Type of fracture
Depending on which bone cortices are disrupted, fractures are characterized as complete or incomplete. Complete fractures divide the bone into two segments (simple complete fracture) or more segments (multifragmental or comminuted complete fracture). Incomplete fractures only involve a portion of the cortex and typically remain aligned and relatively stable. Segmental fractures occur when a segment of bone is isolated by at least two separate fractures. Wedge fractures are segmental fractures created by two oblique fracture lines. These segments may remain intact or multifragmental and are at risk of impairing blood supply.1,7
Direction of fracture lines
The direction of the fracture line describes the fracture pattern. The three main complete fracture configurations are transverse, oblique, and spiral (Figure 3). Simple transverse and oblique fractures are differentiated by the angle of separation. Transverse is a perpendicular fracture line with less than 30 degrees of slope; an oblique fracture line has a diagonal orientation with 30 or more degrees of slope.1 Spiral fractures are created by a torsional force and present with a rotated appearance.
Incomplete fractures typically occur in short or irregularly shaped bones, and some are exclusively seen in children.2 The periosteum in skeletally immature patients is metabolically more active, thicker, and more durable, creating unique fracture patterns. Bowing, greenstick, and torus fractures result from injury to developing bone (Figure 4). A bowing fracture is caused by an accumulation of microfractures that creates a bend with plastic deformity of the bone. A greenstick fracture occurs when a portion of the cortex and periosteum remains intact. A torus fracture is an impaction injury that causes buckling of the cortex.
Fracture position and relationship of the fragments
Nondisplaced fractures remain in anatomic position and are considered relatively stable. Displaced fractures have lost anatomic position and may require additional terms to describe the position accurately (Figure 5). The amount of displacement is first determined by translation or loss of apposition. This is measured by the percentage of the bone's width. Displacement is described based on the position of the distal fragment in relation to the proximal fragment. The fracture alignment is then determined by alterations in longitudinal axis when comparing the proximal and distal fragments, and is measured in degrees of angulation. The direction of the angulation can either be referenced by the relationship of the distal fragment to the proximal fragment, or by the direction of the fracture apex. Common descriptors of angulation direction include valgus/varus, medial/lateral, radial/ulnar, volar/dorsal, and anterior/posterior.
Additional position considerations may include rotation, shortening, or distraction. Rotation of distal fragments may be subtle and more difficult to identify on imaging; therefore, rotation should be adequately assessed during the physical examination. Rotation is described as either internally or externally rotated. Shortening can occur due to impaction or overlapping of the proximal and distal fragments. Complete displacement with overlapping ends of the fracture is commonly referred to as bayonet apposition. Distraction occurs if the fracture fragments create a gap. If shortening or distraction is present, the distance can be further defined by measuring and can be expressed in millimeters or centimeters.
UNIQUE FRACTURE PRESENTATIONS
Occasionally, fractures have unique mechanisms of injury or atypical presentations that alter the typical description. Compression fractures, which typically affect the short bones or vertebrae, are caused by a collapse of bone due to trauma or underlying conditions such as osteoporosis. Avulsion fractures occur when a bone segment is separated from the main body of bone by tractional forces at the insertion of a muscle, ligament, or tendon at a bony prominence. Stress fractures occur from repetitive microtrauma caused by overuse activities or underlying conditions such as osteoporosis.
FRACTURES IN CHILDREN
In children, the compressibility and plasticity of bones and the strength of the periosteum create unique fracture patterns that may lead to misdiagnoses. If the physis is disrupted in a skeletally immature patient, long-term complications may develop. Physes, apophyses, and normal variances in growth plates are commonly mistaken as fractures.8 Clinicians caring for children with fractures must understand the normal anatomy and physiology of the physis.9
Fracture description may vary slightly in a child. Overall alignment, signs of displacement, and anatomic location are described similarly to adult fractures, but the fracture pattern may differ. Additional classification is required for fractures involving the physis. Carefully evaluate for physeal extension or widening, which may be subtle and easily missed.
The Salter-Harris classification is widely accepted for classifying physeal injuries.8-10 This classification system also indicates injury severity and the potential for growth disturbance.2,10 The five types of physeal injuries each correspond to an increasing risk for growth abnormalities (Figure 6).
- Type I fractures are contained within the physis. In a nondisplaced type I fracture, the presumptive diagnosis often is made based on the physical examination.
- Type II fractures, involving the physis and metaphysis, are the most common physeal injuries.8
- Type III fractures involve the physis and epiphysis.
- Type IV fractures pass directly through the metaphysis, physis, and epiphysis. Because these fractures involve the epiphysis, articular involvement is possible.
- Type V fractures typically are caused by crushing trauma to the physis and carry the worst prognosis.10
The mnemonic SALTR often is used for remembering this classification system. Fracture radiograph orientation is essential if using this mnemonic—be sure to view the bone with the metaphysis superior to the physis (Figure 6). Any disruption to the physis can lead to angular deformities or growth arrest, which may cause limb length discrepancy or changes in range of motion or function. The long-term effects of physeal injuries are not immediate, and require close follow-up.10 A working knowledge of the Salter-Harris classification system provides guidance for appropriate timing of consultations, management options, and need for long-term monitoring.8,11
Conditions that predispose the bone to structural weakness can cause pathologic fractures. Describing these fractures can be challenging for clinicians, but recognizing the underlying cause is critical for successful fracture evaluation and management. Osteoporosis is the most common cause of pathologic fractures and may only require the addition of bone quality to the fracture description. However, pathologic fractures due to primary tumors or metastatic disease require multiple additional descriptive features for further assessment considerations (Table 2). Radiographic findings help to determine the growth rate of the tumor but do not distinguish benign and malignant causes.12 Descriptors of aggressive benign or malignant lesions may overlap, leading to the need for advanced imaging, biopsy, and a multidisciplinary team to differentiate potential causes. Patient age and anatomic location of the lesion are critical for narrowing the differential diagnosis and guiding further evaluation.
Plain radiographs remain the most reliable way to evaluate abnormal bony features on imaging.13,14 Enneking introduced a series of four questions to guide the systematic approach to identifying the underlying process:15-17
- Where is the lesion?
- What is the lesion doing to the bone?
- What is the bone doing to the lesion?
- What is in the lesion?
To differentiate potential benign from malignant causes, evaluate the cortices, medullary cavity, and surrounding soft tissue for overall bone quality and concerning features. In general, larger tumors with cortical destruction, ill-defined margins, aggressive periosteal reactions, and an association with a soft tissue mass are more suggestive of malignancy.18 The entire affected bone should be imaged for any additional areas of concern, including skip lesions or extent of metastases. If overall bone quality is reduced, findings may be more suggestive of osteopenia or osteomalacia. Specific lesions identified on radiographs also should be characterized as nonaggressive or aggressive. This decision can be influenced by margins, periosteal reaction, soft-tissue involvement, sclerotic changes, or osteolysis.
Lesions should be determined as lytic, sclerotic, or both. On plain radiographs, lytic lesions appear radiopaque because of the loss of bone mineralization. Sclerotic or blastic lesions appear radiolucent because of the dense increase in bone mineralization. Osteolytic or osteoblastic lesions are more indicative of tumor. Lytic lesions may be benign or malignant; osteoblastic lesions are more likely to be benign. Most bone tumors are osteolytic.
Borders of lytic lesions are the most reliable indicator for potential malignancy. Overall, the lesions should be determined as well-defined or ill-defined. The three radiographic stages for changes in margins provide guidance in determining the growth rate and level of aggressiveness but may not distinguish benign from malignant lesions.14,18
- Type I lesions have a geographic border and are the least aggressive of the three types. The bone destruction is classified further based on the appearance of the transition zone from the lytic lesion to the surrounding normal bone. Types 1A and 1B have well-defined narrow zones of transition with 1A lesions also having a sclerotic border most consistent with a benign lesion. Type IC margins are less well-defined with a wider zone of transition and indicate the potential for malignancy.12
- Type II lesions are infiltrative and extend into the normal bone. Features of these lesions may be consistent with aggressive benign lesions or, more often, malignant causes. Lesions are described as appearing moth-eaten with intermittent areas of lysis.
- Type III lesions also are infiltrative and extend into normal bone. They have the most highly aggressive findings on imaging, and have a higher risk for malignancy, with diffuse lysis and indistinguishable borders. Metastatic carcinoma of the bone has different appearances based on the primary source. Metastatic carcinoma arising from the lung, kidney, or thyroid will appear lytic; prostate metastases may appear sclerotic; and breast metastases commonly show a mix of lytic and sclerotic changes. Aggressive findings must be identified early because patients will require additional imaging and biopsy.14
Periosteal reaction may be appreciated on plain radiographs, and although the finding is nonspecific for the underlying diagnoses, the change reflects the biologic potential of a tumor or evidence of a pathologic fracture.12 Periosteal reactions are assessed by continuity of the reaction and the complexity of the layering. Solid, unilaminar periosteal reactions occur with slower-growing tumors. Multilaminar periosteal reactions cause an onion-skin appearance. Complex appearances such as Codman triangle and sunburst identify increasingly aggressive features and the potential for malignancy. Codman triangle, which appears as a wedged elevation of interrupted periosteum, develops from the inability of the periosteum to ossify from invasion of the lesion. A sunburst pattern consists of disorganized layers of periosteum caused by rapid growth of a lesion.12,14
Other considerations for description and documentation include cortical destruction and matrix calcification. Cortical destruction is a common finding in malignant and locally aggressive benign conditions such as giant cell tumors or aneurysmal bone cysts. The extent of cortical destruction is highly variable; typically, more worrisome destruction is irregular and benign findings of destruction often are uniform. Lack of cortical destruction does not rule out malignancy. Presence of matrix calcification or mineralization does not distinguish between benign and malignant causes.
Correlate radiographic changes with clinical presentation before determining the need for further studies. A comprehensive history is essential to assess presence of trauma and if present, the level of the impact attributing to the fracture and for localized pain before the injury. Ultimately, the way the radiographic findings are described will guide the response of the multidisciplinary team and significantly affect the patient's reaction if concerning features are identified on imaging. Providers must be careful not to unnecessarily worry patients and educate them on the need for referral or additional workup. Some benign conditions have characteristic features on plain radiographs and can be diagnosed without advanced imaging or biopsy. These “no touch” lesions often can be left alone, which is reassuring to patients; a little watchful waiting with serial imaging can be used to monitor the concerning findings and support the benign diagnosis. A diagnosis of malignancy is never based solely on radiographic findings. Although malignant lesions often have aggressive growth patterns such as ill-defined borders, extensive cortical destruction, and significant periosteal reactions, these same findings also are consistent with infectious processes or aggressive benign conditions such as eosinophilic granulomas or giant cell tumors.18 Biopsy provides the only definitive diagnosis.
Fracture description is a basic skill required for clinicians to assess plain radiographs. Appropriate fracture terminology lets clinicians adequately relate findings. Radiographs are a valuable tool in the diagnosis of a fracture but should not replace a quality history and physical examination. Clinicians are responsible for correlating the clinical presentation with imaging results to create a meaningful picture to guide the diagnosis. A systematic approach to identifying and describing fractures will improve patient care by supporting quality documentation, allowing for better understanding of the injury, and directing the timeline for referral and acute care management.
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Keywords:Copyright © 2019 American Academy of Physician Assistants
fractures; terminology; clinical presentation; radiographs; interpretation; imaging