GSD Health Issues – Hip Displasia

Overview

• This malady is, unfortunately, a too-common occurrence. It happens primarily to large breed dogs and is caused by complex genetics (polygenic) and environmental factors.
• It is usually a disease of young dogs (less than 2yrs) but can develop in older individuals, as well.
• The uppermost aspect of the thigh bone (the femur) consists of an angled appendage (the femoral neck & head) at whose end there is a hemispheric component (the head) that normally fits into a hollowed/concave hemispheric space known as the acetabulum on the pelvis (hip bone).
• This arrangement (the "articulation" of the femoral head within the acetabulum) comprises the coxofemoral joint. It is stabilized by fibrous ligaments within and around the joint.
• When the leg moves, the femoral head is supported by and rotates within the acetabulum. Both the head and the acetabulum are coated with a slippery cartilage and the these are further surrounded with a thick, lubricating fluid which, together, provide an environment that prevents friction from leading to damage of structures and maximizes functionality. Ultimately, this prevents joint inflammation (arthritis) and pain.
• In order for this joint to function optimally, the femoral head must articulate at a precise angle appropriate for maximal weight bearing; malalignment of any of the participating structures resulting from inappropriate force, or angle of articulation as well as malformation of the head or the acetabulum will lead to degenerative joint disease, and, potentially life-long pain.

Definition and Causes

• Hip dysplasia is a laxity of the hip joint that develops between birth and skeletal maturity that can result in the abnormal alignment of articular surfaces. Hip dysplasia often leads to painful arthritis. Causes are multifactorial.
• Heredity: Many genetic determinants may, collectively, be responsible; the mechanism(s) which lead to clinical the manifestation of signs is complex and incompletely understood.
• Diet: Basically, rapid growth leads to large body mass. This results in greater stress forces on immature bone and growth plate cartilage. Consequently, microfractures within growth plates and exacerbation of (geneticaly predisposed) joint structure malalignments ensues.
• Excessive High-Impact Exercise: This may similarly affect joint and growth plate integrity.

Diagnosis

Clinical History:

• Young-Dog Syndrome: A young (4-12 months) large-breed canine with sudden decrease in activity or onset of hindlimb lameness may be associated with some loss of hip muscle mass.
• Older-Dog Syndrome: An older (greater than 12 months) large-breed canine with insidious loss of rear limb muscle mass, shifting weight while standing (listing between left and right rear limbs), especially after exercise.
• Palpation of Coxofemoral Joint
• Barden Method   -   Ortolani Sign: This is a complex series of moving leg through various ranges of motion while concurrently palpating the hip joint for signs of subluxation/laxity.

Radiological Signs:

• Precise positioning for radiological evaluation of the hip joint usually requires heavy sedation or anesthesia.
• With standard positioning for the evaluation of the hip joint, there are accepted abnormal radiological signs that are consistent with the diagnosis of hip dysplasia. Evaluation of the shape and congruity of the femoral head with the acetabulum, evidence for abnormal wear of articular surfaces, as well as the presence of degenerative changes are some of the parameters examined.

Treatment Options

Goals:

• Promote increased muscle mass. (Note that atrophy of thigh and pelvic muscles due to disuse [pain?] of hindlimb(s) actually exacerbates the stress on the hip joint and spreads an additional support burden on the remaining limbs)
• Correct Obesity

Exercise:

• Exercise is required to prevent muscle atrophy and may help in the management of obesity.
• Diet Modification (lower caloric density diet or fewer "treats". for example)
• Examples: On Mondays, Wednesdays and Fridays, go for leash walks, swimming (minimal stress to joint while building muscle mass) and mild retrieving...promote the "trot" rather than speed running (which is high impact). Such a regimen will make the dog sore....initially, during the first few weeks. Non-steroidal antiinflammatory medication (check with your veterinarian) could be given on Tuesdays and Thursdays (the "off" days) if needed.

Obesity Management:

• Execise regimen, as described above
• Medical and laboratory evaluation to rule out underlying causes (e.g. hypothyroidism) of obesity.

Surgical Options

Triple Pelvic Osteotomy (TPO):

• This is a major surgical procedure in which the angle of the pelvis is changed to to better accomodate the head of the femur within the acetabulum.
• The TPO is ideally performed early (6-12 months of age) before the development of arthritis and degenerative joint disease.

• RULES OF THUMB: This procedure should NOT be done on any animal with degenerative joint disease or who is greater than 18 months of age.
• Total Hip Arthroplasty (THA):
• This procedure involves replacing the entire hip joint with an artificial hip joint (a similar procedure is performed in people.
• Reserved for clinically significant (PAINFUL!) arthritis and degenerative joint disease.
• NOT appropriate if there is significant muscle mass atrophy or if there is infection anywhere (e.g. dental disease/gingivitis, urinary tract, skin).
• Femoral Head and Neck Osteotomy (FHO):
• Involves excision of the articular components of the femur (the head and the "neck"[....the portion of bone that connects to the head of the femur]) and thus bypassing the normal hip joint by promoting the formation of a "false joint".
• This surgery promotes the generation of a fibrous capsule which, along with normal thigh and pelvic muscles, stabilizes and supports the limb and the pelvis. There is no articular surface, per se; hence, this is a "false joint".