LM 4.1: Upper Extremity Osteology

Question 1

what is the shoulder girdle comprised of?

Answer 1

1. clavicle
2. scapula
3. manubrium of the sternum

Question 2

what is the function of the clavicle?

Answer 2

it serves as a strut to keep the limb away from the body wall and allows a free range of motion of the arm

it is the only bony connection between the upper limb and the axial skeleton and importantly transmits forces from the upper limb to the axial skeleton

Question 3

what movements can the clavicle make?

Answer 3

1. elevation
2. depression
3. anterior and posterior rotation

Question 4

what is the weakest point of the clavicle?

Answer 4

the infection point

it’s the change in curvature between the medial 2/3rds and the lateral 1/3rd of the clavicle

the inflection point is the location where the clavicle cannot flex to absorb a load and resulting in a place where fractures are likely to occur

Question 5

the clavicle is a landmark for the insertion of what?

Answer 5

most anterior portion of the clavicle is a major palpatory landmark for insertion of a catheter into the subclavian vein (venous access)

at this palpable point the subclavian vein (s.c.v.) sits posterior and superior to the bone and is running in a direction to hit the sternal notch, a feature of the manubrium

Question 6

where is the scapula located?

Answer 6

the scapula rests at a position on the posterior thorax approximately 2 inches from the midline, between the second through seventh ribs

the scapula articulates with Acromioclavicular (AC) and Sternoclavicular (SC) joints and ALSO a scapulothoracic “joint” which is not a true anatomic joint

Question 7

what is the anatomy of the ventral surface of the scapula?

Answer 7

a broad concavity called the subscapular fossa

Question 8

what is the glenoid cavity?

Answer 8

a shallow articular surface of the scapula that articulates with the head of the humerus

it’s the hole in the scapula that the humerus fits into

the cavity forms the glenohumeral joint (shoulder joint)

the rim of the cavity is slightly raised to give attachment to a fibrocartilaginous structure called the glenoid labrum which deepens the cavity for added joint stability of the glenohumeral joint

Question 9

what is the acromium process?

Answer 9

the continuation of the scapular spine where it articulates with the clavicle to form the acromiclavicular joint (AC joint)

the process forms the “point of the shoulder”

Question 10

what is the supraglenoid tubercle?

Answer 10

a region of the scapula from which the long head of the biceps brachii muscle attaches

it is a small, rough projection superior to the glenoid cavity near the base of the coracoid process

inflammation of the tendon of the long head of the biceps brachii originates at the supraglenoid tubercle in about 30% of cases

Question 11

what is tendinitis?

Answer 11

inflammation of a tendon, often developing after degeneration (tendinopathy)

Question 12

what is tenosynovitis?

Answer 12

tendinitis with inflammation of the tendon sheath lining

symptoms usually include pain with motion and tenderness with palpation.

chronic deterioration or inflammation of the tendon or tendon sheath can cause scars that restrict motion

Question 13

what is the infraglenoid tubercle?

Answer 13

the region of the scapula from which the long head of the triceps brachii attaches

Question 14

what is the largest bone in the upper extremity?

Answer 14

humerus

Question 15

what does the humerus articulate with?

Answer 15

at the proximal end, the head of the humerus articulates with the glenoid cavity of the scapula to form the glenohumeral joint

the humeral head 3X larger than the glenoid cavity so the major reinforcement to help stabilize this joint is the glenoid labrum, which deepens the socket for added stability

at the distal end, the humerus articulate with the radius and ulna to form the elbow joint

Question 16

what’s the difference between the anatomical and surgical neck of the humerus?

Answer 16

the anatomical neck is between the head and greater/lesser tubercles and is a line of attachment for the glenohumeral (shoulder) joint capsule

the surgical neck is a common fracture site and is found distal to the greater and lesser tubercles

Question 17

which tuberosities are on the shaft of the humerus?

Answer 17

1. deltoid tuberosity = attachment site for the deltoid muscle
2. radial groove = on the posterior side of the humerus is an oblique radial groove that contains the radial nerve and deep brachial artery

Question 18

what are the names of the condyles of the humerus?

Answer 18

the capitulum articulates with the head of the radius

the trochlea articulates with the trochlear notch of the ulna

Question 19

what are the articulations points of the ulna?

Answer 19

3 bony articulations

two with the radius = a proximal and distal radioulnar joint

one with the trochlea of the humerus

the ulna DOES NOT articulate with the carpal bones

Question 20

does the ulna move?

Answer 20

the ulna is the STABLE bone of the forearm and DOES NOT move during supination and pronation motions

Question 21

which part of the ulna is palpable?

Answer 21

stylus process

Question 22

what are the functions of the radius?

Answer 22

1. main function is to carry out pronation/supination and flexion/extention
2. it receives and transmits stress from the hand through the wrist to the ulna via the interosseous membrane

Question 23

what does the radius articulate with?

Answer 23

1. ulna
2. the proximal row of carpal bones
3. humerus

Question 24

which muscles are used for pronation?

Answer 24

the pronator teres and pronator quadratus

these two muscles work together to achieve pronation by pulling on the radius bone

the radius is designed to rotate at the proximal and distal radioulnar joint

Question 25

which bones are the the proximal row of carpal bones?

Answer 25

lateral to medial = scaphoid, lunate, triquetrum and the pisiform

the proximal row will articulate with the radius

Question 26

which bones are the the distal row of carpal bones?

Answer 26

lateral to medial = trapezium, trapezoid, capitate, hamate

the proximal row will articulate with the radius

Question 27

what is the carpal tunnel?

Answer 27

a volume of space that accommodates 9 flexor tendons and the median nerve on there path to enter the hand

Question 28

what is the target bone in the proximal row of carpal bones?

Answer 28

scaphoid

it sits on the radial side of the lunate

Question 29

what happens when the scaphoid is fractured?

Answer 29

scaphoid fractures may be radiologically occult in the acute setting and may result in avascular necrosis

avascular necrosis can happen because the scaphoid is made of a proximal, distal and neck region but the arterial supply is ONLY to the distal portion so nutrients can only reach the proximal portion via diffusion across the neck of the bone

a consequence of this anatomy is that the proximal fragment following a neck fracture (20% of the cases) receives no blood supply, and therefore has a high probability of undergoing the process of necrosis

Question 30

what is the orientation of the base vs. the head of a metacarpal?

Answer 30

the base is proximal and the head is distal

Question 31

what are the different regions of a phalange?

Answer 31

the phalanges with the exception of the thumb each have a proximal, middle and distal phalanx.