P. 572

An Urban Experience
A femoral head and neck osteoarthropathy resulting
in spontaneous femoral capital physeal fractures
and originally described in young overweight cats is occasionally encountered in dogs and may be dif cult to distinguish from traumatic femoral capital physeal fractures. Diseases of the sti e joint in young dogs include OC/OCD of the lateral and less commonly the medial femoral condyle, patella luxation and a variation of Osgood-Schlatter-Syndrome seen in people. Patella luxation is most commonly seen in small breed dogs. Radiographically, the patella may or may not be luxated medially. Additional  ndings include varus deformity
of the sti e joint and intracapsular soft tissue swelling in case of concurrent cranial cruciate ligamentous injury. In large breed dogs, lateral patella luxation is more common. Osgood-Schlatter-Syndrome in people is a developmental anomaly in which the tibial crest
or tuberosity separates from parent bone. This is occasionally seen in dogs.
Congenital dysostosis and other hereditary, devel- opmental, nutritional and hormonal abnormalities of bony and cartilage development: A large num- ber of diseases falls under these categories. Examples include polydactyly, syndactyly, amelia/hemimelia/phoc- omelia, ectrodactyly, mucopolysaccharidoses, pituitary dwar sm, congenital hypothyroidism, rickets, hyperpara- thyroidism, osteochondrodysplasias, multiple cartilag- inous exostoses, and retained cartilage cores. These diseases are rare in veterinary patients.
Other bone diseases in young animals: Panosteitis
is most common in large breed dogs. Radiographs may be normal or may show focal or multifocal areas of poorly de ned increased opacity within the medullary cavities of the long bones. In advanced stages, periosteal reaction may also be present. Hypertrophic osteodystrophy is a disease of undetermined etiology which results in devel- opment of lucent zones within the metaphysis of long bones paralleling the physis. These lucent zones are of- ten bordered by sclerosis. In advanced stages, extensive periosteal reaction and potentially growth abnormalities may be observed.
Acquired Bone and Joint Diseases (3, 4)
Bacterial osteomyelitis in young animals may be caused by haematogenous spread, while it is most commonly due to direct inoculation (e.g. penetrating wound) in older dogs. Radiographic  ndings include soft tissue swelling, irregular/immature and often columnar periosteal prolif- eration and commonly lysis. Mycotic osteomyelitis (e.g., coccidiomycosis) develops secondary to a systemic infection and hematogenous spread and is often polyos- totic. Radiographically, lesions manifest as aggressive, mixed lytic and proliferative, and can give rise to confu- sion with bone tumours. Joint involvement is possible with both bacterial and mycotic disease (septic arthritis/ mycotic arthritis). Unlike with the infectious form, non-
infectious/ immune mediated arthritides usually involve multiple joints. In the nonerosive form intracapsular soft tissue swelling is the only radiographic abnormality. In the erosive form (e.g., rheumatoid arthritis) intracapsular soft tissue swelling is followed by subchondral lysis progress- ing to extensive erosion with destruction of joint surfaces, collapse of joint spaces, and, in severe cases, (sub)luxa- tion of the affected joint. Neoplasia of the skeletal system is common in dogs. A primary bone tumor (e.g., osteo- sarcoma) results in an aggressive focal lesion, commonly found in the metaphysis of the long bones (proximal humerus, distal radius, distal femur and proximal tibia). Metastases to bone may be seen in the appendicular
or axial skeleton, tend to occur in the vicinity of nutrient foramina, may be small and easily overlooked. Other tumours affecting bone include round cell tumours (e.g., multiple myeloma) and soft tissue neoplasms extending into bone. Radiographic  ndings in these conditions are variable. Joint associated tumours may also be encoun- tered with histiocytic sarcoma, myxomas and synovial cell sarcomas being most common. Radiographically, severe intracapsular soft tissue swelling and multifocal lytic changes of adjacent bony structures are noted. Hypertrophic osteopathy results in extensive columnar periosteal proliferation of the long bones extending from the distal limbs proximally. This condition develops sec- ondary to intrathoracic or less commonly intra-abdominal mass lesions. Trauma to the musculoskeletal system
is a frequent cause of lameness in veterinary patients, and traumatic lesions (e.g. fractures) are usually a fairly straightforward diagnosis. Chronic soft tissue lesions
can result in radiographic changes especially over time. One example is cranial cruciate ligament rupture which is common in large breed dogs and is typically recognized based on intracapsular soft tissue swelling of the sti e joint with displacement of the infrapatellar fat-pad and periarticular osteophytosis. Unlike in people, cranial cru- ciate ligamentous injury in dogs is often partial and may or may not result in cranial subluxation of the tibia. Simi- larly, chronic tendinopathy of the bicipital tendon or  exor tendons of the distal forelimb can result in radiographic soft tissue mineralization and degenerative changes to the proximal and distal humerus, respectively.
1. Barr FJ, Kirberger RM. BSAVA Manual of Canine and Feline Musculoskeletal Imaging. Gloucester: BSAVA; 2006.
2. Thrall DE et al. Section III: The Appendicular Skeleton: Canine, Feline, and Equine. In: Textbook of Veterinary Diagnostic Radiology. 6th. Ed. Thrall DE, editor. St. Louis: Elsevier Saunders; 2013.
3. Johnson KA, Watson ADJ. Skeletal diseases. In: Textbook of Veterinary Internal Medicine, 5th ed. Ettinger SJ, Feldman EC, editors. Philadelphia: WB Saunders; 2000.
4. Pedersen NC, Morgan JP, Vasseur PB. Joint diseases of dogs and cats. In: Textbook of Veterinary Internal Medicine, 5th ed. Ettinger SJ, Feldman EC, editors. Philadelphia: WB Saunders; 2000.

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