Hip Dysplasia

WHAT IS HIP DYSPLASIA:

In simple terms hip dysplasia (CDH), means "badly formed hip".
To understand this problem you first need to know a little about the anatomy of the canine hip joint. This joint is known as a ball and socket joint, comprising of two parts, the acetabulum and the femur. The femur or thigh bone consists of the head (the ball), and the neck( the part of the femur that joins the long shaft of the bone to the head.)The acetabulum forms the socket part of the joint, and it is into this socket that the head of the femur rests.

In dogs which are not affected by HD.there is a good fit between the ball and socket. In the dog with HD. the fit is very poor,(think of a tennis ball inside a cup,there is a good fit, but put the ball in a saucer and the ball will roll around loosely,)hense the poor fit in the displastic dog between the head of fumur and the acetabulum of the hip joint.CDH can also be diagnosed if the femoral neck is shortened or if there is an improper angle between the femoral head and the long axis of the femoral neck.

The hip joint is strengthened by a ligament going from the head of the femur and attaching to the acetabulum.then surrounded by the joint capsule-a thick band of connective tissue.

Dogs are not born with CDH. As puppies grow, laxity of the muscles and ligaments surrounding the joint and the poor fit between the bone produces excess movement of the acetabulum. This seperation is known as subluxation, and at its most severe it can become a total dislocation.The surface of the bones start out completely smooth, but in CDH there begin to be changes remodeling. Bone rubbing against bone causes an irritation which results in irregular bone growth and wear on the articular surfaces.These irregular surfaces result in Osteoarthritis, which in turn can cause significant pain. As the bone of the acetabular rim is ground away, it becomes shallower and it is now more difficult to keep the head of the femur properly seated.

Signs & symptoms
1) From none to severe pain(gait movement may not be affected)
2) Difficulty in rising from a lying or sitting position, or in climbing stairs.
3) A bunny hop gait.
4) A painful reaction to extension of the rear legs.
5) Pushing on the rump may cause the pelvis to drop.
6) When rolled over some affected dogs will resist having their legs spread into a frog-leg position.
7) A side-side sway of the croup.
8) Dogs may resist jumping.
9) Lameness may be seen especially after strenuous exercise.

It is very important to understand that the only way to accurately diagnose CHD is by x-rays.These symptoms may also be seen in dogs with normal hips and affected dogs may display none of these symptoms at all.

DAIGNOSIS

As stated earlier the only way to conclusively diagnose CDH is through x-rays of the hip joint.Positioning of the dog is very important if the films are to be read correctly. It is wise to find a vet. who is experienced, in this procedure.
Once obtained the x-rays are then forwarded onto the BVA/KENNEL CLUB,and scored through their scheme.(details of which will be explained later)

PREVENTION

CDH is an inherited trait that is inflenced by several genes(polygenic). It is not caused by environmental factors, but environment can influence the expression of the disease(Corley,Willis, Carhill/Thorpe-Vargeson, Carricato). In otherwords how you raise your puppy won't determine whether or not he is dysplastic, but it can effect when and perhaps if, he begins to develop symptoms. Some common factors which have been proposed to worson, but not cause, CDH are;

1) Rough play, jumping, climbing stairs or slick floors.
2) Excess weight gain or rapid growth.
3) Calcium supplementation (may increase the bone remodeling).
4) Forced running for any distance, especially on tarmac, asphalt or other hard surfaces.
Therefore it makes sense to keep puppies lean, avoid any type of forced excercise or very rough play and provide surfaces that allow for good traction.

TREATMENT

Non-surgical :

Non-surgical treatment attempts to improve function and reduce pain and inflammation. Drugs that produce these results are aspirin,phenylbutazone, NSAIDS (non steroidal anti-inflamatories) and steroids. All these three drugs can produce significant side effects, and should be used with caution, if at all, under the supervision of a vet.Other products which have shown promising results are glycoaminoglycans such as Adequan, Cosequin and Glycoflex. Adequan is an injectable drug. Glycoflex and Cosequin are both given orally. Vitamin C. can also be effective in reducing inflammation (Corley). Some people have also reported success with herbal medicine. Excercise restriction is also sometimes recommended (Carricato). An ideal type of excercise for a dysplastic dog is swimming which allows excercise without stressing the joints.

Surgical Treatment:

Several surgical prcedures exist to treat CDH. Each procedure has pros and cons associated with it. Different surgeons also have their own techniques, some having more experiences than others, and therefore more skilled with a particular type of surgery. A second opinion before surgery may be helpful.

Surgery is indicated when:
1)Non-surgical management has failed to reduce pain or restore function.
2)Surgery will correct current problems.
3)Function of the dog(i.e. is the dog a working dog, required to perform strenuous activity or is he primarily a pet).
Factors that will be concidered in selecting a type of surgery to be performed should include;
1)age and weight of animal
2)complicating factors such as extensive bone remodeling or osteoarthritis
3)function of the dog.

Before advanced remodeling of the joint has taken place the most often recommended surgical treatment for CDH is the triple pelvic ostomy or TPO. This procedure must be done before the acetabulum has worn down and therefore is usually recommended for young dogs (under 9 months of age), who have clinically diagnosed subluxations. The surgery involves cutting the pelvis in three places and then tilting the bone to a more favourable angle to keep the femoral head in place. A somewhat similar option is the inter-trochanteric osteotomy, which changes the length and angle of the femoral head. Both procedures are aimed at improving the fit between the femur and acetabulum,
(Cargill,Thorpe-Vargas).

After the TPO the dog must be kept on crate for several weeks to allow thw healing process to occur.

If there is already extensive damage to the joint other options include the shelf arthroplasty or BOP procedure, the femoral head and neck excision or a total hip replacement. The shelf procedure seeks to extend the rim of the joint, thus improving stability. This option has been criticized because it does not halt the progression of arthritic changes, thus the animal mat continue to have worsening pain(Cargill, Thorpe-Vargas).

The femoral head and neck excision involves removing both the head and neck of femur. A"sling" of muscles are then used to support and cushion the femoral shaft. This procedure has the best chance for success in dogs weighing less than 50lbs. Because the bone is shortenedthe gait will be affected. This should be considered an end-stage salvage procedure, but costs are usually much lower than other types of surgery.

A total hip replcement involves replacing the head and neck of the femur and the acetabulum with prosthetics. Indications for this radical type of surgery are:

1) Osteoathrits associated with CHD.
2) Failed head and neck excisions.
3) Irreparable head and neck fractures.
4) Non-reducible chronic hip luxations.
5) Avascular necrosis of the femoral head.
6) And repair of afailed total hip arthroplasty (Cargill, Thorpe-Vargas.)

The procedure should be done after the dog has reached adult growth.It is quite costly, but the prosthesis can be expected to last for life, and the dog can weight bear very soon after surgery. As with any orthopedic surgery, infection can pose a serious threat to the recovery and usually antibiotics are prescribed during convalescence.