1. Radiology of Fracture Principles
Suzanne O’Hagan 18 May 2012

2. 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 patello-femoral compartment of the knee and Mortise view at the ankle.
There are exceptions to these rules
Egpolytrauma screen only AP pelvis
Comparison views only when necessary to limit radiation

3. 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

4. Greenstick fracture
The fracture, with minimal dorsal and ulnar axial deviation in the distal third of the radius, is defined above by the wrinkling of the cortex.

5. Buckle fracture
Child who fell on outstretched hand, buckling of metaphyseal cortex

6. 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
Top of metaphysis has an undulating course
giving the appearance of more than one epiphyseal plate

7. Pitfalls Sesamoids Accessory ossicles Old, unhealed fracture fragments
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

8. 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)

9. 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.
Flexor hallucislongus can be injured in the Os Trigonum or "nutcracker" syndrome.
Os  tibiale  externum (accessory navicular) – located posteromedial aspect of navicular where posterior tibialis tendon inserts

10. Accessory ossicles Os Peroneum Os fabella In peroneusbrevis tendon
Posterior to the lateral condyle of the femur.
It exists in the location of the lateral
head of gastrocnemius tendon.
Many more…

11. 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

12. 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
Additional ways of describing comminuted fractures…

13. 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

14. Relationship of Fragments to each other
1. Displacement 2. Angulation 3. Shortening 4. Rotation
4 major parameters used to describe the relationship of fracture fragments to one another. Most fractures display more than one of these abnormalities
By convention abnormalities of the position of bone fragments describes the relationship of the distal fracture fragment relative to the proximal fragment
Eg in this case : medially displaced tibial midshaft fracture, referring to the poisition of the distal fragment
By convention, describe the relationship of the distal fragment relative to theproximal fragment

15. 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)

16. 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)

17. Colles fracture Transverse fracture of distal radius
2.5cm proximal to radiocarpal joint
Dorsal displacement and volar angulation
Draw lines through the long axes of the proximal and distal fragments to get the angle
APEX VOLAR ANGULATION
Apex of itersecting lines

18. 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

19. Midshaft femur fracture

20. Distraction and Impaction
– Shortening with no loss
of bone alignment
Distraction
Increase in overall bone length
2 other related concepts
Distraction: Patellar fracture, usually from fall directly onto knee, distraction is from quadriceps tendon pulling superiorly and patellar tendon pulling inferiorly
Impaction: Neck of femur fracture
Undisplaced, complete = Garden II

21. Rotation

22. 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

23. Relationship of Fracture to Atmosphere
Closed
More common
No communication
Open/compound
Communication
Best diagnosed clinically

24. 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

25. Avulsion fracture lesser trochanter (iliopsoas)
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)

26. Sites and Insertions

27. Dancer fracture
Frontal radiograph of the foot shows an oblique, minimally displaced avulsion fracture at the base of the fifth metatarsal
Image on right shows insertions onto the base of the 5th metatarsal
Lateral component of Plantar aponeurosis
Peroneusbrevis tendon
Peroneustertius tendon
Cuboid bone

28. Don’t confuse with Jone’s Fracture
Jones fracture involves a fracture at the base of fifth metatarsal at metaphyseal-diaphyseal 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.

29. Osgood Schlatter Caused by stress on the patellar tendon
Subacute avulsion injury
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

30. 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

31. SALTER HARRIS CLASSIFICATION
Epiphyseal plate only
Epiphyseal plate + metaphysis
Epiphyseal plate + epiphysis
SALTR: S –same level; A –above; L – beLow; T – Through; R – cRush/compRession
Compression fracture epiphyseal plate
Epiphyseal plate + epiphysis + metaphysis

32. 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

33. 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%
Slipped capital/upper femoral epiphysis

34. “widening of the growth plate”
Salter Harris I
“widening of the growth plate”
left
Slipped Capital Femoral Epiphysis

35. Salter Harris I
Salter 1 Fracture of the Proximal Humeral Epiphysis. Frontal radiograph of the shoulder in external rotation demonstrates slip of the proximal humeral epiphysis medially and inferiorly (black arrow) due to a fracture through the epiphyseal plate that causes widening of the plate

36. Type II: Fracture of the epiphyseal plate and fracture of metaphysis
Most common (75%)
Seen especially in the distal radius

37. “above the growth plate”
Salter Harris II
“above the growth plate”
Fracture of epiphyseal plate and metaphysis
Distal radius
Assoc ulnar fracture

38. 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

39. Salter Harris III “below the growth plate” Distal tibia
Fracture line through the epiphysis itself

40. 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

41. Salter Harris IV “through the growth plate” Ankle joint
Fracture line extends through the epiphysis and metaphysis through the growth plate

42. Salter Harris IV The finger Metacarpals and phalanges also long bones
Epiphysis and metaphysis, through epiphyseal plate (metacarpophalangeal joint)

43. 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

44. Salter Harris V Right Left
Sclerotic band along distal metaphysis of right radius where impaction took place
Small area of bulging ulnar aspect distal radius
Right
Left

45. 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)

46. 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

47. CML: Corner or Bucket Handle Fracture
Frontal radiograph of the ankle shows a rim of bone (arrow) separated from the tibial shaft by the metaphyseal fracture lucency, giving the appearance of a bucket handle.
(b) Lateral radiograph depicts the tibial and fibular fractures as corner fractures (arrows).

48. 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

49. Stress Fractures
15% sensitive in early fractures, increasing to 50% on follow-up (Sensitivity relates to the test's ability to identify positive results)
Sclerotic band (due to trabecular compression and callus formation) usually perpendicular to cortex
Intracortical radiolucent striations (early)
Solid thick lamellar periosteal new bone formation
Endosteal thickening (later
)Follow-up radiography after 2-3 weeks of conservative therapy may reveal fracture not seen earlier

50. 5 MOST COMMON EPONYMS Colle’s Smith’s Jones Boxer’s March
3 in the hand, 2 in the foot
Colle’s
Smith’s
Jones
Boxer’s
March

51. 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.

52. 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

53. 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

54. Boxer’s Fracture
Fracture of head of 5th metacarpal with palmar angulation
Usually results from punching a person or wall

55. March Fracture Type of stress fracture to the foot
Usually shafts of 2nd or 3rd
metatarsals T1

56. EASILY MISSED FRACTURES
Scaphoid fractures
Buckle fractures
Radial head fractures
Supracondylar fractures
Posterior disclocation of the shoulder
Hip fractures in the elderly

57. Scaphoid Fracture
Tenderness in anatomical snuff box after fall on outstretched hand
Hairline thin radiolucencies on scaphoid views (ulnar deviation of wrist)
Fractures across the waist of the scaphoid can lead to AVN of the proximal pole of the bone due to poor blood supply
Plain film and mri

58. 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

59. Radial head fracture Posterior fat pad usually invisible
Anterior fat pad can be visible but is lifted in pathology

60. 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 is a line drawn tangential to the anterior humeral cortex

61. Anterior humeral line Should pass through middle third of capitellum
Normal anterior humeral line, despite cortical disruption and positive posterior fat pad sign

62. Positive Fat Pad Sign
Positive fat pad sign
Distention of the joint will cause the anterior fat pad to become elevated and the posterior fat pad to become visible.

An elevated anterior lucency or a visible posterior lucency on a true lateral radiograph of an elbow flexed at 90° is described as a positive fat pad sign (figure).
Normally on a lateral view of the elbow flexed in 90° a fat pad is seen on the anterior aspect of the joint .
This is normal fat located in the joint capsule. 
On the posterior side no fat pad is seen since the posterior fat is located within the deep intercondylarfossa.
Hemarthros results in an upward displacement of the anterior fat pad and a backward displacement the posterior fat.
Positive fat pad sign (2)
Any elbow joint distention either hemorrhagic, inflammatory or traumatic gives rise to a positive fat pad sign.
If a positive fat pad sign is not present in a child, significant intra-articular injury is unlikely.
A visible fat pad sign without the demonstration of a fracture should be regarded as an occult fracture.
These patients are treated as having a nondisplaced fracture with 2 weeks splinting.
Skaggs et al repeated x-rays after three weeks in patients with a positive posterior fat pad sign but no visible fracture. 
They found evidence of fracture in 75%. 
They concluded that in trauma displacement of the posterior fat pad is virtually pathognomonic of the presence of a fracture.
Displacement of the anterior fat pad alone however can occur due to minimal joint effusion and is less specific for fracture.

Notice that the elbow is not positioned well. 
Try to find out what went wrong in the chapter on positioning.

63. Posterior Dislocation of the Shoulder
Often difficult to detect on the frontal projection whether humeral head is within, anterior or posterior to glenoid cavity
Lightbulb sign: greater tuberosity not seen laterally due to internal rotation
“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

64. 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
Plain film of the hip unremarkable
MRI shows T1 low signal indicating a fracture
MRI again useful for detecting bone oedema in occult fractures in symptomatic patients

65. Secondary signs of fractures
Soft tissue swelling
Disappearance of normal fat stripes
Joint effusion
Periosteal reaction (late)
Disappearance of notmal fat stripes and positive fat pad signs suggest soft tissue swelling or haemarthrosis displacing these normal planes
Should lead you to investigate further for fractures eg with ct, mri or bone scan depending on the clinical picture

66. FRACTURE HEALING Determined by many factors Age of patient
Fracture site
Position of fracture fragments
Degree of immobilization
Blood supply
Mineralisation of bone
Medication
Distal tibia and scaphoid notoriously poor healer due to its weak blood supply
Earlyimmobilisation, adequate duration of immobilisation accelerates fracture healing with physical activity after adequate immobilisation
Osteoporosis, osteomalacia delay healing
Steroids delay healing

67. 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
Internal – indistictness of the fracture line leading to obliteration of the fracture line
External – external callus formation leading to bridging of the fracture site

68. 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

69. Fracture healing complications
Left – non union of femur shaft
Right – old fracture with malunion of humerus

70. 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
Sensitivity relates to the test's ability to identify positive results.
Specificity relates to the ability of the test to identify negative results.

71. Intertrochanteric fracture
Tibial plateau
fracture
A few examples of the application of ct and mri in fracture assessment
T1WI - stress fracture 2nd metatarsal

72. 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.

73. References
Herring, W. Learning Radiology: Recognizing the Basics 2nd Ed p232.
Greenspan, A. Orthopaedic Imaging: A Practical Approach. Chapter 4: Radiologic Evaluation of Trauma
Thompson, JC. Netters Concise Orthopaedic Anatomy. 2010