Muscles: Upper Limb Flashcards
What four muscles make up the rotator cuff and where so they originate/attach?
These guys are the ones that help stabilize the humeral head into the glenohumeral joint while the shoulder moves. Subscapularis inserts on the lesser tuberosity, the rest (supra, infra, teres minor) insert on the greater tuberosity.
Innervation and Function of the rotator cuff muscles
Suprascapular nerve:
- Supraspinatus - Assists deltoid with first 15 degrees of abduction
- Infraspinatus - Externally rotates the arm
Axillary Nerve
- Teres minor - Externally rotates the arm
Subscapular Nerves
- Subscapularis - Internally rotates the arm
What muscles, nerves, and functions do we find in the anterior compartment of the arm?
The anterior compartment is fed by the musculocutaneous nerve andontains three flexors:
- Biceps Brachii -Flexes and supinates forearm
- Brachialis - Flexes the forearm
- Coracobrachialis - Flexes and adducts the arm
What muscles, nerves, and functions do we find in the posterior compartment of the arm?
Radial nerve feeds this guy, and only one muscle, the triceps brachii, which extends the arm.
What muscles, nerves, and functions do we find in the anterior compartment of the forearm?
Pronators and flexors are in this compartment, and all except the flexor carpi ulnaris and the medial part of the flexor digitorum profundus (fed by the ulnar nerve) are fed by the median nerve.
What muscles, nerves, and functions do we find in the posterior compartment of the forearm?
Extensors and supinators (except brachioradialis, which flexes the forearm). All are fed by the radial nerve.
What are the thenar muscles and what innervates them?
There are four thenar muscles:
Recurrent Branch of the Median nerve - Abductor Pollicis Brevis - Abduction - Opponens Policis - Opposition - Flexor Pollicis Brevis - Flexion Ulnar nerve - Adductor policis - Adduction
What are the hypothenar muscles and what innervates them?
All innervated by the ulnar nerve. These guys move the pinky.
- Opponens digiti minimi - Opposition
- Flexor digiti minimi - Flexion
- Abductor digiti minimi - Abduction
Fracture of the surgical neck of the humerus secondary to trauma leads to what clinical findings and why?
The nerve affected, due to its close proximity, is the axillary nerve. This leads to impaired shoulder abduction due to the deltoid and lateral rotation due to the teres minor.
Shoulder dislocations, often due to outstretched arm injuries in sports, cause what clinical findings and why? What else causes symptoms like this?
Also the axillary nerve. This leads to impaired shoulder abduction due to the deltoid and lateral rotation due to the teres minor.
We see this in electrocution as well
A fracture of the mid humerus has what classic clinical features, and why?
The radial nerve runs right along this part.
Thus, we see a wrist drop (note, the triceps is not affected because it gets its branch of the radial nerve much higher).
What else causes a wrist drop besides a midhumeral fracture?
Radial dislocation, as with nurse-maid’s or falling on outstretched arm
If I shot someone in the anterior biceps, what would happen?
You’d hit their musculocutaneous nerve, causing impairment of elbow flexion and forearm supination
Supracondylar fracture of the elbow leads to what clinical findings and why?
Median nerve runs right by here, so we see “the hand of benediction.”
- Impaired wrist flexion, flexion of digits 1-3, and pronation of the forearm.
With this particular fracture, we also see brachial artery interruption and eventual Volkmann ischemic contracture of the forearm/arm
What else causes the hand of benediction, but it not linked to any arterial issues?
Fracture of the lateral epicondyle of the humerus.
Explain carpal tunnel and what is affected.
Carpal tunnel is what happens when you get fat or old or have volume issues…or are fat.
Your median branch is the one that gets compressed in there the most, leading to sensory/muscular deficits in digits 1-3, impaired thenar muscles BUT palm sensation is intact
Fracture of the medial epicondyle of the humerus leads to what
Ulnar nerve damage, so we get:
- impaired interossei muscles
- impaired digit 4-5 flexors and lumbricals
- impaired hypothenars
- impaired wrist flexion on ulnar side
“Claw hand deformity”
What happens if we fracture the hook of the hamate?
Like fracturing the medial epicondyle of the humerus, we get ulnar nerve damage, but it happens so distally, the wrist is not affected, so we do not get the impaired wrist flexion.
- impaired interossei muscles
- impaired digit 4-5 flexors and lumbricals
- impaired hypothenars
What originates/attaches to the coracoid process of the scapula?
Origin - Coracobrachialis and biceps brachii
insertion - Pec Minor
What transverses the scapular notch?
Suprascapular nerve
Pec Major vs. Pec Minor innervation and action
Both of them innervated by the medial and lateral pectoral nerves.
Pec Major flexes, adducts, and medially rotates the arm
Minor Depresses the scapula and elevates the ribs.
Discuss injury to the posterior cord
This is caused by the pressure of the crosspiece of a crutch, resulting in paralysis of the arm called crutch palsy, which results in loss of function of the extensors of the arm, forearm, and hand, and produces a wrist drop
Discuss Erb-Duchenne Paralysis
This is caused by a birth injury or a violent throw from a horse or motorcycle that injures the upper trunk. It results in loss of abduction, flexion, and lateral rotation of the arm, producing a waiter’s tip hand, where the arm tends to lie in medial rotation resulting from paralysis of lateral rotator cuff muscles.
Besides Erb’s Palsy, what else can a difficult delivery cause?
Lower trunk injury or Klumpke paralysis. It causes a claw hand.
Discuss the extensor compartments of the hand
As the extensor tendons cross the wrist joint, they are arranged into compartments by the extensor retinaculum.
The first dorsal compartment encloses the abductor pollicis longus and the extensor pollicis brevis, the second the extensor carpi radialis brevis and longus, the third the extensor pollicis longus, the fourth the extensor digitorum comminus and the extensor indicis, the fifth the extensor digiti minimi and the sixth the extensor carpi ulnaris.
