Nathan C. Nelson Department of Molecular Biomedical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, USA Radiography plays a key role in the diagnosis and classification of orthopedic fractures and monitoring of bone healing after stabilization. Diligent monitoring with radiography is necessary for early diagnosis and avoidance of complications to healing such as nonunion or bone infection. This chapter will describe proper radiographic technique to diagnose fractures, description of fracture location, normal appearance of healing, and potential complications of fracture healing. Complete evaluation of a fractured bone requires a minimum of two orthogonal radiographs, as single radiographs are insufficient to display the complex geometry of most fractures (Figure 9.1). Acquiring multiple radiographs of a fractured leg can be challenging, depending on the site of fracture as well as the degree of patient pain, so high‐quality, well‐positioned radiographs require strong sedation or anesthesia. Radiographs are usually the only imaging performed to plan for surgical repair. Errors in positioning (such as obliquity of the limb) result in incorrect bone geometry on the radiograph, by distorting the bone. This complicates eventual repair by obscuring parts of the fracture or artifactually altering bone measurements. FIGURE 9.1 Lateral (A) and craniocaudal (B) projections of a proximal tibia demonstrating the importance of orthogonal projections. On the lateral projection, no fracture of the tibia is seen (though an oblique fibular fracture is identified). On the craniocaudal projection, a Salter Harris type II fracture of the proximal tibial physis is seen. Some fractures require additional projections to identify or categorize the fracture. Fissure fractures, where there is no displacement of adjacent bone margins, can be particularly difficult to identify as the x‐ray beam must be tangential with the fracture to appear on radiographs (Figure 9.2). This type of fracture is common in juvenile dogs as immature cortical bone tolerates more strain and elastic deformation than mature bone, allowing a fracture to occur through only one cortical edge, rather than completely through the bone (so‐called greenstick fractures) [1]. If clinical suspicion for a fissure fracture is high, additional oblique projections at 10–20° intervals can make them more apparent. FIGURE 9.2 Lateral radiograph of a tibia showing a nondisplaced fissure (arrow). Notice the cortices of this bone remain well aligned, without displacement. Fracture of the small bones in the carpus, tarsus, and digits can be particularly difficult to identify; studies in this region should include not only lateral and dorsopalmar(plantar) projections, but oblique projections as well (Figure 9.3). Fractures of the femoral neck may not align tangentially with the x‐ray beam on lateral projections. Additionally, extension of the hips for traditional positioning of the ventrodorsal (VD) pelvic projection can result in artifactual alignment of the fracture margins, making them difficult to identify. A “frog‐leg” position radiograph in such cases makes diagnosis easier, by relaxing the coxofemoral joint and allowing adjacent fracture margins to malalign (Figure 9.4). While the frog‐leg position is more comfortable for the patient, the extended VD projection of the pelvis should also be performed in such cases as it provides a more complete understanding of fracture geometry, and positions the femur in a craniocaudal projection, allowing better surgical planning. FIGURE 9.3 Dorsopalmar (A) and dorsolateral‐palmaromedial oblique (B) radiographs of a fracture of the proximal phalanx of the fifth digit. Note that on the dorsopalmar projection (A), the transverse fracture (arrow) is not readily apparent as it superimposes with external soft tissue margins. This fracture is more apparent on the oblique projection (arrowhead), as this oblique projection shows a fracture in a different orientation. FIGURE 9.4 Ventrodorsal extended leg projection (A) and frog‐leg position (B) of a dog with bilateral capital physeal fractures. Note that on (A) with the pelvic limbs caudally positioned, capital physeal fractures are not readily apparent. On (B), with the legs in a more neutral frog‐leg position, displacement of the femoral heads from the femoral necks (arrows) is apparent and the fracture lines are seen. Spinal radiographs have only moderate sensitivity in detecting spinal fractures and subluxations compared to computed tomography (CT), and are particularly poor in diagnosing fracture fragments within the vertebral canal [2]. Manipulation should be kept to a minimum in patients with suspected spinal fractures, particularly when sedation or anesthesia is used, as this limits the protective bracing of the paraspinal musculature compared to an awake patient, and may predispose to further injury with manipulation [2]. Lateral radiographs are readily achieved in the recumbent trauma patient, but patient safety may dictate that orthogonal spinal radiographs employ a horizontal beam to prevent rolling the patient, which may result in some image compromise or less than ideal patient position (Figure 9.5). FIGURE 9.5 Lateral (A) and horizontal beam ventrodorsal (B) projections of a patient with a traumatic fracture of L1. On the lateral projection, shortening of the first vertebral segment is appreciated (arrow). On the orthogonal horizontal beam projection, a significant rightward displacement of the fracture is identified (arrowhead). Ultimately, if radiographs are deemed insufficient to diagnose or fully characterize a fracture, CT imaging of the fracture site should be pursued. A complete radiographic description of a fracture should convey all pertinent features and allow a second party (such as a radiologist or orthopedic surgeon) to mentally reconstruct the image of the fracture and its effect on adjacent tissues without actually seeing the radiographs in question [3]. The description begins with the bone(s) involved and the location of the fracture [3]. The fracture may involve the diaphyseal, epiphyseal, or metaphyseal region of the bone. Displacement and the severity of displacement are described by the orientation of the distal fracture fragment relative to the more proximal fragment (Figure 9.6). The term overriding or proximal displacement describes proximal translation of a distal fracture fragment. Distraction occurs when two fracture margins separate from each other, resulting in a wide fracture gap. Numerous other descriptive terms may apply. Fractures are complete when the fracture completely traverses the width of bone, or incomplete when only a portion of the cortical margin is affected (greenstick fractures are examples of incomplete fractures). FIGURE 9.6 Lateral (A) and caudocranial (B) radiographs of a comminuted, caudolaterally displaced fracture of the femoral middiaphysis. There is mild overriding of the fracture. As previously mentioned, fractures may be described as fissures when no displacement of the fracture margins is present and the fracture is incomplete (Figure 9.7). Fissures often occur in conjunction with complete fractures, where a thin fissure line may extend for a significant distance from the major fracture line, and are important to recognize if surgical stabilization is attempted (Figure 9.7). FIGURE 9.7 Lateral (A) and caudocranial (B) and magnified projections (C,D) images of a fissure fracture (arrowhead) extending distally from a more proximal complete displaced fracture. A segmental or multiple fracture is one in which there are two complete fractures on either side of a portion of bone, resulting in a separate osseous fragment. A fracture is open if there is clear extension of bone beyond soft tissue margins. Any gas adjacent to an acute fracture indicates that skin margins were disrupted, and the fracture is assumed open. Lack of gas in the surrounding tissues does not mean a fracture is not open; confirming a fracture to be closed requires visual inspection during physical examination to ensure lack of skin disruption. A fracture is closed if the surrounding skin surface is intact. A comminuted fracture contains adjacent fracture fragments (but not a complete osseous segmental fracture) which may be large or small (Figure 9.6). A folding fracture occurs when an underlying osseous disease results in loss of mineralization, so that only soft matrix remains, increasing bone compliance (Figure 9.8). When an affected patient bears weight, the bone distorts but does not disrupt cortical margins, resulting in the impression of bone folding. This type of fracture is rare and only occurs in endocrinopathies such as renal secondary hyperparathyroidism or inherited dysplasias such as osteogenesis imperfecta. FIGURE 9.8 Ventrodorsal pelvic (A) and lateral femur (B) radiographs of a patient with metabolic bone disease and numerous folding fractures. Notice the diffuse decreased opacity of the bones and the thin cortices. Multiple folding fractures are present (arrowhead). Complete fractures are described based on the orientation of the fracture line. A transverse fracture occurs perpendicular to the long axis of a bone. A short oblique fracture is angled between a transverse fracture and 45° from the long axis of the bone. A long oblique fracture has an angle greater than 45° from the long axis of a bone (Figure 9.9). A spiral fracture wraps around the long axis of its bone, changing its orientation at different locations along the length of the bone. FIGURE 9.9 Radiographs of fractures with multiple different orientations. Long oblique fractures are identified on (A). Short oblique fractures of the distal radius and ulna are identified on (B), and transverse fractures of the tibia and fibula are identified on (C). If the fracture line extends to the surface of a joint, the fracture is articular (Figure 9.10). The terms “T” or “Y” fracture describe fractures that extend from an articular surface to the condylar or supracondylar region along both margins of a bone, resulting in a T or Y shape (Figure 9.10). These are most common in the distal humerus. FIGURE 9.10 Craniocaudal projections of the distal humerus in two dogs. Notice on (A) the fracture extends from the articular surface of the distal humerus through the medial and lateral supracondylar region; this is a T type fracture configuration. In comparison, on (B), the fracture extends from the articular surface to the lateral supracondylar region only, with the medial supracondylar region being normal. Avulsion fractures occur at sites of soft tissue attachments on bone, such as the origin or insertion of tendons or ligaments (Figure 9.11). When a traumatic insult increases strain on those soft tissue structures, a segment of bone may pull from the underlying bone, resulting in a separate fragment. FIGURE 9.11 Ventrodorsal projection of the pelvis with an avulsion fragment of the left tibial tuberosity (arrow). Compression fractures are common in the spine, and occur when forces are applied along the long axis of a bone, resulting in the two fracture margins being driven into each other and an overall shortening of the bony segment. This type of fracture may be difficult to identify, and should be suspected when there are differences in vertebral length between adjacent segments (Figure 9.12). FIGURE 9.12 Lateral projection of the thoracic spine showing a compression type fracture of a midthoracic vertebral segment (arrow), occurring after the dog fell from a great height. The dog was painful on palpation of the midthoracic spine. Notice the decreased craniocaudal length of the segment as well, with mild ventral bony irregularity (arrow) which helps discriminate this from a congenital malformation. A pathologic fracture occurs at a site of underlying bone disease, such as neoplastic or inflammatory lesions. Pathologic fractures are suspected when there is no history of trauma or only mild trauma is reported. Pathologic fractures occur most commonly when there is underlying osseous neoplasia, which weakens the bone, predisposing to fracture. The fracture may distort the osseous anatomy, obscuring the underlying pathology, but the bone fragments should be carefully scrutinized for any underlying bone loss or periosteal proliferation. Underlying bone distortion (collapse, displacement, etc.) also signals that the fracture could be pathologic in origin (Figure 9.13). CT is more sensitive to the lysis or altered medullary architecture that more definitively indicates a fracture as pathologic in nature. For that reason, when radiographs are indeterminate for underlying pathology at a fracture site, CT should be considered as the next imaging procedure.
CHAPTER 9
Fracturesand FractureHealing
Introduction
Radiographic Examination of Fractures
Fracture Description and Classification
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
