X-RAY OF ANKLE JOINT
X-ray Ankle Joint A/P View
Ankle AP
Region: tarsal bone, ankle joint
Pathology: fracture of tarsal bone, tibia and fibula, ligament injury and dislocation of ankle joint
SID: 100 cm (40 inches)
Central Ray: perpendicular beam directed at the midpoint between the medial malleolus and the lateral malleolus
Respiration: unrelated
Position: 1. The patient is placed either in a supine position or in a sitting position and the leg is extended naturally.
2. Place the ankle
joint at the center of the image receptor (IR).
3. Dorsiflex the foot to make it perpendicular to the IR to show in true
antero-posterior projection image.
Collimation: Include tibia, distal portion of fibula and talus bone.
Evaluation:
1. The medial portion of ankle
joint should not overlap.
2. The talotibial
joint must be identifiable and the overlapping of the lateral talus
edge and the distal portion of fibula should
be seen.
3. The half of the distal end of fibula should overlap with the medial portion
of tibia.
kVp-60, mAs-3.2
X-ray Ankle Joint Lateral View
Ankle Lateral
Region: tarsal bone, ankle joint
Pathology: fracture of tarsal bone, tibia and fibula, ligament injury and dislocation of ankle joint
SID: 100 cm (40 inches)
Central Ray: Project perpendicularly toward medial malleolus
Respiration: unrelated
Position:
1. The patient is placed either in lateral decubitus position or in sitting position.
2. Flex the filming leg 45° to place ankle joint on the center of image receptor (IR).
3. Lean the body toward the filming side to make the filming leg in true lateral position.
4. Overlap lateral malleolus with medial malleolus.
Collimation: Include distal portion of tibia and fibula and proximal portion of metatarsal bone.
Evaluation:
1. Tibiotalar joint must be identifiable.
2. Fibula should be overlapped with tibia by posterior shadow.
3. The proximal portion of tibia and fibula, talus bone and calcaneus must be included.
4. Jones fracture could be identified in the fifth metatarsal base, tuberosity, and soft tissue structures.
kVp-60, mAs-3.2
Tip
Anatomy ankle joint
The ankle joint (or talocrural joint) is a
synovial joint located in the lower limb. It is formed by the bones of the leg
(tibia and fibula) and the foot (talus).
Functionally, it is a hinge type joint, permitting
dorsiflexion and plantarflexion of the foot.
In this article, we shall look at the anatomy of the
ankle joint; its articulating surfaces, ligaments, movements, and clinical
correlations.
Fig 1 – The bones of the ankle joint; tibia, fibula and
talus. Note that the calcaneous is not considered part of the ankle joint.
Articulating Surfaces
The ankle joint is formed by three bones; the tibia and
fibula of the leg, and the talus of the foot:
The tibia and fibula are bound together by strong tibiofibular
ligaments. Together, they form a bracket shaped socket, covered in hyaline
cartilage. This socket is known as a mortise.
The body of the talus fits snugly into the mortise
formed by the bones of the leg. The articulating part of the talus is wedge
shaped – it is broad anteriorly, and narrow posteriorly:
Dorsiflexion – the anterior part of the talus is held
in the mortise, and the joint is more stable.
Plantarflexion – the posterior part of the talus is
held in the mortise, and the joint is less stable.
Fig 2 – X-ray of a normal ankle joint. Note the bracket
shaped socket formed by the tibia and fibula.
Fig 3 – The talus. It is broad anteriorly, which strengthens
the joint during dorsiflexion.
Ligaments
There are two main sets of ligaments, which originate from
each malleolus.
Medial Ligament
The medial ligament (or deltoid ligament) is
attached to the medial malleolus (a bony prominence projecting from the medial
aspect of the distal tibia).
It consists of four ligaments, which fan out from the
malleolus, attaching to the talus, calcaneus and navicular bones. The primary
action of the medial ligament is to resist over-eversion of the foot.
Lateral Ligament
The lateral ligament originates from the lateral
malleolus (a bony prominence projecting from the lateral aspect of the distal
fibula).
It resists over-inversion of the foot, and is comprised
of three distinct and separate ligaments:
Anterior talofibular – spans between the lateral
malleolus and lateral aspect of the talus.
Posterior talofibular – spans between the lateral
malleolus and the posterior aspect of the talus.
Calcaneofibular – spans between the lateral
malleolus and the calcaneus.
Fig 4 – Ligaments of the ankle joint.
Clinical Relevance: The Ankle ‘Ring’
The ankle joint and associated ligaments can be visualised
as a ring in the coronal plane:
The upper part of the ring is formed by the
articular surfaces of the tibia and fibula.
The lower part of the ring is formed by the
subtalar joint (between the talus and the calcaneus).
The sides of the ring are formed by the medial and
lateral ligaments.
A ring, when broken, usually breaks in two places (the
best way of illustrating this is with a polo mint – it is very difficult to
break one side without breaking the other).
When dealing with an injury to the ankle joint, a clinician
must bear this in mind. For example, a fracture of the ankle joint may occur in
association with ligament damage (which would not be apparent on
x-ray).
Movements and Muscles Involved
The ankle joint is a hinge type joint, with movement
permitted in one plane.
Thus, plantarflexion and dorsiflexion are the main movements
that occur at the ankle joint. Eversion and inversion are produced at the other
joints of the foot, such as the subtalar joint.
Plantarflexion – produced by the muscles in the posterior compartment
of the leg (gastrocnemius, soleus, plantaris and posterior tibialis).
Dorsiflexion – produced by the muscles in the anterior compartment of
the leg (tibialis anterior, extensor hallucis longus and extensor
digitorum longus).
Neurovascular Supply
The arterial supply to the ankle joint
is derived from the malleolar branches of the anterior tibial, posterior
tibial and fibular arteries.
Innervation is provided by tibial, superficial fibular
and deep fibular nerves.
Clinical Relevance - Ankle Sprain
An ankle sprain refers to partial or complete
tears in the ligaments of the ankle joint. It usually occurs via excessive
inversion to a plantarflexed and weight-bearing foot.
The lateral ligament is more likely to be damaged for two
main reasons:
The lateral ligament is weaker than the medial ligament.
The lateral ligament resists inversion.
The anterior talofibular ligament is the lateral
ligament most at risk of irreversible damage.
Clinical Relevance – Pott’s Fracture-Dislocation
A Pott’s fracture is a term used to describe a bimalleolar (medial
and lateral malleoli) or trimalleolar (medial and lateral malleoli,
and distal tibia) fracture.
This type of injury is produced by forced eversion of the
foot. It occurs in a series of stages:
Forced eversion pulls on the medial ligaments, producing an
avulsion fracture of the medial malleolus.
The talus moves laterally, breaking off the lateral
malleolus.
The tibia is then forced anteriorly, shearing off the distal
and posterior part against the talus.
By Steven Fruitsmaak [CC BY-SA 3.0], from Wikimedia Commons
Fig 5 – Bimalleolar fracture of the ankle. 1 – Fibula, 2 – Tibia.
