Screening Dogs for Hip Dysplasia

In the literature

Haney PS, Lazarowski L, Wang X, et al. Effectiveness of PennHIP and Orthopedic Foundation for Animals measurements of hip joint quality for breeding selection to reduce hip dysplasia in a population of purpose-bred detection dogs. J Am Vet Med Assoc. 2020;257(3):299-304.

The Research …

Although hip dysplasia is a malformation of the hip joint, the consequent degenerative joint disease (DJD) is largely caused by the dynamic and abnormal articulation of the femoral head within the acetabulum. Hip joint laxity can lead to abnormal acetabular contact with the femoral head, which can exacerbate the disease. DJD is the primary reason for medical intervention in older dogs, as pain and decreased range of motion typically impact daily activities, particularly exercise and mobility, posturing to urinate and defecate, overall engagement, and advanced exercises (eg, agility, detection/law enforcement work, guide dog work).  

This study details the PennHIP scoring system for detecting congenital hip dysplasia and suggests that quantifying hip laxity is a key factor in improving hip joint quality scores. PennHIP evaluations are performed by PennHIP specialists to measure passive hip joint laxity of the pelvis under compression or distraction, which changes the femoral head displacement from the center of the acetabulum. The measured distance is then divided by the radius of the femoral head, resulting in a unitless measure of joint laxity (ie, the distraction index [DI]), which is more accurately predictive of DJD risk than subjective methods (eg, the Orthopedic Foundation for Animals [OFA] system—a 7-point scoring system that describes nondysplastic hips as excellent, good, or fair and dysplastic hips as mild, moderate, or severe).^1,2 The PennHIP index is most useful in patients <24 months of age and in females not in estrus, as hormonal changes have been shown to directly correlate with hip laxity.³

… The Takeaways

Key pearls to put into practice:

• DJD is the most common reason military working dogs >5 years of age are discharged.⁴ Attention to multimodal pain management, including joint restorative therapies, is important in these patients.

• When screening for hip dysplasia, it is key to obtain quality radiographs taken with the patient under sedation. The positive predictive value of standard OFA positioning may be enhanced by the addition of DI values to OFA hip joint scores.

• Limitations exist when screening young dogs for hip dysplasia. Environmental factors, estrus, breed, body weight, frame size, history of strenuous activity, and poor muscle mass can contribute to joint laxity. It is thus important to educate pet owners about the specific needs of their dog when deciding whether radiography is warranted to evaluate hip integrity.