Mechanics of Foot/Ankle 10/29 Flashcards
Tibiotalar joint anatomy: how is joint stabilized
- tibia forms a concave surface and fits into the body of the talus
- joint is stabilized by:
deltoid ligament:
- very strong. attaches to the medial malleolus, tuberosity of navicular and sustentaculum tali of calcaneous
- prevents eversion sprains
anterior talo fibular joint (ATF - always tears first in inversion sprain),
- attaches to lateral malleolus and neck and lateral articular facet of talus
- prevents inversion sprain
posterior talofibular joint (PTF)
- attaches to lateral malleolus, prevents inversion sprain
calcaneofibular ligaments:
- attaches to lateral malleolus and calcaneous
- prevents inversion sprains
Major motions of Ankle
Plantar flexion: 50 degrees: ANTERIOR GLIDE OF TALUS
- performed by gastroc and soleus - major players
- minor: tibialis post, flexor hallucis longus, flexor digitorum longus
- some abduction/adduction in plantar flexion
Dorsiflexion: 20 degrees: POSTERIOR GLIDE OF TALUS
- performed by tibialis anterior (major)
- extensory digitorum longus, extensor hallucis longus - minor players
ANKLE IS MOST STABLE IN DORSIFLEXION
Subtalar joint anatomy
Talus on calcaneus
Major motions:
- Calcaneal ABDuction (valgus)
- calcaneal ADDuction (varus)
Talus articulates with navicular, calcaneus with cuboid
Inversion
Medial rot of calc & nav
Increases the height of the medial arch
Cuboid rotates down on calc
Plantar flexion of ankle
Muscles used are tibialis anterior & posterior
Interior muscles
inversion is calc adduction + navicular rotation + glide on talus
These raise the medial portion of the foot and depress the lateral portions
Eversion
eversion is calc abduction + navicular rotation + glide on talus
These raise the lateral portion of the foot and depress the medial portions
Lateral rot of calc & nav
Decreases the height of the medial arch
Cuboid rotates upon calc
Dorsiflexion of ankle
Muscles used are fibularis (peroneus) longus & brevis
Exterior muscles
pronation and supination of foot
Pronation= Eversion + Dorsiflexion + ABduction (calc & foot)
Supination= Inversion + Plantar flexion + ADduction (calc & foot)
Lateral Longitudinal Arch
- Weight bearing & elastic
- Firm osseous structure
- Made up of calcaneus, cuboid, 4th& 5th MTs
- Limited mobility
- Built to transmit weight & thrust to the ground
Medial Longitudinal Arch
- More mobile & higher than the lateral arch
- Made of calcaneus, talus, navicular, the cuneiforms and 1-3MTs
- Controlled by plantar lig, plantar fascia, tib post, FDL, FHL & intrinsic muscles of the foot
- Does not have firm osseous support
- Changes to adapt to terrain
- this arch is in control of gait
- muscles do not support the artch, they help control it for balance and gait
High medial arch
- Caused by ADduction of foot and a varus calcaneus
Dropped medial arch
- Caused by ABduction of foot and a valgus calcaneus & dorsiflexion of the ankle
- Extreme pronation!!!
What are the 3 transverse arches?
Ant Transverse arch
- Made of the MT heads
- Transmits weight to the ground
- Flattens with weight bearing
Post Transverse arch
- Made of MT bases
Tarsal Arch
- Made of navic, cuboid and cuneiforms
- Assists in flexability of the foot as well as rotation
- Decrease of loss of this arch is pesplanus (flat feet)
- increase in arch = pescavus
Hammertoes vs. Claw Toes, and bunions
Hammer toes have a flexion deformity of the PIP & an extension deformity of the DIP
Claw toes have flexion deformities of the PIP & DIP joints
A bunion is the medial deviation of the 1st MTP with lateral deviation of the proximal phalanx of the hallux (great toe)
- The MTP can be very tender, erythematous and swollen
Gait
- Stance phase
- heel strike
- Foot rolls to lateral edge
- Weight should roll back to ant transverse arch
- The great toe should push (toe) off
- Swing phase
Acute inversion sprain
- most common
- ligaments involved:
- Anterior talofibular (ATF) - Always tears first
- Calcaneofibular
- Posterior talofibular (rare—generally seen with fx dislocation)
- Mechanism of injury
- Inversion and plantar flexion
- Generally by stepping on an uneven surface (ie. landing on someone else’s foot after rebounding a basketball)
Sx:
- Swelling
- Eccymosis
- TTP (tenderness to paplpation) depending on degree of injury
- Decreased ROM
- Antalgic gait
- Poor lower extremity propreoception
- Assessed with one leg standing test
Grades of Sprains
Grade 1-microtears with the ligament
- Swelling and disability but no instability (no laxity)
Grade 2-partial tear of the ligament
- Severe swelling over the ankle, mild instability, antalgic gait (limping), mild ligamentous laxity, laxity is noted with a good end point, decreased ROM
Grade 3-complete tear
- marked loss of function and complete instability, no endpoint noted on provocative testing
Acute inversion ankle sprain dx
Negative x-ray
- X-ray determination is based on the Ottawa ankle rules
- +ant drawer test (in 2nd and 3rd degree tears only) - Asses ATF only
- +Talar tilt test - Asseses the ATF & calcaneofibular ligaments
- Always check the arches of the foot after a sprain. IF the arch is acutely flat; this may indicate tear of tibialis posterior tendon (a stabilizer of the foot)
- Order MRI
- If Tib Post tendon is torn—it must be surgically corrected within 14 days for optimal outcome to prevent degeneration of the foot
Ottawa ankle rules
- only used on people over age of 18
Ankle X-ray is only required if there is any pain in the malleolar zone and any one of the following:
- Bone tenderness along the distal 6 cm of the posterior edge of the tibia or tip of the medial malleolus, OR
- Bone tenderness along the distal 6 cm of the posterior edge of the fibula or tip of the lateral malleolus, OR
- An inability to bear weight both immediately and in the emergency department for four steps.
Additionally, the Ottawa foot rules indicate whether a foot X-ray series is required. It states that it is indicated if there is any pain in the midfoot zone and any one of the following:
- Bone tenderness at the base of the fifth metatarsal (for foot injuries), OR
- Bone tenderness at the navicular bone (for foot injuries), OR
- An inability to bear weight both immediately and in the emergency department for four steps.
