CANINE HIP DYSPLASIA

 

 

CHD is an abnormal development of the coxofemoral joint.  CHD is controlled by several genes that interact with environmental factors such as nutrition to produce phenotypic expression.  CHD affects individuals of all breeds but is mainly a clinical disease in large dogs.  30% of all large breed dogs may be affected by CHD.  In 200 golden retrievers and 132 Rottweilers CHD prevalence was 74% and 69% respectively (Penn Hip data).  Clinical signs vary dramatically and are often not well correlated with radiographic findings.  The diagnosis and treatment of the many presentations of CHD remain debated and are continually changing as new information and medications are discovered and new methods of diagnosis and treatment are developed or refined.

 

A)  Clinical Signs

 

1.    Clinical signs of Dogs less than 1 year of age

 

a)    Stilted pelvic limb gait that is usually worse with   exercise and improves somewhat with rest.

 

b)    Difficulty climbing, jumping, and holding a normal “sit” position.

 

c)    Usually advance both pelvic limbs simultaneously when running (“bunny-hopping gait”).

 

d)    Palpable joint laxity and pain on extension of the hip.

 

2.  Clinical signs in Mature dogs

 

a)    Usually have a chronic history of decreased activity (less running and jumping).

 

b)    Muscle atrophy is common.

 

c)    There is a restricted range of hip motion and pain on extension of the joint.

 

d)    Many mature dogs with signs of CHD are presented for acute lameness caused by an ACL/CCL injury.

 

B)  Diagnosis

 

1.    Barden test: patient is anesthetized and in lateral recumbency.  Place one finger on the greater trochanter with the limb in “normal standing” position.  Put pressure from medial to lateral on the femur and see if the femoral head displaces from the acetabulum.

 

2.    Barlow’s sign: dog is in same circumstances as above.  Place one hand at the flexed knee and the other above the acetabulum.  Push with both hands to see if the femoral head displaces over the dorsal acetabular rim.

 

3.    Ortolani test: do Barlow sign then abduct the limb to see if there is a palpable clunk noted as the femoral head reduces into the acetabulum.  Most young dogs have some hip laxity so the accuracy of palpation is poor in puppies at 6-18 weeks of age but improves as dogs approach 6 months old.

 

4.    Radiography

 

a)    Signs of CHD

 

1.    Femoral head subluxation (joint laxity).

 

2.    Signs of DJD or OA

 

a.     Femoral periarticular osteophytes.

 

b.     Craniodorsal acetabular sclerosis.

c.     Acetabular osteophytosis.

 

d.     Joint remodeling.

 

e.     Caudolateral curvilinear osteophyte (CCO) (Morgan’s line) on caudal margin of the femoral neck indicates a dog is 3.7 times more likely to eventually have clinical signs of hip OA than a dog without a CCO.  In one study CCO was the first radiographic change seen in 76% of 29 dogs with hip OA.  Overall, 95% of dogs with a CCO had histopathological lesions of OA.

 

f.      Dorsal acetabular rim only covers 50% of the femoral head.

 

b)    Hip extended view (OFA)

 

1.    33% of dogs with OFA “good” have a positive Ortolani sign.

 

2.    55% of dogs with a passing OFA evaluation will become dysplastic as they age.

 

3.    53% of OFA excellent cases have Penn Hip Distraction Indexes (DI) greater than 0.3; 77% of “goods” were greater than 0.3 and 93% of fairs were greater than 0.3.  OFA passes many dogs susceptible to hip OA.

 

4.    Used mainly as a screening view to evaluate obvious subluxation and OA.

 

 

 

c)    Penn Hip

 

1.    Measures passive laxity (distraction index: DI)

 

2.    German shepherds with DI of 0.7 or higher have a probability of 0.82 for developing OA.  Labrador retrievers, goldens and rottweilers with the same hip laxity (DI) were half (0.39) as likely to develop hip OA.

 

3.    Probability of OA in a Labrador with a DI of 0.5 is only 6%.

 

4.    Dogs with a DI less than 0.3 almost never develop hip OA.

 

5.    Penn Hip has an 88% accuracy rate in predicting normal hips in 4 month old dogs but only a 57% accuracy in determining dysplastic dogs (48% false positives and 12% false negatives).

 

6.    Penn Hip views reveal 2.5 times more joint laxity than the hip extended view.

 

 

 

C.   Treatment

 

1.    Conservative/Medical Management

 

a)    Short-term for severely lame patient

 

1.    Rest for at least 2 weeks.

 

2.    Slow leash walks only for activity.

 

3.    NSAIDS.

4.    Physical therapy

 

a.     Cold packs first 24 hours.

 

b.     Hot packs for 1-4 days beginning on day 2.

 

b)    Long-term treatment

 

1.    Weight-control (25% of dogs losing as little as 11-18% of body weight had significant improvement).

 

2.    Controlled activity (minimize running, jumping and climbing).

 

3.    NSAIDS as needed.

 

4.    Glucosamine continually.

 

5.    Swimming if possible.

 

6.    Slow uphill walking to strengthen muscles.

 

7.    Omega 3 fatty acids (Joint diet).

 

2.    Surgical Treatment prior to OA

 

a)    Triple Pelvic Osteotomy (TPO): The pelvis is cut to allow ventral rotation (ventroversion) of the acetabulum to improve stability of the hip and increase the surface area of force transfer between the articular cartilage of the femoral head and acetabulum.  The femoral head is shifted medially with TPO.  Medial shift decreases the magnitude of the hip reaction force and associated articular stresses.  Follow up arthroscopy of TPO hips confirm preservation of healthy articular cartilage.  Rotation angles are ideal between 20-30%.

1.    Lameness resolved in 92% of cases.

 

2.    Minimal progression OA.

 

3.    Improved weight-bearing as measured by force plate.

 

c)    Juvenile pubic symphysiodesis (JPS): JPS is a prophylactic procedure designed to fuse the pubic symphysis in growing dogs.  Fusion results in ventroversion of the acetabulum and potentially similar advantages as those achieved with TPO. Only the pubic symphysis is fused. The remainder of the pelvic symphysis is allowed to grow.

 

1.    Dogs are best operated between 12 and 16 weeks of age.

 

2.    Severe laxity (DI between 0.6 and 1.0) or surgery after 24 weeks greatly diminish the benefit of JPS.  Surgery at 24 weeks only produces 6º of ventroversion.

 

3.    JPS provides the most ventroversion if performed on dogs between 12-16 weeks.

 

4.    In one study results of JPS were compared to control dogs after 2 years.  JPS dogs had 31% more acetabular coverage than they had preop.  JPS improved hip conformation and stability as evaluated radiographically and by conversion of the Ortolani sign to negative in operated dog.

 

5.    25% of dysplastic puppies developed OA after JPS compared to 83% of control pups.

 

6.    Puppies should be fed a restricted diet and have limited activity postop.

 

7.    JPS dogs should be spayed or neutered when JPS is performed.

 

8.    Technique involves electrocautery applied every 2-3 mm along the pubic symphysis at 40 watts for 12-30 seconds.

 

C)  Femoral Head and Neck Excision (FHNE): FHNE is performed preferably with a bone saw to remove the entire femoral head and neck, but to always preserve the lesser trochanter (should always palpate lesser trochanter prior to FHNE).  Following FHNE a pseudarthrosis forms that hopefully results in better limb function than the dog had prior to surgery.

 

1.    Age is not associated with postoperative results.

 

2.    In a recent (2003) study weight did not appear to influence outcome.

 

3.    Dogs with an acute cause of lameness or minimal muscle atrophy at the time of surgery do better than dogs with a long history (greater than 6 months) or marked muscle atrophy.

 

4.    Owners and dogs are usually very satisfied with the results of FHNE even though recovery may take several months and measured abnormalities of limb function persist.

 

5.    Postoperative physical therapy and NSAIDS may improve recovery.

 

3.    Surgical treatment after OA develops.

 

a)    See FHNE 2-C.

 

b)    Total Hip Replacement (THR)

 

1.    THR is now available in cemented and titanium coated varieties.

 

2.    Success rates are 85-95%.

 

3.    Major complications of cemented hips include infection, luxation, and implant loosening.

 

4.    Failed cases may improve following removal of cement and implants.

 

5.    An improved surgical technique and use of porous-coated implants helps minimize both short and long-term complications of infections and implant loosening.