IHDI Classification of Hip Dysplasia
The IHDI classification has been found reliable and useful to guide treatment by numerous authors. The position of the proximal femoral metaphysis (instead of the ossific nucleus) is used as the important reference landmark to determine the position of the femoral head. The H-point is the midpoint of the superior margin of the ossified metaphysis. As with the Tönnis system, the H-line is drawn through the top of the tri-radiate cartilages bilaterally. The standard P-line is then drawn perpendicular to the H-line at the superolateral margin of the acetabulum.
Unlike previous classification systems, an additional diagonal line (D-line) is then drawn 45 degrees from the junction of H-line and P-line. The position of the H-point then determines the IHDI grade. In an IHDI grade I hip, the H-point is at or medial to the P-line. In grade II, the H-point is lateral to the P-line and at or medial to the D-Line. For grade III, the H-point is lateral to the D-line and at or inferior to the H-line. Finally, in grade IV hips, the H-point is superior to the H-line (Table 1, Fig. 1).
Pavlik harness application and skill acquisition
Video of a recommended method for initial fitting of the Pavlik harness:
This instructional video is based on the consensus recommendations of a panel of International Experts from the IHDI Medical Advisory Board. The video demonstrates details of proper positioning along with tips for adjustments as needed. Dr. Kelley and colleagues at the Hospital for Sick Children also developed a method of evaluating competency for application of the Pavlik harness. This is available as an Objective Structured Assessment of Technical Skill (OSATS) that determines proficiency in applying the Pavlik harness to infants (https://www.ncbi.nlm.nih.gov/pubmed/26057066). Please view this video and share it with other physicians who use the Pavlik harness to treat DDH.
Expert-Based Consensus on the Principles of Pavlik Harness Management of DDH.
This publication describes commonly agreed upon indications for treatment and management decisions during Pavlik harness use for the care of an infant with DDH . Click here to view the article.