Brief description of imaging findings in hip impingement syndrome. From Donna G Blankenbaker Kirkland W. Davis. Diagnostic Imaging: Musculoskeletal Trauma . 2nd Edition. Elsevier, 2016.

1. Femoroacetabular impingement
imaging findings

2. cam type
young men
pincer type
middle-aged women
mixed type

3. cam type
modified morphology
of femoral head/neck junction
 impingement on acetabular rim

4. pincer type
modified morphology
of acetabular rim
 impingement on femoral head/neck junction

5. cam type morphology on AP standing pelvic X ray
decreased offset at femoral head/neck junction
which can be flat
or bumpy due to osseous excrescence
best seen with frog leg lateral view
coxa magna
short broad femoral neck with mushroom-shaped femoral head

6. pincer type morphology
acetabular retroversion
 anterior overcoverage of femoral head
coxa profunda
 acetabular fossa medial to ilioischial line
protrusio acetabulum
 femoral head medial to ilioischial line

7. X ray findings often discrete compared to symptoms
(hip pain, reduced mobility)
diagnosis must combine the two
(there are asymptomatic patients with morphologic tendency to FAI)

8. MR arthrography
acetabular cartilage and labral injury
(as a consequence of FAI)
T1 FS axial oblique along femoral neck
for alpha angle (abnormal > 55)

9. most common causes of “idiopathic” hip osteoarthritis
in young people
DDH
FAI

10. Remember
young patient with hip pain and reduced mobility
with modified morphology of femoral head/neck
junction or acetabular rim on AP pelvic X ray
frog leg lateral view best for bony excrescence