5: Lower Leg, Ankle and Foot Flashcards
what purpose do the bones of the foot serve
provide mechanical support for soft tissues, helping foot to withstand the weight og the body whilst standing and in motion
what groups can the bones of the foot be divided into
- tarsal bones: seven irregularly shaped bones, situated proximally in foot
- metatarsals: fice which connect the phalanges to tarsal bones
- phalanges: bones of the toes; each toe has 3 phalanges (proximal, middle and distal) except big toe which only has proximal and distal
what three regions can the foot be divided into
- hindfoot: talus and calcaneus
- midfoot: navicular, cuboid, cuneiforms
- forefoot: metatarsals and phalanges
what are the three articulations of the talus
this is the most superior of the tarsal bones and transmits the weight og the body to the foot
1. superiorly: ankle joint (between the talus, tibia and fibula)
2. Inferiorly: subtalar joint, between the talus and calcaneus.
3. Anteriorly: talonavicular joint, between the talus and the navicular
what is the main function of the talus
to transmit forces from tibia –> calcaneus
- trochlear of the talus articulates w the tibia and fibula
- wider anteriorly than posteriorly and this shape provides additional stability to the dorsiflexed ankle
explain the blood supply to the talus
- although numerous ligaments attached to talus, no muscles originate or insert onto it
- blood supply = retrograde meaning arteries enter bone at distal end
- lack of muscle attachments improve vascularity and retrograde blood supply = high risk of avascular necrosis if talus fractures
what are the articulations of the calcaneus
largest tarsal bone, is inferior to the talus and constitutes the heel
1. Superiorly: subtalar (talocalcaneal) joint, between the calcaneus and the talus
2. Anteriorly: calcaneocuboid joint, between the calcaneus and the cuboid
structure and function of calcaneus
- protrudes posteriorly and takes full weight of body when heel contacts the ground when walking
what is the posterior aspect of the calcaneus marked by
calcaneal tuberosity –> Achilles tendon attaches
what are calcaenus and talus sometimes referred to
proximal row of tarsal bones
what does the intermediate row of tarsal bones contain
navicular
- articulates w talus posteriorly, all three cuneiform bones anteriorly, and the cuboid bone laterally
- on the plantar surface, there is a tuberosity for the insertion of part of the tibialis posterior tendon
what does the distal row of tarsal bones contain
four tarsal bones: cuboid. lateral, intermediate and medial cuneiforms
- cuboid = furthest lateral and articulates proximally with the calcaneus and distally with 4th and 5th metatarsals
- inferior/plantar surface of cuboid marked by groove for the tendon of peroneus longus
- three cuneiforms are wedge-shaped and articulate w navicular proximally and 1st three metatarsals distally
- wedge-shape helps to form the transverse arch of the foot
which muscles insert onto the medial cuneiform
tibialis anterior, tibialis posterior and peroneus longus
tarsometatarsal joint
between metatarsal base and tarsal bone
intermetatarsal joint
between metatarsals and adjacent metatarsals
metatarsophalangeal joint
between metatarsal head and proximal phalanx
describe the ankle joint
ankle or talucrural joint is a synovial joint between bones of the leg (tib fib) and foot (talus)
- functionally a hinge joint allowing dorsiflexion and plantarflexion of the foot
what are the tibia and fibula bound by distally
tibiofibular ligaments at the distal tibiofibular joint
- form a bracket-shaped socket known as a mortise
- trochlea of talus fits snugly into ankle mortise aka malleolar fossa
explain what happens in dorsiflexion and plantarflexion
- dorsiflexion: anterior part of the trochlea is held in the mortise and joint = more stable
- plantarflexion: posterior part of the trochlea is held in the mortise and joint = less table
what muscles produce plantarflexion
muscles in posterior compartment of leg
- gastrocnemius, soleus, plantaris and tibialis posterior
what muscles produce dorsiflexion
muscles in the anterior compartment
- tibialis anterior, extensor hallucis longus, extensor digitorum longus and peroneus tertius
what is range of dorsiflexion usually limited by
passive resistance in muscles of posterior compartment
what is the ankle joint reinforced by
lateral and medial ligaments
what are the three parts of the lateral ligament and their function
- resist inversion of the foot
function of the medial/deltoid ligament
stronger and resists excessive eversion of the foot
- fibres fan out from medial malleolus to attach to talus, calcaneus and navicular
what is the subtalar joint
articulation between talus and calcaneus
- plane type of synovial joint which is on an oblique axis and is the major joint within the foot at which eversion and inversion movements take place
what muscles produce eversion
lateral compartment of leg
- peroneus longus and peroneus brevis
anterior compartment of leg
- peroneus tertius
which muscles produce inversion
anterior compartment
- tibialis anterior
deep posterior
- tibialis posterior
what are the main weight bearing bones during standing
heel and heads of metatarsals
how are the arches of the foot maintained
by the shape of the interlocking bones, the ligaments of the foot, the intrinsic muscles of the foot and the pull of the long tendons of extrinsic muscles(i.e. muscles in the anterior, lateral and posterior compartments of the leg)
arches of the foot
describe the transverse arch
half-arch which makes a full arch when feet are together
describe the medial longitudinal arch
most important clinically
- formed by: calcaneus, talus, navicular, three cuneiforms and the medial three metatarsals
- plantar aponeurosis and the spring ligament (plantar calcaneonavicular ligament; binding the calcaneum to the navicular), together with the tibialis anterior and the peroneus (fibularis) longus tendons play major roles in maintaining the integrity of this arch
- muscles supporting the medial longitudinal arch are the tibialis anterior, tibialis posterior, peroneus (fibularis) longus and flexor hallucis longus
describe the lateral longitudinal arch
- formed by: calcaneus, cuboid and lateral two metatarsals
- ## Contraction of the peroneus (fibularis) brevis muscle may help in supporting the lateral longitudinal arch
what happens to arches in standing/walking position
- standing: arches sink somewhat under the weight of the body, the individual bones lock together, the ligaments binding them are under maximum tension and the foot becomes an immobile ‘pedestal’
- walking: tension is released from the arches which unlock and become a mobile lever system with a spring-like action
what are the signs and symptoms of compartment syndrome
- severe pain in the limb which is excessive to degree of injury increasing and not relieved by analgesia
- clasically exacerbated by passive stretch of muscles
- if compartment syndrome is suspected, surgical decomplression (fasciotomy) should be performed of all affected compartments
what are the short term consequences of compartment syndrome
- increase in intracompartmental pressure leads to decreased perfusion of muscle
- ischaemic muscle releases mediators which further increase capillary permeability and exacerbate the rise in intracompartmental pressure
- in severe cases, rhabdomyolysis (muscle necrosis) and acute kidney injury can result
- neurovascular signs develop late in the process and are often undeveloped at the time of diagnosis
- compartment pressure exceeds the systolic arterial pressure, there will be loss of peripheral pulses and increased capillary refill time
- nerve fibres are susceptible to ischaemia; thin cutaneous nerve fibres are affected more quickly than the motor fibres, so distal paraesthesia precedes loss of motor function
what are the long term consequences of compartment syndrome
- rhabdomyolysis can result in acute kidney injury which may become chronic
- necrotic muscle may also undergo fibrosis leading to Volkmann’s ischaemic contracture, a permanent painful and disabling contracture of the affected muscle groups
define ankle fracture
a fracture of any malleolus with or without disruption to the syndesmosis
what else needs to be considered w ankle fractures and why
co-morbidities: diabetes, neuroopathy, peripheral vascular disease, smoking
- these are likely to affect fracture healing
- e.g. diabetics have almost doube the fracture healing time of non-diabetics
open ankle fractures
- where skin barrier is breached and there is a direct communication between fracture and external environment
- common and require urgent surgery w extensive irrigation and debridement to reduce risk of osteomyelitis
how are the ankle joint and associated ligaments arranged
can be visualised as a ring in the coronal plane
- proximal: articular surfaces of the tibia and fibula, united at the inferior tibiofibular joint by syndesmotic ligaments
- medial: medial (deltoid) ligament
- inferior: subtalar joint (between the talus and the calcaneus)
- lateral: lateral ligament complex of the ankle (anterior talofibular, talocalcaneal and posterior talofibular)
- important to bear in mind that when a ring breaks, it normally breaks in 2 places so when dealing w single fracture, there is likely to be associated ligament damage not apparent on x-ray
- e.g. injury which results in forced eversion or external rotation of foot will push against the lateral malleolus –> oblique fracture and will pull in ligaments –> ruptured deltoid ligaments/transverse fracture of medial malleolus
explain what is meant by talar shift
- when there is disruption out of any 2 syndesmosis, medial or lateral ligaments, ankle mortise = unstable and widens so that the talus can shift medially or laterally within the ankle joint
how are ankle fractures treated
- stable ankle fractures: treated non-operatively w aircast boot or fibreglass cast
- patients can bear weigth safely, low rate of complic e.g. secondary OA
- unstable ankle fractures: need surgical stabilisation which can be high risk in patients w diabtes or peripheral vascular disease
ankle sprain
partial or complete tear of one or more ligaments of the ankle joint
- most heal w time and rest but those that dont heal can cause late ankle instability and sometimes require surgery
how do you test/diagnose for achilles tendon rupture
Thompson’s test
- diagnosis can be made clinically, but MRI and ultrasound can also be used very effectively to demonstrate the gap in the Achilles tendon
different types of toe deformities
claw toe
- often affect all four of the small toes at the same time
- toes are hyperextended at MTPJ and flexed at PIP joint
- sometimes also at DIP joint so toes curl under foot
- corns can develop over dorsum of toe or under head of metatarsal
hammer toe and mallet toe
description + causes
- hammer toe: a deformity in which the toe is flexed at the proximal interphalangeal joint (PIPJ)
- mallet toe: toe flexed at the distal interphalangeal joints (DIPJ)
- causes: ill-fitting pointed shoes, pressure on 2nd toe from adjacent hallux vagus
- tight shoe causes toe to stay in flexed position for too long so the muscle contracts and shortens so harder to extend toe; over time, muscle cannot extend toe even when shoes not worn
what does Charcot arthropathy involve
progressive destruction of bones, joints and soft tissues
- most commonly involved ankle and foot but can affect other jionts e.g. knee
- combination of neuropathy, abnormal loading of foot, repeated microtrauma (w non healing microfractures)
- metabolic abnormalities –> inflammation causing osteolysis (bone resorption), fractures, dislocation and deformity
- as a result of neuropathy, patient = reduced ability to detect touch, temp and pain so may continue to walk on Charcot foot making injury worse
- neuropathy also leads to muscle spasticity e.g. tight Achilles tendon which exacerbates deformity
- severe cases = rocker bottom foot
- pt are often obese which increases load placed through softened bones and usually have poor glycaemic control –> secondary immunosuppression
antalgic gait
- patient walks in manner that reduces pain
- walk w a limp which shortens the stance phase of the painful limb so spend more time walking on less painful limb and minimise time spent weight-bearing on the affected limb
- automatically shortens the swing phase in the unaffected limb so uneven gait
describe appearance of Trendelenburg gait
- pelvis drops on the unaffected side so patient tries to compensate for this by swinging their torso over towards affected side
- resulting gait is sometimes describes as ‘waddling’
explain typical presentation of a patient with hemiplegic gait
- flexed upper limb and extended lower limb
- patient cannot flex their hip, knee or ankle so to take a step, they lean towards unaffected side of body then circumduct the paralysed leg
- patient cannot bear much weight on paralysed leg so stance phase on limb = very short
- gait = short step w unaffected leg followed by circumduction of affected leg
diplegic gait
spasticity affects both lower limbs most commonly due to cerebral palsy
- pt walks w very narrow-based gait dragging both legs and scraping their toes on the ground
- spasticity in the hip adductors can cause legs to cross midline (scissoring)
- spasticity in the hamstrings means knees are slightly flexed
- spasticity in the gastrocnemius and soleus results in plantar-flexion of ankles
- commonly the forefoot that makes inital contact with the ground
state the arrangement of structures posterior to the medial malleolus of the ankle from anterior to posterior
identify muscles of anterior leg
- tibialis anterior
- extensor digitorum longus
- peroneus tertius
- extensor hallucis longus
