Lower Limb Radiography: Positioning and Procedures

Comprehensive practice flashcards covering radiographic positioning, central ray angulations, reference points, patient and part positioning, and evaluation criteria for lower limb radiography (toes, sesamoids, foot, calcaneus, subtalar joint, leg, knee, ankle, patella, and femur).

What is the central ray direction and angle for an AP projection of the toes?

Perpendicular

What is the reference point for the central ray in an AP projection of the toes?

3rd MTP joint

What is the patient position for an AP projection of the toes?

Seated or supine on the radiographic table

How is the affected limb positioned for an AP projection of the toes?

Flex the knee of the affected leg and center the toes over one half of the IR

Under what condition can an AP projection of the toes be performed according to the notes?

If the demonstration of the IP joint spaces is not critical

What evaluation criteria indicate absence of rotation on an AP projection of the toes?

Soft tissue width and midshaft concavity equal on both sides of the phalanges

What structures are shown on an AP projection of the toes?

The 14 phalanges of the toes, distal portions of the metatarsals, and IP joints

What is the patient position for a PA projection of the toes?

Prone position with the dorsal aspect of the foot to the IR

How is the part positioned for a PA projection of the toes?

Elevate the toes and center the toes over one half of the IR

Identify the labeled anatomy in this PA radiograph of the toes (Fig. 6-21):

Distal IP joint, distal phalanx, middle phalanx, proximal IP joint, proximal phalanx, MTP joint, sesamoids, phalanges, and metatarsals 1 through 5

What is the patient position for an AP oblique projection (medial rotation) of the toes?

Seated or supine; flex the knee enough for the sole of the foot to rest on the table

What angle relative to the IR should the plantar surface of the foot form for an AP oblique projection of the toes?

$30^\circ$ to $45^\circ$

What are the central ray angle and reference point for an AP oblique projection of the toes?

Perpendicular to the 3rd MTP joint

Which joint spaces are demonstrated open in an AP oblique projection of the toes, and which may not always be opened?

Open IP and second through fifth MTP joint spaces; the first MTP joint is not always opened

What are the patient position and part position for a PA oblique projection (medial rotation) of the toes?

Prone position with the dorsal aspect of the foot to the IR; elevate the toes and center them over one half of the IR

What is the patient position for a lateral projection of the toes?

Lateral recumbent position

How does part positioning differ between the great/second toe and the third/fourth/fifth toes in a lateral toe projection?

For the great toe / second toe, place the IR under the medial foot; for the third, fourth, and fifth toes, place the IR under the lateral foot. Both require holding the heel and knee and adjusting the toe to true lateral with MTP joints perpendicular to the IR.

What is the reference point and central ray orientation for a lateral projection of the toes?

Perpendicular to the PIP joint

In a lateral toe projection, if superimposition of adjacent toes cannot be avoided, what structure must be shown?

The proximal phalanx

What two methods are listed for tangential projections of the sesamoid bones?

Lewis and Holly method, and Causton method

What are the patient position and stability aid for the Lewis method of the sesamoids?

Prone position, elevating the ankle of the affected side on sandbags for stability

How is the part positioned for the Lewis method of imaging the sesamoids?

Rest the great toe on the IR and place the ball of the foot perpendicular to the horizontal plane

What are the patient position and part position for the Holly method of imaging the sesamoids?

Sitting position with the ankle elevated on sandbags for stability; stretch the affected leg and place the foot perpendicular to the IR

What are the central ray and reference point for the Lewis and Holly methods?

Perpendicular to the 1st MTP joint

What are the structures shown in a tangential projection of the sesamoids using the Lewis and Holly methods?

Tangential projection of the metatarsal head in profile and the sesamoids

What are the patient and part positioning for the Causton method of imaging the sesamoids?

Lateral recumbent position with knee flexed; foot in true lateral position, placing the first metatarsophalangeal (MTP) joint perpendicular to the horizontal plane of the IR

What are the central ray angle, direction, and reference point for the Causton method?

$40^\circ$ towards the heel, directed to the prominence of the 1st MTP joint

Identify the projection method and radiographic structures shown in this diagram and radiograph:

Tangential projection of the sesamoids (Causton method), demonstrating the medial sesamoid and lateral sesamoid projected axiolaterally with slight overlap

What is the patient position for an AP projection (dorsiplantar) of the foot?

Supine or seated position, with the knee of the affected leg flexed

What are the part positioning guidelines for an AP projection of the foot?

Ensure the entire plantar surface rests on the IR, flex the knee enough for the IR to not slip, and prevent foot rotation

What are the central ray angulation options for an AP projection of the foot?

Perpendicular, or $10^\circ$ to $15^\circ$ posteriorly

What is the reference point for the central ray in an AP projection of the foot?

Base of the third MT

What anatomy and diagnostic criteria are evaluated on an AP projection of the foot?

Tarsometatarsal articulation, location and extent of fractures, fragment alignments, joint space abnormalities, soft tissue effusions, and anatomy from toes to tarsals (may include portions of talus and calcaneus) without rotation

How many degrees is the leg rotated for an AP oblique projection (medial rotation) of the foot?

$30^\circ$ to $40^\circ$ medially

What are the central ray direction and reference point for an AP oblique projection (medial rotation) of the foot?

Perpendicular to the base of the 3rd MT

Which tarsal bones and structures are clearly shown on an AP oblique projection (medial rotation) of the foot?

Intertarsal joints, cuboid, calcaneus, lateral cuneiform, open sinus tarsi, and the 5th MT tuberosity well seen

How many degrees is the leg rotated for an AP oblique projection (lateral rotation) of the foot?

$30^\circ$ laterally

What are the central ray and reference point for an AP oblique projection (lateral rotation) of the foot?

Perpendicular to the base of the third MT

What specific structures are shown on an AP oblique projection (lateral rotation) of the foot?

1st and 2nd MT, space between medial and intermediate cuneiforms, and navicular bone

What is the patient position for a lateral projection (mediolateral) of the foot?

Have the patient lie on the radiographic table and turn toward the affected side until the leg and foot are lateral; place the opposite leg behind the affected leg

What are the part positioning steps for a lateral (mediolateral) foot projection?

Keep heel off IR and medial foot parallel to IR; position forefoot plantar surface perpendicular to IR; dorsiflex foot to $90^\circ$ with lower leg

What is the central ray reference point for a lateral projection (mediolateral) of the foot?

Medial cuneiform at the level of the base of the 3rd MT

Identify the labeled anatomy in this lateral foot radiograph (Fig. 6-51):

Phalanges, metatarsals, tarsals, calcaneus, sinus tarsi, talus, navicular, tibiotalar joint, tibia, and fibula

What is the patient position for a weight-bearing lateral projection of the foot?

Upright position

How is the part positioned for a weight-bearing lateral projection of the foot?

Have the patient stand in a natural position, one foot on each side of the IR, with weight equally distributed; adjust the IR centered to the base of the third metatarsal, placing the medial surface of the foot against the IR

What are the central ray angle and reference point for a weight-bearing lateral projection of the foot?

Perpendicular to the base of the third MT

What is pes planus as defined in the evaluation criteria of a weight-bearing lateral foot?

Commonly known as flat feet or fallen arches; a postural deformity where the inner arch of the foot collapses and the entire sole touches the ground

What is Bohler's critical angle and what is its normal range?

The angle between the superior apex of the mid-calcaneus to the anterior process of the calcaneus, normally measuring $20^\circ$ to $40^\circ$

What projection and structural features are shown in Fig. 6-55?

Weight-bearing lateral foot showing the longitudinal arch and a centimeter measuring scale built into the standing platform

What is the patient position for an AP axial projection (weight-bearing) of the feet?

Upright position; have the patient stand on the IR with weight distributed equally on both feet (may hold the x-ray tube crane for stability)

What are the central ray angle, direction, and reference point for an AP axial projection (weight-bearing) of the feet?

$10^\circ$ to $15^\circ$ posteriorly towards the heel, centered at the midpoint between the feet at the level of the base of the third MT

What is a Lisfranc injury as defined in the foot evaluation criteria?

Damage to the bones or ligaments in the middle part of the foot (midfoot arch) where the long metatarsal bones connect to the tarsal bones

What central ray angles are used for Exposure 1 and Exposure 2 in the AP axial weight-bearing composite method of the foot?

Exposure 1: $15^\circ$ posteriorly; Exposure 2: $25^\circ$ anteriorly

What are the reference points for Exposure 1 and Exposure 2 in the composite AP axial foot method?

Exposure 1: Scaphoid / base of the third MT; Exposure 2: Posterior surface of the ankle at the level of the lateral malleolus

How does the patient adjust their feet for the two exposures in the AP axial composite foot method?

Place the opposite foot one step backward for exposure of the forefoot, and one step forward for exposure of the hindfoot or calcaneus

What are the three deviations demonstrated in congenital clubfoot?

Equinus (plantar flexion and inversion of the calcaneus), Adduction (medial displacement of the forefoot), and Supination (elevation of the medial border of the foot)

What is the primary clinical objective of congenital clubfoot projections?

Demonstration of the anatomy of the foot and bones or ossification centers of the tarsal and their relation to one another

What is the cardinal rule regarding the alignment of the foot when positioning an infant for the Kite method?

No attempt should be made to change the abnormal alignment of the foot

How is the infant positioned for the AP projection of the Kite method?

Supine position, with hips and knees flexed to permit the foot to rest flat on the IR with ankles extended slightly; hold knees together so legs are exactly vertical

What are the central ray angle and reference point for the AP projection (Kite method)?

$15^\circ$ posteriorly, directed to the tarsals

What criteria are evaluated on the AP projection using the Kite method?

Degree of adduction of the foot and degree of inversion of the calcaneus, with no medial or lateral angulation of the leg

Identify the pathology and projection demonstrated in Fig. 6-65:

AP projection of an infant foot showing clubfoot deformity with nearly 90-degree adduction of the forefoot

How is the infant positioned for the lateral projection of the Kite method?

Place infant on side in as near lateral position as possible, flex uppermost limb forward; place support of same thickness as IR under knee, and hold toes with tape or a protected hand

What are the central ray, reference point, and structures shown for the lateral projection (Kite method)?

Perpendicular to midtarsal area; shows anterior talar subluxation, degree of equinus (plantar flexion), and fibula overlapping posterior half of tibia

What are the patient position and allowable heel deviation for the Kandel method of imaging congenital clubfoot?

Vertical or bending-forward position with plantar surface on IR; moderate elevation of the heel is acceptable when equinus deformity is well marked

What are the central ray angle and reference point for the axial projection of the foot using the Kandel method?

$40^\circ$ anteriorly, directed through the lower leg / calcaneus

What five projections are listed for the calcaneus / os calcis?

Axial projection (plantodorsal), Axial projection (dorsoplantar), Axial projection (weight-bearing coalition method), Lateral projection, and Lateromedial oblique projection (weight-bearing)

How is the patient and part positioned for an axial projection (plantodorsal) of the calcaneus?

Supine or seated with leg fully extended; place gauze around foot and have patient pull into acute flexion (right-angle dorsiflexion) so plantar surface is perpendicular to IR

What are the central ray angle and reference point for the axial projection (plantodorsal) of the calcaneus?

$40^\circ$ cephalad to the calcaneal tuberosity / base of the third MT

What structures and pathologies are evaluated on a plantodorsal axial calcaneus radiograph?

Axial projection of the calcaneus, pathologies, fractures with medial and lateral displacement, and the subtalar joint

What are the patient position and part position for an axial projection (dorsoplantar) of the calcaneus?

Prone position; elevate the ankle enough for it to be in dorsiflexion and the foot is perpendicular against the IR

What are the central ray angle and reference point for an axial projection (dorsoplantar) of the calcaneus?

$40^\circ$ caudal to the long axis of the foot, entering the posterior / dorsal surface of the ankle joint

Identify the labeled anatomy in this axial (dorsoplantar) calcaneus radiograph (Fig. 6-78):

Trochlea, sustentaculum tali, lateral process, and tuberosity

What are the patient position and part position for the Harris-Beath method (weight-bearing coalition)?

Upright position; have the patient stand on the IR and place the opposite foot one step forward

What are the central ray angle and reference point for the Harris-Beath coalition method?

$40^\circ$ anteriorly to the posterior surface of the ankle

What structures and conditions are shown in the Harris-Beath method?

Calcaneotalar fusion, bony lesions involving talus, calcaneus, and talocalcaneal joint, and extent/alignment of fractures

What are the central ray and reference point for a lateral projection (mediolateral) of the calcaneus?

Perpendicular to a point 1 inch inferior to the medial malleolus

What evaluation criteria indicate a proper lateral calcaneus radiograph?

Tuberosity in profile, open tarsal sinus and calcaneocuboid joint space, and entire calcaneus included without rotation

How is the part positioned for a lateromedial oblique weight-bearing calcaneus projection?

Adjust the patient's leg to ensure it is exactly perpendicular, and center the lateral malleolus to the midline axis of the IR

What are the central ray angle and reference point for the weight-bearing lateromedial oblique calcaneus?

$45^\circ$ medially, centered to the lateral malleolus

What structures are visualized on a weight-bearing lateromedial oblique calcaneus radiograph?

Calcaneal tuberosity, stress fracture of the calcaneus, sinus tarsi, cuboid, lateral cuneiform, and proximal metatarsals

How many articular surfaces does the calcaneus possess for the subtalar (talocalcaneal) joint?

Three: anterior, middle, and posterior

What are the central ray angles for the PA axial projection (lateral rotation) of the subtalar joint?

$5^\circ$ anterior and $23^\circ$ caudal

What is the reference point for the PA axial projection (lateral rotation) of the subtalar joint?

1 to 1 ½ inches distal to the ankle joint

What structures are shown on a PA axial projection (lateral rotation) of the subtalar joint?

Middle and posterior articulation, sinus tarsi, and the lateral malleolus

How is the foot positioned for an AP axial oblique projection (Broden method, mediolateral rotation)?

Dorsiflex the foot and rotate the leg and foot $45^\circ$ medially

What is the central ray reference point for the Broden method (mediolateral rotation)?

2 to 3 cm caudo-anteriorly to the lateral malleolus

In the Broden method (mediolateral rotation), what structure is demonstrated at a $10^\circ$ cephalad central ray angle?

Posterior portion of the talus and sustentaculum tali

In the Broden method (mediolateral rotation), what structure is demonstrated at a $20^\circ$ cephalad central ray angle?

Anterior portion of the anterior articulation

In the Broden method (mediolateral rotation), what structure is demonstrated at a $30^\circ$ cephalad central ray angle?

Anterior portion of the posterior articulation

In the Broden method (mediolateral rotation), what structure is demonstrated at a $40^\circ$ cephalad central ray angle?

Posterior portion of the joint (anterior portion of the posterior facet)

How is the part positioned for the Broden method with lateromedial rotation of the subtalar joint?

Rotate the leg and foot $45^\circ$ laterally

What are the central ray angle and reference point for the Broden method with lateromedial rotation?

$15^\circ$ cephalad, centered 2 cm distal and 2 cm anterior to the lateral malleolus

What structures are shown in the Broden method with lateromedial rotation?

Posterior facet of the calcaneus and articulation between talus and sustentaculum tali

How is the patient and part positioned for the Isherwood method with medial rotation of the foot?

Semisupine or seated; flex knee, lean leg and foot medially; with medial border of foot resting on IR, place a 45-degree foam wedge under the elevated leg

What are the central ray and reference point for the Isherwood method (medial rotation of the foot)?

Perpendicular to a point 1 inch distal and 1 inch anterior to the lateral malleolus

Which projection method produces an image representation similar to the Isherwood medial rotation of the foot?

Feist-Mankin method

What structures are shown in the Isherwood method with medial rotation of the foot?

Anterior subtalar articulation, anterior talar articular surface, and oblique projection of the tarsals

How is the part positioned for the Isherwood method with medial rotation of the ankle?

Rotate the leg $30^\circ$ medially; dorsiflex the foot, then invert it

What are the central ray, reference point, and criteria for the Isherwood method (medial rotation of the ankle)?

$10^\circ$ cephalad to 1 inch distal and 1 inch anterior to the lateral malleolus; shows middle articulation of the subtalar joint and 'end-on' projection of open sinus tarsi