Which joint surfaces of the ankle joint are open with an ap projection of the ankle?

Citation, DOI & article data

Citation:

Gorton, S., Murphy, A. Ankle (lateral view). Reference article, Radiopaedia.org. (accessed on 05 Nov 2022) https://doi.org/10.53347/rID-40861

The ankle lateral view is part of a three view ankle series; this projection is used to assess the distal tibia and fibula, talus, navicular, cuboid, the base of the 5th metatarsal and calcaneus.

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This projection aids in evaluating fractures, dislocations and joint effusions surrounding the ankle joint, and helps to assess the severity of a calcaneal fracture by measuring the Böhler angle and Gissane angle.

• patient is in a lateral recumbent position on the table
• the lateral aspect of the knee and ankle joint should be in contact with the table resulting in the tibia lying parallel to the table
• the leg can be bent or straight 
• foot in dorsiflexion 
• place the opposite leg behind the injured limb to avoid over-rotation

• mediolateral projection
• centering point
  • the bony prominence of the medial malleolus of the distal tibia
• collimation
  • anteriorly from the hindfoot to extent of the skin margins of the most posterior portion of the calcaneus
  • superior to examine the distal third of the tibia and fibula
  • inferior to the skin margins of the plantar aspect of the foot
• orientation  
  • portrait
• detector size
  • 18 cm x 24 cm
• exposure
  • 50-60 kVp
  • 3-5 mAs
• SID
  • 100 cm
• grid
  • no

The distal fibula should be superimposed by the posterior portion of the distal tibia.

The talar domes should be superimposed allowing for adequate inspection of the superior articular surface of the talus.

The joint space between the distal tibia and the talus is open and uniform.

Superior-inferior malalignment of the superior aspect of the talus is resultant of the tibia not lying parallel to the image receptor. To adjust this, either lower the knee to suit the ankle better or place the ankle on a small wedge sponge to better suit the knee. 

Anterior-posterior malalignment of the talar domes is due to over or under rotation of the foot. To adjust this, check that the heel or the toes are not raised too far up. If the patient cannot correct this position, it can be aided with a small wedge sponge.

In trauma, it may not be possible to place the patient as above, in these cases, the same principles can be applied with a modified horizontal beam view. The patient can remain supine with an image receptor placed vertically adjacent to the lateral aspect of the upright ankle, and the x-ray beam is directed horizontally, centered at the bony prominence of the medial malleolus of the distal tibia.

References

Related articles: Imaging in practice

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Citation, DOI & article data

Citation:

Gorton, S., Jones, J. Ankle (mortise view). Reference article, Radiopaedia.org. (accessed on 05 Nov 2022) https://doi.org/10.53347/rID-40730

The ankle AP mortise (mortice is equally correct) view is part of a three view series of the distal tibia, distal fibula, talus and proximal 5th metatarsal.

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Mortise and mortice are variant spellings and equally valid 4.

This projection is the most pertinent for assessing the articulation of the tibial plafond and two malleoli with the talar dome, otherwise known as the mortise joint of the ankle 1,2.

The most common indication is a trauma to the ankle in the setting of suspected ankle fractures and/or dislocations including talar fractures.

Other indications include:

• assessment of fragment position and implants in postoperative follow up
• evaluation of fracture healing
• osteochondral injuries of the talus
• osteoarthritis of the ankle

• the patient may be supine or sitting upright with the leg straightened on the table
• the leg must be rotated internally 15° to 20°, thus aligning the intermalleolar line parallel to the detector. This usually results in the 5th toe being directly in line with the center of the calcaneum
• internal rotation must be from the hip; isolated rotation of the ankle will result in a non-diagnostic image
• foot should be in slight dorsiflexion

• anteroposterior projection
• centering point
  • the midpoint of the lateral and medial malleoli
• collimation
  • laterally to the skin margins
  • superiorly to examine the distal third of the tibia and fibula
  • inferior to the proximal aspect of the metatarsals
• orientation  
  • portrait
• detector size
  • 24 cm x 30 cm
• exposure
  • 50-60 kVp
  • 3-5 mAs
• SID
  • 100 cm
• grid
  • no

• the lateral and medial malleoli of the distal fibula and tibia, respectively, should be seen in profile
• uniformity of the mortise joint should be seen without any superimposition of either malleolus
• the base of the 5th metatarsal must be included in the inferior aspect of the image

In Australia, the mortise view is part of a three-part ankle series, yet in other countries, including the United Kingdom, the mortise view is the primary 'AP projection' of the ankle alongside the lateral projection. 

Aligning the 5th  toe to the center of the calcaneus is a practical way to gauge optimal internal rotation needed to demonstrate the mortise joint. Another way to ensure correct positioning is by rotating the leg internally until the central line of the collimation field is in line with the 5th metatarsal.

Often if the foot is not in dorsiflexion, the mortise joint will not be in full profile.

In trauma, it is important to obtain a diagnostic mortise view for the proper assessment of the mortise joint. Trauma patients may not have the ability to rotate their lower limb internally, in this case, the x-ray beam can be angled 15-20° medially to achieve the view although this will result in some artifactual elongation of structures.

Fractures of the 5th metatarsal may also be seen and the medial clear space might be assessed in this view 3.

References

Related articles: Imaging in practice

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