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Hip Dysplasia

by Dra.Flávia Mª. Maruch Hallack and Dr. Guilherme Luiz O. de Noronha

Hip Dysplasia is a pathology characterized by a genetic malformation of the hip joints, causing the development of various degrees of arthritis (osteoarthrosis) and worsened by instability affecting the area. It was first reported in dogs in 1935 and has since been diagnosed also in other species such as cats, bovines, equines, wild animals and even people. It affects every breed, being most commonly observed in the medium and big sized ones and in those that grow up too quickly, like the German Shepherd, Brazilian Fila, Rottweiller, Saint Bernard, Labrador among others, regardless of gender.

Dysplasia occurs with dogs who are born with normal joints connecting their rear limbs and femurs. Subsequently, progressive structural alterations occur, such as articular relaxation, swelling, wearing out and tearing of ligaments, razing of the articular cavity, subluxation of the hip ball, erosion of the articular cartilage, subcondral ossification, remodeling along the femoral head and neck, acetabular rim changes, such as termed osteophytes or bone spurs and various degrees of trabecular bone pattern changes.

Etiology

It is believed that the etiology of HD is influenced by several factors, being the following factors related to the development of the disease:

Other factors such as hypotrophy of the miofibers of the pectin muscle, alterations that increase the volume of the synovial fluids, hormonal alterations (maternal hyperestrogenism), insufficient synthesis of proteins, deficiency of vitamin C, exercising in excess during the growing up period and long stays on smooth flat floors that lead to articular instability are also related to the development of HD. The most remarkable factor though is genetic, while the additional factors may only worsen some existing genetic predisposition.

Diagnosis

The diagnosis of HD is exclusively radiological. The diagnosis only from clinical signs is not sufficient, as they are sometimes not compatible with the radiological findings. Therefore, the animal cannot be diagnosed as free from dysplasia just because of the absence of symptoms. Every animal must be submitted to a radiograph.

In order to have the radiograph taken, the animals must be sedated so as to put them in the adequate position more easily. The animal must be placed on its back in dorsal recumbency with the rear limbs well stretched and parallel to each other, slightly rotated internally. The pelvis must be symmetrical and the spine parallel to the limbs.

There are different techniques for the evaluation of the radiography. The most commonly used are those developed by the Orthopedic Foundation for Animals-USA (OFA), by the University of Pennsylvania, USA (PennHip), by the British Veterinarian Association, England (BVA), and the Norberg Method (HD). For the ultimate report, the animals must be 12 months old or older for the BVA and Norberg Methods, or older than 24 months for the OFA. The bitches must be radiographed at least 30 days before or after a heat cycle, as the possible increased joint laxity (subluxation) from hormonal variations may mislead the results.

The anatomical structures to be analysed through radiographic evaluation are: 1- Craniolateral acetabular rim; 2- Cranial acetabular margin; 3-Femoral head (hip ball); 4-Fovea capitus (normal flattened area on hip ball); 5-Acetabular notch ; 6-Caudal acetabular rim; 7-Dorsal acetabular margin; 8-Junction of femoral head and neck; 9-Trochanteric fossa.

In the radiographic evaluation, the animal may be included in one of the following categories, according to the existing alterations:

HD- (equivalent to OFA’s excellent and good): Animal free of HD. As per the Norberg Method, it displays an angle of approximately 105° (just as reference).

Excellent hips
HD+/- (equivalent to OFA’s fair and borderline: Animal that may develop HD. As per the Norberg Method, it displays an angle of approximately 105° (just as reference).

Fair hips
HD+ (equivalent to OFA’s mild): Animal with mild HD and still good for mating. As per the Norberg Method, it displays an angle of approximately 100°;

Mild HD
HD++ (equivalent to OFA’s moderate): Animal with moderate HD. Flattening of the hip ball, razing of the hip socket, subcondral ossification, loss of the articular space, formation of osteophytes, alterations at the femoral neck, occurrence of subluxation. As per the Norberg Method, it displays an angle superior to 90°;
HD+++ (equivalent to OFA’s severe): Animal with serious HD. As per the Norberg Method, it displays an angle of less than 90°; Severe HD

Symptoms and Treatment

The first clinical signs generally start to show by 5 to 8 months of age, although in some cases they will not show until some 36 months of age. The symptoms are extremely variable, ranging from difficulty to walk, to get up, to run or to go up stairs to an arched dorsum, a staggering pace and claudication. Symptoms may also include reduction of the extent of the rear limbs movement, atrophy of the muscles of the rear limbs and local sensitivity that can be exacerbated after exercising. It is important to remark that there isn’t always a relationship between the symptoms and the degree of dysplasia that the animal may be suffering from. That is, animals with severe dysplasia may sometimes run, jump and play while others with moderate dysplasia may claudicate strongly.

There is no cure for HD. The treatments aims at minimizing the pain and fight the symptoms, giving the animal a higher quality of life. In the milder cases it is recommendable decreasing the animal’s weight so as to reduce the mechanic stress on the joints and also physiotherapy (like swimming, that is a non-weight bearing exercise) to prevent or relieve the ongoing inflammatory process. In the most severe cases, non-steroid anti-inflammatory drugs to control the pain. These medicines can also be associated with precursors of proteoglycans, which are important constituent material that forms the joint-lining hyaline cartilage. Surgical treatments include triple pelvic osteotomy (TPO), complete removal of the femoral head and neck, complete arthroplasty of the joint, among others.

Final Remarks

The puppies of medium and big sized breeds must be given specific nourishment, so as to control their development and prevent them from growing up exaggeratedly fast. Obesity and exercise in excess should also be avoided while still in the age of growing up.

It is important to point out that as it is a multiple gene inherited disease, HD may be minimized but not eliminated that way. Even when mating normal animals, puppies may show dysplasia, although at a lower proportion.

For controlling HD, owners and breeders must bear in mind the importance of obtaining the radiological reports of animals to be used as reproducers from veterinarians who are experienced in the area of radiodiagnosis, in order to minimize the incidence of HD in their breeding.

Reference bibliography

  • FLO B. P. M. Handbook of small animal orthopedics & fracture treatment. WB Saunder Company, 2nd edition, 1990, pp. 355-356.
  • MORGAN R.V. Handbook of small animal practice. WB Saunder company, 2nd edition, 1992, pp. 866-868.
  • WHITTICK W. G. Canine Orthopedics. Lea & Fediger, 2nd edition, 1990, pp. 796-797.
  • The Site of the Orthopedic Foundation for Animals (www.offa.org)

Illustrations:

  • The Site of the Orthopedic Foundation for Animals (www.offa.org)

Dra Flávia Mª Maruch Hallack and o Dr Guilherme L. O. de Noronha are Veterinarians working in the Greater Belo Horizonte area, breeders of Labrador Retriever and are sponsored by EUKANUBA

Published on the Brazilian magazine Cães de Fato – year 5 – issue 17. 2000.
Published under permission from De Fato Promoções e Eventos Ltda