Bones - Foot Flashcards
What are the three types of bones in the foot?
How else can the foot be a arranged into groups?
From proximal to distal:
1) Tarsals - a set of seven bones situated in the ankle area.
2) Metatarsals - connects phalanges to tarsals - there are five.
3) Phalanges - each toes has three phalanges (proximal, middle and distal), except for the big toes, which has two.
The foot can also be divided up into three regions:
1) Hindfoot - talus and calcaneus
2) Midfoot - navicular, cuboid and cuneiforms
3) Forefoot - metatarsals and phalanges
Tarsals - Hindfoot
Proximal tarsal bones are the talus and calcaneus. They provide the supportive framework for the heal and proximal ankle.
1) Tarsal - most superior bone of the tarsal bones - transmits weight of body to the foot. It has three articulation:
i) Superiorly - ankle joint - articulates between talus, tibia and fibula.
ii) Anteriorly - talonavicular joint - between talus and navicular.
iii) Inferiorly - subtalar joint - between talus and calcaneus.
Intermediate midfoot
Contains one bone: the navicular bone.
Postioned medially. Articulates with 5 bones:
Laterally - articulates with the cuboid bone.
Posteriorly - articulates with the talus bone.
Anteriorly - articulates with the three cuneiform bones.
On the plantar surface, there is a tuberoisity, which provides part of the attachment for the tibialis posterior tendon.
Distal midfoot
Contains four tarsal bones - the cuboid and the cuneiforms.
Cuboid - furthest lateral - lies anterior to the calcaneus - posterior to the 4th and 5th metatarsals. The inferior is marked by a groove for the fibularis longus.
Cuneiforms (lateral, intermediate and medial) - articulates with the navicular posteriorly and metatarsals anteriorly. The shape of the foot helps form the transverse arch across the foot. They are also the attachment point for a few muscles:
Medial cuneiform - tibialis anterior, (part of) tibialis posterior, fibularis longus.
Lateral cuneiform - flexor hallucis brevis
Clinical relevance - fractures of the talus and calcaneus
Talus
Most commonly occurs at the neck of the talus (50%). Can occur in the body and lateral processes, with those in the talar head being the least common.
Neck fractures - high energy injuries - caused by excessive dorsiflexion of the foot, The neck of the talus is pushed against the tibia. In this fracture, the blood supply may be affected, leading to avascular necrosis.
Body fractures - usually occurs from jumping from a height.
Calcaneus
Occurs as a result from axial loading, typically from falling from a height. Lower limb and lumbar injuries should also be checked.
Bone can break into several pieces - called a comminuted fracture. Upon X-ray, it will appear shorter and wider.
Even after treatment, there can be additional problem. The sub-talar joint may become arthritic. Patient will experience pain upon eversion and inversion. The calcaneocuboid joint can also be affected.
Forefoot - Metatarsals
They are number I-V (medial to lateral).
From distal to proximal, they consist of a head, neck, shaft and base.
They are convex dorsally.
They have three or four articulations:
1) Proximally - tarsometatarsal joint - between metatarsals and tarsals.
2) Laterally - intermetatarsal joints - between metatarsals
3) Distally - metatarsophalangeal joints - between metatarsals and phalanges.
fibClinical relevance - fractures of the metatarsal bones
Occurs by three mechanisms:
1) Direct blow - usually by a heavy object dropped on the foot
2) Stress fracture - incomplete fracture by repeated stress to the bone. Common in athletes in the necks of the second and third metatarsals and the proximal fifth metatarsal.
2) Excessive inversion - fibularis brevis can avulse and tear off the base of the fifth metatarsal.
Phalanges
Each phalange consists of base, shaft and head.
Each toe has three phalanges.
Big toe has two.
