Osteoporosis has been defined as a structural change in bone wherein the supporting tissue is reduced in amount but remains highly mineralized. It is a non-specific response of the skeleton to a number of disturbances such as inadequate dietary intake, loss of normal activity, vascular and hormonal changes. The condition may appear at six to eight weeks of age (usual history in puppies and kittens). In puppies it appears commonly in large breeds such as the German Shepherd Dog and Saint Bernard. In these breeds there are obviously large requirements for calcium during rapid skeletal growth and nutritional insufficiency in relation to need may
Normal mineralization requires an adequate intake of calcium, phosphorus and vitamin D; the latter is more important if the calcium/phosphorus ratio is wide. When dietary intake of calcium and phosphorus is adequate and the ratio is approximately 1:1 or 1:2, requirements for vitamin D are low, but they increase as calcium or phosphorus intake or both, becomes inadequate or when the ratio is wide. The vitamin D elaborated from skin sterols by the action of ultra violet light is a major source of supply to animals that are exposed to daylight. Vitamin D may be an important factor in puppies that are kept inside without adequate exposure to sunlight.
Juvenile osteoporosis is more common than rickets and occurs more often in cats than dogs. It is seen soon after weaning in animals on a high meat diet that is low in calcium and high in phosphorus. An affected puppy is usually well developed but the bones become thin and week. There will be varying degree of lameness and, sometimes, the front legs are bowed. If a bone becomes very weak it may collapse due to a folding fracture. This leads to a deformed, painful limb and a severely lame puppy. Juvenile osteoporosis is diagnosed by an X-ray of the bones and an investigation of the diet. The condition can be reversed by correcting the diet but any fractures will need temporary support and the bone will remain deformed.
- The Dog Owners Veterinary Handbook. John Bower, David Youngs, James Herriot
- Handbook of Small Animal Radiological Differential Diagnosis. Ruth Dennis, Robert Kirberger, Robert Wrigley
- Some Skeletal Disorders In Domestic Animals. J. R. Holmest