Advanced Radiographic Positions for the Lower Extremities

By Prof. Jarek Stelmark

Anatomy Review of the lower Extremity

Longitudinal archThe bones of the foot are arranged in longitudinal and transverse arches, providing a strong, shock-absorbing 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. TibiaB. CalcaneusC. Tuberosity of calcaneusD. CuboidE. Fifth metatarsal tuberosityF. Superimposed cuneiformsG. NavicularH. Subtalar jointI. Talus

A. FibulaB. CalcaneusC. CuboidD. Tuberosity at base of fifth metatarsalE. NavicularF. TalusG. Sinus tarsiH. Anterior tubercleI. Tibia

A. Medial and lateral intercondylar tubercles; extensions of intercondylar eminence (tibial spine)B. Lateral epicondyle of femurC. Lateral condyle of femurD. Lateral condyle of tibiaE. Articular facets of tibia (tibial plateau)F. Medial condyle of tibiaG. Medial condyle of femurH. Medial epicondyle of femurI. Patella (seen through femur)

A. Base of patellaB. Apex of patellaC. Tibial tuberosityD. Neck of fibulaE. Head of fibulaF. Apex (styloid process) of head of fibulaG. Superimposed medial and lateral condylesH. Patellar surface

AP WEIGHT-BEARING PROJECTIONS: FOOT

Pathology DemonstratedThese 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 DemonstratedPathologies 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 DemonstratedAny 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 Ray1. 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)

Central Ray

 Direct CR perpendicular to IR and lower leg.•Direct CR 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).

Holmblad method variations

AP AXIAL PROJECTION: KNEE–INTERCONDYLAR FOSSABéclere 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 DemonstratedPatellar fractures are evaluated before the knee joint is flexed for other projections.

• 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).

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.

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 DemonstratedSubluxation 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.