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Pitfalls in Orthopedic Radiography Interpretation

Michelle Lin, MD FAAEMAssistant Clinical Professor of Medicine, UC San Francisco

San Francisco General Hospital Emergency Services

[email protected]

MEDICOLEGAL SIGNIFICANCE

1. Missed orthopedic injuries, such as fractures and dislocations, comprise the largest source ofmalpractice claims in the emergency department, according to a study conducted by the

American College of Emergency Physicians during the period of 1974-1985. [44%

pelvis / vertebra, 22% extremity, 14% hand]

2. Various studies corroborate that these injuries comprise a significant # of medical claims.

Pennsylvania Hospital Insurance Company (1977-1981): 19% of 200 ED malpracticecases were due to misinterpretation of radiographs. (Trautlein et al.)

Chicago (1975-1994): Retrospective study of 18860 malpractice claims showed 12%involved radiology cases, of which missed diagnoses was the #1 cause of litigation.

(Berlin and Berlin) Massachusetts Joint Underwriters Association: Missed fractures comprised 20% (during

1980-1987) and 10% (1988-1990) of malpractice claims. (Karcz et al, 1993)

3. The majority of malpractice claims on misread radiographs are those whose radiographs were

taken during off hours.

63% malpractice suits occur from incidents during 6 pm-1 am (weekends) and midnight-7 am (weekdays)

ED radiograph interpretations during non-business hours are often provided by EPs. Over 80% acute care hospitals do not have 24/7 radiologist interpretation available. Radiographic interpretation discrepancy rate between an EP and radiologist = 2-11%.

(Lufkin et al, Robinson et al, Scott et al)

ERRORS IN RADIOGRAPH INTERPRETATION

Commonly missed, high-risk injuries on radiographs can beremembered by using my mnemonic DOH. (similar

to what your response might be when a patient is

recalled for your incorrect radiology interpretation)


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Ortho Radiography (Lin) 2

D islocations O ccult fracture H alf of injuries missed

Wrist Scapholunate DS Scaphoid GaleazziPerilunate DL and Lunate DL Triquetrum Distal Radius Fx + Carpal Injury

Elbow Radial head DL Radial head Monteggia

Pelvis/ Hip Hip DL Femoral neck Another ring fractureSacrumAcetabulum

Knee Knee DL Tibial plateau Maisonneuve

Segond

Patella

Foot Lisfranc injury Calcaneus Thoracolumbar + Calcaneus fx

Talus

Abbreviations: DL dislocation, DS dissociation, Fx fracture

WRISTNormal Anatomy

PA View (R Wrist):

3 smooth arcsalong carpals

Intercarpaldistance < 3 mm

PA

View

Lateral View (Right Wrist):

Alignment: Smootharticulation of distal

radius to lunate, lunate tocapitate, and capitate to

3rd

metacarpal Scapholunate angle < 30-

60 degrees

Lateral

View


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D islocation

1. SCAPHOLUNATE DISSOCIATION

Most common and significant ligamentous injury of wrist.Rotatory subluxation of scaphoid into more transverse

orientation.Mechanism: Fall on outstretched hand (FOOSH)

Xray: PA view: >4 mm widening of scapholunate space

(Terry Thomas sign)

PA view: Scaphoid has signet ring sign Lateral view: Scapholunate angle > 60 deg

PA View of R Wrist

2. PERILUNATE DISLOCATION

Mechanism: Hyperextension of the wrist

Xray: Lateral view: Capitate is not vertically aligned with

the lunate and radius.

PA view: Smooth middle arc alignment of carpalbones is disrupted.

Complications: Median nerve injury, SLAC

Lateral View of R Wrist

3. LUNATE DISLOCATION

Mechanism: Fall backwards on outstretched hand

Xray:

Lateral view: Lunate is rotated out of alignment intospilled teacup position

PA view: Smooth proximal arc of carpal bones is disrupted PA view: Lunate appears triangular (rather than

quadrilateral)

Complication: Median nerve injury, SLAC

Lateral View of R Wrist

O ccult Fracture

1. SCAPHOID FRACTURE

2nd

most common fractured bone of the wrist [#1=distal radius]At a teaching hospital ED, the miss rate was greatest for

scaphoid fractures (13%) (Freed and Shields)

Mechanism: FOOSH

Exam: Tenderness to snuffbox area of wrist

Xray:

Normal in up to 20% cases (Waeckerle) Ulnar deviated AP View Consider obtaining additional scaphoid views of R Wrist


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Teaching Pearl: Apply thumb spica splint to all wristswith snuffbox tenderness regardless of normal xrays

Complication:

Avascular necrosis (AVN) Nonunion rate increases 5-45% when treatment is delayed > 4 weeks (Langhoff and

Andersen) SLAC (Scapholunate Advanced Collapse) Scaphoid and/or lunate undergoes AVN and

collapses

2. TRIQUETRUM FRACTURE

Accounts for 10% of carpal bone fractures

Mechanism: FOOSH

Exam: Tenderness to ulnar aspect of dorsal wrist

Xray: Most easily seen on lateral since triquetrum is most

dorsal carpal bone

Oblique View of R Wrist

Oblique View of R Wrist

H alf of Injuries Missed1. GALEAZZI FRACTURE

Distal-third fracture of the radius AND disruption of distal radioulnar joint (DRUJ)

Mechanism: FOOSH with forearm hyperpronated

Signs of DRUJ:

Lateral view: Ulna does not overlie radius Lateral view: Ulnar styloid is not aligned with dorsal triquetrum PA view: Ulnar styloid fracture PA view: Widening of DRUJComplication: Chronic disability when DRUJ disruption is

missed > 10 wks

Lateral viewof R forearm

2. DISTAL RADIUS FX + CARPAL INJURYBecause of the same FOOSH mechanism of injury, scapholunate dissociation may also be

present. In a small retrospective study of 52 patients, 69% of distal radius fractures wereassociated with scapholunate dissociation (Lee et al.)

Radial styloid fractures are associated with scaphoid / lunate fractures & ligamentous injury.


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ELBOWNormal Anatomy

LATERAL VIEW

Fat pads: Collections of fat tissueadjacent to elbow joint capsule

(appears black on xrays) Anterior fat padCan be normalIf displaced and elevated, ispathologic (sail sign)

Posterior fat padAlways abnormal if visualized

AP VIEW

Lines: Misalignment of normal

structures can be a subtle

indicator of a fracture ordislocation

Radiocapitellate line: On boththe AP and lateral views, a

longitudinal line drawnthrough the midshaft radius

should bisect the capitellum.

An abnormal alignmentsuggests a radial head

dislocation.

Anterior humeral line: On thelateral view, a longitudinal linedrawn along the anterior

aspect of the humerus should

bisect the capitellum. Anabnormal alignment suggests a

supracondylar fracture.


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D islocationRADIAL HEAD DISLOCATION

When identified, must look for a proximal ulnar fracture (see Monteggia Fracture)

O ccult FractureRADIAL HEAD FRACTUREAt a teaching hospital ED, the miss rate was 2

nd

greatest for elbow fractures at 10.8%. In adults,

these fractures were primarily missed radial headfractures. (Freed and Shields)

Mechanism: FOOSH

Lateral viewof R elbow

Xray:

Cortical break in the radial head may be very subtle or even absent in a nondisplaced fx

Large anterior fat pad (Sail sign) Any posterior fat pad In the study by Freed and Shields: >80% had an associated fat pad and >40% had ONLY

a fat pad sign as indicator of a fracture.

H alf of Injuries MissedMONTEGGIA FRACTURE

Proximal ulna fracture AND radial head dislocationMissed in 50% pediatric population importance of

alignment of radiocapitellate line (Gleeson

and Beattie)

Mechanism: FOOSH with rotational forcesXray:

Obvious proximal ulna fracture Lateral view of R elbow Misalignment of radiocapitellate linePearl: Beware of diagnosis of isolated proximal ulna fx!


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PELVIS / HIPNormal anatomy

AP View

Dislocation

HIP DISLOCATION

Most commonly posterior from dashboard injuries in MVAs.

Posterior: Affected leg is shortened and internally rotated

Anterior: Aftected leg is shortened and externally rotated

Since hip dislocations are associated with femoral head /

acetabular fxs, consider a CT for unsuccessful reductionto assess for intraarticular bone fragments.

AP view of L Hip

O ccult Fracture

1. FEMORAL NECK FRACTURE

Most commonly missed hip fracture

Sometimes elderly patients can weight-bear despite a fx.

Mechanism: From direct blunt trauma (fall)

Xray:

Can be very subtle Cortical disruption or impacted hyperlucency Loss of smooth cortical transition from femoral

neck to head. Trabecular disruption AP view of R hip

Delay in Diagnosis: Radiographically occult hip fxs occur in 2-9%. One study had 16/825 missed hip fractures. 15/16 were initially nondisplaced but

became displaced secondary to the delayed diagnosis. (Parker)

Additional Imaging: Consider MRI (CT is ok alterative) if still clinically suspicious

because of the risk of missing a nondisplaced fracture and having the patient return with adisplaced fracture. MRI sensitivity and specificity = 100%.


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KNEENormal Anatomy

AP

View

Lateral

View


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D islocationKNEE DISLOCATION

Not a subtle clinical or radiographic finding

40% have associated popliteal artery injuryregardless of pedal pulses and reducibility.

Requires angiography Lateral view ofR knee

O ccult Fracture1. TIBIAL PLATEAU FRACTURE

32% of all knee fractures

Mechanism: Valgus force with axial load (knee vs. car bumper)Sensitivity of radiographs: 79% for 2-view, 85% for 4-view

(Gray et al.)

Pearl: When a patient with knee pain from blunt trauma can not

walk, be sure that oblique views are obtained to assess for a

tibial plateau fracture. Consider CT despite radiographicallynegative findings in a patient.

Additional Imaging: AP view of R knee Oblique views (plain radiographs), CT to assess for severity

2. SEGOND FRACTURE

Small proximal lateral tibial avulsion fxOften associated with an ACL tear

AP View

of L knee

3. PATELLA FRACTURE

40% of all knee fractures

Additional Imaging: Sunrise view

Lateral

Viewof R knee

H alf of Injuries MissedMAISONNEUVE FRACTURE

Proximal fibula fracture AND medial malleolus (or deltoid ligament) fracture Mechanism: Abduction and external rotation of ankle

PLUS

AP View of R Knee AP View of R Ankle


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FOOTNormal Anatomy

Lateral View

PA

View

PA View: The medial edges of the 2nd

metatarsal and 2nd

cuneiform should align.

Lateral View:

Bohlers angle (generated by a linebordering the superior aspect of the

posterior calcaneal tuberosity and aline connecting the superior subtalar

articular surface and superior aspect

of the anterior calcaneal process)

normally is 20-40 degrees. A Bohlers angle < 20 degrees

implies an occult calcaneal fracture.

Oblique

View

Oblique View: The medial edges of the 3rd

metatarsal and 3rd cuneiform should align.


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D islocationLISFRANC INJURY

Tarsal-metatarsal (MT) fracture/dislocation pattern

20% are initially missed (Goossens and DeStoop)

LisFranc ligament: Attaches 2nd MT base to 1st cuneiform.

Xray: Fracture of 2nd metatarsal base or Lisfrancligament and subsequent dislocation of MT #2-5

from the midfoot

Pearl: An avulsion fracture of the 2nd metatarsal base alone

is a LisFranc fracture DESPITE a normal alignment of

the metacarpals with the tarsal bones, because the AP view of R footLisFranc ligament inserts at its base.

Complications: Compartment syndrome

O ccult Fracture

1. CALCANEUS FRACTUREAt a teaching hospital ED, the miss rate was 3rd

greatest for

calcaneal fractures at 10%. (Freed and Shields)

Most commonly fractured tarsal bone

Mechanism: Often from fall on heels from a height

Xray: A Bohlers angle < 20 degrees suggests a fracture.Additional Imaging:

Consider obtaining a calcaneal view Often requires CT imaging to assess fragments Lateral View of L footComplication: Compartment syndrome

2. TALUS FRACTURE

Second most commonly fracture tarsal bone

The neck is the most common location of a talar fracture.

Mechanism: Excessive dorsiflexion of ankle

Xray: Can be subtle cortical break on lateral view

Complications of neck fracture: Avascular necrosis,

subchondral collapse, and degenerative arthritis

Lateral View of R foot

H alf of Injuries MissedCALCANEUS FRACTURES:

10% associated with THORACOLUMBAR FRACTUREbecause of load on axial skeleton when landing on the heels

Lateral View of

Lumbar Spine


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