1. IHDI Classification of Hip
Dysplasia
Unni G. Narayanan, Kishore Mulpuri,
Charles T. Price, Pablo Castaneda, Nick
M.P. Clarke, Peter Cundy, Jose HerreraSoto, James R. Kasser, John H. Wedge
J Child Orthop (2011) 5 (Suppl1):S10
2. 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.
4. H-Point at or medial
to Perkins’ line
H-Point lateral to D-Line
& at or inferior to H-line
H-Point lateral to P-Line
& at or medial to D-line
H-Point superior to H-line
6. 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
7. 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.
8. 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.
9. RESULTS: RELIABILITY
• Inter-rater reliability: All raters
RELIABILITY
IHDI
TÖNNIS
RIGHT HIP
ICC (95% CI)
0.90
(0.83-0.95)
0.63
(0.46-0.80)
LEFT HIP
ICC (95% CI)
0.95
(0.91-0.98)
0.60
(0.43-0.78)
• There was no significant difference between the
ICCs of the 6 experts and two trainees.
10. 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 interrater 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