Flashcards in MSK clinical Deck (256)
What causes Erb's palsy?
Damage to ROOTS C5 and C6 from excessive increase in the angle between neck and shoulder. This can happen in a difficult birth or due to shoulder trauma
What are the symptoms and signs of Erb's palsy?
Affects nerves derived from primarily C5 and C6:
1. Waiter's tip deformity
In Erb's palsy why the following muscles are paralysed: biceps brachii, brachialis, coracobrachialis, supraspinatous, infraspinatous, subclavius, deltoid and teres minor
C5 and C6 nerve roots make up the following peripheral nerves:
1. Musculocutaneous: BBC muscles
2. Axillary: deltoid, teres minor (triceps brachii long head - triceps not paralysed due to lateral head innervation by radial nerve)
3. Suprascapular nerve: innervates supraspinatous and infraspinatous
4. Subclavian nerve: innervates subclavius
The following movements are lost or greatly weakened in Erb's palsy– abduction at shoulder, lateral rotation of arm, supination of forearm, and flexion at shoulder. Why is shoulder abduction affected?
Supraspinatous - first 15 degrees of arm
Deltoid - 15-90 degrees
Both muscles are paralysed due to loss of C5,C6 innervation
The following movements are lost or greatly weakened in Erb's palsy– abduction at shoulder, lateral rotation of arm, supination of forearm, and flexion at shoulder. Why is lateral rotation of the arm affected?
Deltoid (posterior fibres), infraspinatous and teres minor are involved in lateral (external) rotation. These are weakened/paralysed in Erb's palsy
The following movements are lost or greatly weakened in Erb's palsy– abduction at shoulder, lateral rotation of arm, supination of forearm, and flexion at shoulder. Why is supination of the forearm affected?
The main supinator of the forearm is biceps brachii which is paralysed by lack of innervation by the musculocutaneous nerve
The following movements are lost or greatly weakened in Erb's palsy– abduction at shoulder, lateral rotation of arm, supination of forearm, and flexion at shoulder. Why is flexion at the shoulder affected?
(Coracobrachialis), biceps brachii, deltoid (anterior fibres) and pectoralis major contribute to shoulder flexion. In Erb's palsy coracobrachilais, biceps, deltoid are all paralysed leaving pec major unable to complete the action fully on its own
Why is there a loss of sensation down the lateral side of the arm in Erb's palsy?
Due to the loss of sensory innervation by the cutanous branches of the axillary and musculocutaneous nerves
Describe the actions affected that give the 'waiter's tip' deformity that is seen in Erb's palsy
The arm hangs limply. There is unopposed medial rotation by Pec major (the external rotators of the deltoid and infraspinatous are paralysed) and the forearm is pronated due to loss of the main supinator, biceps brachii
Klumpke's palsy is a lower brachial plexus injury. It is less common than the upper brachial plexus injury, Erb's palsy. What causes it?
Excessive abduction of the arm e.g. catching hold of a branch of a tree when falling
What nerve root and therefore peripheral nerves are affected by Klumpke's palsy?
It affects T1 nerve root and therefore mainly the ulnar and median nerves
Why in Klumpke's palsy are the small intrinsic muscles of the hand affected by not the flexors of the forearm?
The T1 nerve root is affected, therefore affecting mainly the ulnar and median nerves. These nerves together supply all the flexor muscles of the forearm and the intrinsic muscle of the hand. However the flexor muscle of the forearm are innervated by different roots of the median and ulnar nerves and are therefore unaffected
Where is sensory loss felt in Klumpke's palsy?
Along the medial side of the arm - T1 dermatome
What would you observe if a patient had damage to their long thoracic nerve and pushed their arms against a wall?
Winging of the scapula due to paralysis of the serratus anterior muscles - these muscles no longer hold the scapula against the ribcage whilst their upper limbs reach anteriorly
How can the long thoracic nerve become damaged?
Axillary node clearance for breast cancer
What is a common cause of damage to the axillary nerve?
Fractures of the upper humerus where the axillary nerve wraps around
What movements of the arm would be impaired with axillary nerve damage?
Abduction of the arm - beyond 15 degrees
The median nerve is not commonly damaged at the brachial plexus. Where is it vulnerable to damage?
Elbow - supracondylar fractures of the elbow
Wrist - lacerations, carpal tunnel syndrome
If the median nerve is damaged at the elbow causing LONG-STANDING DAMAGE what would you observe?
Hand of benediction - when asking a patient to form a fist they would be able to flex their 4th and 5th digit but not their 1st, 2nd or 3rd - due to the paralysis of their lateral two lumbricals, long flexors of the forearm and the lateral half of FDP. The 4th and 5th digit are unaffected because they are innervated by the ulnar nerve
What signs of short-term damage to the median nerve may you observe?
Almost unopposed extension and supination
Hand signs may occur (including loss of thumb flexion)
Why might a superficial laceration at the wrist cause loss of sensation of the lateral palmar surface of the hand and first digit but not a loss of sensation on palmar surface of the 2nd,3rd and half of the 4th digit and dorsal surface of the tips of the 1st, 2nd and 3rd digits?
In the wrist the median nerve throws off a branch called the palmar cutaneous branch before it enters the flexor retinaculum. Superficial cuts at the wrist can damage this cutaneous nerve but not affect the median nerve below which is protected by the thick connective tissue of the retinaculum. The median nerve then throws off digital cutaneous branches which supply the dorsal tips of the lateral three digits and the palmar surface of the 2nd, 3rd and half of the 4th digit
What is a common cause of radial nerve damage?
Injuries can occur in the axilla, commonly form shoulder dislocation - which pulls on the radial nerve due to its close connection with the humerus in the radial groove
What would be the signs of radial damage at the brachial plexus in a patient?
Paralysis of the triceps (lateral and medius heads) and the extensors of the forearm, leading to wrist drop (unopposed flexion).
Loss of sensation of the posterior and lateral upper arm and posterior forearm
What shoulder position causes the least protection to the contents of the axilla - puts them most at risk of damage?
Abduction of the shoulder
Why are the axillary nodes cleared in some cases of breast cancer?
75% of lymph from the breast drains into the axillary lymph nodes (along with lymph from the upper arm). If breast cancer is found these nodes are sampled to look for spread. If any contamination these nodes need to be surgically cleared
In knee injuries which ligaments are commonly damaged?
Sometimes all three = 'unhappy triad'
If you damage the medial collateral ligament what else is likely to be damaged?
Medial meniscus- they are firmly attached to each other
How are you likely to get the 'unhappy triad' knee injury?
1. Blows to the side of the knee
2. Lateral twisting of the knee
When is the anterior cruciate ligament susceptible to injury?
When the knee is flexed because it is taut.