Lower Limb Radiography

Dorsi Plantar ProjectionPositioning: Plantar aspect of foot in contact with image receptorCentring: To the cuboid navicular region* with a VCRCollimate to include distal phalanges, calcaneum and medial and lateral soft tissue margins.Other info: 100cm SIDCriteria: Collimate properly, phalanges separated, shafts of metatarsals separate, tarsal bones overlapped, talus & calcaneum superimposed over tibia and fibula, sharp image showing soft tissue, bony trabecular patterns of bones except talus & calcaneum should be evident

Foot

Dorsi Plantar ObliquePositioning: Plantar aspect of foot in contact with IR, patient internally rotates foot until dorsal aspect is parallel to the IR or 30 degreesCentring: To the cuboid navicular region* with a VCRCollimate to include distal phalanges, calcaneum and medial and lateral soft tissue margins. 100cm SIDCriteria: Same as DP but separation of tarsal bones except medial and intermediate cuneiform which are superimpoed and overlap of intermediate and lateral cuneiformsLateralPositioning: Hip and knee flexed. Patient externally rotates foot so lateral aspect is in contact with the IR & plantar aspect makes an angle of 90 degrees with IRCentring: Middle of medial aspect (navicular cuboid region) of the foot with VCR. 100cm SIDCriteria: Phalanges superimposed, MT overlapped with 1st MT lying more superiorly & 5th MT more inferiorly, sharp image of bony trabecular pattern of the tarsal bones 

Toes

Dorsi Plantar Patient position: Patient sat on x-ray table with hip and knee of affected leg flexed. Positioning criteria: Plantar aspect of foot in contact with image receptorCentring:For big toe: Over 1st metatarsophalngeal joint with a VCROther toes: Over proximal interphalangeal joint of affected toe with a VCR.*Other info: 100cm SID.Collimate to include distal phalanx and MTP jointCriteria: all phalanges & distal half of MT included, symmetry of phalangeal condyles, joint spaces of interphalageal joint spaces, separation of toes and MT heads, sharp image showing soft tissue margins, bony cortex & trabeculae of phalanges 

Dorsi Plantar Oblique  Positioning criteria: Plantar aspect of foot in contact with image receptor. Leg is internally rotated until dorsum of foot is parallel to IR or internally rotated 30 degreesCentring:For big toe: Over 1st metatarsophalngeal joint with a VCROther toes: Over proximal interphalangeal joint of affected toe with a VCR.*Other info: 100cm SID.Collimate to include distal phalanx and MTP jointCriteria: all phalanges and distal half of metatarsals should be included, as much separation of the phalanges as possible, sharp image showing soft tissue margins of the toes, bony cortex and trabeculae of phalanges

Lateral Toes 

Lateral Hallux Positioning: Patient seated on x-ray table. From the DP position, the patient’s foot is internally rotated so that the medial side of the foot is in contact with the image receptor. A bandage is looped around the other toes and the patient either pulls toes forwards of backwards to clear them from the big toeCentre to the MTP joint* with a VCRCollimate to include distalphalanx, 1st MT and dorsal and plantar skin marginsCriteria: relevant phalanges & ten metatarsophalangeal joint, clear interphalangeal & MTP joints shown with the phalangeal condyles superimposed, sharp image demonstrating the soft tissue margins of the toe, bony cortex and trabeculae of the phalanges 

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Indications for foot x-ray

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Mostly trauma Toes - crush injuries Foot - fractured metatarsals (direct blow) March fracture - stress fracture Fractured base of 5th metatarsal (Jones' fracture) - due to an inversion injury  Lisfranc injuries - traumatic subluvations or dislocations at the base of the metatarsals with or without fracture. Involves some or all of the joints. Mainly caused by road traffic collisions Hallux valgus - foot deformity caused by pressure from footwear & degenerative joint disease  Gout - red, painful swollen joint caused by deposition of uric acid crystals in the joint Pes planus - flat feet due to loss of medial longitudinal arch. Can be flexible or rigid  Rheumatoid arthritis - inflammatory disorder of connective tissue which can destruct the articular cartilage & underlying bone  Osteoarthritis - hallux 

Ankle

Antero-posterior Positioning - Leg fully extended and posterior aspect of ankle in contact with IR. Foot is dorsi flexed so the plantar aspect makes an angle of 90 degrees with IR. Ankle is internally rotated so the malleoli are equidistant from the IRCentring - Midway between the malleoli with a VCR: 100cm SIDCollimate - distal third of the tibia and fibula, ankle joint, malleoli and soft tissue margins Criteria - tibiotalar joint is shown with equal space surrounding the superior surface of the talus, talus & its articulation with the malleoli should be shown & free of superimposition, distal tibofibular joint obscurred, sharp image showing soft tissue margins, cortex and trabecular pattern of tibia and fibula, cortical margins of superior aspect of tibia demonstrated

Lateral Positioning: Patient turns onto affected side so the lateral aspect of ankle in contact with IR. Foot is dorsi-flexed. From this position the ankle is internally rotated through 15 degrees so that the malleoli are superimposed Centre; Over medial malleolus with a VCR; 100cm SIDCollimate: include distal third of tibia and fibula, ankle joint, talus, calcaneum, navicular and surrounding soft tissueCriteria: Medial and lateral borders of talus are superimposed to give a clear joint space, extreme distal aspect of fibula superimposed centrally over distal tibia although the shaft becomes more posterior proximally, single line demonstrating superior articular surface of talus, sharp image showing soft tissue, bony cortex and trabecular pattern 

Common injuries (trauma): Aversion and inversion injuries, alvusion fractures and torn ligaments  Can be x-rayed for R.A. The ankle joint can be painful & unstable  Most ankle fractures involve one or both malleoli  The direction of the applied forces determine the particular fracture/fractures & any associated ligamentous damage i.e. caused by abduction & external rotation forces and adduction forces  We look for:  Obvious fracture Joint space even and around 4mm all the way around Overlap of distal tib and fib on AP - any clear separation makes us question whether the interosseous membrane is torn Talar shift - ligamentous damage as talus has shifted from its normal position 

Clinical Indications for an ankle

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Tibula and Fibula 

APPositioning: Posterior aspect of tibia in contact with the IR. Leg internally rotated so that the malleoli are equidistant to the IR. Centring: To the middle of the anterior border of the tibia midway between the ankle and knee joints with a VCR - 100cmCollimation: knee joint proximally, ankle joint distally and soft tissue margins of lower leg Criteria: Separation of tibia and fibula shafts, proximal tibiofibular joint should show slight superimposition of tibia and fibula, distal tibiofibular joint should show slight superimposition of tibia and fibula, show joint space between talus & medial malleolus & between talus & lateral malleolus, sharp image of soft tissue, bony cortex and trabecular pattern of tibia & fibula, penetration of ankle and knee joint 

Lateral Positioning: From AP position, the leg is externally rotated so that the lateral aspect of the lower leg is in contact with IR. Hip and knee flexed. The malleoli need to be superimposed Centring: Midway between the ankle & knee joints with a VCR - 100cmCollimate: knee and ankle joints & soft tissue margins Criteria: Mid-shaft of fibula should project slightly posterior to tibia, proximal end of fibula should be slightly posterior to tibia with some superimposition, distal end of fibula should be superimposed over the middle of the distal tibia, sharp image showing the soft tissue margins, bony cortex and trabecular pattern of tibia and fibula, penetration of ankle and knee joint 

Clinical Indications of Tib and Fib

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Trauma (transverse, spiral, complex) Location of foreign body Pain ? Cause (bone tumours)Problems Length of patient’s leg – sometimes too long to fit the ankle & knee joint on the same receptor. Many tib / fib fractures are unstable – use of a horizontal beam lateral. TAKE CARE WHEN MOVING Many fractures are compound – risk of infection to you and patient. WEAR GLOVES.