Download Recognizing an acute fracture

Radiology of Fracture Principles
Suzanne O’Hagan
18 May 2012
Radiographic Principles
• When analysing and ordering x-rays you should remember
the rule of two’s:
• Two views. At 90 degrees, usually anterior-posterior and
lateral.
• Two joints. The joints above and below.
• Two occasions. Some fractures are not easily visible
immediately after trauma.
• Two limbs. If required for comparison.
• NB: In certain injuries, ‘special’ views are required. These
include Scaphoid views, Skyline views for the patellofemoral compartment of the knee and Mortise view at the
ankle.
Recognizing an acute fracture
Disruption in the continuity of all or part of the cortex of a bone
Complete:cortex broken through and through, traversing the
width of the bone
Incomplete: part of cortex fractured. Tend to occur in bones that
are “softer” such as in children or in adults with bone-softening
diseases such as osteomalacia or Paget’s disease
Examples of incomplete fracture in children are:
-Greenstick fracture, involves only one part of the cortex
- Buckle fracture, compression of cortex
Greenstick fracture
Buckle fracture
Fracture Lines
• More lucent than other lines normally found in bones such
as nutrient canals
• Abrupt discontinuity of the cortex
• Straighter in their course yet more
acute in their angulation than naturally
occurring lines such as epiphyseal
plates
• The edges tend to be jagged and rough
Pitfalls
• Sesamoids
– Bones that form in a tendon as it passes over a joint. The patella is the
largest.
• Accessory ossicles
– These are accessory epiphyseal or apophyseal ossification centres that
do not fuse with the parent bone
Unlike fractures these small bones are corticated and their edges are
usually smooth
Sesamoids and accessory ossicles are usually bilateral and at
anatomically predictable sites
• Old, unhealed fracture fragments
– Can be confused with new fractures
Sesamoid bones at joints
Knee – the patella (within the quadriceps tendon)
Hand– two sesamoid bones commonly found in the distal portions of the first metacarpal bone (within the
tendons of adductor pollicis and flexor pollicisbrevis); also distal portion of second metacarpal bone
Wrist– the pisiform within the flexor carpiulnaris tendon
Foot – first metatarsal bone has two sesamoids at its connection to the big toe, within the tendon of flexor
hallucisbrevis (sometimes only a single sesamoid)
Accessory Ossicles
•
The process of ossification progresses from a primary ossification centre, until the bone is
completely ossified. Irregularly shaped bones such as the tarsal bones may develop a secondary
centre and in some individuals complete ossification does not occur. The secondary centre remains
separate from the rest of the bone, forming an accessory ossicle.
Os trigonum – the separated posterolateral
tubercle of the talus.
Os tibiale externum (accessory navicular) –
located posteromedial aspect of navicular
where posterior tibialis tendon inserts
Accessory ossicles
• Os Peroneum
In peroneusbrevis tendon
• Os fabella
Posterior to the lateral condyle of the femur.
It exists in the location of the lateral
head of gastrocnemius tendon.
Many more…
Describing fractures
• 4 major parameters
– Number of fragments
– Direction of fracture line
– Relationship of fragments to each other
– Communication of the fracture with the outside
atmosphere
Number of fracture fragments
• 2 fragments = simple fracture
• >2 = comminuted fracture
– Segmental fracture
A portion of the shaft exists as an isolated fragment
– Butterfly fragment
Central fragment has a triangular shape
Direction of fracture lines
• Transverse: Fracture line perpendicular to long axis of
bone (perpendicular force)
• Oblique: Fracture line diagonal relative to long axis
(force usually applied along same direction as long
axis)
• Spiral: Caused by a twisting force, usually unstable and
often associated with soft tissue injury
Relationship of Fragments to each other
1.
2.
3.
4.
Displacement
Angulation
Shortening
Rotation
By convention, describe the relationship of the distal
fragment relative to theproximal fragment
Displacement
• Amount by which the distal fragment is offset,
front to back and side to side, from the
proximal fragment
• Described in terms of percent or fractions (e.g.
50% the width of the shaft or ½ the width of
the shaft of the proximal fragment)
Angulation
• Angle between the distal and proximal
fragments
• Described in degrees and by position
– State direction of distal bone
• Superior, inferior, anterior, posterior, medial, lateral,
volar, dorsal
– State degree of angulation relative to proximal
bone
– Medial (varus), Lateral (valgus)
Colles fracture
Transverse fracture of distal radius
2.5cm proximal to radiocarpal joint
Dorsal displacement and volar angulation
Shortening
• How much, if any, overlap there is of the ends
of the fracture fragments
• How much shorter the fractured bone is than
it would be had it not been fractured
• Shortening is described in centimetres
Midshaft femur fracture
Distraction and Impaction
• Distraction
– Increase in overall
bone length
•Impaction
– Shortening with no loss
of bone alignment
Rotation
Rotation
• Unusual
• Almost always involving the long bones
• Describes the orientation of the joint at one end relative to
the orientation of the joint at the other end of the
fractured bone
• Eg proximal tibia oriented in frontal projection while distal
tibia and ankle oriented laterally
• Both the joint above and below the fracture need to be
included to appreciate rotation
Relationship of Fracture to
Atmosphere
• Closed
– More common
– No communication
• Open/compound
– Communication
Best diagnosed clinically
Avulsion fractures
• Common mechanism of fracture production
• Avulsed fragment is pulled from its parent bone by contraction of a
tendon or ligament
• More common in young athletes
• Derive many of their names from athletic activity e.g. dancer’s
fracture, skier’s fracture, sprinter’s fracture
• Occur in anatomically predictable locations where tendons are
known to insert
• May heal with exuberant callous formation
• Some may resemble a neoplastic or infectious process
• Some may have an aggressive appearance that may include areas of
mixed lysis and sclerosis
• The appearance depends on whether acute, subacute or chronic
Avulsion Fractures: common in the pelvis
In the pelvis, the newly formed secondary centers of ossification, the apophyses, are most likely to
avulse· Apophyses tend to form at the time of puberty = time of pelvic avulsions
Avulsion fracture lesser
trochanter (iliopsoas)
Avulsion fracture
ischialtuberosity
(hamstrings)
Sites and Insertions
Dancer fracture
Don’t confuse with Jone’s Fracture
Jones fracture involves a
fracture at the base of fifth
metatarsal at metaphysealdiaphyseal junction
A Jones fracture is located
within 1.5 cm distal to
tuberosity of 5th metatarsal
Avulsion fracture more
common and affects the 5th
metatarsal styloid process
proximally.
Osgood Schlatter
•
•
•
•
Caused by stress on the patellar tendon
Patellar tendon attaches the quadriceps muscle to the tibial tuberosity
Adolescent growth spurt, repeated stress from quadriceps contraction is transmitted through the tibial tuberosity
Causes multiple subacute avulsion fractures with inflammation along the tendon leading to excess bone grwoth in
the tuberosity
SALTER-HARRIS FRACTURES
Epiphyseal plate fractures in children
• In growing bone, the hypertrophic zone in the
growth plate (epiphyseal plate or physis) is
most vulnerable to shearing injuries
• Account for as many as 30% of childhood
fractures
• SH classification helps determine treatment
and predict complications
• Represent a spectrum of accidental injuries in
children
SALTER HARRIS CLASSIFICATION
Epiphyseal
plate only
Epiphyseal
plate +
metaphysis
Epiphyseal
plate +
epiphysis +
metaphysis
Epiphyseal
plate +
epiphysis
Compression
fracture
epiphyseal
plate
Prognosis
• Types I and II heal well
• Type III fractures can develop arthritic changes
or asymmetric growth plate fusion
• Types IV and V are more likely to develop early
fusion of the growth plate with angular
deformities and shortening of that bone
Type I: Fractures of the epiphyseal
plate alone
• Difficult to detect without comparison views
• SCFE is a manifestation of a SH I injury
– Tall, heavy teenage boys
– Bilateral in 25%
– Can result in avascular necrosis due to interrupted
blood supply in 15%
Salter Harris I
“widening of the
growth plate”
Slipped Capital Femoral Epiphysis
Salter Harris I
Type II: Fracture of the epiphyseal
plate and fracture of metaphysis
• Most common (75%)
• Seen especially in the distal radius
Salter Harris II
“above the
growth plate”
Distal radius
Assoc ulnar fracture
Type III: Fracture of the epiphyseal
plate and epiphsysis
• Longitudinal fracture through epiphysis itself;
fracture invariably enters the joint space and
fractures the articular cartilage
• Risk of osteoarthritis later in life
• Can result in premature and asymmetric
fusion of the growth plate with subsequent
deformity
Salter Harris III
“below the
growth plate”
Type IV: Fracture of epiphysis and
metaphysis through the epiphyseal
plate
• Poorer prognosis
– premature and possibly asymmetric closure of
growth plate
• May lead to differences in limb length, angular
deformities and secondary OA
Salter Harris IV
“through
the growth
plate”
Salter Harris IV
Salter Harris V
• Rare
• Associated with vascular injury
• Almost always result in growth impairment
through early focal fusion of the growth plate
• Most common in the distal femur, proximal
tibia and distal tibia
• Difficult to diagnose on conventional
radiographs until later when they complicate
Salter Harris V
Right
Left
Non-accidental injury patterns
• Metaphyseal corner fractures
• Rib fractures
– Especially multiple and posterior
• Head injuries
– Skull fractures tend to be bilateral, comminuted
and cross suture lines (associated subdurals, SAH,
cerebral contusion)
CML: Classic Metaphyseal Lesion
Virtually pathognomonic of abuse
• series of microfractures across the metaphysis
• the fracture line is oriented essentially parallel to the
physis, although it may not travel the entire width of the
bone
• precipitating force is a shearing injury across the bone end,
the result of horizontal motion across the metaphysis,
therefore not a feature of falls or blunt trauma
• force is generated by manual to-and-fro manipulation of
the extremities (eg, holding and shaking an infant by the
feet or hands or shaking the infant while he is held around
the chest)
• CML is seen almost exclusively in children less than 2 years
of age
CML: Corner or Bucket Handle Fracture
Stress Fracture
• Bone subjected to repeated stretching and
compressive forces
• Numerous microfractures
• Conventional radiographs may initially appear normal
in up to 85%
• Fracture may not be diagnosable until after periosteal
new bone formation or healing occurs
• Bone scans or MRI will usually be positive earlier
• Common locations include the shafts of long bones,
the calcaneus and the 2nd and 3rd metatarsals
Stress Fractures
5 MOST COMMON EPONYMS
3 in the hand, 2 in the foot
•
•
•
•
•
Colle’s
Smith’s
Jones
Boxer’s
March
Colle’s Fracture
•
Colles' fracture is
a fracture of the
distal metaphysis
of the radius with
dorsal
displacement and
volar angulation
leading to a
’dinner fork
deformity’.
•
Colles fractures
are seen more
frequently with
advancing age
and in women
with osteoporosis.
•
Mostly an
Smith’s Fracture
Reversed Colle’s
Occurs in younger patients
Results from high energy trauma on the volar flexed wrist Volar displacement and
dorsal angulation
Intra-articular extension more common
Jone’s Fracture
• Transverse fracture of 5th metatarsal 1.5cm
from its base
• Caused by plantar flexion of the foot and
inversion of the ankle
• Less common than avulsion fracture
Boxer’s Fracture
• Fracture of head of 5th metacarpal with palmar angulation
• Usually results from punching a person or wall
March Fracture
• Type of stress fracture to
the foot
• Usually shafts of 2nd or 3rd
metatarsals
EASILY MISSED FRACTURES
•
•
•
•
•
•
Scaphoid fractures
Buckle fractures
Radial head fractures
Supracondylar fractures
Posterior disclocation of the shoulder
Hip fractures in the elderly
Scaphoid Fracture
• Tenderness in anatomical snuff box after fall on outstretched hand
• Hairline thin radiolucencies on scaphoid views (ulnar deviation of wrist)
Radial Head Fracture
• Common in adults
• Look for a positive fat pad sign:
– Posterior fat pad usually invisible
– Crescenticlucency of fat along the posterior aspect
of the distal humerus is produced by normally
invisible fat that is lifted away from the bone by
swelling of the joint capsule due to haemarthrosis
Radial head fracture
Supracondylar Fracture
• Most common fracture of the elbow in a child
• Most produce posterior displacement of the
humerus
• True lateral, anterior humeral line should
bisect the middle third of the ossification
centre of capitellum
• In most supracondylars, this line passes
anterior to its normal location
Anterior humeral line
Positive Fat Pad Sign
Posterior Dislocation of the Shoulder
“Y” view (oblique view of the shoulder),
head will lie lateral to the glenoid in
posterior dislocation
Frontal: Humeral head fixed in internal
rotation, resembles a light bulb
Hip Fractures in the Elderly
Frequently related to osteoporosis
Take x-rays with leg in internal rotation to display the neck in profile
Look for angulation of the cortex and zones of increased density (impaction)
Look for secondary signs
MRI or bone scan will be required when indicated
Secondary signs of fractures
• Soft tissue swelling
• Disappearance of normal fat stripes
• Joint effusion
• Periosteal reaction (late)
FRACTURE HEALING
• Determined by many factors
– Age of patient
– Fracture site
– Position of fracture fragments
– Degree of immobilization
– Blood supply
– Mineralisation of bone
– Medication
FRACTURE HEALING PROCESS
• Immediate: Haemorrhage into fracture site
• First few weeks: Osteoclasts act to remove
diseased bone (fracture line may widen)
• Next few weeks: New bone (callus) begins to
fill the fracture defect.
• 8 – 12 weeks: Remodelling
– Mechanical forces adjust bone back to its original
shape
– Fast in children, slow in adults
COMPLICATIONS OF FRACTURE
HEALING
• Delayed union
– Fracture does not heal in expected time
– Most will eventually heal if immobilisation extended
• Malunion
– Healing occurs in a mechanically or cosmetically unacceptable
position
• Non-union
– Implies that fracture healing will never occur
– Smooth, sclerotic margins with distraction of the fracture
fragments
– Pseudarthrosis may form
– Motion at the fracture site may be demonstrated on stress
views or with fluoroscopy
Fracture healing complications
Role of CT and MRI
• CT usually requested to obtain further detail for surgical planning
especially in fractures of:
–
–
–
–
–
Tibial plateau
Acetabulum
Ankle (?trimalleolar)
Calcaneus
Cervical spine
• MRI usually cases of doubt to detect bone marrow oedema particularly in
occult fractures of:
– Hip
– Scaphoid
– Stress fractures eg tibia, metatarsal
Also gives additional information regarding the soft tissue components
Bone scan low specificity
Intertrochanteric fracture
Tibial plateau
fracture
T1WI - stress fracture
2nd metatarsal
Conclusion
• Radiological interpretation of fractures is a
huge topic. Classifications are detailed and can
sometimes be clumsy.
• A good starting point is to be able to describe
a fracture correctly using the principles
discussed in this lecture.
References
• Herring, W. Learning Radiology: Recognizing
the Basics 2nd Ed 2012. p232.
• Greenspan, A. Orthopaedic Imaging: A
Practical Approach. Chapter 4: Radiologic
Evaluation of Trauma
• Thompson, JC. Netters Concise Orthopaedic
Anatomy. 2010
• www.wheelessonline.com/ortho/trauma_fract
ures