MSK 8 Flashcards
How does injury to the PCL occur?
- hyperextension of the knee
- blow to tibial tuberosity
- testing PCL injury by trying to close the drawer
What structures run underneath the calcaneal tendon around medial malleolus to get into the bottom of the foot?
Tom: tibialis posterior
Dick: flexor digitorum
And: tibial artery
Not: nerve
Harry: flexor holocus longus
What innervates the antero-lateral compartment of the leg?
- sciatic nerve wrapping around neck of fibula
- becomes superficial cutaneous to supply antero-lateral aspect of leg and top of foot
What deficit results from a lesion to the fibular nerve?
- foot drop
- unable to dorsiflex
- may exaggerate flexion of entire limb while walking so that the plantarflexed foot can clear the ground
Where does the blood supply for the antero-lateral compartment of the leg come from?
- popliteal artery
- posterior tibial artery goes through a hole in interosseous membrane as it branches from the popliteal artery
- emerges at front of foot as anterior tibial artery
What do the posterior and anterial tibiofibular ligaments create?
- functional mortise
- u shape for talus to fit in
When is the ankle most stable?
- anterior and posterior tibiofibular ligaments keep the joint as a continuous unit
- as you slide tibia and fibular towards front in dorsiflexion, it jams the talus into that joint
- dorsiflexion has more stability
- plantarflexion has more mobility
What is the deltoid ligament?
- located on medial side of the ankle
- attaches tibia, talus, calcaneus
What are the ligaments on the lateral side of the ankle?
- not able to resist forces put on it very well
- anterior talo-fibular, posterior talo-fibular, calcaneo-fibular ligaments
What ligaments are affected by an inversion sprain of the ankle?
- particularly the lateral ankle ligaments are affected
- can also have problems with anterior and posterior tibio-fibular ligaments
Where does weight distribution go on the foot?
- goes onto talus
- 50% is then directed to calcaneus then 50% is directed towards the metatarsals
- metatarsals gets divided again to 25% each time
- acts as a shock absorber
What are the arches of the foot?
- transverse arch from the ligaments binding the metatarsals
- longitudinal arch separates the 50% going to the front and 50% going to the back maintained by the calcaneo-navicular ligament and tibialis posterior tendon/peroneus longus tendon used with flat foot when people only use muscles to maintain the longitudinal arch
What are the intrinsic muscles of the foot?
-not too important because we have a minimal ability to abduct/adduct the toes and flex the metacarpalphalangeal joints
What are the deep and superficial veins that return blood to the heart?
- superficial return blood at rest, deep return blood during exercise
- deep veins have same name as arteries
- dorsal venous plexus on top of foot
- on medial calf there is a vein that joins with the popliteal which is the lesser saphenous
- greater saphenous runs up entire medial aspect of thigh and calf that drains into the femoral
- muscle contractions squeeze deep veins which forces more blood during exercise by the deep set
What happens to valves of veins over time?
- become deficient especially in sedentary people
- valves collapse and allow pooling of blood called varicose vein; superficial veins dilate
Where does visual input for balance arise from?
- retina particularly in extrafoveal region which detects motion, brightness, direction
- information is sent to superior colliculus which provides this to the cerebellum
Describe proprioceptive input for balance
-muscle spindles and golgi tendon organs in the muscle
What aspect of the cerebellum does balance input go to?
- medial cerebellum
- responsible for axial skeleton
What detector detects static equilibrium in the inner ear?
- macula of utricle
- macula of saccule
What detector of the inner ear detects dynamic equilibrium?
-crista of semicircular canals
(or ampula)
What fluid is contained in the bony and membranous labyrinth?
- bony labyrinth contains perilymph
- membranous labyrinth is floating in perilymph and contains endolymph
- tube that goes directly from subarachnoid space of brain in through the bone to the inner ear (perilymphatic duct) and it goes back through endolymphatic sac
- not sure where endolymph comes from (not a continuation with perilymph)
How is static equilibrium detected?
- hair cells are contained in gelatin which has otoliths
- hair cells located horizontally in macula of utricle so they can detect movement side to side
- hair cells located vertically in macula of saccule so they can detect movement up and down
How does automatic head position happen?
-sternocleidomastoid and upper fibres of trapezius have input from CN 8
hair cells– CN 8– brainstem– cerebellum and CN11
How is dynamic equilibrium detected?
- when you accelerate, it causes the endolymph to flow in the semicircular canals
- fluid flow is detected by hair cells within ampula
- 3 semicircular canals to detect movement in any of 3 planes: forward and backward (pitch), left to right (yaw), up and down acceleration (roll)
- brain detects inputs from the two systems of semicircular canals (they do not work independently of each other)
How does fluid flow translate into dynamic equilibrium signal?
- fluid flows and bends the crista ampularis (gelatinous mass) which bends the hair cells embedded here
- depolarization of axons transmitted by CN8
Where do central projections of vestibular apparatus go?
- auditory nuclei in medulla located more laterally
- vestibular nuclei in medulla located more medially
Where do outputs go to maintain orientation and balance?
-eye muscles, neck muscles, back muscles, lower limb muscles (pes anserine- gracilis, semitendinosis, sartorius. all of these muscles part of different groups and different innervations)
What can cause vestibular dysfunction?
- otoliths in static system (macula) come loose and they get into semicircular canals: vestibulolithiasis
- gives you impression you are rapidly accelerating on one side which makes you dizzy
- meniere’s diease: high fluid pressure within ear- endolymph puts pressure on sensory receptors which can cause permanent damage to these hair cells (part of CNS) which causes hearing and balance problem
- detect with Romberg test
What are symptoms of vestibular dysfunction?
- imbalance
- nausea
- poor death perception
- vertigo
- blurry vision- nystagmus (jerky eye movements)
