Devon Rex Miositis

Introduction

There are several possible ways of classifying the musculoskeletal diseases and the accuracy of any classification depends on the available information. The classification used here (Table 8.1) is simple and probably most relevant to the clinician.

Bone fractures are not uncommon in cats. The exact traumatic episode is generally unknown; cats either arrive home or are found in an injured state. Road traffic accidents or falls from a height are the most likely cause. Various surveys have been reported and indicate that the femur, tibia, mandible and pelvis are the most commonly fractured bones (Carter, 1964; Hill, 1977; Knecht, 1978). In a survey of feline pelvic fractures (Bennett, 1975) the average age of cats sustaining pelvic injury was 1.3 years; it is suggested that young animals learn to cope with their environmental hazards through experience, but the very young cat is more likely to remain close to the home environment and is thus more protected.

The repair of fractures is beyond the scope of this chapter. Various surgical techniques can be used, although conservative treatment is often gratifying as,

Traumatic disease

Fractures

Table 8.1 Classification of diseases of the feline musculoskeletal system

Traumatic disease

Fractures

Luxations/subluxations Tendon injuries

Bone infections

Bacterial Mycotic

Metabolic bone diseases

Nutritional secondary hyperparathyroidism Osteodystrophy of mature cats Rickets (osteomalacia) Hypervitaminosis A Hypovitaminosis A

Renal secondary hyperparathyroidism Primary hyperparathyroidism Primary hypoparathyroidism

Arthritis

Traumatic arthritis Osteoarthritis

Infective arthritis Immune-based arthritis

Neoplastic and neoplastic-like lesions

Osteocartilaginous exostoses Osteosarcoma Extraskeletal osteosarcoma Extraskeletal osteoma Parosteal osteoma Chondrosarcoma Osteoma Osteoid osteoma Multilobular chondromas Osteoclastoma Giant cell sarcoma Spindle cell sarcoma Fibrosarcoma Synovioma Synovial sarcoma Aneurysmal bone cyst Fibrous dysplasia

Continued

Table 8.1 (continued)

Neoplastic and neoplastic-like lesions (continued)

Metastatic neoplasms of bones and joints Direct extension of neoplasms to bone Synovial cyst

Synovial osteochondrometaplasia

Inherited, congenital and developmental disorders

Osteogenesis imperfecta

Sacrocaudal dysgenesis in Manx Cats

Kinked tail

Polydactylia

Ectrodactylia

Syndactylia

Amelia and hemimelia

Arrested development of long bones of forelimbs

Mandible ramus aplasia

Congenital duplication

Arthrogryposis

Chondrodysplasia

Achondroplasia

Congenital hypothyroidism

Maxillofacial compression

Craniofacial malformation in Burmese cats

Pectus excavatum

Other skeletal abnormalities

Other congenital abnormalities

Mucopolysaccharidosis

Other lysosomal storage diseases

Patellar luxation

Proximal femoral metaphyseal osteopathy Feline capital physeal dysplasia syndrome Hip dysplasia Osteochondrosis

Neuromuscular diseases Inherited myopathies

Feline X-linked muscular dystrophy Nemaline myopathy Generalised ossifying myositis Myotonia

Hereditary myopathy of the Devon Rex Glycogen storage diseases for example, with pelvic fractures. Recent studies have shown that the external fixator is well tolerated by the cat and can be used to treat a number of fracture problems in this species (Langley-Hobbs et al, 1997). In general, cats are very co-operative orthopaedic patients and healing complications are relatively rare.

Luxations/subluxations

Traumatic luxations of joints usually follow a suspected road accident or fall from a height. The hip is the most commonly dislocated joint of the cat

Acquired myopathies

Myositis

Hypokalaemic polmyopathy Burmese sporadic myopathy Localised ossifying myositis

Neuromuscular junction disorders

Myasthenia gravis Organophosphate toxicity

Inherited neuropathies

Hyperoxaluric neuropathy

Neuropathy associated with hyperchylomicronaemia Neuropathy associated with sphingomyelinase deficiency Distal axonopathy of Birman cats

Acquired neuropathies

Ischaemic polyneuropathy (aortic thromboembolism) Polyneuropathy associated with salinomycin Diabetic polyneuropathy Traumatic neuropathy Neoplasia

Other myopathies

Tetanus

Fibrotic myopathy

Contracture of the gastrocmenius muscle/tendon

Dystrophy-like myopathies

Others

Diseases of the vertebral column

Intervertebral disc protrusions Spondylosis deformans and ankylosing hyperostosis Bacterial discospondylitis Atlantoaxial subluxation

Miscellaneous diseases

Hypertrophic pulmonary osteoarthropathy

Disuse osteopenia

Osteopetrosis

Myelofibrosis/osteosclerosis synd rome Feline hyperaesthesia syndrome

(Figure 8.1) (Bennett, 1975). This is usually treated successfully by external reduction under general anaesthesia. Strapping of the leg is not advisable in cats, since they tend not to tolerate the sling at all well. Recurrent hip luxations may be treated by transarticular pinning (Bennett & Duff, 1980) or by femoral head excision, although cats can often manage well with a permanently luxated hip (Bennett, 1975).

Total luxation or subluxation of the femorotibial joint may occasionally be seen following road traffic injuries (Figure 8.2). Such luxations are associated with cruciate and collateral ligament rupture. Careful

Manx Cat Sacrocaudal Dysgenesis
Figure 8.1 Craniodorsal radiograph of the pelvis showing a craniodorsal hip luxation.

reconstruction of the damaged ligaments is recommended in these cases, although stabilisation of the joint with cross-pins or a single transarticular pin has been described (Figure 8.3); the pins are removed after 3 weeks. Antebrachiocarpal luxation in the cat is occasionally encountered and is best treated by carpal arthrodesis using a 2.7/2.0 mm hybrid carpal arthrodesis plate (Li et al., 1999). The femoropatellar joint may also luxate secondary to trauma and usually responds to capsular tightening. The patella may also luxate in association with a dislocated hip joint. The tarsocrural joint is commonly luxated or subluxated, often associated with fractures of the medial and/or lateral malleoli of the hock (Figure 8.4). Treatment is by fixation of the fractured malleoli, usually by a tension band wiring technique or by reconstructing the collateral ligaments of the hock. Although most ligament tears in cats are associated with major trauma, there is a report suggesting that there may be a gradual failure of the cranial cruciate rupture akin to that seen in dogs (Janssens et al., 1991; Schrauwers & Appeldoorn, 1991). Furthermore, a tentative association between cruciate failure and cardiomyopathy in the cat has been suggested (Janssens et al., 1991). However, most cranial cruciate ligament failures in the cat are caused by major trauma and

Arthritis Joint Pain

Arthritis Joint Pain

Arthritis is a general term which is commonly associated with a number of painful conditions affecting the joints and bones. The term arthritis literally translates to joint inflammation.

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