Anatomy

• Which bony landmark forms the socket for the femoral head?
  The acetabulum forms the cup-shaped socket that articulates with the femoral head to create the hip joint.
• Which structure is the ball of the hip joint and where does it articulate?
• The femoral head articulates with the acetabulum to form the hip joint.
• Where is the fovea capitis and what attaches there?
  It’s the small pit on the femoral head where the ligamentum capitis femoris attaches.

Positioning

• Why is the leg internally rotated 15–20° for the AP hip?
  Internal rotation brings the femoral neck parallel to the IR, minimizing foreshortening and making the lesser trochanter less conspicuous.
• Why must both ASIS be equidistant from the tabletop on the AP hip?
  Equal ASIS-to-tabletop distances ensure the pelvis isn’t rotated, preserving symmetric obturator foramina and iliac wings.
• Why is the IR set parallel to the femoral neck and the unaffected leg elevated for the axiolateral (Danelius-Miller)?
  Making the IR parallel to the neck and clearing the unaffected leg aligns beam/IR/neck geometry so the femoral neck is shown without superimposition in a true lateral.
• Why avoid internally rotating the affected leg for the axiolateral in trauma?
  Manipulation can worsen an occult fracture or dislocation; the cross-table view is designed to image without moving the injured limb.
• Why flex the knee/hip and abduct the thigh ~45° for the AP oblique Modified Cleaves?
  Flexion relaxes the hip capsule; ~45° abduction places the neck in a lateral projection with minimal superimposition by the greater trochanter and shows the lesser trochanter in profile.
• Why must bilateral frog-legs have equal abduction angles?
  Equal abduction creates comparable projections of both femoral necks for side-to-side assessment.
• Why is the patient asked to hold still for all hip views?
  To eliminate motion that can blur cortical margins of the femoral neck and acetabular rim.

Technique & Image Evaluation

• On an AP Hip projection, how can you tell the leg was internally rotated 15–20°?
  The lesser trochanter is barely visible or not seen; the greater trochanter is in profile laterally, and the femoral neck is elongated with crisp cortical margins.
• On an AP Hip projection, how do you confirm the pelvis wasn’t rotated?
  The obturator foramina and iliac wings are symmetric, and the sacrum/coccyx align with the pubic symphysis on a full pelvis view.
• On an AP Hip projection, how do you verify coverage?
  The acetabulum and proximal one-third of femur are included.
• On an Axiolateral (Danelius-Miller) projection, how do you confirm the IR was parallel to the femoral neck? The femoral neck is long and free of greater-trochanter superimposition; if the neck appears foreshortened or partially obscured by the greater trochanter, the IR wasn’t truly parallel.
• On an Axiolateral (Danelius-Miller) projection, how do you detect pelvic/leg rotation errors?
  Asymmetry of the ischial tuberosity and lesser trochanter contours, or the neck appearing wide on one side and narrow on the other, indicates rotation or malalignment of the IR/beam/neck triad.
• On an Axiolateral (Danelius-Miller) projection, how do you check for technical adequacy (especially with prostheses)? Cortical and trabecular detail is sharp through the acetabulum and femoral head/neck (or prosthesis) with no grid cutoff or saturation; the joint space is penetrated without losing bone detail.
• On an AP Oblique Modified Cleaves projection, how can you tell the thigh was appropriately abducted (~45°)? The femoral neck is seen with minimal foreshortening and without superimposition by the greater trochanter; the lesser trochanter is in clear medial profile. If the greater trochanter overlies the neck, abduction is excessive; if the neck remains foreshortened and the lesser trochanter is not well profiled, abduction is insufficient or the femur isn’t truly frog-legged.
• On an AP Oblique Modified Cleaves projection, how do you verify positioning symmetry on bilateral views? Both femoral axes diverge from the pelvis at equal angles, and the appearance of greater/lesser trochanters is similar side-to-side.
• On an AP Oblique Modified Cleaves projection, how do you confirm coverage and exposure?
  The acetabulum, femoral head, neck, and trochanters are included; trabecular pattern is visible across the head/neck without noise or burnout.
• How can you confirm adequate exposure on the axiolateral image?
  The acetabulum, femoral head, and prosthetic components (if present) are all sharply visible with cortical and trabecular detail and no burnout.
• How can you verify that motion did not occur?
  Cortical margins of the femoral neck and acetabular rim appear sharp with no double edges or blur.

Clinical Applications

• Why should all orthopedic hardware or prostheses be included in the image?
  Full visualization ensures that fixation devices or prosthetic components are intact, properly seated, and not showing loosening or displacement.
• Why is the axiolateral (cross-table) projection critical in trauma?
  It allows complete evaluation of the femoral head and acetabulum without moving the injured leg, minimizing further injury or pain.
• Why is a frog-leg view sometimes performed postoperatively?
  It provides a comparative lateral of both femoral necks to assess alignment, joint integrity, and range of motion.
• How can you tell a postoperative hip study is adequate?
  All hardware components and the entire prosthesis are included with the acetabulum; interfaces are sharp without signs of loosening, subsidence, or fracture lines.
• How do you verify a trauma series captured the joint?
  The axiolateral shows the femoral head seated (or displaced) relative to the acetabulum and includes the entire head/neck with the acetabular margin.