MSK 4 Flashcards
What are the two major causes of back pain?
- mechanical: ligament sprain or muscle strain (lifting something using your back)
- neurogenic: compression of spinal nerves
Describe symptoms of mechanical back pain
- well localized
- usually in the midline
- often bilateral
- sacrospinous and sacrotuberous ligaments stabliize the sacroiliac joint
Describe symptoms of neurogenic pain
- pain radiates down the particular nerve that is being affected
- usually myotomal motor loss and dermatomal loss for sensory distribution
- unilateral
- nerve that is being compressed is compressed by tissues that find the least path of resistanc therefore it is a diffuse radiating unilateral pain
How can neurogenic back pain start?
- degenerated disc (disc compression/spinal stenosis): extra pressure on intervertebral disc
- narrowed intervertebral foramina: compression or arthritis which can cause a narrowing of the joint because the bone becomes remodelled (small projections of bone can push on the nerve)
What is sciatica? What are common spinal levels that are affected?
- not the sciatic nerve being affected
- pain, abnormal gait, body leaning to the right side, short stride, weak foot movement
- radiating pain on one side of body
- common disc herniation occurs between L5 and S1 (disc bulges and catches the S1 nerve as it’s exiting out the cauda equina)
- second most common disc herniation occurs between L4 and L5 which catches the L5 nerve
Why is it rare for a disc herniation to happen in the midline?
-the posterior longitudinal ligament protects the back of the spinal canal
What effects do you expect to see with an L3/L4 disc herniation?
- L4 nerve compression
- pain and numbness: lower back, postero-lateral thigh, anterior leg
- weakness/atrophy: knee extension, quadriceps
- reflexes: knee jerk diminished
What effects do you expect to see with an L4/L5 disc herniation?
- L5 nerve compression
- pain and numbness: hip, lateral thigh, lateral leg, middle three toes
- weakness/atrophy: dorsi-flexsion (foot drop), antero-lateral m
- reflexes: changes in knee jerk and/or ankle jerk (uncommon)
What effects do you expect to see with an L5/S1 disc herniation?
- L5 nerve compression
- pain and numbness: hip, postero-lateral thigh, leg, and foot
- weakness and atrophy: plantar flexion, gastrocnemius, soleus
- reflexes: ankle jerk diminished or absent
Describe how to use the straight leg test for neurogenic causes of back pain
- if there is pain present at 0 degrees, likely L2-L3 affected
- if there is pain present at 30 degrees, likely L4 affected
- if there is pain present at 90 degrees, likely L5 affected
- if there is no pain during range of motion, probably is mechanical cause of back pain
What structures are pierced during a lumbar puncture?
- going in between adjacent vertebrae
- skin
- superficial fascia
- supraspinous ligament
- interspinous ligament
- ligamentum flavum
- epidural fat space (lower pressure in here so as soon as you go through ligamentum flavum you will feel pop in this space)
- dura
- arachnoid
- CSF can be collected from subarachnoid space
Where is an epidural anesthetic injected?
- infiltrates the epidural fat space which anesthetizes the nerves as they go out
- done below L2 so that the nerve roots that could be damaged are floating as the cauda equina in CSF
- Respiratory diaphragm: separates thorax and abdomen
- Pelvic diaphragm: forms the floor of the pelvis
- Urogenital diaphragm: supports external genitalia
Where does the respiratory diaphragm insert? What is its innervation?
- bottom of the ribs then inserts into a central tendon which the heart sits
- annular ring of skeletal muscle pulls the central tendon down so air can enter
- phrenic nerve C3, C4, C5
- skeletal muscle so it is voluntary control (not autonomic)
What is the innervation of the pelvic diaphragm?
-sacral plexus and ventral ramus of S3, S4
What is the innervation of the urogenital diaphragm?
-off of sacral plexus; pudendal nerve S2, S3, S4 “keeps the junk off the floor”
How does the innervation of the axial skeleton differ from the innervation of the appendicular skeleton?
- axial skeleton is innervated by 1 spinal level
- appendicular skeleton is innervated by several spinal levels (plexus)
What does the musculocutaneous nerve innervate?
- biceps brachii/other muscles in the arm
- crosses the elbow and becomes a cutaneous nerve then it innervates the skin on the lateral aspect of the forearm
What does the median nerve innervate?
- doesn’t do much until it passes the elbow
- then it innervates the flexor compartment of the forearm
- crosses at the wrist where it becomes a cutaneous nerve and innervates the skin on the palm, thumb, index, and middle finger
What does the ulnar nerve innervate?
- gives off some muscular innervation to a few forearm muscles
- supplies intrinsic flexors of the hand
- crosses the metacarpal phalangeal joint where it becomes cutaneous nerve to innervate the ring and pinky finger
What does the axillary nerve innervate?
- large nerve that wraps around surgical neck of the humerus to innervate the deltoid
- gives off small cutaneous nerve on lateral aspect of arm
- much smaller sensory component
What does the radial nerve innervate?
- enters the arm where it is plastered against bone by triceps
- gives off early cutaneous branches after giving off muscular branches to triceps
- crosses the elbow and innervates extensors on posterior surface of the forearm
- no intrinsic extensors on the back of the hand so radial doesn’t do much muscular innervation passed the elbow
Describe the dermatome map
- how sensory information gets back from the skin
- on anterior part of arm, this happens via the musculocutaneous, median, and ulnar nerves
- on the posterior part of the arm, this happens via the radial and axillary nerves
How can narrowing of the interscalene triangle occur?
- scalene hypertrophy: these muscles can get hypertrophy (asthmatic, weight lifter) then brachial plexus can become entrapped as its leaving the scalene triangle to get to the upper limb
- anterior, middle, and posterior scalene arise from the levels of the cervical spine and attach at the 1st rib
- when they contract, they elevate the first and second rib
- compresses upper nerve roots
What occurs with a super-numary rib?
- subclavian artery and the brachial plexus have to come up and over the top of the rib to get into the upper limb
- compresses lower nerve roots
What is saturday night palsy?
- armpit is compressed by the back of a chair
- brachial plexus nerve compression leading to wrist drop and sensory loss
- as radial nerve gets from brachial plexus into the back of the upper limb it’s compressed by the triceps muscle
- bigger impact on radial nerve
What is hyperabduction syndrome?
- brachial plexus is wrapped around the head of the humerus
- when you sleep with your arm above your head, it causes the blood vessels and nerves to be stretched
- get paralysis and pins/needles
What are examples of proximal brachial plexus nerve root injuries to the upper roots?
- difficult delivery and baby’s head is stretched at an angle that puts traction on the nerve and breaks it
- Erb’s palsy
- tearing the nerve roots at their origins before they get into the brachial plexus
- deficits: sensory loss which radiates along the dermatomes of C5, C6, effects that are more proximal on the limb
What are examples of proximal brachial plexus nerve root injuries to the lower roots?
- difficult delivery; pulling on a limb which can stretch the lower roots of the brachial plexus
- traction more on the lower parts as they go into the upper limb
- Klumpke’s palsy
- deficits: more distal problems, sensory loss in C8 and T1 dermatomal regions
Where does latissimus dorsi originate from? What is its action?
- thoracolumbar fascia and lower spinous processes of lumbar vertebrae
- attaches to the front of the humerus
- when it contracts, it can be the main extensor of the upper limb
What muscle’s fibres run directly opposite to the trapezius?
- rhomboids
- work antagonistically with respect to one another
What main muscle groups are used to elevate the scapula?
-levator scapulae and the upper fibres of the trapezius muscle
What main muscle groups are used to depress the scapula?
- gravity
- lower fibres of trapezius
What main muscle groups are used to protract the scapula?
- serratus anterior
- attached to the medial border of the scapula
- assisted by pectoralis minor muscle
What main muscle groups are used to retract the scapula?
- protraction causes a stretch in the middle fibres of the trapezius muscle, you can contract the middle fibres of the trapezius to retract the scapula
- rhomboids
- levator scapulae
What main muscle groups are used to laterally rotate the scapula?
- lower fibres of the trapezius insert onto the top of the spine of the scapula; muscle contracts and rotates the scapula
- this allows the humerus to go from 90 degrees to 180 degrees because it points glenoid fossa up
What main muscle groups are used to medially rotate the scapula?
- levator scapulae
- rhomboids rotate scapula back to the original position
What does pectoralis major do?
- attaches from the sternum and the proximal part of the ribs and attaches to the humerus
- when it contracts, it flexes the humerus
Where does the pectoralis minor attach? What does it do?
- attaches onto the coracoid process
- pectoralis minor attaching onto coracoid process can then drag the entire pectoral girdle towards the front and get any extra few inches of reach of protraction of the scapula
Where does deltoid attach? What does the deltoid do?
- runs from the clavicle to the spine of the scapula
- attaches to the humerus
- anterior part assists pectoralis major in flexion of humerus
- posterior part assists the trapezius/latissimus dorsi in extension of humerus
- middle part is responsible for abducting to 90 degrees
What muscle groups are involved with abduction of the shoulder?
- supraspinatus contracts and brings humerus to 20 degrees and straightens the fibres of the middle deltoid
- middle fibres of deltoid then finish abduction to 90 degrees
- beyond 90 degrees to 180, rotation of the pectoral girdle and scapula happens to abduct the humerus
