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 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

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 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.

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

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

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

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. 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

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…

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 Additional ways of describing comminuted fractures…

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. 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

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 Draw lines through the long axes of the proximal and distal fragments to get the angle APEX VOLAR ANGULATION Apex of itersecting lines

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 – 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

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 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)

Sites and Insertions

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

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.

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

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

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% Slipped capital/upper femoral epiphysis

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

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

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

“above the growth plate” Salter Harris II “above the growth plate” Fracture of epiphyseal plate and metaphysis 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” Distal tibia Fracture line through the epiphysis itself

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” Ankle joint Fracture line extends through the epiphysis and metaphysis through the growth plate

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

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 Sclerotic band along distal metaphysis of right radius where impaction took place Small area of bulging ulnar aspect distal radius 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 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).

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 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

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

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.

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 T1

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) 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

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 Posterior fat pad usually invisible Anterior fat pad can be visible but is lifted in pathology

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

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

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.

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

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

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

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

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

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 Left – non union of femur shaft Right – old fracture with malunion of humerus

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.

Intertrochanteric fracture Tibial plateau fracture A few examples of the application of ct and mri in fracture assessment 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_fractures