Hip - Adult

Question 1

Kerboul combined necrotic angle

Answer 1

< 190 - Low risk
190 - 240 - Moderate group
> 240 - High risk

Risk of femoral head collapse with AVN.
Measure necrosis arc on Mid-saggital and Mid-coronal MRI and combine the numbers.

Question 2

Indications for Acetabular Fracture ORIF

Answer 2

Incongruent reduction
Step > 2mm
Retained fragment
Instability
Posterior wall >40% fracture
Weight bearing dome disrupted
- Matta roof angle <45 degrees
- <10mm subchondral roof on CT

Question 3

Contraindications to hip Arthrodesis

Answer 3

AVN
Bilateral
Inflammatory (polyarticular condition)
Lumbar spine disease
Ipsilateral knee stiffness
Contralateral hip stiffness
Bone stock insufficient

Question 4

Position of hip Arthrodesis

Answer 4

Flexion 25
External Rotation 15
Adduction 5

FErAd
Also (<2cm LLD)

Aim to preserve pelvic and femoral anatomy to be able to convert to THR
Intra-articular arthrodesis difficult in Paeds due to too much cartilage
Preserve abductors to be able to convert to THR

Question 5

Key steps in Sunderland Method of hip Arthrodesis

Answer 5

Smith Petersen approach
Preserve abductors
Take off reflected head
Dislocate hip
Prepare joint (reamers for acetabulum)
Thomas test to check Pelvis position (other leg draped)
150 degree DHS through posterior superior acetabulum (into ileum)

Question 6

Long-term risks of Hip Arthrodesis

Answer 6

At 20 years:
Back pain (60%, similar to genPop)
Knee pain (40%, ipsilateral knee pain)
Hip pain (20%, contralateral)
MCL laxity (ipsilateral knee)

Question 7

Causes of FemoroAcetabular Impingement

Answer 7

Pethes
DDH
SUFE
Trauma
Retroversion of the acetabulum
Osteotomy - previous PAO
Coxa Profunda (deep socket)
Coxa Breva (short neck)
Coxa Magna (large head)
Coxa Vara (Varus neck shaft angle)
Protrusio

Question 8

What is the alpha angle in FAI and what is the number that suggests its pathology

Answer 8

Alpha angle:
Draw circle that best fits most of the head
Draw a line from center along femoral neck
Draw a line from center to where the CAM lesion starts on the head (escapes from drawn circle)

If alpha angle >55, suggests CAM impingement

Bonus:
Beta angle is the angle between the start of the CAM and the acetabular rim. Hip should be in 90 degrees flexion for this.

Question 9

Definition of FAI

Answer 9

Abnormal morphology of the acetabulum and or proximal femur causing early contact , leading to pain and eventual degeneration. Usually classified into CAM / Pincer or Mixed.