Foot and ankle Flashcards
How many bones are there in the foot?
26 bones and 2 sesamoid bones
Functional requirements of the foot (4)
Withstand high load (body weight)
Adapt to terrain
Be durable
Transfer loads from lower extremity
What are the 4 joints in the foot
Subtalar
Midtarsal
Ankle
Metatarsal break
What are the articulating bones in the subtalar joints
Calcaneus and Talus
What are the articulating bones in the midtarsal joints
Cuboid/Navicular and Calcaneus/talus
What are the articulating bones in the ankle joint
Tibia and talus (atypical hinge joint)
What foot movement is TIBIAL INTERNAL ROTATION coupled to
Foot eversion
What foot movement is TIBIAL EXTERNAL ROTATION coupled to
Foot inversion
Factors affecting coupled kinematics in foot
Shape of foot
Magnitude of load (high loads –> less coupling)
Bone loaded (loading the foot vs tibia –> more coupling)
What is the consequence of congenital fusion of subtalar joint?
Leads to ball-and socket ankle joint
What structural characteristic of the foot allows it to adapt to different terrains (3)
Medial & lateral longitudinal arches
Transverse arches
Plantar fascia
What 2 parts of the foot bear the most weight and what proportions
Talus/Calcaneus - 60%
Metatarsals - 30%
What 2 movements of the MTP joint characterise Hallux Valgus
Medial of 1st MTP head
Lateral deviation if 1st toe
What is the angle above which the toe is classificed as valgus
Greater than 15 degrees
Risk factors for Hallux valgus (4)
Female sex
Older age
ligament laxity
Footwear
What muscles and ligaments control ab/adduction of the hallux
Adductor hallucis via the lateral collateral ligament
Abductor hallucis via the medial collateral ligament
What is the effect on gait (3)
More pressure on hallux
Weight distribution centred more medially - changes moment arm of foot muscles
Eversion of foot
Treatment of hallux valgus
Bunionectomy/Exosectomy Osteotomy MTP Arthrodesis (fusion)
What bone changes are seen in Gout
Osteophytes
Osteolysis
Cartilage damage
How does gait change in Gout (2)
Slower walking
Load bearing is more evenly distributed (as opposed to being bore by calcaneus)
3 methods of MTP fusion
K wires
Wires
Dorsal locking plates
Effects of MTP fusion (3)
Shorter stride length
Reduced plantarflexion
Increased load on other 4 toes
Explain the Windlass mechanism
When hallux is dorsiflexed to prepare for toe-off/propulsion the plantar fascia is stretches
Plantar fascia moves proximally
Reduces distance between calcaneus and metatarsals which raises medial longitudinal arch
Allows foot to act as a rigid lever
