Anatomy & Joints

• How many phalanges are in the foot?
  There are 14 total — each toe has three (proximal, middle, distal), except the great toe, which has only two.
• What distinguishes the first digit from the other toes?
  It has only two phalanges (proximal and distal) instead of three.
• What are sesamoids?
  They are calcifications (bones) that form in tendons at points of stress, commonly found under the head of the first metatarsal.
• What is the function of the sesamoid bones of the foot?
  They help reduce friction, absorb weight-bearing stress, and act as pulleys to improve tendon leverage at the first MTP joint.
• What type of joints are the interphalangeal (IP) joints of the toes?
  Diarthrodial, hinge type.
• What type of joints are the metatarsophalangeal (MTP) joints?
  Diarthrodial, condyloid type.
• What type of joints are the tarsometatarsal (TMT) joints?
  Diarthrodial, gliding type.

Positioning

• Why are oblique toe projections performed?
  To separate the digits and prevent superimposition, allowing the side of interest to be closest to the IR and reducing magnification.
• Why is the lateral projection performed with the toe of interest closest to the IR?
  To minimize magnification and superimposition of adjacent digits, and improve recorded detail.
• Why is the CR angled 10–15° posteriorly for AP toes?
  To open interphalangeal and MTP joint spaces by aligning the CR with the joint orientation.
• Why must the toe be positioned parallel to the IR in the lateral projection?
  To open the interphalangeal joint spaces and prevent foreshortening of the phalanges.
• Why is centering directed to the metatarsophalangeal (MTP) joint of the toe of interest?
  To ensure the entire digit and associated joint space are demonstrated without cutoff.
• Why are bilateral AP toes sometimes taken on one IR?
  For efficiency, but collimation must still restrict exposure to the area of interest.
• Why is a wedge filter sometimes used in toe radiography?
  To create a more uniform density between the thicker metatarsal region and the thinner phalanges.
• Why should the foot be dorsiflexed slightly for toe projections?
  To place the toes closer to the IR and reduce OID, minimizing magnification.
• Why is the central ray directed perpendicular to the IR (instead of angled) for some AP toe studies?
  When joint space evaluation is not the primary goal, perpendicular CR reduces distortion while still showing overall bony anatomy.

Technique & Image Evaluation

• How do you know the AP toe was not rotated?
  The concavity of the shafts of the phalanges and metatarsals is equal on both sides.
• How do you know the CR angle was correct on the AP axial toes?
  The interphalangeal and MTP joint spaces are open without foreshortening of the phalanges.
• What error is indicated if joint spaces appear closed on the AP toe even with correct CR angle?
  The toe was flexed and not kept parallel to the IR.
• How can you tell the lateral toe was parallel to the IR?
  The joint spaces are open and the phalangeal shafts are not foreshortened.
• What does it mean if joint spaces are closed on an AP axial toe?
  The CR angle was insufficient, or the phalanx was not parallel to the IR.
• How do you confirm proper rotation on oblique toes?
  The increased concavity is seen on the elevated side of the phalanges, and joint spaces are open with minimal overlap of adjacent digits.
• What error is indicated if the distal phalanx is foreshortened on a lateral toe?
  The toe was angled relative to the IR and not positioned parallel.
• What error is indicated if the digits overlap on an oblique toe?
  The toe was under-rotated.
• How do you know collimation was correct on toe radiographs?
  The digit of interest is centered and all phalanges, adjacent metatarsal head, and soft tissues are included.
• What error is indicated if soft tissue overlap obscures the joint spaces on an oblique toe?
  The toe was over-rotated.
• How do you know a lateral great toe was positioned correctly?
  The phalanges are superimposed, the toenail appears in profile, and the joint spaces are open.
• What error is indicated if the nail of the great toe appears obliqued rather than in profile on a lateral?
  The toe was rotated instead of being placed in a true lateral position.
• How can you tell patient motion occurred during a toe exposure?
  Bony trabeculae and soft tissue margins appear blurred instead of sharp.
• How do you know the sesamoids were captured without rotation?
  Both sesamoids appear free of superimposition, equidistant from the first metatarsal head.

Clinical Applications

• Why are AP and oblique projections of the toes obtained?
  To evaluate fractures, dislocations, osteoarthritis, and alignment of the phalanges and MTP joints.
• Why are lateral projections of the toes important?
  They provide a profile view that can show subtle fractures or foreign bodies that may not be seen on AP/oblique.
• Why might the sesamoids require separate tangential projections?
  To evaluate sesamoiditis, stress fractures, or bipartite sesamoids, which can mimic pathology if not imaged clearly.
• Why is dorsiflexion of the foot preferred for sesamoid projections?
  It reduces foreshortening and places the plantar surface perpendicular to the IR, allowing the sesamoids to be separated from the metatarsal head.
• Why might weight-bearing sesamoid views be ordered?
  To assess pain or pathology that occurs under stress, such as hallux valgus (bunion) or plantar forefoot pain during walking.