Canine Hip Dysplasia: Algorithms for When to Refer for Surgery

Hip dysplasia is one of the most common orthopedic conditions in dogs. Although researchers continue to determine the best methods for predicting its development, it is important that veterinarians know how to evaluate dogs of all ages for the condition.

Identifying Hip Laxity

Regardless of whether clinical signs are present, all dogs of predisposed breeds should be physically examined between 12 and 20 weeks of age for evidence of hip joint laxity, such as a positive Ortolani sign, which indicates a dog is at risk for development of osteoarthritis secondary to hip dysplasia.

An Ortolani test is performed with the dog in lateral recumbency. The examiner places the hip in a neutral position with the upper leg parallel to the table, then applies a proximally directed force against the stifle, driving the femur toward the pelvis. This encourages the femoral head to subluxate out of the acetabulum. The limb is then slowly abducted as the examiner feels and listens for a “clunk,” indicating reduction of the femoral head and confirming hip joint laxity.¹

Unfortunately, a negative Ortolani test does not guarantee a healthy hip later in life. The Ortolani sign may not be present if degenerative changes have occurred, such as acetabular remodeling. In some cases, it may be difficult to elicit an Ortolani sign even if subluxation is present due to limited clinician experience or factors related to the dog, such as a puppy that is difficult to restrain.

Standard ventrodorsal radiographs provide valuable information regarding hip conformation, subluxation, and the presence of osteoarthritis. However, a more objective method for evaluating hip joint laxity is a PennHIP radiographic study, in which the hips are distracted during imaging; the resulting radiographs are used to measure a distraction index (DI).^2-4 A DI of 0.7 or greater is associated with an increased risk of osteoarthritis development by 2 years of age.⁵ Standard extended limb ventrodorsal radiographs frequently do not show subluxation or secondary arthritic changes at this age, potentially delaying a diagnosis of hip laxity until arthritic changes are present. See BOX 1 for additional resources on the radiographic evaluation of hip dysplasia.

Surgical Options

Dogs younger than 20 weeks with mild to moderate hip laxity may benefit from a juvenile pubic symphysiodesis (JPS), which stops pubic growth, resulting in ventrolateral rotation of the acetabula and better femoral head coverage as the pelvis continues to develop.^2,6,7 JPS has been shown to be most effective at restoring hip congruity in puppies with a PennHIP DI of 0.4 to 0.6 (ideally < 0.5).⁷ To be of benefit, this procedure is best performed by 12 to 16 weeks of age as future potential growth is a requirement, highlighting the importance of early patient screening.

As all dogs continue to grow, they should be regularly examined for hip dysplasia, including a lameness exam, Ortolani test, and hip manipulation.^8,9 Radiographs are recommended for dogs aged 5 to 10 months with hip joint laxity and clinical signs of hip dysplasia (e.g., lameness, bunny hopping, gait abnormalities, pain on manipulation). Again, PennHIP radiographs are recommended, but extended limb ventrodorsal radiographs may give information regarding hip laxity and secondary arthritic changes. If a dog of this age has subluxation on ventrodorsal hip–extended radiographs, but there is still contact between the femoral head and acetabulum and the hip angle of subluxation (a measure of femoral head coverage by the acetabulum) is less than 30°, a double pelvic osteotomy (DPO)¹⁰ or triple pelvic osteotomy (TPO)¹¹ may be considered.

These DPO and TPO procedures change the position of the acetabulum to provide more femoral head coverage; they are not meant for dogs that have severe subluxation or degenerative changes present on radiographs.¹²

For dogs that are older than 10 months, that have degenerative joint disease or severe subluxation, or whose owners have financial limitations, conservative management is instituted. This may include weight loss, exercise modification, physical therapy, nonsteroidal anti-inflammatory drugs, chondroprotective agents, or other treatments.^13,14

If conservative treatments have been exhausted and clinical response is not satisfactory, surgical salvage procedures such as total hip replacement, hip denervation, or femoral head and neck excision can be considered.^15-21

DI = distraction index; DJD = degenerative joint disease; DPO = double pelvic osteotomy; FHO = femoral head ostectomy; JPS = juvenile pubic symphysiodesis; OA = osteoarthritis; THR = total hip replacement; TPO = triple pelvic osteotomy