Week 9 finished Flashcards
What is the function of the clavicle? What part of the
clavicle is most frequently fractured?
Functions include:
-Serves as a rigid strut from which the scapula and
free limb are suspended, thus permitting scapular
movement on thoracic wall and increasing ROM of arm.
-Provide area of muscle attachments
-Afford protection to the neurovascular bundle
supplying upper limb
-Transmits force (shocks) from upper extremity to
the axial skeleton and links the shoulder to the axial skeleton via SC joint.
Fracture
This relatively slender bone transmits forces from the upper limb to the trunk, thus it is frequently fractured. It is most commonly fractured at the junction of middle and lateral thirds. Often in children due to a FOOSH. The weight of the UEX drags the lateral end down (drooping shoulder) and the strong SCM drags the medial end up
What are the muscle attachments of the proximal humerus?
Greater Tuberosity: Insertion of
o Supraspinatus (sup)
o Infraspinatus (mid)
o Teres minor (inf)
-Lesser Tuberosity:
o Insertion of subscapularis
-Bicipital Groove o Lateral lip: insertion of pec major o Medial lip: Teres Major o Floor: Insertion of Lat Dorsi o Floor contains tendon of Long Head of Biceps
-Deltoid Tuberosity
o Insertion of Deltoid
What structures increase stability and force dissipation at thesternoclavicular (SC) joint? How does this affect the susceptibility to dislocation and osteoarthritis?
Only joint connection the shoulder to the body,
therefore very strong joint.
The SC joint is divided into two compartments by an articular disc. The disc is firmly attached to the anterior and posterior sternoclavicular ligaments, thickening of the fibrous layer of the capsule, as well as the interclavicular ligament. The strength of the joint is due to these attachments:
- Anterior & posterior sternoclavicular ligaments (reinforce the capsule and check anterior and posterior movements of the head of the clavicle)
- The interclavicular ligament (reinforces the capsule superiorly. It extends across the suprasternal notch of each sternal end of the clavicle and has fibers that extend to the manubrium. Limits depression or downward glide of the clavicle which would compress the brachial plexus. Because of the strong stabilising and force dissipating structures there is minimal intra-articular movement)
• The costoclavicular ligament: (Limits elevation of the pectoral girdle and runs between the first rib and the clavicle).
Because of the strong stabilising and force dissipating structures there is minimal intra-articular movement and this joint is rarely dislocated and uncommonly affected by OA.
Its a badass joint.
What ligaments support the acromio-clavicular (AC) joint? How does the orientation of the AC joint surfaces
protect neurovascular structures?
Not a very strong joint and dislocation and OA are very common vs SC.
-Ligaments:
o Weak joint capsule attaches to margins of articular surfaces.
o Superior and inferior acromioclavicular ligaments
reinforce the joint capsule.
o The coracoclavicular ligament is a very strong
extracapsular ligament running between the coracoid
process of the scapula and the clavicle:
- It is divided into two parts:
-Conoid (Triangle in shape, root coracoid process to
inferior clavicle)
-Trapezoid (Superior surface of coracoid process to the trapezoid line on the clavicle)
The two are separated by adipose tissue and a bursa:
- Prevents upward rotation of scapula at AC joint.
-Transfers medially directed forces from the scapula
to the clavicle & in turn, the strong SC joint.
-Produces longitudinal rotation of the clavicle to
increase range of arm elevation.
Which ligaments support the glenohumeral (GH) joint?
GH: Ball and socket joint, thats mobility = instability. Most stability comes from not the ligaments but the muscles surrounding the joint.
Ligaments of the GH:
Large, loose articular capsule, taut sup & loose inf in the resting position. On abduction & lat rotation, the capsule twists and tightens, dictating the close-packed position of the GH.
Types of Ligaments: 6 ligaments
1-3 Glenohumeral Ligaments Superior, middle and inferior (Three fibrous bands in the internal aspect of the capsule.
Superior = coracoid process, labrum to the neck of the humerus. Inferior = may have up to 3 parts helps with stability at 90 degrees)
4-Coracohumeral Ligament
(Has two bands originating from the coracoid process. The first inserts into the edge of supraspinatus and onto the greater tubercle of the humerus. The second inserts into the subscapularis and onto the lesser tubercle. The two bands form a tunnel for the long head of biceps. Prevents inferior translation of the humeral head)
5- Transverse Humeral Ligament
(is a band between the greater and lesser tubercles of the humerus, which forms a canal for tendon of the long head of the biceps and its synovial sheath)
6- Coracoacromial (Suprahumeral) Arch
( Formed by the coracoid process and acromion of the scap & the coracoacromial ligament between them.
Forms a vault over the humeral head –suprahumeral space– through which the subacromial bursa, supraspinatus tenon and long head of biceps tendon pass. )
Why is the GH joint susceptible to dislocation?
-Dislocation of GH joint is common due to great range of motion at expense of stability – small glenoid cavity, less than robust ligaments. Anterior dislocation more common
– usually traumatic.
- Recurrent dislocation is common. May injure the axillary nerve by compression in quadrangular space. May damage axillary artery. May stretch radial nerve as it is bound tightly to posterior humerus. Posterior dislocation is rare (epilepsy, electrocution).
- Anterior Dislocation: occurs often in young, athletes. It is caused by extension and lateral rotation of the humerus. The humerus head is driven infro-anteriorly
Note that while the ligaments of the GH joint, help to support the joint, the majority of stability is conveyed by as dynamic stability of the rotator cuff muscles.
Which bursae communicate with the synovial capsule of the GH joint?
Bursae that communicate with capsule:
o Bursa of subscapularis
o Bursa of the Long head of biceps
The subtendinous bursa of subscapularis and the bursa around the long head of biceps are really outfoldings of the synovial membrane.
Bursae that don’t
o Subacromial bursa
-Lies between the arch superiorly and the tendon and tubercle inferiorly (allows for movement of the supraspinatus tendon moving over the greater tubercle of the humerus.
*NB It can extend all the way down to the insertion of the deltoid when inflamed, this is why people with rotator cuff strain can present with deltoid insertion pain. *supraspinatus tendinopathy = subacromial bursitis
o Coracoid bursa (under the bursa
o Supraacromial bursa (between skin and acromion)
o Tendons (ie corachobrachialis, teres major, triceps, lat dorsi.) IE bursa of the tendons
What structures support the GH joint in the static neutral position? How does posture
affect this mechanism?
In the static, unloaded, neutral GH joint, tension in the superior glenohumeral ligament, the superior capsule and the coracohumeral ligament (rotator interval capsule) is sufficient to maintain joint position against gravity.
Passive tension in the supraspinatus and subscapularis muscles may also make some contribution.
There is no muscle activity required.
Posture? no idea…
List the muscles which connect the UPPER EXTREMITY to the TRUNK?
2 groups:
- Anterior Axio-appendicular muscles
- Pectoralis major
- Pectoralis minor
- Subclavius
- Serratus anterior - Posterior Axio-appendicular:
- Trapezius
- Lattissimus Dorsi
- Levator- Scapularis
- Rhomboid minor and major
What is the innervation to serratus anterior? How could this nerve be injured? What would be the result?
Serratus anterior = Long thoracic nerve ( C5,6,7)
The long thoracic nerve is superficial down the lateral thoracic wall it is vulnerable to damage.
Usually, injury to this nerve occurs due to trauma, direct blow to the rib area, over stretching or strenuous repetitive movements of the arms, and sustained bearing of excessive weight over the shoulder.
-Bullets, knife fights, or shives (if you’re a badass mofo probably in jail)
Results scapula winging and a loss of normal elevation of the upper extremity as the serratus is unable to rotate the glenoid cavity superiorly for complete abduction of the limb.
What structures contribute to dynamic stability of the GH joint?
Dynamic stability conveyed to the GH joint is done by the rotator cuff muscles.
- The rotator cuff is composed of supraspinatus, infraspinatus, teres minor and subscapularis.
- Their tendons blend with and reinforce the GH capsule.
- Contraction of the rotator cuff muscles compresses the GH joint, drawing the humerus into the glenoid.
- The infraspinatus, teres minor and subscapularis also exert an inferior pull on the humerus, which counteracts the superior pull of the deltoid.
- Infraspinatus and teres minor also contribute to abduction by externally rotating the humerus to prevent impact of the greater tubercle on the acromion.
List the structures supplied by each of the terminal branches of the brachial plexus?
Musculocutaneous
From the lateral cord (C5-7)
Path:
- Leaves the axilla and pierces coracobrachialis
- Passes distally between brachialis and biceps brachii
- Lateral the biceps tendon it pierces the brachial fascia
- Running down the lateral aspect of the forearm as the Later Cutaneous Nerve of the forearm.
Supplies: BBC
- Biceps brachii
- Brachialis
- Coracobrachialis
Sensory: The lateral cutaneous nerve of forearm (skin of the lateral forearm)
Damage: RARE
List the structures supplied by each of the terminal branches of the brachial plexus?
Axillary
Comes off the posterior cord of the brachial plexus (C5,6)
Path:
-Enters the posterior compartment of the arm through the quadrangular space
-Winds around the surgical neck of the humerus
-Travels with the posterior circumflex artery
-Gives off the Superior Lateral cutaneous Branch
Supplies:
- Deltoid
- Teres Minor
- GH joint
Sensory: Superior Lateral Cutaneous Branch
-Regimental patch over the
Damage:
- Brachial plexus: TOS, traction, trauma
- Axilla + inferior GH: Dislocation of GH, surgical neck fracture, crutches, surgeris
- Quadrangular space: FOOSH, over use
- Deep to deltoid: injections
List the structures supplied by each of the terminal branches of the brachial plexus?
Radial
Originates from the posterior cord C5-T1
- Exits the axilla and enters the posterior compartment of the arm via the LATERAL Triangle of the posterior shoulder.
- Travels with the profunda brachii artery in the radial groove between the medial and lateral heads of triceps .
- At the lateral border of the humerus it pierces the lateral intermuscular septum of the arm and to enter the forearm, the radial nerve moves anteriorly over the lateral epicondyle of the humerus.
- Can be seen in the lateral aspect of the cubital fossa
- Passes into supinator where it divides into deep and superficial branches
Supplies:
Triceps, (lateral and medial)
-Anconeous
DEEP branch:
- Becomes the posterior interosseous nerve
- Passes deep to the arcade of frosche
- pierces supinator
Supply: All wrist extensors MM
- ECR
- ECU
- EDM, EI, EPL, EPB, ABD PL
Superficial branch:
- Travels deep to brachioradialis
- Emerges to become superior between the tendons of BR, and ECRL
- Passes over the snuffbox
Sensory:
There are 4 branches of the radial nerve that provide cutaneous innervation to the skin of the upper limb.
Three of these branches arise in the upper arm:
Lower lateral cutaneous nerve of arm – Innervates the lateral aspect of the upper arm, below the deltoid muscle.
Posterior cutaneous nerve of arm – Innervates the posterior surface of the upper arm.
Posterior cutaneous nerve of forearm – Innervates a strip of skin down the middle of the posterior forearm.
The fourth branch – the superficial branch – is a terminal division of the radial nerve. It innervates the dorsal surface of the lateral three and half digits, and their associated palm area.
Damage: Arm: -Lateral triangle space = triangle sydrome -Fracture of humerus -Saturday night palsy
Forearm:
- Anterior capsule of radiohumeral joint
- Radial tunnel
- Arcade of frosche
- Supinator
List the structures supplied by each of the terminal branches of the brachial plexus?
Median Nerve
Is the union of the lateral and medial cords
Pathway:
- It enters the anterior compartment of the arm with the brachial artery.
- Moves lateral to medial across the brachial artery as it descends the humerus.
- Enters the cubital fossa on the medial aspect to enter the anterior compartment of the forearm.
- It passes between the two heads of Pronator Teres
- Here it gives off the Anterior Interosseous Nerve, then dives deep to the anterior interosseous membrane.
- Median Nerve Proper continues between Flexor Digitorum Profundus and Flexor Digitorum Superficialis
- Gives off the Palmar Cutaneous Nerve prior to entering the flexor retinaculum.
-The nerve leaves the carpal tunnel with the other 9 tendons, where it divides into the Recurrent branch and the Palmar digital branches.
Supply:
-Median Nerve Proper: Flexor Carpi Radialis, Pronator teres, palmaris longus, Flexor Digitorum Superficialis
Anterior interosseous: Flexor Palmaris Longus, Pronator Quadratus, and lateral half of the Flexor Digitorum Profundus
Recurrent: Thenar muscles
Palmar digital and proper: Lateral 2 lumbricles
Sensory:
- Palmar Cutaneous: Palm of the hand (medial)
- Palmar Digital: 3 + 1/2 Digits and the tips of the fingers
Damage:
Elbow: Supracondylar fracture, Ligament of struthers (13.5%), thickened biceps aponeurosis, between heads of PT
-Carpal Tunnel
*NB Martin-gruber anastamosis = cross connection between ulna and median 7.5-23% ppl
