Complications of Osseous Trauma

There are many complications of skeletal trauma, although in most cases fracture healing is uncomplicated. Complications can result from direct trauma to bone and soft tissue or from the treatment of the fractures. Complications may be systemic or local and involve the bones or the adjacent soft tissues and joints. In this chapter an overview is presented of the various complications in which radiology plays a role in evaluation and the imaging appearances of these complications. Complications discussed include delayed union, nonunion with pseudarthrosis formation, malunion, cartilage damage, early degenerative changes, growth disturbance, posttraumatic osteomyelitis, avascular necrosis, posttraumatic osteoporosis and osteolysis, Sudeck atrophy, and posttraumatic cyst and pseudotumor formation. Other complications related to infections, vascular and nerve injuries, and soft tissue aspects are discussed elsewhere.

Prevalence, Epidemiology, and Definitions

Complications of trauma can be acute, subacute, or chronic. Acute is defined as having occurred immediately and usually refers to the injuries to the adjacent soft tissues, nerves, and vessels caused by the fracture fragments. Subacute is defined as having occurred after days to a week and is typified by infection. Chronic is defined as having developed weeks to several months after an injury and is typified by delayed union, nonunion, pseudarthrosis formation, malunion, osteoarthritis, or growth abnormalities. Further definitions are found within each subsection.

The incidence of fractures has been reported as 7.4 to 10 per 1000 persons per year. The incidence of nonunion in tibial fractures has been reported as 2.5% and that of delayed union as 4.4% in 22 series that included 5517 fractures.

The incidence of osteomyelitis after open fractures is reported to be 2% to 16%, and in cases with operative management for closed fractures it is between 0.5% and 2%.

The tibia is the most common site for open fractures and the most common site for posttraumatic osteomyelitis.

Manifestations of the Disease

Delayed Union, Pseudarthroses, or Nonunion of Fractures

Evaluation of fracture healing is done clinically and radiologically. Different bones heal at different rates, with the normal duration of fracture healing ranging from 4 to 20 weeks. Delayed union is the failure of union at the expected date with clinically evident motion at the fracture site and a persistent fracture line with deficient or scarce callus on radiographs.

Nonunion is the complete cessation of the healing process, and this term is usually reserved until after the fracture is at least 6 months old. The terms delayed union and nonunion are often used interchangeably because there are no well-defined criteria to separate the two. In both circumstances, the area between the fracture fragments is filled with dense fibrous tissue. Nonunion can be “hypertrophic,” with marked callus formation, or “atrophic,” without significant callus formation. Delayed union or nonunion is most common in the tibia, fibula, and scaphoid.

Pseudarthrosis, a term referring to formation of a false joint at the site of injury, is sometimes used interchangeably with nonunion. In this situation, fluid or a mixture of fluid and fibrous material develops between the fracture fragments and may result in continued motion at the fracture site that retards healing. Radiologically, it may be difficult to differentiate pseudarthrosis from nonunion. However, with pseudarthrosis formation there is often hypertrophic excessive sclerotic bone with rounded smooth edges.

Causes of nonunion and delayed union include interruption of blood supply, anatomic distortion with multiple comminuted fractures, loss of bone fragments, severely displaced fractures, open fractures, and extensive soft tissue damage. The general condition of the patient, age, nutrition status, infection, and other concurrent diseases also play a role in the healing of fractures. The use of corticosteroids can also delay fracture healing.

Radiography

In the early stages no distinct features are present. Serial radiographs will either show an abundance of callus without bridging in the case of hypertrophic nonunion or paucity of callus in atrophic nonunion. In hypertrophic nonunion, the margins of the fracture fragments are well defined, sclerotic, and smooth, and the medullary cavity is occluded with eburnation (sclerosis). In atrophic nonunion, there is little or no callus formation and the gap of the fracture is widened and filled with fibrous tissue. When the fracture fragments remain widely separated, soft tissue interposition should be suspected and excluded by other imaging tests, such as ultrasonography, CT, or MRI.

Pseudarthrosis formation is diagnosed clinically with motion and instability at the site of the old fracture. The radiographic manifestations include persistence of the fracture line with sclerosis of the margins and smooth rounded edges ( Fig. 42-1A ).

$FIGURE 42–1, Pseudarthrosis. A , Lateral radiograph of the distal tibia shows persistent fracture line with surrounding sclerosis. B , Sagittal reconstructed CT image shows the nonbridging callus and persistence of the fracture line.$

Multidetector Computed Tomography

Cross-sectional imaging with CT allows visualization of the fracture without overlying structures and can discriminate between union and nonunion by detection of bridging callus. Reconstruction in multiple planes (sagittal and coronal) with correction for patient positioning is possible. CT is optimal for reviewing complex fracture cases and for showing involvement of joints, allowing more accurate surgical planning (see Fig. 42-1B ).

Magnetic Resonance Imaging

Magnetic resonance imaging may be rarely used when a delayed union, nonunion, or pseudarthrosis is clinically suspected or if there are any other unusual features. Discontinuity of bone on T1-weighted sequences and the presence of fluid between the fracture fragment edges are helpful imaging features for evidence of inadequate healing ( Fig. 42-2A-E ).

$FIGURE 42–2, Nonunion. A , Oblique coronal short tau inversion recovery (STIR) image of the humerus. B Sagittal T2 spectral attenuated inversion recovery (SPAIR) and ( C ) sagittal T1-weighted images of a 60-year-old woman, 24 months after complex fracture of the middle third of the humerus. Nonunion with pseudarthrosis is present. This was clinically obvious with free motion at the fracture site. The patient presented with radial nerve palsy, due to fracture impingement. D , Transverse T1 and ( E ) T2 SPAIR images at the level of the fracture showing the lack of consolidation and the space between the fracture fragments.$

Malunion, Cartilage Damage, and Early Degenerative Changes

Malunion is fracture healing in an abnormal position or alignment. Rotational malalignment is never corrected spontaneously, so it should be evaluated carefully on radiography or CT, although it is often difficult to detect.

In children, angulations up to 30% may correct spontaneously, but in adults, spontaneous healing rarely occurs even with angulations much less than 30%.

Trauma to the skeleton may be associated with premature degenerative joint disease due to altered biomechanics. Fracture involvement of joint surface increases the likelihood of early osteoarthritis, particularly when there is a gap or offset of the cortical joint surfaces. Fracture fragments remaining within the joint also predispose to joint degeneration.

Radiography

Radiography is the standard modality used in the follow-up of all patients with fractures. Linear and angular deformity can be well demonstrated ( Fig. 42-3A,B ). Orthoradiograms show limb-length discrepancies due to malunion ( Fig. 42-4 ). Radiographs, however, are not able to demonstrate mild rotational deformity, and CT is suggested for that circumstance.

FIGURE 42–3, A and B , Conventional radiographs of the knee showing posttraumatic structure and contour alteration of the femur with early degenerative changes in the knee joint.

$FIGURE 42–4, Orthoradiogram of a 52-year-old man showing significant shortening of the right leg due to malunited fracture of the right femur.$

Degenerative changes seen on radiographs include the presence of osteophytes, joint space reduction, subchondral sclerosis, and formation of geodes ( eFig. 42-1 ).

$eFIGURE 42–1, Radiographs of the knees of a 52-year-old man with malunited femoral posttraumatic fracture, showing the secondary osteoarthritic features of the knee joint on the right with joint space narrowing and osteophytic spurring.$

Multidetector Computed Tomography

Computed tomography is useful for rotational deformity, which is not easily detected on radiography. Degenerative changes such as osteophyte formation, joint space narrowing, sclerosis, and geode formation are also well demonstrated with CT, especially because sagittal and coronal reconstructions may be easily obtained.

Magnetic Resonance Imaging

Magnetic resonance imaging with its superior tissue contrast clearly shows the changes in bone, joint, and soft tissues ( Fig. 42-5 ). It is also the gold standard for the assessment of cartilage lesions after trauma. The location, size, and depth of the lesions and the presence of any underlying bony abnormalities should be described. Cartilage flaps or fissures may be more amenable to therapy with early surgery. MRI is useful in the demonstration of posttraumatic cartilage damage, which can lead to early degenerative changes. This technique shows all the features of degeneration and also the presence of joint fluid, bone marrow contusion, and free joint bodies.

FIGURE 42–5, Coronal T1-weighted MR image showing the malunited femur with thickening of the cortex and significant shortening. Note the posttraumatic fatty atrophy of the adjacent muscles.

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