Transcript Advanced Radiographic Positions for the Lower Extremities

Advanced Radiographic Positions for
the Lower Extremities
By Prof. Jarek Stelmark
Anatomy Review of the lower Extremity
Longitudinal arch
The bones of the foot are arranged
in longitudinal and transverse
arches, providing a strong, shockabsorbing support for the weight of the
body. The springy, longitudinal arch
comprises a medial and a lateral.
The transverse arch is located
primarily along the plantar surface
of the distal tarsals and the
tarsometatarsal joints.
A. Tibia
B. Calcaneus
C. Tuberosity of calcaneus
D. Cuboid
E. Fifth metatarsal tuberosity
F. Superimposed cuneiforms
G. Navicular
H. Subtalar joint
I. Talus
A. Fibula
B. Calcaneus
C. Cuboid
D. Tuberosity at base of fifth metatarsal
E. Navicular
F. Talus
G. Sinus tarsi
H. Anterior tubercle
I. Tibia
A. Medial and lateral intercondylar
tubercles; extensions of intercondylar
eminence (tibial spine)
B. Lateral epicondyle of femur
C. Lateral condyle of femur
D. Lateral condyle of tibia
E. Articular facets of tibia (tibial plateau)
F. Medial condyle of tibia
G. Medial condyle of femur
H. Medial epicondyle of femur
I. Patella (seen through femur)
A. Base of patella
B. Apex of patella
C. Tibial tuberosity
D. Neck of fibula
E. Head of fibula
F. Apex (styloid process) of head of fibula
G. Superimposed medial and lateral
condyles
H. Patellar surface
AP WEIGHT-BEARING PROJECTIONS: FOOT
Pathology Demonstrated
These projections are useful for demonstrating the bones of the feet to show the
condition of the longitudinal arches under the full weight of the body.
AP
• Take radiograph with patient standing
erect, with full weight evenly distributed
on both feet.
• Feet should be directed straight ahead,
parallel to each other.
Central Ray
• Angle CR 15° posteriorly to midpoint between feet at level of base of
metatarsals.
Structures Shown and Position: • AP
projection shows bilateral feet from soft
tissue surrounding phalanges to distal
portion of talus.
Exposure Criteria: •Optimal density and
contrast should visualize soft tissue and
bony borders of superimposed tarsals and
metatarsals. Adequate penetration of
midfoot region. Bony trabecular markings
should be sharp.
Lateral
• Have patient stand erect, with weight evenly
distributed.
• Have patient stand on wood blocks placed on a
step stool or the foot rest attached to the table.
You also may use a special wooden box with a
slot for the cassette.
• Provide some support for patient to hold onto
for security.
• Support vertical cassette between feet, with
long axis of foot aligned to long axis of IR.
• Change cassettes and turn patient for lateral of
other foot for comparison after first lateral has
been taken.
Central Ray
• Direct CR horizontally to level of
base of third metatarsal.
• Minimum SID of 40 inches (100 cm)
Structures Shown and Position: • entire foot should be demonstrated,
along with a minimum of 1 inch [2 cm] of distal tibia-fibula. • Distal fibula
should be seen superimposed over posterior half of the tibia, and plantar
surfaces of heads of metatarsals should appear directly superimposed if no
rotation is present.
Exposure Criteria: •Optimal density and contrast should visualize soft tissue
and bony borders of superimposed tarsals and metatarsals. Adequate
penetration of midfoot region. Bony trabecular markings should be sharp.
PLANTODORSAL (AXIAL) PROJECTION: LOWER LIMB–CALCANEUS
Pathology Demonstrated
Pathologies or fractures with medial or lateral displacement are
demonstrated.
Part position:
Center and align ankle joint to CR and to portion
of IR being exposed.
• Dorsiflex foot so plantar surface is near
perpendicular to IR.
• Loop gauze or a tourniquet around foot, and
ask patient to pull gently but firmly and hold the
plantar surface of foot as near perpendicular to
IR as possible. (Do not keep patient in this
position any longer than is necessary because it
may be very uncomfortable.)
Central Ray
• Direct CR to base of third metatarsal to emerge at a level just distal to lateral
malleolus.
• Angle CR 40° cephalad from long axis of foot
• Minimum SID is 40 inches (100 cm).
Radiographic Criteria
Structures Shown: •Entire calcaneus should be visualized from the
tuberosity posteriorly to the talocalcaneal joint anteriorly.
Position: •No rotation; a portion of the sustentaculum tali should appear in
profile medially.
LATERAL-MEDIOLATERAL PROJECTION: LOWER LIMB–CALCANEUS
Pathology Demonstrated
Any extent and alignment of fractures.
• Center calcaneus to CR and to
unmasked portion of IR, with long axis of
foot parallel to plane of IR.
• Place support under knee and leg as
needed to place plantar surface
perpendicular to IR.
• Position ankle and foot for a true lateral
• Dorsiflex foot so that plantar surface is
at right angle to leg.
Central Ray
• CR perpendicular to IR, directed to a point 1 inch (2.5 cm) inferior to medial
malleolus
• Minimum SID of 40 inches (100 cm)
Structures Shown: •Calcaneus is demonstrated in profile with the talus and distal tibia-fibula
demonstrated superiorly, as well as the navicular and the open joint space of the calcaneus and
cuboid distally.
Position: •No rotation as evidenced by superimposed superior portions of the talus, open
talocalcaneal joint, and lateral malleolus superimposed over the posterior half of the tibia and
talus. Tarsal sinus and calcaneocuboid joint space should appear open.
Collimation and CR: •CR and the center of the collimation field should be about 1 inch [2.5
cm] distal to the tip of the lateral malleolus as seen through the talus. • Four-sided collimation
should include ankle joint proximally and talonavicular joint and base of fifth metatarsal
anteriorly.
PA AXIAL PROJECTION–TUNNEL VIEW: KNEE–INTERCONDYLAR FOSSA
Pathology Demonstrated
Intercondylar fossa, femoral condyles, tibial plateaus, and the intercondylar
eminence are demonstrated and may show evidence of bony or
cartilaginous pathology, ornarrowing of the joint space.
Camp Coventry method—prone position (40° to 50° flexion)
Patient Position
Take radiograph with patient prone; give pillow
for head (Camp Coventry method).
Central Ray
1. Prone: Direct CR perpendicular to lower leg (40° to 50° caudad to match
degree of flexion) to midpopliteal crease.
•Minimum SID is 40 inches (100 cm)
Holmblad method—kneeling position (60° to 70° flexion)
Have patient kneel on x-ray table (Holmblad
method).
Central Ray
Direct CR perpendicular to IR and lower leg.•Direct CR to midpopliteal
crease.
•Minimum SID is 40 inches (100 cm)
Holmblad method variations
AP AXIAL PROJECTION: KNEE–INTERCONDYLAR FOSSA
Béclere Method
Note: This is a reversal of the PA axial projection for those who cannot assume the prone
position. This, however, is not a preferred projection because of distortion from the CR angle
and increased part-IR distance, unless a curved cassette is available. This projection also
enhances exposure for the gonadal region.
Flex knee 40° to 45°, and place support
under cassette as needed to place cassette
firmly against posterior thigh and leg
• Adjust cassette as needed to center IR to
mid-knee joint area.
Central Ray
• Direct CR perpendicular to lower leg (40° to 45° cephalad).
• Direct CR to a point ½ inch (1.25 cm) distal to apex of patella.
• Minimum SID is 40 inches (100 cm
PA PROJECTION: PATELLA
Pathology Demonstrated
Patellar fractures are evaluated before the knee joint is flexed for other
projections.
Notes: With potential fracture of the patella, extra care should be taken to not flex
knee and provide support under thigh (femur) so as not to put direct pressure on patellar area.
The projection also may be taken as an AP projection positioned like an AP knee if patient cannot
assume a prone position.
• Align and center long axis of
leg and knee to midline of table
or IR.
• True PA: Align
interepicondylar line parallel to
plane of IR. (This usually
requires about 5° internal
rotation of anterior knee.)
Central Ray
• CR is perpendicular to IR.
• Direct CR to midpatella area (which is usually at approximately the mid-popliteal crease).
• Minimum SID is 40 inches (100 cm).
Structures Shown: •Knee joint and patella are shown, with optimal recorded detail of patella
because of decreased OID if taken as a PA projection.
Position: •No rotation is present, as evidenced by symmetric appearance of the condyles. •
The patella will be centered to the femur with correct slight internal rotation of the anterior
knee.
Collimation and CR: •Centering and angulation are correct if the knee joint is open and the
patella is in the center of the collimated field.
TANGENTIAL (AXIAL OR SUNRISE/SKYLINE) PROJECTIONS: PATELLA
Warning: This acute flexion of the knee should not be attempted until fracture of the
patella has been ruled out by other projections.
Pathology Demonstrated
Subluxation of the patella and other abnormalities of the patella and
femoropatellar joint are demonstrated.
Settegast method
Take radiograph with patient in the
prone position, with cassette under
knee; slowly flex knee to
a minimum of 90°; have patient
hold onto gauze or tape to maintain
position.
Central Ray
• Direct CR tangential to femoropatellar joint space (15° to 20° from lower leg).
• Minimum SID is 40 inches (100 cm)
Settegast seated variation—90° flexion of knee
The major advantage of this position is that the patient can be examined while
sitting in a chair. This position also requires little manipulation of the x-ray tube.