Hip and Pelvis

• The minimum recommended projection of the pelvis is AP.
• The minimum recommended projections of the femur are unilateral AP and lateral frog leg.
• The hips are placed in 15 degrees of internal rotation during an AP pelvis.
• Sheton's hip line follows the medial and superior surface of the obturator foramen.
• The average femoral neck angle is 130 degrees.
• A femoral neck angle of less than 120 is indicative of coxa vara.
• A femoral neck angle of more than 130 degrees is indicative of coxa valga.
• Femur fractures

  A) femoral head

  B) subcapital

  C) femoral neck

  D) intertrochanteric

  E) subtrochanteric

  F) shaft

  
• The majority of pelvic fractures are the result of motor vehicle accidents. Others may be caused by falls or pedestrian accidents.
• Stable pelvic fractures do not disrupt any of the joint articulations.
• Stable ischiopubic ramus fractures comprise half of all pelvic fractures.
• Unstable pelvic fractures are a disruption at two or more sites on the pelvic ring and are frequently associated with internal hemorrhage.
• Avascular necrosis is more common in intracapsular fractures.
• Almost 90% of hip dislocations are posterior. Fractures of the acetabulum, femoral head, and patella are most often involved.
• The femoral head will appear larger on an AP film if there is an anterior dislocation.
• The femoral head will appear smaller on an AP film is there is a posterior dislocation.
• The radiographic findings on Hip DJD are joint space narrowing, sclerotic subchondral bone, osteophyte formation at the joint margins, cyst or pseudocyst formation, and superior migration of the femoral head.
• The radiologic findings of hip RA are:

  • Osteoporosis of periarticular areas
  • Symmetrical and concentric joint space narrowing
  • Articular erosions
  • Synovial cysts
  • Periarticular swelling and joint effusions
  • Axial migration of the femoral head
  • Acetabular protrusion (expansion of the acetabulum into the pelvis)
• Avascular necrosis is an interruption of blood supply to the femoral head leading to bone tissue death.
• The first signs of avascular necrosis on radiographs are sclerosis and cyst formation at the femoral head.
• SCFE is a posterior and inferior displacement of the proximal femoral epiphysis that occurs during childhood or adolescence.
• The radiologic findings of SCFE are blurring and widening of the physis and a decreased height of the epiphysis relative to the contralateral hip.
• FAI is a mechanical pathological condition that results from the abutment of the femoral head with the acetabulum. This may result in injury to the labrum.
• The two types of FAI and pincer and cam.
• CAM FAI occurs when the femoral head and neck junction offset and the femoral head cannot fully clear the acetabular rim.
• Pincer FAI is an over coverage of the femoral head by the acetabulum.