Elbow and Forearm Complex

Question 1

Cubitus Valgus

Answer 1

Normal is ~15 degrees, if angle is greater than 20, it is valgus, 10 degrees or less it is varus

Question 2

Articular Capsule

Answer 2

encloses humero-ulnar, humero-radial, proximal radio-ulnar

Question 3

Sensory organs of articular capsule

Answer 3

Pacinian corpuscles (pressure, vibration), Ruffini (tension, temp), GTOs (not in capsule, tension mediated inhibitory reflex), free nerve endings (pain)

Question 4

Medial Collateral Ligament (MCL)

Answer 4

consists of anterior, posterior and transverse fibers, anterior fibers are the strongest and stiffest of MCL, resists valgus forces. Posterior fibers resist valgus force and become taut in the extremes of elbow flexion. Transverse fibers provide only limited articular stability.

Question 5

Lateral/Ulnar Collateral Ligament (LUCL)

Answer 5

Splits into two primary fibers, ulnar and radial. the ulnar collateral ligament provides resistance against a varus producing force at the elbow. Taut at full flexion. Also helps prevent excessive external rotation of the proximal forearm relative to the humerus. The radial collateral ligament merges with the annular collateral ligament and also resists varus forces.

Question 6

Elbow normal flexion and extension and functional arc

Answer 6

Normal ranges from -5 of extension to 145 degrees of flexion. The functional arc is 100 degrees of flexion and extension with 30 degrees of extension and 130 degrees of flexion.

Question 7

Open and closed packed positions of elbow

Answer 7

Open packed: 70 degrees of flexion with 10 degrees of forearm supination

Closed packed: full extension and maximum forearm supination

Question 8

Joint Contractures

Answer 8

can occur if maintained in flexion for too long

Question 9

Arthrokinematics of elbow

Answer 9

Coronoid and olecranon processes limit flexion and extension, respectively. Surface congruency mostly limits motion to sagittal motion.

Question 10

Interosseous Membrane

Answer 10

Two perpendicular exceptions, oblique cord, distal oblique fibers

Functions: binding, muscle attachment site, force transmitter

Question 11

Upper extremity weight-bearing

Answer 11

compressive forces transmitted to ulna via IM, 80% on radius and 20% on ulna

Question 12

Upper extremity distraction and how does it fatigue the elbow

Answer 12

distractive forces slackens IM, active tissues engage to limit distraction, associated forces tighten IM

The elbow fatigues because the contraction of the elbow flexors and all primary supinators work to pull the radius proximally towards the capitulum of the humerus when the elbow is at or near full extension.

Question 13

Normal ROM in pronation and supination

Answer 13

75 degrees in pronation

85 degrees in supination

Question 14

Annular Ligament

Answer 14

Holds radial head against ulna, the internal circumference of the ligament is lined with cartilage to reduce friction against the radial head during pronation and supination. The external surface of the ligament receives attachments from the elbow capsule, RCL, and supinator muscle.

Question 15

Quadrate ligament

Answer 15

the ligament stabilizes the proximal radio-ulnar joint, and is stretched throughout movement, most notably supination.

Question 16

Triangular Fibrocartilage (TFCC)

Answer 16

Primary stabilizer of the distal radio-ulnar joint. Dorsal (posterior) and palmer (anterior) capsular ligaments, ulnar collateral ligament, and the articular disc holds the head of the ulna snugly against the ulnar notch of the radius during pronation and supination. Frequent flyer in clinic

Question 17

Distal Radioulnar joint function arc (supination and pronation)

Answer 17

100 degrees is within functional limits, 50 degrees either in supination or pronation

Question 18

Arthrokinematics at proximal and distal radioulnar joints

Answer 18

With regard to roll and slide, proximal is opposite and distal is the same during pronation and supination. Does not apply when hand is fixed.

Question 19

Elbow flexor moment arms

Answer 19

elbow flexor torques produced with the forearm supinated are about 20% to 25% greater than those produced with the forearm fully pronated. Difference is due to bicep moment arm

Question 20

Triceps moment arm

Answer 20

Max force potential: 80-90 degrees

Max moment arm: 0 degrees (complete elbow extension)

Question 21

supination

Answer 21

supinator recruited first in supination, biceps is normally recruited during higher power supination activities. the nervous system usually recruits the supinator for low-power tasks that require a supination motion only while the biceps remain relatively inactive.