Femoro-acetabular (hip) impingement - FAI

Question 1

What is it

Answer 1

> Abnormal contact between acetabulum + femoral head/neck junction

Question 2

2 types

Answer 2

> CAM type - femoral side
Pincer type - acetabulum side
* can happen in normal hips if repeated end range motion e.g gymnasts/ballet dancers
+ Can have mixed with both CAM + Pincer

Question 3

CAM impingement

Answer 3

> Irregular osseous prominence of proximal femoral neck or neck-head junction

• symptomatic especially in young male athletes where growth plate has been stressed - extra bone growth
• bony protrusion at the anterosuperior aspect of femoral head-neck junction

> Diagnosis - Dunn view radiograph (alpha angle -measured) - 90 degrees flexion + 20 abduction
- centre of head to head-bump junction - between 55 degrees and 60 degrees is normal

Question 4

Pincer impingement

Answer 4

> Excessive acetabular coverage of femoral head
global - deepened acetabulum (coxa profunda)
focal anteriorly - altered orientation of acetabulum (acetabular retraction)
Results in abutment of femoral head-neck junction against rim - damages cartilage + labrum

> Diagnosis - lateral centre edge angle during AP view (greater than 40 degrees = impingement)

Question 5

Cause + Risk factors

Answer 5

> Cause: combo of deformity at birth and overuse (repetitive abutment + wear of cartilage)
> Risk factors 
- High level sports
- repetitive hip motion
- paediatric hip disease
- femoral neck fractures
- previous hip surgery

Question 6

Symptoms

Answer 6

> Sitting cross legged = painful
> Difficulty putting on socks + shoes 
> Sitting for long periods of time - difficult
> limp
> Adductor symptoms
> walking long distances - painful (pain doesn't immediately disappear with rest)
> Significant pain after sports
> buttock + low back pain 
*may not be symptomatic

Question 7

Diagnosis

Answer 7

> Imaging

+ surgery is not always necessary as not a guarantee of OA in later life