Page 393 - Canine Lameness

20.5 Hip Dysplasia 365

(A) (C) (G)

(D)

(B) (E) (F)

Figure 20.12 Coxofemoral osteoarthritis in patients with (A–F) mild and (G) severe juvenile hip dysplasia:
images (A–F) are from the patient with juvenile hip dysplasia that did not show (A) evidence of pathology
on routine ventrodorsal radiographic views. Based on clinical suspicion, the (B) PennHIP distraction
technique was used to establish the diagnosis. Please note that the image is for the purpose of illustration
of the distraction device and its position only; appropriate protective equipment should be worn when
performing the procedure. PennHIP radiographs consist of a (C) distraction view that allows for measuring HIP REGION
of the distraction index (DI). This is performed by (D) placing a circle over the acetabulum (indicated by blue
circle) and the femoral head (indicated by red circle). The distance (d) between these two is then divided by
the radius (r) of the femoral head circle. When performing PennHIP, it is important to avoid cavitation
(see white arrow in image (E) indicating gas bubbles from excessive distraction) since this does not allow
for accurate readings. As such, Ortolani testing should not be performed until after the procedure. Image
(F) illustrates the frog leg view also requested by PennHIP that is used to evaluate acetabular filling. Image
(G) is of a juvenile patient of the same age that is displaying obvious subluxation (white arrow). In this case,
further evaluation with PennHIP is not necessarily due to the severity of the disease.

the distraction films to conventional hip extended pelvic radiographs (Flückiger et al. 1999).
The dorsolateral subluxation test is another method that evaluates joint subluxation with dogs
positioned in a weight-bearing position and can be performed between 4 and 8 months of age
(Farese et al. 1998).
Other specific radiographic techniques to evaluate for evidence of HD include the DAR radio-
graphic projection (Meomartino et al. 2002), and the Norberg angle (NA). The DAR projection is
used to evaluate and measure the dorsal acetabular slope (DAS). In a normal dog, the DAR is
sharply pointed; whereas, with the development of HD, the rim progresses from being slightly
blunted and rounded to eroded. The DAS slope increases with worsening (more laxity) of HD.