Elbow Biomechanics Flashcards
What joints make up the elbow (4)
- Humeroulnar
- Humeroradial
- Proximal radioulnar
- Distal radioulnar
What is the shape of the radial head
More oval than spherical
What are the points of articulation for the proximal radioulnar joint (2)
- Radial head
2. Radial notch of the ulna
What are the points of articulation for the distal radioulnat joint (2)
- Ulnar head
2. Ulnar notch of the radius
What does TFCC stand for
Triangular FibroCartilage Complex
What type of joint are the humeroulnar and humeroradial joints
Hinge joint, uniaxial diarthrodial
What motion occurs at the humeroulnar and humeroradial joints
Flexion and extension
What type of joint are the proximal and distal radioulnar joints
Pivot joint (trochoid joint), uniaxial diarthrodial
What motion occurs at the proximal and distal radioulnar joints
Supination and pronation
True or False:
The joint capsule of the elbow is fairly large, loose, and weak anteriorly and posteriorly
True
What are the sides of the capsule reinforced by
Ligaments
What joints does the capsule enclose (3)
- Humeroulnar
- Humeroradial
- Proximal radioulnar
Does the joint capsule enclosing 3 joints have any potential problems
Yes, there is the potential for cross contamination of infection
What are the ligaments of the elbow (4)
- Ulnar collateral ligament (medial)
- Radial collaterla ligament (lateral)
- Annular ligament
- Interosseous membrane
What are the 3 parts of the UCL
- Anterior
- Oblique
- Posterior
Where does the anterior UCL run
Medial epicondyle to coronoid process
What does the anterior UCL stabilize against
Valgus stress
When does the anterior UCL protects the best
20-120 of flexion
True or False:
We don’t need the anterior UCL to be effective at 0-20 due to the oleranon
True
Where does the posterior UCL run
Medial epicondyle to ulnar coronoid process and olecranon
What is the posterior UCL’s main function
Primary co-stabilizer against valgus stress at 120 flexion
What is the posterior UCL’s secondary function
Secondary stabilizer at 30 and 90 flexion (NOT A RANGE)
What are the other names for the oblique UCL
Transverse and Cooper’s
Where does the oblique UCL run
Olecranon and coronoid process
What is the function of the oblique UCL
Helps hold down the anterior and posterior UCL
What happens because the oblique UCL holds down the anterior and posterior UCL ligaments
The oblique UCL helps maintain joint surface approximation
Where does the RCL run
Inferior lateral epicondyle to annular ligament and olecranon
What does the RCL resist (2)
- Varus stress
2. Distractive forces of joint surfaces
What does the annular ligament do
Stabilizes head of radius to ulna`
What is it called when the radial head dislocates from the annular ligament
Nurse maids elbow
What is the shape of the annular ligament
Circular
Does the annular ligament and radial head have a perfect match
No
what is the interosseous membrane between
Radius and ulna
Which directions are the fibers of the interosseous membrane
Every direction
What does the fibers being in every direction do
Provides strength
What are the arthrokinematics of the humeroulnar and humeroradial joints
Concave on convex
What arthrokinematic motions occur with flexion and extension at the humeroulnar and humeroradial joints
Flexion: Anterior roll, Anterior glide
Extension: Posterior roll, Posterior glide
What are the arthokinematics of the proximal radioulnar joint
Spin of radial head on capitulum
Which way is the radial head longer when supinated
A-P
Which way is the radial head longer when pronated
M-L
What are the arthrokinematics of the distal radioulnar joint
Concave radius on convex ulna
What are the arthrokinematic motions of the distal radioulnar joint during pronation and supination
Pronation: Anterior roll, Anterior glide
Supination: Posterior roll, Posterior glide
Where is the axis of motion at the elbow joint
Fixed through the center of trochlea and capitulum
What projects more distal capitulum or trochlea
Trochlea
Is the axis of rotation at the elbow perfectly in the M-L axis
No
What is the average angle of the axis of rotation at the elbow
5-15
What is cubitus valgus
More than 15 carrying angle
What is cubitus varus
Less than 5 carrying angle
Who has a greater cubitus valgus males or females and why
Females due to the greater pelvic angle
What does cubitus mean
Elbow
What makes the carrying angle
The axis of motion at the elbow
How do you measure the carrying angle
Using the long axis of the humerus and ulna then take the angle made at the intersection of the lines
Why do you measure from the ulna and not center of the forearm
The ulna is fixed so the angle will not vary if measured from it
What is the normal carrying angle for men
5
What is the normal carrying angle for women
15
What motions cause the carrying angle to disappear
Pronation and full elbow flexion
Why does the carrying angle disappear with pronation and full elbow flexion
Change in the orientation of the forearm levers due to the radius gliding over the ulna
What is the open pack position
The position in which the joint capsule and ligaments have the greatest laxity
What is the close pack position
The position in which the joint capsule and ligaments are the most taut
True or False:
The close pack position is most often the position where the most joint congruency occurs
True
What is normal elbow extension
0