Radiology at Legevakten
* Claude Pierre-Jerome, MD, PhD
** Knut Grønseth,
in progress unfinished
update: April 24 2001
1. Trauma. General considerations *
1a) Biomechanical principles of bone
1b) Definition of fracture and ”occult fracture or bone bruise”
1c) Types of fracture
1d) Fractures in childhood
1e) Complications of fracture
1f) Imaging modalities – at Oslo Legevakt (Emergency Service) and Ullevål Hospital
2. Thorax **
3. Upper extremity *
4. Lower extremity *
5. Spine *
4c) Lumbal and lumbo-sacral
6. Abdomen *
1. Trauma. General considerations
The recognition of injury in the trauma patient requires a detailed knowledge of gross anatomy and of normal variants that may be mistaken for fractures. The radiologist - or the assigned physician at the emergency unit – must be able to accurately recognize the injury (fracture, dislocation or both). An accurate diagnosis will facilitate a better patient management. It is generally recommended to obtain at least two views of the affected bone. Each view should include two joints adjacents to the injured bone. This would reduce the risk of missing an additional fracture and/ or dislocation at a site remote from the primary injury.
In children, a radiograph of the opposite (normal) extremity is usually necessary for comparison.
1a) Biomechanical principles of bone
Bone is anisotropic and has several mechanical properties when loaded in different directions. The load can be by compression, tension or shearing. The cortical bone in adults withstands the greatest stress in compression, less in tension and the least with shear loading. When force is applied to bone, the muscles (adjacent to the affected bone) will contract. The contraction of muscles will alter the stress distribution and may allow the bone to withstand higher load than expected.
With greater speed of loading, more energy is stored before failure; and as fracture occurs, this energy will dissipate rapidly resulting in extensive damages of the adjacent soft tissues. Also, repeated loading reduces the amount of total weight a bone can withstand owing to fatigue of muscles that normally redistribute the stress.
1b) Definition of fracture and ”occult fracture”
A complete fracture is by definition a total disruption or break in the continuity of a bone (fig.1). When only some of the bony trabeculae are disrupted while others are intact or bent, the fracture is called incomplete (fig.2). Both complete and incomplete fractures are visible on conventional radiographs.
An ”occult fracture” or bone bruise (also called bone contusion, trabecular microfracture or bony trabecular injury) is a trabecular fracture that is not visible on conventional radiographs but evident with bone scintigraphy and magnetic resonance imaging (MRI). The lesion appears hypointense on T1-weighted and hyperintense on T2-weighted and short Tau inversion recovery (STIR) images (fig.3).
1c) Common types of fractures:
1c1). Closed or Simple fracture. Absence of open wound in the skin during clinical examination..
1c2). Open (or compound) fracture. The bone fragment (s) will communicate with the exterior through an open wound in the skin (clinical observation).
1c3). Complete fractures (see definition above) can be:
1c3a). Transverse (horizontal fracture line) (fig.4)
1c3b). Oblique (oblique fracture line) (fig.5)
1c3c). Spiral (spiral fracture line) (fig.6)
1c3d). Longitudinal (longitudinal fracture line) (fig.7)
1c3e). Comminuted (a fracture with more than two fragments)
1c4). Incomplete fractures (see definition above) are most often seen in children. There are 3 major types:
1c4a) Torus fracture (a buckle of the affected cortex) (fig.8)
1c4b) Greenstick fracture (incomplete fracture on the tension side (fig.9).
1c4c) Bowing or Plastic fracture (bending without angular deformity of a long bone) (fig.10).
1c5) The fracture can also be called according to:
1c5a) Anatomic site or location:
1c5a1) Supracondylar (proxima1 to the condyles)
1c5a2) Intra- articular (if the fracture line goes through the articulating surface or Extra-articular (if the fracture line has no contact with the articulating surface
1c5b) Apposition (Contact of the ends of the fracture fragments)
1c5b1) Anatomic or non-displaced
1c5b2) Displaced: fragments can be displaced anterior, posterior, lateral, medial, or a combination of these. The degree of displacement is either measured or expressed as a percentage of cross-sectional diameter.
1c5b3) Lack of apposition: Complete loss of contact of the bone ends.
1c5b3a) ”Bayonet apposition” is used when the fragments overlap one another.
1c5b3b) Distraction. Complete lack of apposition of the fragments (with a gap in between). Most commonly due to excessive traction, interposed tissue, or resorption of fragment ends subacutely.
1c5c) Alignement (Relationship of the long axes of the fracture fragments.
1c5c1) Angulation: is the loss of alignment of the fragments. It is important to specify the direction of angular displacement of the distal fragment:
1c5c1a) Varus angulation: the distal part of the distal fragment points toward the body midline (the fracture apex points away).
1c5c1b) Valgus angulation: the opposite of varus. The distal part of the distal fragment points away from the body midline (and the apex points toward the midline).
1c5d) Rotation. Both proximal and distal joints adjacent to the fracture must be seen on the same radiograph for a better appreciation of the rotation of the distal fragment There can be:
1c5d1) Internal rotation or
1c5d2) External rotation
1c6) Other types of fractures:
1c6a) Chip fracture. Presence of an isolated bone fragment
1c6b) Avulsion fracture. When the fragment is separated (from the main bone ) due to traction from an attached tendon or ligament.
1c6c) Fracture with diastasis. Diastasis is the separation of a slightly movable joint (eg. Diastasis of the distal tibiofibular joint with lateral malleolus fracture).
1c6d) Fracture with an associated dislocation (at the adjacent joint)
1c6e) Compression fracture (eg. Compression fracture of the vertebral body)
1c6f) Impaction fracture (eg: impaction fracture of caput humeri)
1c6g) Depression fracture (eg: depression fracture of the tibia plateau)
1c6h) Stress fracture (or fatigue). Excessive stress applied to a normal bone (eg: stress fracture with jogging)
1c6i) Insufficiency fracture. Normal stress appiled to an abnormal bone (eg: fracture of osteoporotic bone )
1c6j) Pathological fracture. Fracture secondary to pre-existing lesion (eg: primary tumor or metastasis)
1d) Fractures in children
Fractures in childhood are very special due to the following:
a) The bones in children are more porous (immature), which frequently result in incomplete fractures
b) There is greater possibility of remodeling and malalignement depending on:
1) number of years of growth left
2) location of the fracture (near the growing end of the long bone)
3) whether the angular deformity is in the plane of movement of the adjacent joint.
c) The epiphyseal plate (in children bone) is the weakest, and it is a frequent site of fractures in the long bones. The fracture of the epiphyseal plate is classified into 5 types (Salter-Harris classification):
. Type I : Fracture through the epiphyseal plate itself
. Type II: Fracture through the plate and extending through the metaphysis.
** This is the most common type and the prognosis for healing without deformity is good.
. Type III: Fracture through the plate and extending through the epiphysis
. Type IV: Fracture through the epiphysis and metaphysis
. Type V: Compression fracture through the growth plate.
N.B. Types IV and V are relatively rare and have high complication rates. These complications are partial premature epiphyseal plate closure and deformity.
1e) Complications of fractures are:
1) Avascular necrosis
2) Infection (osteomyelitis, gas gangrene)
3) Reflex sympathetic dystrophy (Sudeck dystrophy)
4) Complications of the healing process:
4a) Delayed union: fracture that does not unite within 16 to 18 weeks. This depends also on the patient’s age and the fracture site.
4b) Malunion: union of the bone fragments in an unacceptable or faulty position.
4c) Nonunion: When the fracture just fails to unite. Radiographically, nonunion is characterized by sclerosis (eburnation) and rounded edges of the fragments ends. There is a gap between the fragment ends and motion between the fragments can be seen under fluoroscopy. Nonunion can be:
4c1) Reactive nonunion (hypertrophic or oligotrophic)
4c2) Nonreactive (atrophic)
4c3) Infected nonunion
4c4) A variant of nonunion is:
Pseudoarthrosis: There is formation of a false joint cavity with a synovial-like capsule (with fluid) at the fracture site. Some refer to pseudoarthrosis when the fracture fails to heal within eight months.
5) Disuse osteoporosis (also called demineralization or osteopenia)
It is characterized by radiolucent areas of decreased bone density secondary to atrophy of the bony trabeculae and thinning of the cortex. Disuse osteoporosis may occur following a fracture (united or nonunited) or dislocation; it is due to disuse of the extremity due to pain and immobilization in the plaster cast.
6) Volkman ischemic contraction
This complication may develop following a supracondylar fracture of the humerus; it is caused by ischemia of the muscles folloed by fibrosis. Volkman ischemic contraction is characterized by 5 ”P”:
7) Myositis ossificans (postraumatic)
It is characterized by an enlarging, painful mass at the site of injury. By the third to fourth week following the trauma, calcifications and ossifications begin to develop in the mass; and at six to eight weeks well organized cortical bone appears at the periphery of the mass.
The hallmark of myositis ossificans on X-ray or C.T. scan is the presence of the so-called ”zonal phenomenon”. This phenomenon is characterized by a radiolucent area in the center of the mass, indicating the formation of immature bone, and by a dense zone of mature ossification at the periphery. The ossific mass usually separates from the adjacent cortex by a thin radiolucent cleft.
1f) Imaging modalities (used at lLegevakten and Ullevål hospital):
1f1) Conventional (digitalized) radiographs
1f2) Magnetic resonance imaging (Legevakten and Ullevål)
1f3) Computed Tomography (C.T.scan) (Ullevål)
. Technical notes – Different projections and indications
. Fibrosis (different causes)
. Infiltrate vs. Fibrosis
. Adenopathy (hilar and mediastinal)
. Pleura calcifications – Asbestosis
. Tumor – “Coin lesion”
3. Upper extremity
. Anatomic and Radiological considerations
. Fractures (proximal humerus, scapula, clavicle)
. Dislocations. Different types
. Acromioclavicular luxation. Grades
. Tendinitis calcarea
. Labrocapsular complex lesion (MRI)
3a1) Anatomic and Radiological considerations
The shoulder girdle is made of :
. the proximal humerus
. the scapula
. and the clavicula
. the glenohumeral
. and the acromioclavicular
and many muscles, ligaments and tendons that reinforce the joint capsule. All these structures - along with the cartilage and the capsulo-labral complex - can be visualized with magnetic resonance imaging (MRI). C.T scan images with 3-dimensional reconstruction are excellent in displaying the bone fragments and their location. C.T scan is particularly useful for preoperative evaluation. The injured shoulder must be first evaluated with plain films. The standard X-ray examination includes:
1) the anteroposterior (AP) projection with the arm in neutral position. Occoasionally, images can be taken with the arm in internal or external rotation allowing a better visualization of differents aspects of the humeral head (Fig…). A variant of the AP view is the so- called Grashey projection; it is obtained with the patient rotated 40degrees toward the affected side. It is particularly efficient in the diagnosis of posterior dislocation of the humeral head (Fig…..).
2) the axillary projection, which gives a superoinferior view of the shoulder. It helps to assess the relationship of the humeral head and the glenoid fossa (Fig….). Lawrence view and West Point view are variants of the axillary view.
3) the transthoracic lateral projection (Fig….) It permits a useful evaluation of the proximal humerus.
The site of injury to the shoulder girdle varies with age. Fractures of the proximal humerus are more common in the elderly. Dislocations of the shoulder and the acromioclavicular separations occur more frequently in the third and fourth decades. Factures of the clavicula are more frequent in children and adolescents.
3a2) Fractures of the proximal humerus
Fractures of the upper humerus (proximal shaft, neck and head) are usually due to fall on the outstretched arm – more often in elderly – or from a direct blow to the humerus. The different projections described above permit an accurate assessment of the fracture (Fig……). The classification of proximal humerus fractures can be found in any classical Orthopedic Radiology book (see bibliography below).
3a3) Fractures of the scapula
Fractures of the scapula result from motor vehicle accident, fall from a height or from direct trauma. The AP view and the transscapular view (or Yview) are usually sufficient to display the fracture. C.T. scan may be required especially in case of comminut, intraarticular fractures for the localization of the different fragments (Fig…).
3a4) Fractures of the clavicle
80% of fractures of the clavicle involve the middle third.
15% involve the distal third or lateral. In these cases, the coracoclavicular ligament may be affected and its integrity should be evaluated. 5% involve the proximal or medial third. The straight AP view and a modified AP view with 15 degrees cephalad angulation of the tube are best for the evaluation of clavicle fracture (Fig….).
N.B. Remember the rhomboid fossa. It is a concave, irregular fossa located at the inferior aspect of the medial clavicle. It’s the site of attachment of the costoclavicular ligaments.
3a5) Shoulder dislocations
3a5a) Anterior dislocation. It represents about 97% of
shoulder dislocations. It results from indirect force applied to the arm (a combination of external rotation, extension and abduction). The humeral head moves anteriorly and medially.
During dislocation, The posterolateral portion of the humeral head impacts the on the anteroinferior portion of the glenoid. This wedge-shape impaction (or defect) of the humeral head is called the Hill-Sachs lesion. This lesion is best seen on an AP view with internal rotation.
The fracture (chip fracture) of the anteroinferior rim of the glenoid is called the Bankart lesion. It can be demonstrated on the AP view with the arm in neutral position. The Hill-Sachs or Bankart lesion may be seen either acutely in 30% to 40% of cases or after recurrent dislocation. Both lesions can be detected with C.T. scan and MRI. The MR images in coronal oblique and axial planes are useful in showing associated lesion of the cartilaginous labrum. The detection of theses lesions is important since they may predispose to recurrent dislocation and shoulder instability. (Fig….).
3a5b) Posterior dislocation. It’s less frequent. It represents only 2% to 3% of the dislocations of the glenohumeral joint. The causes include: direct blow to the anterior aspect of the shoulder, indirect force applied to the arm (combination of adduction, flexion and internal rotation), seizures and accidental electric shock.
The humeral head is located posterior to the glenoid fossa. For the diagnosis, an axillary lateral view and a AP view with the patient rotated 40 degrees toward the affected side.
In posterior dislocation, a compression fracture of the anteromedial aspect of the humeral head is frequently seen (the trough sign); it is a reverse Hill-Sachs. A reverse Bankart lesion at the posterior aspecrt of the glenoid may be present. These lesions are readily demonstrated on an AP view with the arm externally rotated (Fig…..).
3a6) Acromioclavicular (AC) luxation (Fig…..)
Grades of the acromioclavicular separation:
Grade I: Mild sprain. Minimal widening of the AC joint space
(normal: 0.3-0.8 cm)
Coracoclavicular distance is within normal range
Grade II: Moderate sprain.
Widening of the AC joint space to 1.0 – 1.5 cm
Increase of coracoclavicular distance to 25% -50%
Grade III: Severe sprain
Widening of the AC joint space to > 1.5 cm
Increase of coracoclavicular distance to >50%
3b) The Elbow
. Anatomic and Radiological considerations
. Nursemaid’s elbow
. Fracture/luxation (Monteggia and Galeazzi)
. Tennis elbow (lateral epicondylitis)
. Golf elbow (medial epicondylitis)
. Ulnar neuritis (MRI)