or motor function, including weakness or paralysis. It may arise from direct injury or secondary conditions, emphasizing the importance of early identification and management.

• Compartment Syndrome: This serious condition occurs when increased pressure within a closed muscle compartment compromises circulation and muscle function. It requires immediate surgical intervention (fasciotomy) for pressure relief to prevent irreversible muscle damage and dysfunction.

2. Outline the Bony Anatomy of the Elbow

The elbow joint comprises three major bones:

• Humerus: The distal end features the trochlea (articulating with the ulna) and the capitulum (articulating with the radius), allowing for hinge-like movement that facilitates flexion and extension of the forearm. It plays a significant role in weight-bearing activities as it transfers loads from the arm to the forearm.

• Ulna: Situated on the medial side of the forearm, this larger bone includes the olecranon (the bony tip) crucial for extending the elbow joint and the coronoid process, which provides stability when flexing the elbow. The ulna's stability is vital for activities that require elbow flexion.

• Radius: The radial head articulates with the capitulum of the humerus, contributing to forearm rotation (pronation and supination). The radius allows for diverse motions essential for various tasks, such as turning a doorknob or using tools.

Joint Types

• Hinge Joint (Humeroulnar): Allows for flexion and extension, providing a stable range of motion crucial for movements like lifting and pushing.

• Pivot Joint (Proximal Radioulnar): Enables rotation of the radius over the ulna, facilitating actions such as typing and using utensils.Both joints are stabilized by ligaments including the ulnar collateral ligament and the radial collateral ligament, which help prevent dislocation and maintain joint integrity during movement.

3. Vasculature Around the Elbow

Arteries

• Brachial Artery: The primary artery that bifurcates into the radial and ulnar arteries at the elbow, playing a critical role in supplying blood to the forearm and hand, especially during physical activities.

• Collateral Arteries: Including the superior and inferior ulnar collateral arteries and radial collateral artery, these arteries form anastomoses that ensure continued blood supply, especially when elbow movement interferes with direct flow.

Veins

• Basilic Vein: Located on the medial side of the forearm, it drains into the brachial vein, playing a role in venous return from the forearm.

• Cephalic Vein: Found laterally, this vein drains into the axillary vein, often accessed for venipuncture due to its superficial nature.

• Median Cubital Vein: This superficial vein at the anterior elbow is typically used for venipuncture, providing a convenient site for blood draws without deep penetration.

Nerves Around the Elbow

The major nerves associated with the elbow are vital for motor and sensory functions and follow closely with the vascular structures. Their proximity to the arteries and veins can affect surgical outcomes and injury management.

• Median Nerve: Flows along with the brachial artery and enters the forearm through the cubital fossa. It provides motor innervation to the forearm’s flexor muscles and is crucial for thumb opposition and innervates some intrinsic hand muscles.

• Ulnar Nerve: This nerve traverses posterior to the medial epicondyle, running in close association with the artery. It is responsible for innervating the intrinsic muscles of the hand, including those responsible for finger abduction and coordination.

• Radial Nerve: Running along the radial artery, it spirals around the humerus and enters the forearm, providing motor function to the extensors of the forearm and sensory innervation to parts of the hand. Its proximity to bone makes it prone to injury in humeral fractures, which can affect the vascular structures previously described.

4. Reasons for Absence of Radial Pulse After a Fracture

Vascular Injury

• Direct Damage: A fracture can sever or lacerate the brachial or radial artery, leading to an immediate loss of pulse and requiring urgent surgical intervention.

• Compression: Bone fragments from a fracture or a hematoma can compress the artery, causing reduced blood flow and absence of the radial pulse, which necessitates imaging studies to evaluate vascular compromise.

• Compartment Syndrome: This can arise from trauma or fracture, increasing pressure in a confined space and compromising arterial blood flow, resulting in ischemia and potential tissue necrosis.

• Dislocation: An elbow dislocation can stretch or compress blood vessels, resulting in altered blood flow patterns, which could lead to the absence of pulse.

5. Why Fractures Can Lead to Nerve Damage

Mechanisms

• Direct Trauma: Fractured bone fragments can directly sever nerves, leading to complete loss of function in affected areas.

• Compression: Post-injury swelling or hematoma formation exerts pressure on adjacent nerves, potentially leading to neuropathy that requires timely management.

• Stretching: Displacement of fractured bone can stretch nerves beyond their normal limits, causing functional impairment that can lead to chronic pain or motor deficits.

6. Nerves Potentially Damaged by Upper Limb Fractures

• Axillary Nerve: Frequently damaged with fractures of the surgical neck of the humerus, resulting in loss of sensation over the lateral shoulder and weakness in shoulder abduction, impacting coordination in overhead movements.

• Radial Nerve: Often injured in midshaft humeral fractures, leading to wrist drop (inability to extend the wrist and fingers). This can severely affect grip strength and function of the upper extremity.

• Median Nerve: Can be compromised in supracondylar fractures of the humerus, affecting thumb opposition and sensory function on the palmar side of the lateral 3½ fingers, which could impair fine motor skills essential for daily tasks.

• Ulnar Nerve: Injured by medial epicondyle fractures or elbow dislocations, leading to deficits in finger abduction and loss of sensation on the medial 1½ fingers, affecting hand dexterity and grip.

7. How to Test the Median, Ulnar, and Radial Nerves

• Median Nerve:

  • Motor Exam: Assess thumb opposition by asking the patient to touch the thumb to the little finger, evaluating the integrity of the nerve function.

  • Sensory Exam: Check sensation on the palmar surface of the lateral 3½ fingers to assess sensory function.

• Ulnar Nerve:

  • Motor Exam: Test finger abduction by having the patient spread their fingers against resistance.

  • Sensory Exam: Test sensation on the palmar and dorsal surfaces of the medial 1½ fingers to determine the extent of sensory loss.

• Radial Nerve:

  • Motor Exam: Evaluate wrist extension strength by resisting wrist extension, confirming motor function.

  • Sensory Exam: Assess sensation over the dorsum of the hand on the lateral side, excluding fingertips, to confirm sensory integrity.

8. Course of the Major Nerves of the Upper Limb

• Axillary Nerve:

  • Origin: Posterior cord of the brachial plexus (C5-C6).

  • Course: Travels through the quadrangular space, innervating the deltoid and teres minor muscles, responsible for shoulder abduction and external rotation, underscoring its importance in upper limb mobility.

• Radial Nerve:

  • Origin: Posterior cord of the brachial plexus (C5-T1).

  • Course: Spirals around the humerus in the radial groove, crossing the elbow, and bifurcating into superficial (sensory) and deep (motor) branches, supplying the posterior aspect of the arm and forearm, highlighting its significance in extension movements.

• Median Nerve:

  • Origin: Formed from contributions of the medial and lateral cords of the brachial plexus (C6-T1).

  • Course: Descends through the arm and enters the forearm through the cubital fossa, eventually passing through the carpal tunnel to innervate the anterior forearm and intrinsic hand muscles, indicating its pivotal role in hand function.

• Ulnar Nerve:

  • Origin: Branches from the medial cord of the brachial plexus (C8-T1).

  • Course: Travels posterior to the medial epicondyle, providing sensory and motor innervation to the medial aspect of the forearm and hand, indicating its critical role in fine motor skills and grip strength.