Sesamoids - Axial

Radiographic Positioning

Adult

Other related pages of interest Applied Radiography Radiographic Anatomy Radiographic Protocols

Name of projection	Foot - Axial - Sesamoids
Area Covered	Head of the first metatarsal, sesamoid bones
Pathology shown	Extent of injury to sesamoid bones
Radiographic Anatomy	Foot Radiographic Anatomy
IR Size & Orientation	18cm x 24 cm Landscape
Film / Screen Combination	Detail (CR and DR as recommended by manufacturer)
Bucky / Grid	No
Filter	No
Exposure	50 kVp 2 mAs
FFD / SID	100cm
Central Ray	Directed to the first metatarsophalangeal joint Perpendicular to the IR
Collimation	To include the distal 1st, 2nd and 3rd metatarsals
Markers	Distal and lateral Marker orientation AP
Shielding	Gonadal (check your department's policy guidelines)
Respiration	Not applicable
Positioning	Lewis Method Patient is prone on the table Make the patient comfortable - pillow for their head, sponges under their knee and ankle Ensure the long axis of the foot is not rotated Place the big toe on the IR in a dorsiflexed position Place the ball of the foot so that it is perpendicular to the IR The plantar surface should be about 20° from the vertical Holly Method Patient is seated on the table, legs extended Position foot so that the plantar surface is about 20° from the vertical (that is, the foot is slightly extended) The toes are held in a flexed position by the patient (using a strip of bandage to assist them)
Critique PACEMAN	Positioning Sesamoids are in profile sesamoids are not superimposed by the metatarsals Correct dorsiflexion of the foot shown by the distal ends of the 1st, 2nd and 3rd metatarsals seen in profile Area Covered Distal 1st, 2nd and 3rd metatarsals, MTP joint, sesamoids Collimation Centre: The first metatarsophalageal (MTP) joint Shutter A: Open to include the 1st to 3rd distal metatarsals Shutter B: Open to include the soft tissue of the ball of the foot and the distal metatarsals Exposure bony trabecular patterns and cortical outlines are sharply defined soft tissues are visualised
Special Notes	Although the Holly Method is usually more comfortable for the patient, the increased object to image receptor distance (OID) is greater, so the sesamoids will appear more magnified, with some accompanying loss of definition.