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Questions and Answers
The total range of motion (ROM) for the elbow is $0-150$ degrees.
The total range of motion (ROM) for the elbow is $0-150$ degrees.
True
The carrying angle at the elbow is typically greater in males than in females.
The carrying angle at the elbow is typically greater in males than in females.
False
The ulnohumeral joint bears 60% of the weight during axial loading in an extended elbow.
The ulnohumeral joint bears 60% of the weight during axial loading in an extended elbow.
False
The radial head is covered by cartilage for approximately 240 degrees.
The radial head is covered by cartilage for approximately 240 degrees.
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The sublime tubercle on the ulna is where the anterior bundle of the radial collateral ligament attaches.
The sublime tubercle on the ulna is where the anterior bundle of the radial collateral ligament attaches.
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The elbow joint operates as a pivot joint.
The elbow joint operates as a pivot joint.
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The axis of rotation in the elbow passes through the lateral epicondyle.
The axis of rotation in the elbow passes through the lateral epicondyle.
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The ulnohumeral articulation is classified as a hinge joint.
The ulnohumeral articulation is classified as a hinge joint.
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Activating the elbow joint contributes significantly to the ability to perform daily living activities.
Activating the elbow joint contributes significantly to the ability to perform daily living activities.
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The coronoid fossa on the distal humerus connects with the olecranon during elbow extension.
The coronoid fossa on the distal humerus connects with the olecranon during elbow extension.
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The primary function of the medial collateral ligament (MCL) is to resist valgus stresses.
The primary function of the medial collateral ligament (MCL) is to resist valgus stresses.
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The brachialis muscle attaches 6 mm distal to the tip of the coronoid.
The brachialis muscle attaches 6 mm distal to the tip of the coronoid.
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Loss of 50% or more of coronoid height can lead to elbow instability.
Loss of 50% or more of coronoid height can lead to elbow instability.
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The lateral collateral ligament complex (LCL) includes only the radial collateral ligament (RCL).
The lateral collateral ligament complex (LCL) includes only the radial collateral ligament (RCL).
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The posterior bundle of the MCL is primarily responsible for restraining valgus stress when the elbow is fully extended.
The posterior bundle of the MCL is primarily responsible for restraining valgus stress when the elbow is fully extended.
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The distal attachment of the anterior capsule of the elbow is located at the level of the coronoid tip.
The distal attachment of the anterior capsule of the elbow is located at the level of the coronoid tip.
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The accessory collateral ligament contributes significantly to lateral elbow stability.
The accessory collateral ligament contributes significantly to lateral elbow stability.
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The radial head is responsible for approximately 50% of valgus stability at the elbow.
The radial head is responsible for approximately 50% of valgus stability at the elbow.
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Dynamic stabilizers of the elbow joint include the anconeus and brachialis muscles.
Dynamic stabilizers of the elbow joint include the anconeus and brachialis muscles.
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The musculocutaneous nerve innervates the triceps muscle at the elbow.
The musculocutaneous nerve innervates the triceps muscle at the elbow.
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Optimal stability at the elbow is achieved without any tension on the lateral collateral ligament.
Optimal stability at the elbow is achieved without any tension on the lateral collateral ligament.
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The annular ligament aids in the stability of the proximal radioulnar joint.
The annular ligament aids in the stability of the proximal radioulnar joint.
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The capsule of the elbow contributes most to stability when the elbow is in a flexed position.
The capsule of the elbow contributes most to stability when the elbow is in a flexed position.
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The radial nerve exits from the anterior cord of the brachial plexus.
The radial nerve exits from the anterior cord of the brachial plexus.
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The median nerve lies deep to the brachialis muscle at the level of the elbow joint.
The median nerve lies deep to the brachialis muscle at the level of the elbow joint.
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The ulnar nerve traverses anterior to the medial epicondyle as it runs through the cubital tunnel.
The ulnar nerve traverses anterior to the medial epicondyle as it runs through the cubital tunnel.
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The brachial artery splits into the radial and ulnar arteries at the elbow.
The brachial artery splits into the radial and ulnar arteries at the elbow.
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The first motor branch to the flexor carpi ulnaris (FCU) is located proximal to the elbow joint.
The first motor branch to the flexor carpi ulnaris (FCU) is located proximal to the elbow joint.
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Flexion and extension at the elbow occur around an axis of rotation located at the center of the trochlea.
Flexion and extension at the elbow occur around an axis of rotation located at the center of the trochlea.
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The cubital fossa contains the brachial artery positioned medially relative to the biceps tendon.
The cubital fossa contains the brachial artery positioned medially relative to the biceps tendon.
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The superior and inferior ulnar collateral are principal branches of the radial artery.
The superior and inferior ulnar collateral are principal branches of the radial artery.
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Joint reaction forces in the elbow are minimal due to long lever arms around the joint.
Joint reaction forces in the elbow are minimal due to long lever arms around the joint.
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Study Notes
Elbow Biomechanics
- The elbow joint consists of the ulnohumeral, radiocapitellar, and proximal radioulnar joints.
- The elbow is crucial for daily living activities, acting as a lever arm for hand positioning and a fulcrum for forearm leverage.
- Functional range of motion (ROM) for flexion/extension is 0-150 degrees.
- Supination/pronation is 50 degrees.
- Normal valgus carrying angle is 5-10 degrees for males and 10-15 degrees for females, diminishing with flexion during axial loading.
- 40% of weight is transmitted through the ulnohumeral joint, and 60% through the radiohumeral joint in the extended elbow position.
Osteology & Arthrology
- The humerus shaft has a spiral groove posteriorly, containing the radial nerve, approximately 13cm proximal to the trochlea's articular surface.
- The distal humerus flare incorporates the medial and lateral epicondyles, representing half of the elbow joint.
- The trochlea is spool-shaped and positioned medially.
- The capitellum is located laterally.
- The sublime tubercle on the ulna is where the anterior bundle of the medial ulnar collateral ligament attaches.
- The distal humerus contains medial and lateral columns.
Arthrology
- The joint surface of the elbow is anteriorly tilted approximately 30 degrees relative to the humerus shaft.
- The elbow displays 6 degrees of valgus and 5 degrees of internal rotation.
- The axis of rotation is centred at the trochlea and capitellum, passing through the anteroinferior medial epicondyle.
Joint Type
- The radiohumeral articulation is a pivot joint; the radial head is covered by cartilage for approximately 240 degrees.
- The lateral 120 degrees lack cartilage, crucial for radial head fracture internal fixation.
- The ulnohumeral articulation is a hinge joint.
- The coronoid fossa on the distal humerus receives the coronoid process in deeper flexion.
- The coronoid tip acts as a buttress to prevent posterior dislocations.
- The elbow capsule is maximally distended at 70-80 degrees of flexion.
- The distal attachment of the anterior capsule is located 6 mm distal to the coronoid tip.
- The coronoid is an intra-articular structure.
Muscles of the Elbow
- Flexors: Biceps (distal attachment at the radial tuberosity), brachialis (11 mm distal to the coronoid tip).
- Extensors: Triceps.
- Other: Brachioradialis.
Ligaments & Stability of Elbow
- The ulnohumeral joint (coronoid) is a primary static stabilizer.
- Loss of 50% or more of coronoid height may cause elbow instability.
- The medial collateral ligament (MCL) comprises anterior, posterior, and transverse bundles; it resists valgus and distractive stress.
- An important component of the MCL is the anterior bundle.
- The posterior bundle acts as the cubital tunnel floor, limiting flexion to an extent.
- Radial collateral ligament (RCL) and lateral ulnar collateral ligament (LUCL) make up the lateral collateral ligament complex (LCL), resisting varus and external stress during full elbow motion.
- The LCL's origin is the posterior lateral epicondyle and insertion is the supinator crest of the ulna.
- The annular ligament stabilizes the proximal radioulnar joint.
Secondary Static Stabilizers
- The radiocapitellar joint helps restrain valgus stress; the radial head provides approximately 30% of valgus stability, notably important in 0-30 degrees of flexion/pronation.
- The capsule contributes most to stability during full elbow extension.
Dynamic Stabilizers
- Muscles crossing the elbow joint, including anconeus, brachialis, triceps, and biceps, contribute compressive stability.
Nerve of the Elbow
- Musculocutaneous nerve: Originates from the lateral cord of the brachial plexus.
- Radial nerve: Originates from the posterior cord of the brachial plexus; runs between the brachialis and brachioradialis muscles, located superficially to the joint capsule at the level of the radiocapitellar joint.
- Median nerve: Originates from the medial/lateral cords of the brachial plexus.
- Ulnar nerve: Originates from the medial cord of the brachial plexus; traverses behind the medial epicondyle through the cubital tunnel.
Blood Supply of Elbow
- The brachial artery courses medially in the upper arm.
- It enters the cubital fossa laterally, containing the biceps tendon (lateral) and the brachial artery (medial).
- Continuing proximally, it branches into the radial and ulnar arteries.
Kinematics
- The axis of flexion/extension is at the trochlea centre.
- The pronation/supination axis is along the capitellum, radial head, and distal ulna.
- Joint reaction forces are considerable due to the elbow's lever arm design.
- This contributes to degenerative changes.
Free Body Diagram
- Free body diagrams demonstrate elbow inefficiencies.
- Static loads are close to body weight; dynamic loads exceed body weight.
- Sum of moments(M) = 0.
Arthrodesis
- Optimal unilateral arthrodesis position: 90° flexion, 0-7° valgus.
- Optimal bilateral arthrodesis position: One elbow at 110° flexion (feeding), the other at 65° flexion (perineal hygiene).
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Description
Explore the complexities of elbow biomechanics and osteology, focusing on joint structures, range of motion, and functional significance. Understand the anatomical relationships and mechanical principles that govern elbow function in various activities.
