Elbow Lecture 1 2023 PDF

DPT 512 Quote of the Day: Biomechanics “Nothing in the /Kinesiology II world can take the place of persistence.” Calvin Coolidge...

DPT 512 Quote of the Day: Biomechanics “Nothing in the /Kinesiology II world can take the place of persistence.” Calvin Coolidge Elbow - part 1 Eric Folkins, PT, DPT, DHSc Fall 2024  Define classification of joints at the elbow Objectives complex Describe how connective tissue provides stability during movement Identify open chain and close chain activities at the elbow Describe Active and Passive insufficiency at the elbow. Describe greatest moment arms of elbow flexors and extensors Identify class of lever of muscles acting on elbow The Elbow complex Functions of the elbow – Mobility to place hand in space – Stability for forceful movements The Elbow joint Compound joint Functions as a modified or loose hinge joint Modified Hinge Joint 1 degree of freedom – Flexion and extension in the sagittal plane – Slight axial rotation and side-to-side motion of the ulna during flex and ext (therefore modified or loose hinge joint) Closed-pack position: extension Open-pack position: 70-90 degrees flexion Elbow joint Structure – Articulating surfaces on the humerus 5 Elbow joint Structure – Articulating surfaces on the humerus 6 Elbow joint Structure – Articulating surfaces on the radius and ulna 7 Elbow joint Structure – Articulating surfaces on the radius and ulna 8 Elbow joint Articulation 9 Elbow joint 10 Elbow joint Joint capsule Single joint capsule for the three joints Capsule fairly large, loose and weak anteriorly and posteriorly Reinforced with ligaments medially and laterally 11 Joint Capsule Elbow joint Ligaments - Medial Posterior UCL fused with common flexor tendon Anterior UCL primary ulnar restraint of valgus stress at 20-120° of elbow flexion ulnar Limits extension at end range Guides joint motion throughout flexion Provides some resistance to longitudinal distraction 13 Activities that stress the Medial Collateral Ligament Elbow joint Ligaments - Lateral LCL fused with common extensor tendon Radial Stabilizes against varus stress and combined varus and supination stress especially in extension Reinforces humeroradial joint Stabilizes radial head Secure ulna to humerus Weaker than MCL RLCL primary Varus 15  Activities that Stress the Lateral Collateral Ligament Posterior Dislocation Posteroloateral Rotary Instability Elbow joint Function –Stability Full extension (closed-packed position) Bony contacts UCL prevents valgus stress/force RCL prevents varus stress/force The joint capsule ability to prevent varus and valgus stress depends on elbow position Co-contraction of flexor and extensor muscles of the wrist and elbow help to provide stability 17 Palpation medial epicondyle medial collateral ligament lateral epicondyle lateral collateral ligament radial head coronoid process Ulnar nerve Elbow joint Function – Axis of motion Not as fixed as previously thought Axis of Motion centered in middle of trochlea 19 Elbow joint Carrying angle – cubitus valgus In anatomical position Caused by configuration of articulating surfaces Medial epicondyle extends caudally more Normal 10°-15° Females > Males At 30° of flexion the carrying angle disappears 20 Elbow joint Function – Mobility The amount of range of motion available depends on Type of motion (active or passive) AROM Flex 135°-145° PROM Flex 150°-160° Position of forearm (supination and pronation) Body mass index Position of the shoulder (two joint muscle) Swelling 21 Active and Passive Insufficiency For Multijoint muscles Active – Shortened so it can’t apply enough force to provide movement. Passive – Muscle can’t stretch anymore.  Triceps and shoulder position 0 degrees shoulder elevation – Long head of tricep most active 90 and beyond – Medial head most active Why? Kholinne, E et al. The different role of each head of the triceps brachii muscle in elbow extension. Acta Acta Orthopaedica et Traumatologica Turcica 52 (2018) 201-205. Elbow joint Muscles Posterior aspect of elbow Anterior aspect of elbow joint joint Triceps brachii Brachialis Anconeus Biceps brachii Supinator Brachioradialis Extensor carpi radialis Supinator longus Pronator teres Extensor carpi radialis Flexor carpi radialis brevis Flexor carpi ulnaris, Extensor carpi ulnaris, Flexor digitorum Extensor digitorum superficialis communis Palmaris longus Extensor digiti minimi 24 Muscle Force Vectors Draw Muscle Force Direction and Moment arm of Brachialis at 0 and 90 degrees Muscle Force Vectors Draw Muscle Force Direction and Moment arm of Bicep Brachi at 0 and 90 degrees Muscle Force Vectors Draw Muscle Force Direction and Moment arm of Brachioradialis at 0 and 90 degrees Muscle Force Vectors Draw Muscle Force Direction and Moment arm of Tricep Brachi at 20 and 90 degrees. Elbow joint Function – Muscle Action Brachialis Flexor One joint muscle A mobility muscle Large physiological cross sectional area (PCSA) Moment arm greatest at 100° of flexion Unaffected by forearm position Active during all types of contractions (isom, conc, ecc) and speeds 29 Elbow joint Function – Muscle Action Biceps Brachii Flexor Two-joint muscle A mobility muscle The long head has the largest volume amongst the flexors Relatively small PCSA Moment arm greatest between 80°-100° of flexion Affected by shoulder position Activation depend on forearm position and magnitude of resistance - More force more activation and with lighter loads less active with greater pronation. 30 Elbow joint Function – Muscle Action Brachioradialis Flexor Compression One joint muscle Small PCSA Moment arm greatest at 100°-120° of flexion Affected by forearm positions and types of contractions 31 Elbow joint Function – Muscle Action Triceps brachii Extensor Two-joint muscle and one- joint muscle Small PCSA Maximum isometric torque produced at 90° of flexion Not affected by forearm positions Synergist during supination when biceps brachii is active Moment arm decreases with increase flexion 32 Tricep  Dip in Chair When is the movement easiest and why? When is the movement hardest and why? Why did you lean fwd to push up?