6. Elbow.pdf

TOPIC 6: ELBOW BIOMECHANICS Elbow Shortening and lengthening of the arm for positioning of the hand. Provides stability for use for wrist and hand Very stable joint, between two very moveable joints. Forearm Proximal radio-ulnar Distal radio-ulnar Both joints work together t...

TOPIC 6: ELBOW BIOMECHANICS Elbow Shortening and lengthening of the arm for positioning of the hand. Provides stability for use for wrist and hand Very stable joint, between two very moveable joints. Forearm Proximal radio-ulnar Distal radio-ulnar Both joints work together to make pronation/supination to happen to help in positioning the hand. The elbow complex: Structure Uniaxial, diarthrodial = synovial hinge joint Three bones; humerus, radius, ulna 1 degree of freedom of motion (sagittal plane) Articulations of the elbow ↳ spaid carsule -Humeroulnar -Humeroradial Chand I -Proximal radio-ulnar 1, Humero-ulnar joint Modified hinge joint with 1 degree of freedom: flexion/extension “Modified” because ulnar experiences slight amount of axial rotation and side-to-side motion 2. Humero-radial joint  Even though the humeroradial joint has the surface of a “ball and socket” type of joint, due to the presence of the annular ligament, that anchors radius to ulna, it behaves more like a “pivot” joint. Radial head “pivoting” around the humerus capitulum. 3. Proximal radioulnar joint Not part of the hinge joint. Involved in PRONATION and SUPINATION of the forearm. It’s a Pivot Joint (rotation around an axis) Muscles of the elbow complex Anterior: Biceps Brachii, Brachioradialis, brachialis (flexors) Posterior: Triceps, Anconeus (extensors) Ligaments of the elbow complex Medial collateral ligament Lateral collateral ligament Flexion - Extension: Osteokinematics Axis is not purely transversal Trochlea is longer medially Limitations for Flexion Muscle Mass Coronoid and radial head contact Triceps Posterior capsule tension Limitations for Extension Olecranon contact Tension of the flexors Anterior capsule tension Open Kinematics chain Distal segment is FREE to move on the proximal segment. ULNA and RADIUS move on top of the HUMERUS Concave on the Convex movement: roll and glide SAME DIRECTION Closed Kinematics chain Distal segment is fixed and th proximal segment performs the movement. Radius and ulna are fixed, only way to execute movement is to move the humerus. Convex on concave movement = roll and glide OPPOSITE DIRECTION Humero-radial and humero-ulnar joint Open kinematic chain and Closed kinematic chain Arthrokinematics of Pronation and supination Rotational movements that occur when: -Distal end of the RADIUS moves over the distal end of the ULNA by rotating the radius in the pivot joint formed by the circular head of the radius. Kinetics: Pronation / Supination muscles Muscles Supination: Supinator, Biceps Brachii Pronation: Pronator teres, Pronator Quadratus Osteokinematics of Pronation and Supination Movement of the head of the radius and ulna in a simultaneous war in order to change the movement of the hand. Radial- Ulna and Radial-Humerus. Axis of the movement comes from the radial head and the distal epiphysis of the ulna. Pronator teres and biceps: both work Limits to Supination Tension of the pronators Tension of the triangular ligament Annular ligament Limits to Pronation Tension of the Supinator Tension for the posterior fibers of the triangular ligament Tension of the annular ligament Arthrokinematics of pronation and supination Movement of the radius over the sigmoid cavity of the ulna. Proximal Radial- Ulna proximal joint. Convex moves over concave; gliding and roll are in opposite directions. Kinetics Biceps at 90 degree -extensors control the movement Elbow joint - The carrying angle The angle formed between the long axis of the humerus and the long axis of the forearm when the arm is in the anatomical position Average carrying angle: -Males: 5 to 10 degrees -Females: 10 to 15 degrees It helps keep the hand away from the body, providing clearance during activities such as walking.