Missed Radiologic Injuries

Transcription

1 Missed Radiologic Injuries Michelle Lin, MD Associate Residency Director, UCSF-SFGH Emergency Medicine Residency Assistant 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 of malpractice claims in the emergency department, according to a study conducted by the American College of Emergency Physicians during the period of [44% pelvis / vertebra, 22% extremity, 14% hand] 2. Various studies corroborate that these injuries comprise a significant # of medical claims. Pennsylvania Hospital Insurance Company ( ): 19% of 200 ED malpractice cases were due to misinterpretation of radiographs. (Trautlein et al.) Chicago ( ): Retrospective study of 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 ) and 10% ( ) 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 EP s. 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 be remembered by using my mnemonic DOH. (similar to what your response might be when a patient is recalled for your incorrect radiology interpretation )

2 Ortho Radiography (Lin) 2 D islocations O ccult fracture H alf of injuries missed Wrist Scapholunate DS Scaphoid Galeazzi Perilunate 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 fracture Sacrum Acetabulum Knee Knee DL Tibial plateau Maisonneuve Segond Patella Foot Lisfranc injury Calcaneus Thoracolumbar + Calcaneus fx Talus Abbreviations: DL dislocation, DS dissociation, Fx fracture Normal Anatomy WRIST PA (R Wrist): 3 smooth arcs along carpals Intercarpal distance < 3 mm PA Lateral (Right Wrist): Alignment: Smooth articulation of distal radius to lunate, lunate to capitate, and capitate to 3 rd metacarpal Scapholunate angle < degrees Lateral

3 Ortho Radiography (Lin) 3 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) 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 of R Wrist 2. PERILUNATE DISLOCATION Mechanism: Hyperextension of the wrist Lateral view: Capitate is not vertically aligned with the lunate and radius. PA view: Smooth middle arc alignment of carpal bones is disrupted. Complications: Median nerve injury, SLAC 3. LUNATE DISLOCATION Mechanism: Fall backwards on outstretched hand Lateral view: Lunate is rotated out of alignment into spilled 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 O ccult Fracture 1. SCAPHOID FRACTURE 2 nd 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 Normal in up to 20% cases (Waeckerle) Consider obtaining additional scaphoid views Lateral of R Wrist Lateral of R Wrist Ulnar deviated AP of R Wrist

4 Ortho Radiography (Lin) 4 Teaching Pearl: Apply thumb spica splint to all wrists with 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 Most easily seen on lateral since triquetrum is most dorsal carpal bone Oblique of R Wrist Oblique of R Wrist H alf of Injuries Missed 1. 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 DRUJ Complication: Chronic disability when DRUJ disruption is missed > 10 wks Lateral view of R forearm 2. DISTAL RADIUS FX + CARPAL INJURY Because 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 were associated with scapholunate dissociation (Lee et al.) Radial styloid fractures are associated with scaphoid / lunate fractures & ligamentous injury.

5 Ortho Radiography (Lin) 5 ELBOW Normal Anatomy Capitellum: Portion of distal humerus which articulates with the radial head LATERAL VIEW Fat pads: Collections of fat tissue adjacent to elbow joint capsule (appears black on xrays) Anterior fat pad Can be normal If displaced and elevated, is pathologic (sail sign) Posterior fat pad Always abnormal if visualized AP VIEW Lines: Misalignment of normal structures can be a subtle indicator of a fracture or dislocation Radiocapitellate line: On both the AP and lateral views, a longitudinal line drawn through the midshaft radius should bisect the capitellum. An abnormal alignment suggests a radial head dislocation. Anterior humeral line: On the lateral view, a longitudinal line drawn along the anterior aspect of the humerus should bisect the capitellum. An abnormal alignment suggests a supracondylar fracture.

6 Ortho Radiography (Lin) 6 D islocation RADIAL HEAD DISLOCATION When identified, must look for a proximal ulnar fracture (see Monteggia Fracture ) O ccult Fracture RADIAL HEAD FRACTURE At 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 head fractures. (Freed and Shields) Mechanism: FOOSH Lateral view of R elbow 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. Pearl: Sling patients with elbow pain and abnormal fat pads despite no obvious fracture. H alf of Injuries Missed MONTEGGIA FRACTURE Proximal ulna fracture AND radial head dislocation Missed in 50% pediatric population importance of alignment of radiocapitellate line (Gleeson and Beattie) Mechanism: FOOSH with rotational forces Obvious proximal ulna fracture Misalignment of radiocapitellate line Pearl: Beware of diagnosis of isolated proximal ulna fx! Lateral view of R elbow

7 Ortho Radiography (Lin) 7 Normal anatomy PELVIS / HIP AP D islocation HIP DISLOCATION Most commonly posterior from dashboard injuries in MVA s. 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 fx s, consider a CT for unsuccessful reduction to assess for intraarticular bone fragments. O ccult Fracture AP view of L Hip 1. FEMORAL NECK FRACTURE Most commonly missed hip fracture Sometimes elderly patients can weight-bear despite a fx. Mechanism: From direct blunt trauma (fall) 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 fx s 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, but less sensitive) if still clinically suspicious because of the risk of missing a nondisplaced fracture and having the patient return with a displaced fracture. MRI sensitivity and specificity = 100%.

8 Ortho Radiography (Lin) 8 2. SACRAL FRACTURE In one study: 72% of sacral alar fractures were missed initially. (Jackson et al.) Subtle break in smooth sacral alar lines Additional Imaging: Pelvic outlet views improve visualization of the sacrum and rami. CT required to assess severity of sacral fracture and additional fx s. AP view of sacrum 3. ACETABULAR FRACTURE Anterior acetabular fracture: Detected by break in iliopubic line Posterior acetabular fracture: Detected by a break in the ilioischial line; look specifically behind superimposed femoral head Additional Imaging: Can get additional Judet views to assess for clinically suspicious cases Requires CT assessment to assess severity and because 40% of associated intraarticular bone fragments and 50% of femoral head fractures are missed initially. (Lipman) AP of R hip H alf of Injuries Missed PELVIC RING DISRUPTION Because of the inflexible, ring-like structure of the pelvis, pelvic bone injuries are often found in multiples. In addition to the already mentioned injuries, also beware of subtle rami fractures and sacroiliac dissociation.

9 Ortho Radiography (Lin) 9 Normal Anatomy KNEE AP Lateral

10 Ortho Radiography (Lin) 10 D islocation KNEE DISLOCATION Not a subtle clinical or radiographic finding 40% have associated popliteal artery injury regardless of pedal pulses and reducibility. Requires angiography Lateral view of R knee O ccult Fracture 1. 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 radiographically negative findings in a patient. Additional Imaging: Oblique views (plain radiographs), CT to assess for severity AP view of R knee 2. SEGOND FRACTURE Small proximal lateral tibial avulsion fx Often associated with an ACL tear 3. PATELLA FRACTURE 40% of all knee fractures Additional Imaging: Sunrise view AP of L knee Lateral of R knee H alf of Injuries Missed MAISONNEUVE FRACTURE Proximal fibula fracture AND medial malleolus (or deltoid ligament) fracture Mechanism: Abduction and external rotation of ankle PLUS AP of R Knee AP of R Ankle

11 Ortho Radiography (Lin) 11 Normal Anatomy FOOT Lateral PA PA : The medial edges of the 2 nd metatarsal and 2 nd cuneiform should align. Lateral : Bohler s angle (generated by a line bordering the superior aspect of the posterior calcaneal tuberosity and a line connecting the superior subtalar articular surface and superior aspect of the anterior calcaneal process) normally is degrees. A Bohler s angle < 20 degrees implies an occult calcaneal fracture. Oblique Oblique : The medial edges of the 3 rd metatarsal and 3 rd cuneiform should align.

12 Ortho Radiography (Lin) 12 D islocation LISFRANC INJURY Tarsal-metatarsal (MT) fracture/dislocation pattern 20% are initially missed (Goossens and DeStoop) LisFranc ligament: Attaches 2 nd MT base to 1 st cuneiform. Fracture of 2 nd metatarsal base or Lisfranc ligament and subsequent dislocation of MT #2-5 from the midfoot Pearl: An avulsion fracture of the 2 nd metatarsal base alone is a LisFranc fracture DESPITE a normal alignment of the metacarpals with the tarsal bones, because the LisFranc ligament inserts at its base. Complications: Compartment syndrome O ccult Fracture 1. CALCANEUS FRACTURE At a teaching hospital ED, the miss rate was 3 rd greatest for calcaneal fractures at 10%. (Freed and Shields) Most commonly fractured tarsal bone Mechanism: Often from fall on heels from a height A Bohler s angle < 20 degrees suggests a fracture. Additional Imaging: Consider obtaining a calcaneal view Often requires CT imaging to assess fragments Complication: 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 Can be subtle cortical break on lateral view Complications of neck fracture: Avascular necrosis, subchondral collapse, and degenerative arthritis H alf of Injuries Missed CALCANEUS FRACTURES: 10% associated with THORACOLUMBAR FRACTURE because of load on axial skeleton when landing on the heels AP view of R foot Lateral of L foot Lateral of R foot Lateral of Lumbar Spine

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