LM 4.1: Upper Extremity Osteology Flashcards
what is the shoulder girdle comprised of?
- clavicle
- scapula
- manubrium of the sternum
what is the function of the clavicle?
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
what movements can the clavicle make?
- elevation
- depression
- anterior and posterior rotation
what is the weakest point of the clavicle?
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
the clavicle is a landmark for the insertion of what?
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
where is the scapula located?
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
what is the anatomy of the ventral surface of the scapula?
a broad concavity called the subscapular fossa
what is the glenoid cavity?
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
what is the acromium process?
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”
what is the supraglenoid tubercle?
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
what is tendinitis?
inflammation of a tendon, often developing after degeneration (tendinopathy)
what is tenosynovitis?
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
what is the infraglenoid tubercle?
the region of the scapula from which the long head of the triceps brachii attaches
what is the largest bone in the upper extremity?
humerus
what does the humerus articulate with?
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
what’s the difference between the anatomical and surgical neck of the humerus?
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
which tuberosities are on the shaft of the humerus?
- deltoid tuberosity = attachment site for the deltoid muscle
- radial groove = on the posterior side of the humerus is an oblique radial groove that contains the radial nerve and deep brachial artery
what are the names of the condyles of the humerus?
the capitulum articulates with the head of the radius
the trochlea articulates with the trochlear notch of the ulna
what are the articulations points of the ulna?
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
does the ulna move?
the ulna is the STABLE bone of the forearm and DOES NOT move during supination and pronation motions
which part of the ulna is palpable?
stylus process
what are the functions of the radius?
- main function is to carry out pronation/supination and flexion/extention
- it receives and transmits stress from the hand through the wrist to the ulna via the interosseous membrane
what does the radius articulate with?
- ulna
- the proximal row of carpal bones
- humerus
which muscles are used for pronation?
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
which bones are the the proximal row of carpal bones?
lateral to medial = scaphoid, lunate, triquetrum and the pisiform
the proximal row will articulate with the radius
which bones are the the distal row of carpal bones?
lateral to medial = trapezium, trapezoid, capitate, hamate
the proximal row will articulate with the radius
what is the carpal tunnel?
a volume of space that accommodates 9 flexor tendons and the median nerve on there path to enter the hand
what is the target bone in the proximal row of carpal bones?
scaphoid
it sits on the radial side of the lunate
what happens when the scaphoid is fractured?
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
what is the orientation of the base vs. the head of a metacarpal?
the base is proximal and the head is distal
what are the different regions of a phalange?
the phalanges with the exception of the thumb each have a proximal, middle and distal phalanx.
