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Long bones – fractures

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Abstract

Radiography remains the mainstay for imaging long bone fractures, partly because it is readily available but also because it generally provides all the information required by a clinician to manage a fracture appropriately. This chapter concerns itself with the radiographic features of long bone fractures, their healing and the complications thereof, with sections on alternative imaging techniques and abnormal image findings.

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Figures

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10.1 (a) Sagittal CT image in a bone window of the distal tibia of a 7-month-old Husky showing a type II Salter–Harris injury of the physis. CT was used to image this injury at the same time as a complex pelvic injury was being investigated using this modality. (b) Dorsal plane T2-weighted MRI image of the left humeral condyle in a 3-year-old Springer Spaniel showing thoracic limb lameness. There is clear evidence of an intracondylar fissure that could not be detected radiographically. (a, Courtesy of Ingrid Gielen, CT-MR Unit, Ghent University, Belgium)
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10.2 Salter–Harris classification of physeal injury. (a) Type I: a proximal femoral physeal injury in a 7-month-old Labrador Retriever. The fracture line passes along the line of the physis. (b) Type II: a proximal tibial physeal injury in a 6-month-old Boxer. The fracture line passes along part of the physis and out through the metaphysis. (c) Type III: a distal humeral physeal injury in a 4-month-old Labrador Retriever. The fracture line passes through the epiphysis and along part of the physis. (d) Type IV: a distal humeral physeal injury in a 3-month-old Bulldog. The fracture line passes through the epiphysis, across the physis and out through the metaphysis. (e) Type V: (ei) a suspected distal ulnar physeal injury with impaction of the physis in association with a transverse fracture of the radius and an oblique fracture of the distal ulna in a 13-week-old Border Collie. Mediolateral (ML) radiograph taken immediately after internal fixation using a bone plate; (eii) six weeks after treatment the fracture has healed by bowing of the radius with valgus deformity occurring as a result of retarded growth in the distal ulnar physis. (f) Type VI: an incomplete fracture of the distal radius is associated with a periosteal reaction medially that has bridged the distal physis and will influence further growth at this point. Drawn by Vicki Martin and are reproduced with her permission.
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10.3 (a) An open fracture of the radius and ulna in a 3-year-old Boxer. A gas opacity can be seen (arrowed) within the soft tissues proximal to the fracture site. (b) An open fracture of the humerus in a 4-year-old Domestic Shorthair cat caused by an air-gun pellet.
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10.4 (a) Complete fracture of the tibia in a 6-year-old Border Collie. (b) Incomplete (greenstick) fracture of the distal radial metaphysis with complete fracture of the ulna in a 6-month-old Labrador Retriever. (c) Incomplete fracture of a humeral condyle in a 5-year-old Springer Spaniel showing forelimb lameness. This was probably predisposed to by incomplete ossification of the humeral condyle. The periosteal reaction on the lateral humeral epicondyle suggests a stress fracture (see also Figure 10.8b ).
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10.5 (a) A Transverse fracture of the tibia in a 4-year-old terrier. (b) An oblique fracture of the tibia in a 14-month-old Staffordshire Bull Terrier. Many such fractures will have a spiral element to them. (c) A spiral fracture of the tibia in a 15-week-old Cocker Spaniel. (d) Comminuted fractures: (di) a reconstructable comminuted fracture of the femur in a 7-month-old German Shorthaired Pointer; (dii) a non-reconstructable comminuted fracture of the femur in a 23-month-old Labrador Retriever. (e) A segmental (or multiple) fracture of the radius (with accompanying transverse fracture of the ulna) in a 3-year-old Domestic Longhair cat.
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10.6 (a) Avulsion of the tibial tuberosity in a 6-month-old Greyhound. The fragment has become distracted as a result of contraction of the quadriceps muscle group. (b) An impacted fracture, with the ends driven into one another, of the radius and ulna in a 6-month-old Great Dane.
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10.7 (a) A simple folding fracture of the femur in a 6-week-old German Shepherd Dog. Note how thin the cortices are. The puppy was suffering from nutritional secondary hyperparathyroidism. (bi) Pathological fracture of the tibia in an 8-year-old Dobermann. Note the subtle lysis of the ends of the two bone fragments. (bii) Pathological fracture of the femur in a 6-year-old Dobermann. Note the irregular margins to the fracture ends caused by the pre-existing periosteal reaction. (c) Pathological fracture of the humerus in a 10-year-old Labrador Retriever × Collie. The region of abnormal radiolucency in the diaphysis at the proximal extremity of the fracture is clearly evident in this radiograph, which was taken after internal fixation.
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10.8 (a) Stress fracture of metacarpal V in a racing Greyhound. Note the periosteal reaction present at the time of fracture. (b) Stress remodelling of the lateral humeral epicondyle in a 5-year-old Springer Spaniel (same case as Figure 10.4c ).
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10.9 (a) Postoperative radiograph taken following internal fixation of a Monteggia fracture in a 4-year-old Border Collie. The plate is over-contoured, creating elbow joint incongruity, which requires correction. (b) Postoperative radiograph taken following external skeletal fixation of an open tibial fracture in a 7-year-old Lurcher. Spatial realignment of the crus is not perfect but is acceptable given the functional appearance of the limb alignment as judged clinically. (c) Postoperative radiograph taken following internal fixation of a non-reconstructable, comminuted femoral fracture, which involved the femoral neck, in a 7-year-old Cocker Spaniel. Note that the bone screw and K-wire used to stabilize the femoral neck both enter the coxofemoral joint space and need to be replaced and withdrawn, respectively. (d) Postoperative radiograph taken following internal fixation, using a T-plate, of a distal radial fracture in a 15-month-old Toy Poodle. The plate encroaches on the carpal joint and may cause irritation because of this or by lying under extensor tendons. Implant positioning cannot be improved at this stage, but it is likely that implant removal will be necessary after fracture healing if maximal return of limb function is to be achieved.
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10.10 Postoperative (a) Craniocaudal (CrCd) and (b) ML radiographs of a reconstructed femoral fracture in a 7-month-old German Shorthaired Pointer.
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10.11 Postoperative radiograph of a non-reconstructed femoral fracture showing bridging fixation, using a bone plate, with satisfactory spatial alignment of the bone ends in a 23-month-old Labrador Retriever (same case as in Figure 10.5dii ).
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10.12 (ai) ML and (aii) CrCd radiographs taken postoperatively of a spiral distal tibial fracture in a 7-year-old cat. The fracture has been reconstructed and stabilized with an intramedullary pin and cerclage wire. (b) ML radiograph taken postoperatively of a comminuted femoral fracture in a 1-year-old cat. The fracture has not been reconstructed. The cerclage wires do not compress the fracture lines but simply gather the fragments like a ‘bundle of sticks’. This situation will offer little resistance to axial, rotational or bending forces. The IM pin is also too long and enters the stifle joint space.
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10.13 Postoperative radiograph of a non-reconstructed open radial fracture showing bridging fixation using an external skeletal fixator, in an 18-month-old collie cross-breed. Note that one of the fixation pins is encroaching on a fracture line. Limited purchase and early loosening can be expected for this implant.
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10.14 (a) Preoperative CrCd radiograph of a lateral humeral condylar fracture in a 6-year-old English Springer Spaniel. The fracture had occurred 3 days earlier and was preceded by the dog showing lameness in that limb for 3 weeks. Note the amount of remodelling present on the lateral epicondyle (arrowed). This was presumed to be the result of stress associated with incomplete ossification/incomplete fracture of the humeral condyle prior to the development of a complete humeral condylar fracture. (b) ML radiograph of the same dog as in (a) taken immediately postoperatively. Note the evidence of pre-existing activity on the epicondyle (arrowed).
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10.15 Classical fracture healing. (a) Haematoma at fracture site. (b) Bridging callus at the fracture site mineralized peripherally but with hyaline cartilage at the level of the fracture site. (c) Compaction and remodelling of the mineralized callus. Drawn by Vicki Martin and are reproduced with her permission.
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10.16 Primary bone healing. (a) Direct or contact healing. (b) Gap healing. Drawn by Vicki Martin and are reproduced with her permission.
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10.17 Bridging osteosynthesis. Non-reconstructable comminuted tibial fracture bridged with (a) a plate or (b) an external skeletal fixator. (c–d) The resulting fracture callus forms while the implants protect the fracture site from adverse forces (‘load sparing’). Drawn by Vicki Martin and are reproduced with her permission.
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10.19 Radiographic progression of classical fracture healing and bridging osteosynthesis for a tibial fracture in an adult terrier cross, treated by external coaptation. (a) At the time of fracture the fragments show sharp borders. After 7–10 days the fragment edges become less distinct and an indistinct periosteal reaction may be noted. (b) After 2–3 weeks a bridging callus is just visible, which will gradually become more mineralized. (c) By 6–8 weeks the callus is mineralized from proximal to distal. The bridging mineralized callus will remodel over a period of months or years to restore normal bone architecture.
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10.20 Radiographic appearance of primary union by primary bone healing. (a) Radiograph taken 14 weeks after internal fixation of a transverse radial fracture in a 19-month-old Italian Greyhound. In adult bone, a fracture treated by reconstruction and interfragmentary compression should heal without callus formation and the only radiographic finding should be a loss of any faint radiolucent line noted in the bone on postoperative radiographs. The ulna shows non-union, which is not uncommon after healing of the radius under plate fixation. (b) Radiograph taken 7 weeks after internal fixation of a transverse radial fracture in an 8-month-old Lurcher. In immature bone, despite the same management, periosteal irritation will produce a visible callus.
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10.21 Radiographic anomalies of fracture healing. (ai) Radiograph taken 2 months after internal fixation of a reconstructed, comminuted femoral fracture in an 8-month-old Northern Inuit. A spur of callus is seen extending from the proximal segment. This is a result of injury to the attachment of the adductor muscle. (aii) Radiograph taken 6 weeks after fixation of a long spiral femoral fracture in a 5-month-old Boxer. Treatment involved reconstruction of the bone using an intramedullary pin and cerclage wire, followed by the application of a two-pin unilateral, uniplanar external skeletal fixator with the intramedullary pin ‘tied in’ to the frame. The external fixator was removed immediately prior to the radiograph being taken. A spur of callus is seen extending from the distal segment as a result of injury to the attachment of the adductor muscle. Note also the pocket of gas, distal and caudal to the fracture site. This was associated with the distal fixation pin track; a mixture of bacteria, including sp., was cultured from the site. The infection resolved completely following a 2-week course of broad-spectrum antibiotic treatment. (bi) Radiograph taken 2 months after internal fixation of a Salter–Harris type I injury of the proximal femoral physis in a 5-month-old Labrador Retriever. A limited craniolateral approach was used to reduce the epiphysis and the K-wires were placed in a normograde fashion. A mild ‘apple core’ effect is noticeable in the femoral neck. (bii) Radiograph taken 3 months after internal fixation of a Salter–Harris type I injury of the proximal femoral physis in a 7-month-old Labrador Retriever. A trochanteric osteotomy was used to aid exposure of the fracture and accurate reduction of the epiphysis. A marked ‘apple core’ effect is visible in the femoral neck and severe acetabular remodelling is evident as a result of postoperative instability. (biii) Radiograph taken 2 months after internal fixation of a Salter–Harris type I injury of the proximal femoral physis in a 7-month-old Border Collie. A limited craniolateral approach was used to reduce the epiphysis and the K-wires were placed in a normograde fashion. An iliofemoral suture was placed to improve joint stability during the immediate postoperative period. The tunnels the suture was placed through in the ilium and greater trochanter are still evident. A moderate ‘apple core’ effect can be seen in the femoral neck. (biv) Radiograph taken 5 months after internal fixation of a Salter–Harris type I injury of the distal femoral physis in a 5-month-old Border Collie. A mild ‘apple core’ effect is noted on the cranial aspect of the femur.
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10.22 CrCd views of a non-reconstructable tibial fracture in a 6-year-old Border Collie (same case as in Figure 10.4a ) taken (a) immediately post surgery and (b) 9 weeks postoperatively. In (b), bridging fixation has been achieved using a bone plate and so healing has been by virtue of bridging osteosynthesis. Good bone union is evident with no evidence of implant failure, and exercise restriction is no longer required.
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10.23 (ai) ML radiograph of a transverse tibial fracture in a 4-year-old terrier, taken 6 weeks after internal fixation using an intramedullary pin (same case as in Figure 10.5a ). There was no bridging callus evident radiographically, although the fracture felt stable. This can be termed a delayed union, resulting from some rotational instability. (aii) ML radiograph of the same case 6 weeks later. Radiographic union is now evident. (bi) Postoperative ML radiograph of a comminuted proximal humeral fracture in a 16-year-old cat. The fracture has been stabilized with an intramedullary pin and external skeletal fixator. A synthetic cancellous bone substitute has been packed into the fracture site (arrowed). (bii) ML radiograph taken 6 weeks later. Callus is forming but bone union is incomplete. The distal fixation pins were removed after radiography to increase loading of the bone. (biii) ML radiograph taken 12 weeks after injury. Bone healing is now good and the remaining implants were removed.
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10.24 Radiographic appearance of a radial/ulnar fracture in a 3-year-old Labrador Retriever, taken 6 weeks after treatment using external coaptation. There is no evidence of bridging callus and the medullary canals have sealed. This appearance indicates a non-union.
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10.25 Types of so-called biologically active or viable non-unions. (a) Hypertrophic non-union (‘elephant’s foot’ callus). Radiographic appearance of a transverse femoral fracture in a 5-year-old German Shepherd Dog, 4 months after treatment by internal fixation using an intramedullary pin. Note that the pin has migrated proximally, leaving a radiolucent track in the distal bone segment. (b) Slightly hypertrophic non-union (‘horse’s foot’ callus). Radiographic appearance of a radial fracture in a 4-year-old Toy Poodle after 8 weeks of treatment using external coaptation. (c) Oligotrophic non-union. Radiographic appearance of an olecranon fracture in a 7-year-old West Highland White Terrier taken 1 month after injury and no specific treatment. There is no evidence of any mineralized callus formation.
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10.26 Types of so-called biologically inactive or non-viable non-unions. (a) Necrotic non-union: radiographic appearance of a transverse radial/ulnar fracture in a 20-month-old Bedlington Terrier 8 weeks after internal fixation using an intramedullary Kirschner wire. The radius has fractured again at the end of the pin, creating a necrotic segment of bone within the fracture gap. (b) Defect non-union: radiographic appearance of the same fracture as in (a), 4 weeks after debridement of the fracture gap. The defect remains a barrier to bone union. (c) Atrophic non-union: radiographic appearance of an ulnar fracture in a 4-year-old Toy Poodle after 8 weeks of treatment using external coaptation. Note the ‘pencilling’ of the ulna due to receding ends of the bone fragments. The radius is showing evidence of a slightly hypertrophic non-union.
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10.27 Malunion. (a) Functional malunion of an open tibial fracture in a 7-year-old Lurcher treated with external skeletal fixation (same case as in Figure 10.9b ). (b) Non-functional malunion of a radius/ulna fracture in a 2-year-old Border Collie, managed with external coaptation. The dog showed lameness associated with the valgus deformity and a corrective osteotomy was required to resolve this condition.
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10.28 Fatigue failure of an implant. Radiographic appearance of a fractured femur in a 3-year-old Labrador Retriever, 10 days after treatment by partial reconstruction and application of a bridging plate. The implant was inadequate to fulfil such a function and has failed by fracture through a distal plate hole. (Courtesy of MR Owen)
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10.29 Fatigue failure of an implant caused by inappropriate application. (a) Postoperative radiographic appearance of a fractured femur in a 5-year-old Rough Collie, treated by internal fixation using a bone plate. The oblique fracture has not been reconstructed or compressed, leaving a defect in the medial cortex (opposite the centre of the plate). Thus, the plate is not functioning as a neutralization plate, for which it would have been adequate, but as a bridging plate. (b) Radiographic appearance 4 weeks later. The plate has bent through the screw hole closest to the fracture line. Had the fracture ends been reconstructed so that the plate functioned as a neutralization plate this complication would not have occurred.
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10.30 (a) Radiographic appearance of a fractured radius and ulna in a 5-year-old Border Collie, 8 weeks after treatment by external skeletal fixation: (ai) CrCd and (aii) ML views show lysis around the more proximal fixation pins. This appearance was accompanied by excessive pin tract drainage. The cause was infection, resulting in bone necrosis around the implants. (b) Radiographic appearance of a fractured femur in a 3-year-old Domestic Shorthair cat, 4 months after treatment involving internal fixation using a bone plate. The proximal plate screws have loosened as a result of bone resorption caused by excessive levels of stress at the bone–metal interface. The use of more plate screws on either side of the fracture would have helped to avoid this complication, or possibly the use of a cancellous bone graft to facilitate fracture healing, thus reducing the time for which the implants were subjected to adverse stress. (c) Radiographic appearance of a femoral fracture in an 8-month-old Springer Spaniel, 18 days after treatment involving internal fixation using an intramedullary pin. Instability at the fracture site resulted in the pin ‘walking’ proximally and this has led, ultimately, to failure of fixation.
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10.31 Radiographic appearance of a comminuted fracture of the tibia in a 2-year-old terrier cross, 1 month after treatment by internal fixation using an intramedullary pin and cerclage wire. A profound periosteal reaction is present along the entire length of the tibia. Lucency around the pin may indicate loosening, and a fragment close to the cerclage wire may be forming a sequestrum. Such changes are typical of established osteomyelitis.
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10.32 (a) Radiographic appearance of a fractured radius (the ulna remained intact) in a 7-month-old Collie, 8 weeks after treatment by internal fixation using a bone plate. Multiple sinus formation had occurred by 14 days post surgery, and at that time one of the plate screws had been removed. The radial fracture line has almost disappeared but under the empty plate hole is a linear mineralized fragment of bone (sequestrum) lying within a saucer-shaped defect in the radius. (b) Radiographic appearance of a humeral Y-fracture in a 5-year-old German Shepherd Dog, 4 years after treatment by internal fixation. Recurrent sinus formation had led to sequential removal of implants but the sinuses still recurred. In the absence of implants it is now possible to see two sequestra sitting within an involucrum (arrowed). (c) ML radiograph of the hock of a 4-year-old German Shorthaired Pointer taken 8 weeks after treatment for gastrocnemius tendinopathy. A tunnel had been created in the calcaneus for placement of tendon sutures. The density of the bone and/or dullness of the drill bit has caused damage to the surrounding bone due to overheating. The dead bone has formed a ‘ring sequestrum’. In this particular case it was of no consequence. However, this effect can also be created around fixation pins (as part of external skeletal fixation) applied with poor technique, when it can be associated with persistent drainage following pin removal.
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10.33 Radiographic appearance of the stifle of a 5-year-old Dobermann, 3 months after hip luxation. Complications involving infection following internal stabilization led to excision arthroplasty. Subsequent to this, the dog developed quadriceps contracture. Note the proximal position of the patella and overextended appearance of the femorotibial joint. A similar effect can result in puppies with quadriceps tie-down following (inappropriate) treatment of a femoral fracture.
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10.34 (a) Radiographic appearance of the humerus of a 6-year-old Lurcher taken 4 years after treatment of a humeral non-union fracture. An area of lysis proximal to the plate is suggestive of neoplasia being the cause of the recent-onset lameness. (b) Radiographic appearance of the distal femur of a 9-year-old German Shepherd Dog that had a distal femoral fracture treated by lag screw fixation as a puppy. Lysis around the implant and a local periosteal reaction were associated with pain on manipulation and palpation of the region. Implant removal and biopsy confirmed the cause to be osteosarcoma.

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