IHDI Classification of Hip Dysplasia

Unni G. Narayanan, Kishore Mulpuri, Charles T. Price, Pablo Castaneda, Nick M.P. Clarke, Peter Cundy, Jose Herrera-Soto, James R.

Kasser, John H. Wedge

J Child Orthop (2011) 5 (Suppl1):S10

RADIOGRAPHIC CLASSIFICATION (IHDI)• Based on lateral & proximal migration of hip adapted

from Tönnis method• Hilgenreiner’s horizontal line (level of tri-radiate) instead

of superolateral margin of the acetabulum • Perkins’ vertical line• Diagonal line (45° line from junction of H & P lines)• H-Point: center of the superior margin of metaphysis is

the center of the femoral head arc of rotation• Supine AP x-ray of pelvis with the hips at rest while the

lower limbs are held gently in the neutral position without traction and the patellae forward.

RADIOGRAPHIC CLASSIFICATION (IHDI)

H-Point at or medial to Perkins’ line

H-Point lateral to P-Line & at or medial to D-line

H-Point lateral to D-Line & at or inferior to H-line

H-Point superior to H-line

RADIOGRAPHIC CLASSIFICATION (IHDI)

H LINE

D LINE

P LINE

HPOINT

IHDI GRADE IIIIHDI GRADE I

AIM OF THE STUDY• Test the reliability of the IHDI method of

radiographic classification of the severity of hip displacement in DDH.– Experts– Trainees

• Compare the reliability of the IHDI method with that of Tönnis classification

METHODS

• 20 standardized AP x-ray of the pelvis of children with untreated DDH (n = 40 hips)

• Purposeful sample– Age: New born to 24 months at presentation– Full spectrum of severity

• Classified by Tönnis method & IHDI method• 6 experienced pediatric orthopaedic surgeons from– USA, Canada, United Kingdom, Australia, Mexico– 2 (trained) senior Orthopaedic Residents

• Analysis: Inter-rater reliability was tested– Intra Class Correlation coefficient (ICC) to measure

concordance between raters.

RESULTS• All 40 hips were classifiable by the IHDI method

by all raters. • 10 /40 (25%) of hips could not be classified by

the Tönnis method because of the absence of the ossific nucleus.

RESULTS: RELIABILITY• Inter-rater reliability: All raters

• There was no significant difference between the ICCs of the 6 experts and two trainees.

RELIABILITY IHDI TÖNNIS

RIGHT HIPICC (95% CI)

0.90(0.83-0.95)

0.63(0.46-0.80)

LEFT HIPICC (95% CI)

0.95(0.91-0.98)

0.60(0.43-0.78)

CONCLUSIONS• IHDI method is a new radiographic classification of

the severity of hip displacement in DDH– Four grades– Based on location of the center of the femoral head arc

of rotation (H-Point) relative to the acetabulum. • IHDI method of classification has excellent inter-

rater reliability both among experts and novices• Reliability is superior to that of Tönnis method • IHDI method can be applied reliably even when

the ossification centre is absent– In conjunction with the ultrasound