9.2SKELETAL CHANGES 9.2 SKELETAL CHANGES

Ossification of the costochondral junctions gives an irregular radiodense pattem which may be mistaken for neoplasia or osteomyelitis.

Spondylosis is benign new bone development bridging adjacent vertebrae in the spine and it is particularly common in some breeds such as brachycephalics. The new bone deposition is usually smooth and of little consequence unless it entraps spinal nerves as they leave the spinal column. Spondylosis is particularly common at the lumbosacral junction and at this site a single lesion needs to be differentiated from diswhich may also occur in older animals. In the latter cases there are clinical signs of pain, pyrexia and sometimes neurological deficits and on radiography there is usually narrowing of the joint space, loss of bone in adjacent vertebral endplates, and sclerosis either side of the joint space as well as ventral (and lateral on dorsoventral projections) new bone bridging between the vertebrae.

Demineralisation of bone occurs in renal secondary hyperparathyroidism often before owners report the clinical signs such as polydipsia and polyuria associated with the underlying renal disease. Poorly mineralised bones with thin cortices are seen on survey radiographs, and the mandible is one of the first bones to be affected with teeth on radiographs of affected animals appearing to float' in the poorly radiodense bone.

Chronic, smooth spurs of new bone and smooth surfaced osteophytes may develop around joints (particularly on the distal femur and proximal tibia of the stifle, and at the interphalangeal joints) and they may be of no clinical significance. They need to be differentiated from the more aggressive new bone deposition associated with degenerative joint disease or osteoarthritis. It is useful to radiograph the contralateral joint to compare unusual benign appearances on radiographs. If the radiographic appearance is the same in both limbs it is unlikely to be directly related to unilateral clinical signs such as lameness.