Elbow Flashcards
What are the joints at the elbow and forearm?
- Humeroulnar
- Humeroradial
- Proximal radioulnar
- Distal radioulnar
Is the humeroulnar or humeroradial joint more stable?
Humeroulner; due to processes and grooves reinforced with capsule and ligaments
Humeroradial joint provides about ___% of resistance to a valgus-producing force to the elbow.
50%
What are the normal ranges of carrying angle?
13 degrees ( + or - 6 degrees)
- females typically have 2 degrees more than makes
- 5 to 25 degrees is functional
Gunstock deformity; forearm is deviated medially 5 degrees
Cubitus varus
What is usually the cause of varus or valgus deviation of the elbow?
Fracture through the growth plate of the distal humerus
Excessive cubital valgus (20-25 degrees) may overstretch and damage _______ nerve on the medial side of the elbow
Ulnar
What would be considered excessive cubitus valugus?
lateral deviation of 30 degrees (according to Jason, book says 20-25 degrees)
What is the ROM at the elbow in the saggital plane?
Elbow Flexion = 145°
Elbow Extension = 0° to 5° beyond neutral
How many degrees do you need to have functional elbow motion?
100 degree functional arc from 30 - 130 degrees
[Convex/Concave] trochlea of humerus. [Convex/Concave] trochlear notch of ulna
Convex; concave
What can potentially limit passive elbow extension?
- Anterior skin
- Flexor muscles
- Anterior capsule
- Anterior fibers of the medial collateral ligament
- Broad tendon of the brachialis muscle
- Olecranon process of ulna becomes wedged into the olecranon fossa of the humerus
What can potentially limit passive elbow flexion?
- Posterior capsule
- Extensor muscles
- Ulnar nerve
- Posterior fibers of the medial collateral ligament
At the humeroradial joint: [Concave/convex] fovea of radial head. [Concave/convex] capitulum of humerus. What happens during active flexion?
Concave; convex; muscle pulls fovea against the capitulum (minimal boney contact during full extension)
The Radial head is held against the proximal ulna by a ring consisting of 75 % ______ and 25% _______.
Annular ligament; radial notch of the ulna
What are the functions of the interosseous membrane between the radius and ulna?
- Binds the radius to the ulna
- Stable attachment for some extrinsic muscles of the hand
- Provide a mechanism for transmitting force proximally through the upper extremity
What force pulls the interosseous membrane taut?
compression force, greater during active pronation
Distal radioulnar joint: [Convex/ concave] head of ulna into the [convex/concave] ulnar notch of radius. Head of ulna also fits into the proximal surface of the _____
Convex; concave; articular disc
Occupies most of the ulnocarpal space between the head of the ulna and the ulnar side of the wrist; Primary stabilizer of the distal radio-ulnar joint; functions similar to meniscus (periphery heals we’ll)
Articular disc AKA triangular fibrocartilage couples (TFCC)
[Pronation/Supination]
- Places palm down
- Thumb same side as medial epicondyle of elbow
[Pronation/ Supination]
- Places palm up
- Thumb same side as lateral epicondyle of elbow.
What does the axis of rotation connect?
Pronation; supination; radioulnar joint
- Radius, wrist, and hand rotate together around a fixed ulna and humerus
What is the ROM for the forearm? what is the reference point?
{horizontal plan/vertical axis}
Pronation = 75°
Supination = 85°
Thumb up position
How many degrees do you need to have functional forearm motion?
100 degree functional arc from 50-50 degrees
What is the close-packed position for the humeroradial joint? Humeroulnar? Proximal radioulnar? Distal Radioulnar?
Humeroradial joint – 90°elbow flexion, 5°supination
Humeroulnar joint – Full elbow extension and supination (anatomic position)
Proximal radioulnar joint - 5° supination
Distal radioulnar joint - 5° supination
What is the open-packed position for the humeroradial joint? Humeroulnar? Proximal radioulnar? Distal Radioulnar?
Humeroradial joint – Full elbow extension and supination (anatomic position)
Humeroulnar joint – 70°elbow flexion, 10° supination
Proximal radioulnar joint - 70° elbow flexion, 35° supination
Distal radioulnar joint - 10° supination
When is intracapsular pressure the lowest?
80 Degrees of elbow flexion
- “position of comfort” when joint is inflamed and swollen
What does the “wounded paw” position predispose a pt to?
Elbow flexion contracture
- tightening of tissue that restricts normal passive extension
- difficult to get back extension
How does the MCL of the elbow rupture?
- Fully extended elbow is forced into excessive values - Often from a fall on an outstretched arm
- Repetitive valgus forces to elbow in non-weightbearing activities - Pitching a baseball or spinning a volley ball; Tommy John surgery to fix
What injury may be associated with the rupture of the MCL?
Fracture within humeroradial joint or alone radius
What structures limit supination?
- Pronator teres
- pronator quadratura
- TFCC (excessive), especially palmar capsular ligament
- Interosseous membrane
What structures limit pronation?
- Biceps
- supinator muscles
- TFCC, especially dorsal capsular ligament
Occupies space distal to the head of the ulna; consists of articular disc, capsular ligaments of distal radioulnar joint, and ulnar collateral ligament; Primary stabilizer of distal radioulnar joint; Tears can result in dislocations, instability, and limited/painful pronation, supination, and motions at the wrist
TFCC
Anterior motion of the humerus on a fixed ulna and radius results in
Posterior elbow dislocation (tearing of anterior capsule and brachialis muscle)
- can be caused from a fall onto an outstretched arm
Dislocation of proximal radioulnar joint; Radius pulled distal to annular ring; Caused by sharp pull of the hand
Pulled-Elbow syndrome
- Children more susceptible bc ligament laxity, reduced strength, slower reflexes and likelihood of parents pulling on arms
What causes radial head fractures?
Compression of Radial Head/Fovea against Capitulum - over time, compression forces cause narrowing of joint
(OA)
- need smoothness for movements
What ligament is stretched taut in valgus, extension and flexion?
Anterior fibers of MCL
What ligament is stretched taut in valgus and flexion?
Posterior fibers of MCL
What ligament is stretched taut in varus and external rotation?
Radial collateral ligament
What ligament is stretched taut in varus, external rotation, and flexion?
Lateral (ulnar) collateral ligament
What ligament is stretched taut during distraction and external rotation?
Annular ligament
What ligament fibers provide the most resistance agains a valgus force to the elbow?
Anterior fibers of the MCL
What muscles resist excessive valgus producing strain at the elbow and are thus referred to as the dynamic medial stabilizers?
Proximal fibers of the wrist flexor and pronator group of muscles, most notably the flexor carpi ulnaris
What ligament would be injured when the fully extended elbow is violently force into excessive valgus (fall on an outstretched arm and hand) or repetitive valgus-producing forces on the elbow such as pitching a baseball and spiking a volleyball?
MCL
- An extreme force as this may also fracture the radius (anywhere along its length), ulnar nerve, or proximal attachments of pronator wrist flexor muscles
What are the two fiber bundles of the LCL?
- Radial collateral ligament
2. Lateral (ulnar) collateral ligament
What are the stabilizers of the distal radio-ulnar joint?
- TFCC
- Pronator quadratura
- Tendon of extensor carpi ulnas
- Distal fibers of interosseous membrane
What complete dislocation or generalized instability of the distal radio-ulnar joint, making probation and supination motions, as well as motions of the wrist, painful and difficult to perform?
Tears or disruptions of the TFCC
What muscle creates significant compression forces associated with a proximal migration of the radius? what movement causes more compression forces?
Pronator teres; pronation
In open chain kinematics the [radius/ulna] rotates around the [radius/ulna] in supination and pronation.
Radius; ulna
In close chain kinematics the [radius/ulna] rotates around the [radius/ulna] in supination and pronation.
Ulna; radius
It is important to not that closed chain pronation and supination kinematics are essentially an expression of….
active ER and IR of the glenohumeral joint
-the ulna and humerus rotate as a unit during this motion
Muscles that attach distally on the ____ flex or extend the elbow but possess no ability to pronate or supinate the forearm. Muscles that attach distally on the ____ may flex or extend the elbow, but also have the potential to pronate or supinate the forearm.
Ulna; radius
What two fundamental features must a muscle have to be considered a supinator or pronator?
- the muscle must attach on both sides of the axis of rotation (proximal on humerus or ulna, distal on radius or hand)
- the muscle must produce a force that acts with an internal moment arm around the axis of rotation for rotation and supination
What are the primary supinator muscles?
- supinator
2. biceps brachii
