Skeletal trauma
INTRODUCTION
GENERAL CONSIDERATIONS
it is poor at soft tissue assessment
a lipohaemarthrosis (fat and blood within the joint space) is evidence of an intra-articular fracture
it is much more sensitive than XRMRI
This is ideal for assessing the ligaments, tendons, cartilage and muscle 
it is very sensitive for the detection of bone oedema (T1WI: low SI 
T2WI: high SI)
• Normal tendons and ligaments are devoid of signal on all routine pulse sequences 
sprains and tears increase their water content (T2WI: high SI) 
fat-suppressed sequences increase the conspicuity of any increased signal
• Tendinitis: this leads to tendon enlargement and increased intratendinous signal intensity
Partial tear: this may be seen as an irregularity within the tendon shape with associated high SI (T2WI)
Complete tear: the tendon is discontinuous, absent or unrecognizable
US
High-resolution transducers are ideal for assessing tendon, ligament and muscle injuries
• Normal tendons appear as hyperechoic parallel lines within the longitudinal plane 
artefactual areas of hypoechogenicity may result from incorrect transducer placement
• Tendinitis: this is seen as an increased tendon thickness with altered echogenicity (focal or diffuse)
• Tear: this appears as a hypoechoic gap within the tendon (often fluid is seen within the tendon sheath)
• Pathological fracture: this occurs where substantially less force is required to cause a fracture in a weakened bone
‘Banana fracture’: pathological fractures tend to be oriented transversely within long bones
Causes: metastatic disease 
benign tumours (e.g. an enchondroma or a solitary bone cyst) 
Paget’s disease 
renal osteodystrophy 
osteogenesis imperfecta
• Stress fracture (fatigue fracture): this occurs due to chronic repetitive trauma on normal bone 
a subtle periosteal reaction or a transverse band of linear sclerosis may develop 1–2 weeks after the onset of symptoms
Common sites: metatarsal shafts (‘march fractures’) 
pubic rami 
femoral neck 
tibial and fibular shafts 
calcaneal tuberosity
• Insufficiency fracture: this is caused by normal activity on abnormal bone (e.g. osteopenic bone in the elderly)
• Joint prosthetic loosening: a widened radiolucency at either the bone–cement or prosthesis–bone interface (> 2mm) 
prosthetic migration 
periosteal reaction
FRACTURE DESCRIPTION
• Location: e.g. proximal, middle or distal shaft
• An open (disruption of the overlying skin, suggested by gas within the adjacent soft tissues) vs a closed fracture (with intact overlying skin)
• A complete (a fracture extending across the full width of the bone) vs an incomplete fracture (e.g. a paediatric greenstick fracture)
• A transverse vs an oblique vs a spiral (due to significant torsional force) fracture
• Distraction (separation) vs impaction vs overriding (overlapping without impaction) of the fracture fragments
• Joint dislocation (the articular surfaces are completely separated) vs subluxation (there is partial contact between the articular surfaces)
• An avulsion fracture: there is separation of the bone fragment at the ligament or tendinous attachment site (it is usually a transverse fracture)
• An osteochondral fracture: there is disruption of the articular cartilage and underlying subchondral bone 
a fracture fragment can become a joint loose body
patella 
talar dome• Comminuted fracture: > 2 separate bone fragments
• Butterfly fragment: a large triangular fragment usually orientated along the long axis of the bone
• The proximal fragment is considered the point of reference when describing the displacement of a distal fragment:
Anterior, posterior, medial or lateral (e.g. one shaft width medial displacement)
Angulation of the long axis of the distal fragment relative to the proximal fragment (varus vs valgus)
• Associated soft tissue injuries:
this can be seen on a horizontal lateral view of the knee 
it can also be seen within the shoulder
ASSESSMENT OF CERVICAL SPINE INJURIES
ASSESSMENT OF CERVICAL SPINE INJURIES
NORMAL RADIOLOGICAL ANATOMY (LATERAL XR)
• The cervical spine is normally lordotic – this may be absent due to patient positioning, the presence of a hard collar or muscular spasm
• All seven cervical vertebrae (including the C7–T1 junction) must be visualized 
this may require a swimmer’s view if they are not demonstrated on the lateral view
• Four imaginary continuous curves should be present: (1) anterior vertebral body line, (2) posterior vertebral body line, (3) spinolaminar line and (4) posterior spinous process line
NB: in children, the spinolaminar line may have an offset of 2 to 3mm at the C2–C3 and C3–C4 levels with flexion and extension
• A perfectly positioned lateral view: the right and left facet joints are superimposed (otherwise the facet joints partially overlap) 
any facet joint overlap should be uniform at all levels – an abrupt change in the amount of overlap within adjacent levels indicates abnormal rotation along the longitudinal axis of the spine
The articular surfaces of each facet must be congruent – this may otherwise indicate a subluxed or dislocated facet
• The odontoid process is usually tilted posteriorly on the body of C2 – however this may otherwise indicate an odontoid fracture
• The atlantoaxial distance measured at the base of the dens between the anterior cortex of the dens and posterior cortex of the anterior arch of C1:
• Assessment of the prevertebral tissues (to exclude a retropharyngeal haematoma):
< 22mm (at the level of C6)
< 14mm (at the level of C6)
RADIOGRAPHIC SIGNS OF INSTABILITY
• The cervical spine is divided into 3 columns:
Anterior column: the anterior longitudinal ligament and the anterior ½ of the vertebral body
Middle column: the posterior ½ of the vertebral body and the posterior longitudinal ligament
• Instability is suggested if there is: abnormal spinous process fanning 
a widened disc space 
horizontal displacement of one body on another (> 3.5mm) 
angulation > 11º 
disrupted facets or multiple fractures
• Instability is more likely if more than one column is disrupted
PEARLS
• Fractures and dislocations are most common within the lower cervical spine (C4–C7)
Usually the upper vertebral body is displaced anteriorly relative to the lower vertebral body
There is often an anterior wedge compression fracture of the lower vertebral body and fractures involving the laminae, facets, or spinous processes
Alternatively, there may be disruption of the joint capsule of the facet joints and interspinous ligament without associated fractures
At times there may be no significant fracture associated with a dislocation, since the injury is limited to the intervertebral disc, facet joint capsules and intervening ligaments
• Paraspinal haematomas (e.g. a retropharyngeal mass) may point to an otherwise obscure fracture or dislocation
SPINAL INJURIES
JEFFERSON FRACTURE (C1)
DEFINITION
• The oblique superior articulating surfaces of the lateral masses of the atlas are driven down and laterally – this disrupts the anterior and posterior arches of the atlas (there can be a single disruption of each arch)
it is an uncommon injury
a widened space between the dens and medial border of the C1 lateral massesLateral XR
It may be impossible to distinguish this from an isolated fracture of the posterior arch of the atlas
take care with differentiating it from neural arch gaps that are normal variations
HANGMAN’S FRACTURE (C2)
DEFINITION
• Bilateral fractures of the neural arch anterior to the inferior facets (traumatic spondylolysis of the axis)
• It is often associated with dislocation of C2 on C3 (there may be an associated avulsion fracture of the anteroinferior C2 margin) 
the fracture lines tend to be oblique and symmetrical
• Any neurological deficit is often less severe than anticipated (as the normal cervical cord occupies only up to 50% of the spinal canal AP diameter and bilateral isthmus fractures can produce canal decompression)
ODONTOID (DENS) FRACTURE (C2)
DEFINITION
• This can be mistaken for an os odontoideum (either congenital or post traumatic)
• Type 1 (high): an avulsion fracture of the superolateral portion of the tip of the dens by the intact alar ligament – STABLE injury
• Type 2 (high): a transverse fracture at the base of the dens (the commonest type) – UNSTABLE injury
• Type 3 (low): a fracture of the superior portion of the axis body with extension through one or both of its superior articular facets (it is not technically a dens fracture) – UNSTABLE injury
prevertebral soft tissue swelling
EXTENSION TEARDROP FRACTURE (C2)
DEFINITION
• A fracture of the anteroinferior corner of body of C2 (which is avulsed by an intact anterior longitudinal ligament) 
it is not associated with a neurological deficit
• It may occur in isolation or be associated with a hangman’s fracture 
it may occasionally involve the lower cervical vertebral bodies
MECHANISM
FLEXION TEARDROP FRACTURE (C3–C7)
DEFINITION
XR
It is characterized by a triangular fragment at the anteroinferior aspect of the involved vertebral body (the ‘teardrop’) 
the anterior vertebral body height is reduced with associated prevertebral soft tissue swelling
• Posterior displacement of the fractured vertebra and diastasis of the interfacetal joints indicates longitudinal ligament, intervertebral disc and posterior ligament complex disruption
UNILATERAL LOCKED FACETS/UNLATERAL INTERFACETAL DISLOCATION (C3–C7)
DEFINITION
• Dislocation of the interfacetal joint on the side opposite to the direction of rotation (the dislocated facet comes to rest anterior to the subjacent facet and is thus ‘locked’)
Lateral XR
The dislocated vertebra is anteriorly displaced by <50% of the sagittal vertebral body diameter 
the spine above the level of dislocation is obliquely oriented (the spine below is in direct lateral orientation)
• ‘Bow tie’ or ‘butterfly’ appearance: the appearance of the articular masses on an oblique projection
BILATERAL LOCKED FACETS/BILATERAL INTERFACETAL DISLOCATION (C3–C7)
DEFINITION
• Both facet joints at the level of injury are dislocated and all the interosseous ligaments (including the intervertebral disc) are disrupted
the articular masses of the superior vertebrae lie anterior to the articular masses of inferior vertebrae (thus ‘locking’ the facets) 
there are often associated
HYPERFLEXION SPRAIN (C3–C7)
DEFINITION
Lateral XR
Localized kyphotic angulation 
widening of the interspinous and interlaminar space (‘fanning’) 
interfacetal joint subluxation 
posterior widening and anterior narrowing of the intervertebral disc (± 1–3mm of vertebral anterior displacement)
• It is accentuated by flexion views (but must be supervised by a radiologist) 
the injury is associated with delayed instability
SIMPLE WEDGE (COMPRESSION) FRACTURE (T1–L5)
DEFINITION
• Compression of a vertebral body between adjacent vertebral bodies 
it is associated with a paraspinous haematoma
RADIOLOGICAL FEATURES
XR
• Anterior wedged vertebral body deformity and vertebral end-plate depression (which is usually superior) 
impaction is identified by a faint sclerotic band just beneath the deformed end-plate
• Decreased anterior vertebral body height (the anterior cortical margin may be disrupted, angulated or impacted) 
the posterior height is maintained (as the posterior elements remain intact)
• Lumbar spine: a fracture is usually limited to the superior end plate and subjacent vertebral body
• Paraspinous haematoma: a localized lateral bulge of the mediastinal stripe
PEARLS
Lesions that may mimic a compression fracture
• A non-united vertebral ring epiphysis 
Schmorl’s nodes (an irregular lucent defect at the end-plate with irregular sclerotic margins) 
a limbus vertebra (a distant separate ossicle found on the anterosuperior margin of the vertebral body and representing a developmental abnormality of the ring apophysis)
Burst fracture
• This is common at the thoracolumbar junction (resulting from an axial compression force) 
a fragment from the superoposterior vertebral body may be displaced into the spinal canal with the potential for neurological injury
• Unlike a simple compression fracture the vertebral body posterior cortex is disrupted
• STABLE injury (it may become an UNSTABLE injury if there is a neurological deficit or retropulsed fragments)
FRACTURE–DISLOCATION (T10–L2)
DEFINITION
• This most commonly occurs at the T10–L2 level (at the junction of mobile and relatively immobile segments) 
neurological injury is common
Stable: limited to a vertebral body or the posterior elements only
Unstable: involving both the vertebral bodies and the posterior elements
• Mechanism: it is due to a combination of shearing, rotation and flexion forces
RADIOLOGICAL FEATURES
AP XR
Wide separation of the spinous processes
• There may be a disrupted intervertebral disc, facet joint or interspinous ligament without an associated fracture
• Vertebral body above the injury level: anterior dislocation
• Vertebral body below the injury level: an anterior wedge compression fracture with a triangular bony fragment avulsed from its anterosuperior surface
CHANCE FRACTURE (L1–L5)
DEFINITION
• Horizontal splitting of the vertebral body with little compression (a ‘seatbelt’ fracture)
• It is commonly associated with intra-abdominal and neurological injuries
• Mechanism: anterior hyperflexion over an object (e.g. a seatbelt) that serves as a fulcrum
RADIOLOGICAL FEATURES
Lateral XR
A horizontal fracture involving the spinous processes, laminae, articular masses and vertebral body
• The vertebral body is tilted (with a widened interspinous space) at the injury site with little anterior wedging
• There may be disruption of the ligaments and intervertebral discs without an associated fracture
SHOULDER INJURIES
ANTERIOR SHOULDER DISLOCATION
DEFINITION
it is associated with an avulsion fracture of the greater tuberosity
there is an increased risk for recurrent dislocations
there is an increased risk for recurrent dislocations
it is due to a large haemarthrosis
the humeral head impinges upon the acromion, which acts as a fulcrum 
the arm is ‘locked’ in abductionPOSTERIOR SHOULDER DISLOCATION
DEFINITION
• This is related to seizures, electrocutions or a direct blow to the humeral head 
it accounts for 5% of all shoulder dislocations
there is subtle widening of the joint (> 6mm) or the bones overlap on a Grashey view (a Y or axillary view can confirm this)FRACTURES OF THE SCAPULA AND CLAVICLE
DEFINITION
they are usually located within the scapular neck or body
pulmonary contusions and pleural effusionsClavicle
• Evaluation requires a straight and a cranially angled AP view 
fractures of the mid-third are the most common 
distal fractures may disrupt the coracoclavicular ligaments (± involve the acromioclavicular joint)
the coracoclavicular distance is 11–12mm
the clavicle is elevated less than a complete shaft width above the acromion
PROXIMAL HUMERAL FRACTURES
DEFINITION
• Fractures tend to be spiral (they can also be angulated and overriding due to muscular contraction on the individual fragments)
• They are most commonly seen in the elderly 
they usually involve the surgical neck and are associated with separation of the greater tuberosity
| 1 part | There is no displacement of the fracture fragments |
| 2 part | There is displacement of 1 fragment |
| 3 part | There is displacement of 2 fragments (1 tuberosity remains in contact) |
| 4 part | There is displacement of 3 fragments |
SLAP LESIONS
DEFINITION
• Tears affecting the anterosuperior labrum, with biceps tendon involvement
• SLAP: Superior Labrum from Anterior to Posterior (in relation to the biceps tendon insertion)
B: biceps tendon 
G: glenoid cartilage.SHOULDER IMPINGEMENT SYNDROME/ROTATOR CUFF TEARS
ANATOMY
• There is a restrictive space between the acromion, coracoacromial arch and acromioclavicular joint (superiorly) and the humeral head and greater tuberosity (inferiorly) 
the rotator cuff tendons (supraspinatus, infraspinatus, teres minor and subscapularis) pass through this space
MECHANISM
• There is potential ‘pinching’ of the distal centimetre of the supraspinatus tendon (representing a vascular watershed region) between the coracoacromial arch and humeral head on abduction and external rotation 
variations in the shape of the anteroinferior acromion, together with osteoarthritic change, can exacerbate any impingement
there is no surface defect
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