Is it possible to predict the eventual outcome of a Graf Type IIa Hip by graphical extrapolation?

Deirdre Walden, Princess Anne Hospital, Southampton.


For a Graf Type IIa hip that has not matured to a Graf Type 1 after two ultrasound scans, assuming a linear progression of maturation, is it possible to predict the eventual outcome by graphical extrapolation?


The purpose of the study was to investigate whether it is possible to reduce the number of follow up ultrasound scans for monitoring Developmental Dysplasia of the Hip (DDH). 


244 Infants with high risk factors for DDH referred for hip sonography in a six month period were included in this study.  Sonographic examinations were performed using the Graf technique.  Both hips were measured and the Graf classification determined.


149 infants had Graf Type I hips at the first scan. 

93 infants were referred for a follow up ultrasound scan of which 72 matured to a Graf Type I and 11 were referred for treatment. 

10 were referred on for a third scan, of which 9 matured to a Graf Type I and one referred for treatment.

The results for the 10 infants that required three scans were used to test graphical extrapolation techniques.


The analysis showed that in general there is a linear maturation of the hip.  This means that it is possible to predict the outcome from two scans using graphical extrapolation. In this study, 100% agreement between the extrapolated prediction and the clinical decision was demonstrated when the result from the first and third scan were used.  However only 85% agreement was demonstrated when the first and second scans were used.

The study shows that it is possible to predict the eventual outcome for a Type IIa hip.

The study also shows that follow up scans can be reduced

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