LATERAL-MEDIOLATERAL OR LATEROMEDIAL PROJECTION: FOOT
Pathology Demonstrated:- Location and degree of anterior or posterior displacement of fracture fragments, joint abnormalities, soft tissue effusion, and locations of opaque foreign bodies are demonstrated.
Technical Factors:
- IR size - 18 x 14 cm (8 x 10 inches) - smaller foot, or 24 x 30 cm (10 x 12 inches) - large foot
- Detail screen, tabletop
- 60 +- 5 kV range
- mAs 4
Shielding:
- Place lead shield over pelvic area to shield gonads.
Patient Position:
- Take radiograph with patient in lateral recumbent position; provide pillow for head.
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| Mediolateral foot |
- Flex knee of affected limb about 45 degree; place opposite leg behind the injured limb to prevent overrotation of affected leg.
- Carefully dorsiflex the foot if possible to assist in positioning for a true lateral foot and ankle.
- Place support under leg and knee as needed so that plantar surface is perpendicular to IR. Do not overrotate foot.
- Align long axis of foot to long axis of foot to long axis of IR (unless diagonal placement is needed to include entire foot).
- Center mid area of base of metatasals to CR.
Central Ray:
- CR perpendicular to IR, directed to medial cunieform (at level of base of third metatasals)
- Minimum SID of 40 inches (100cm)
Collimation:
- Collimate to the outer skin margins of the foot to include about 1inch [2 to 3 cm] proximal to ankle joint.
CR or DR:
- Close collimation and lead masking are important over unused portions of image plate to prevent fogging from scatter radiation to the hypersensitive image plate or receptor.
Alternative lateromedial projection:
- A lateromedial projection may be taken as an alternate lateral. This can be more uncomfortable or painful for the patient, but it may be easier to achieve a true lateral in this position.
Radiographic Criteria:
Structure Shown:
- Entire foot should be demonstrated with a minimum of 1inch of 2.5 cm of distal tibiafibula.
- Metatasals will be nearly superimposed with only the tuberosity of the fifth matatasal seen in profile.
Position:
- The long axis of the foot should be aligned to the long axis of IR.
- True lateral position is achieved when the tibiotalar joint is open, the distal fibula is superimposed by the posterior tibia, and the distal metatarsals are seperimposed.
Collimation and CR:
- All soft tissue structure from phalanges to calcaneus should be included in the center of the four-sided collimated field with the center (CR) to the medial cunieform region.
Exposure Criteria:
- Optimal density and contrast should visualize borders of superimposed tarsals and metatasals.
- No motion; cortical margins and trabecular markings of calcaneus and nonsuperimposed portion of other tarsals should appear sharply defined.
