Pathological fractures

image of Pathological fractures
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Pathological fractures occur because an underlying disease process has weakened the bone. Due to this weakness a pathological fracture develops, usually in association with normal activity rather than being associated with a major traumatic event. The chapter reviews neoplasia; hyperparathyroidism; osteogenesis imperfecta; bone cysts; fracture-associated sarcoma; stress riser effect.

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13.1 Craniocaudal radiograph of a pathological fracture of the proximal femur secondary to a primary bone tumour (osteosarcoma). Note the lysis of bone giving a ‘moth-eaten’ appearance, loss of trabecular detail and irregular cortical thinning adjacent to the fracture lines in the metaphyseal and femoral neck areas. A transverse fracture through the metaphyseal region extending to and causing lateral displacement of the greater trochanter is present. Ill-defined new bone is present at the level of the lesser trochanter; this may represent periosteal reaction or a fracture fragment.
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13.2 (a) Mediolateral and (b) craniocaudal radiographs of the antebrachium of an 8-year-old cat with bacterial osteomyelitis of the distal half of the radius and the styloid process of the ulna. The radiographic features (soft tissue swelling, aggressive bone lysis and irregular new bone production) are indistinguishable from those that characterize a neoplastic disease. A previous biopsy tract is apparent in the distal radius. (Courtesy of T Gemmill)
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13.3 (a) Mediolateral radiograph of an oblique pathological fracture of the tibia in an 8-year-old Greyhound. Note the minimal periosteal changes and the reduced bone density at the fracture site. Lucency is present proximal to the butterfly fragment in the proximal fragment (tibia). Scalloped irregular thinning of the cortex is present at the cranial and caudal aspects of the tibia at the fracture level. There is also loss of definition of the fracture margins. (b) Mediolateral radiograph taken immediately postoperatively. Biaxial plating was performed due to a high suspicion of pathological fracture secondary to bone neoplasia, although a biopsy sample obtained at the time of surgery revealed only reactive bone. (c) Follow-up radiograph taken 5 months after surgery. Note the obvious bone lysis and soft tissue swelling at the site of the original fracture and screw loosening and displacement. Destruction of the cortical bone, growth of the tumour beyond the original confines of the bone, thinning of the cortex and an indistinct transitional zone between normal and neoplastic bone are also present.
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13.5 Limb-sparing surgery performed in an 11-year-old Pointer with a pathological fracture of the distal radius and ulna. The most distal screw in the ulna caused propagation of an undetected fissure. The gap left after resection of the area has been filled with an autologous cancellous graft, a coarse osteoallograft and bone morphogenic protein 2 (BMP-2) in a collagen sponge (TruScient). (Courtesy of T Sparrow)
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13.6 Actions of parathyroid hormone (PTH). PTH acts on kidney and bone to increase the serum concentration of calcium. Vitamin D acts on bone and intestine to increase the serum calcium concentration. In the kidney, PTH plays a crucial role in the formation of the most metabolically active form of vitamin D. A negative feedback system exists between PTH and the metabolically active form of vitamin D. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission.
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13.7 (a) Caudocranial radiograph of a displaced mid-diaphyseal pathological femoral fracture in a puppy with nutritional hyperparathyroidism. Note the generalized osteopenia and thin bone cortices. (b) Caudocranial radiograph taken immediately postoperatively following fracture stabilization with an intramedullary pin tied into an external skeletal fixator. (c) Caudocranial radiograph 4 weeks after surgery, which demonstrates healing at the fracture site and a subjective increase in the bone density following the feeding of a normal balanced diet in the postoperative period.
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13.8 Mediolateral radiograph of a puppy diagnosed with osteogenesis imperfecta. Note the healed pathological fractures of the tibial and fibular diaphyses. (Courtesy of N Fitzpatrick)
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13.9 Suspected subchondral bone cyst (arrowed) in a 6-month-old Lakeland Terrier in the head of the 5th metacarpal.
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13.10 Stress fracture of the proximal tibia in a cat through an ESF pin tract. (Courtesy of T Gemmill)
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