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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
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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Ortho Radiography (Lin) 4
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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Ortho Radiography (Lin) 12
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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