CP - Hip Surveillance

Question 1

What are the characteristics of hip dislocation in CP?

Answer 1

• Causes pain, reduced function & deformity
• Mostly preventable
• Silent
• Early detection allows for surgical treatment to aid in preventing ongoing deformity & may reduce the need for more extensive surgery

Question 2

What does hip monitoring involve?

Answer 2

• Regular physical examination including hip abduction ROM & pelvic X-ray
• Commenced at 12months of age or at time of diagnosis
• Varies from 6 to 12 monthly reviews

Question 3

What is the risk of hip displacement in CP?

Answer 3

• Hemiplegic WGH Type 4 gait at risk of late onset progressive hip displacement (monitoring until skeletal maturity)
• Increase in GMFCS level leads to increase risk of hip displacement
• All children with CP require Hip surveillance

Question 4

What is the treatment for hip instability in CP?

Answer 4

• Previously BNTx-A to hip adductors & SWASH brace. Recent findings that this treatment delayed the need for hip surgery but did not prevent it
• BNTx-A injections to hip adductors for functional reasons (gait, positioning in gait trainers, hygiene care)
• Current recommendations for early hip adductor release +/- phenol block to obturator nerve
• May still require bony orthopaedic surgery at a later stag (also dependent on GMFCS level)

Question 5

What positioning is required for hip xrays?

Answer 5

• Positioning for AP pelvis X-ray can alter accuracy of measurement of MP
• Requires neutral hip add/abd, IR/ER
• Pelvis not tilted or rotated (inlet view)

Question 6

What markers are commonly used on hip xray?

Answer 6

• Hilgenreiner’s or H-line: Through the mid point of the tri-radiate cartilage (often not parallel to film)
• Perkin’s line: Vertical line drawn perpendicular to the H-line at the lateral margin of acetabulum
• Edges of femoral head marked & lines drawn perpendicular to H-line

Question 7

How is migration percentage (MP) calculated?

Answer 7

MP = A/B X 100
where A = width of femoral head lateral to the acetabulum
B = width of femoral head overall

Question 8

What is migration percentage?

Answer 8

• Percent of femoral head uncovered by acetabular roof
• Normal adult hip = 0 or negative
• Normal 4 year hip = up to 10%
• > 20% = close monitoring
• > 30% = surgery considered

Question 9

What is acetabular index (AI)?

Answer 9

• Assesses slope of acetabular roof
  Hilgenreiner’s line
• Joins points of inferior and superior acetabular rim
• Birth = 27 degrees
• 3 years = 15 degrees
• 8 years = 11 degrees
• Close association between A.I. & M.P.
• > 27deg needs close monitoring, paediatric orthopedic involvement is vital

Question 10

What is Shenton’s line?

Answer 10

• Apparent line between medial femoral neck curve & superior obturator foramen
• A break suggests a superior displacement

Question 11

What is the femoral neck angle?

Answer 11

• Accuracy of X-ray measurement affected by femoral rotation
• Larger angle means straighter neck
• Larger angle suggests higher risk

Question 12

What is the role of physio in hip surveillance?

Answer 12

• Recognise children at risk of hip displacement & refer to clinic
• Encourage early correct positioning including standing & hip abduction when seated
• Promote development of movement skills
• Monitor hip abduction ROM
• Watch for indicators of pain, discomfort or problems with hygiene care
• Work with families to implement appropriate conservative management strategies
• Assist families to understand the natural history of hip development, best practice for monitoring & management guidelines

Question 13

When should physio refer to orthopaedics?

Answer 13

• MP > 20-30%
• Increase of MP 10% over 6 months
• Hip abduction ROM <25°
• Marked asymmetry
• Difficulties with hygiene care or apparent pain/discomfort for the child