November 30, 2012

Maisonneuve Fracture

Figure 1: AP and lateral ankle radiographs demonstrate a vertical fracture of the medial/posterior malleolus of the distal tibia without a fibular fracture.  

Figure 2: Full-length AP fibular radiograph shows a mildly displaced fracture of the fibular shaft at the junction between the proximal 1/3 and middle 1/3. 

Facts: Rotational Ankle Fractures

  • Rotational ankle fractures are classified according to force direction applied to the foot, while the injured foot can be in a different position (supination/pronation, adduction/external rotation)
  • AO/Weber classification: A, B, C fractures are differentiated by location of fibular fractures. 
  • Fibular fracture below the syndesmosis = AO/Weber A (usually supination-adduction)
  • Fibular fracture at the syndesmosis = AO/Weber B (~ supination and external rotation)
  • Fibular fracture above the syndesmosis = AO/Weber C (~ pronation external rotation)
Facts: Maisonneuve Fractures
  • High fibular fracture above the syndesmosis resulting from external rotation
  • Often, there is injury to the medial ankle either a tranverse medial malleolar fracture, posterior malleolar fracture or disruption of the deltoid ligament
  • Disruption of the syndesmosis and interosseous ligament up to the fibular fracture site
  • Suspicious for this fracture if you see a 1) transverse medial malleolar fracture or 2) posterior malleolar fracture but no fibular fracture on the ankle radiographic series. In these situation, a full-length fibular radiograph should be taken

Sakthivel-Wainford K. Self-assessment in limb x-ray interpretation, 2006
Rockwood CA, Green DP. Rockwood and Green's fractures in adults, 2005

November 26, 2012

Screening Mammography Overdiagnoses Breast Cancer?

The recently published NEJM's original article describes effect of screening mammography on breast cancer incidence in the USA. Bleyer A and Welch HG. N Eng J Med 2012;367:1998 (22 Nov 2012)

Facts: Aim of Cancer Screening

  • We expect cancer screening program to lower cancer-related mortality by a means of 1) earlier detection of disease destined to be fatal and 2) early Rx of screen-detected cancers
  • A cancer screening program should 1) increase incidence of cancer detected at an earlier stage and 2) decrease incidence of cancer presenting at a late stage

What Study Is About And What It Has Found:
  • Breast cancer rate from 1976 through 1978 (mammography was uncommon) ~ baseline incidence
  • Breast cancer rate from 2006 through 2008 ~ current incidence
  • Confounding effects of menopausal hormone therapy were minimized by not including transitory increase in incident breast cancers from 1990 through 2005. Underlying incidence of breast cancer assumed to rise by 0.25% annually
  • Number of cases of early-staged breast cancer rises from 112 to 234 cases per 100,000 women
  • Number of cases of late-staged breast cancer decreases from 102 to 94 cases per 100,000 women
  • "With an assumption of a constant underlying disease burden, only 8 of the 122 additional early-stage cancers diagnosed were expected to progress to advanced disease." This was estimated that breast cancer was overdiagnosed. In 2008, the overdiagnosis would account for 31% of all breast cancer diagnosed
Other Studies Said?
Results of this study concur with other reports (references 2-3) and suggest that improvements in treatment are the main drive in reducing breast cancer mortality - rather than screening mammography. 

It is suggested that "pros and cons of mammography should be incorporated into the counseling that women receive as they decide whether an when to be screened". 

  1. Bleyer A and Welch HG. Effect of three decades of screening mammography on breast cancer incidence. N Eng J Med 2012;367:1998
  2. Kalager M et al. Effect of screening mammography on breast cancer mortality in Norway. N Eng J Med 2010;363:1203
  3. Autier P et al. Breast cancer mortality in neighbouring European countries with different levels of screening but similar access to treatment: trend analysis of WHO mortality database. BMJ 2011;343:d4411
  4. Kaunitz AM. Screening mammography: does overdiagnosis overshadow prevention of advanced breast cancer? Journal Watch Women's Health November 21, 2012

November 20, 2012

Spinal Langerhans Cell Histiocytosis (LCH)

Figure 1: Tc-99m MDP bone scan (posterior image) shows a focus of increased activity at L2 vertebral body in a 24-year-old woman presenting with back pain.

Figures 2&3: Axial GRE T2W and sagittal post-contrast T1W MR images show a round focus of bone destruction surrounded by bone marrow edema and enhancement of L2 body, sparing the posterior elements. 

Facts: LCH
  • Rare, benign disorder of unknown etiology comprises of eosinophilic granuloma (unifocal), Hand-Schuller-Christian disease (multifocal) and Letterer-Siwe disease (disseminated variant) - these are different manifestations of a same disease
  • Clonal proliferation of Langerhans cells
  • Peak incidence 5-10 years but there is a shift toward younger children
Spinal LCH
  • Vertebral involvement in 8-25% of cases
  • Thoracic > cervical, lumbar
  • Vertebral body >> posterior elements
  • Solitary, well-defined osteolytic lesion with scalloped borders eventually progresses to collapse and a classic "vertebra plana"
  • Typically single vertebral body involved. Disc spaces spared
  • Soft tissue mass suggests more aggressive course
Main Imaging Differentials of Spinal LCH
  • Osteomyelitis
  • Ewing sarcoma
  • Leukemia, lymphoma, metastatic neuroblastoma

Hosalkar HS, Greenberg JS, Wells L, Dormans JP. Isolated Langerhans Cell Histiocytosis of the T12 vertebra in an adolescent. Am J Orthop 2007;36: E21-E24.

November 10, 2012

Parotid Warthin Tumor

Figures 1&2: Coronal and sagittal-reformatted CT images of an 80-year-old woman show a well circumscribed mass in the tail of the right parotid gland. There is homogeneous enhancement. 

Facts:  Warthin Tumor
  • Also known as papillary cystadenoma lymphomatosum
  • 14-30% of all parotid tumors
  • Almost always in older adults (peak incidence at 6th-7th decades of life)
  • Most commonly found within parotid gland (esp. tail). Occasionally in minor salivary glands.
  • MRI, although has high specificity and sensitivity for diagnosis, still cannot differentiate all malignant parotid tumors from benign ones. Tissue sampling is required for definitive diagnosis
  • Well-circumscribed solid mass, homogeneous enhancement and without calcification
  • If calcification is present in a benign-appearing parotid mass, pleomorphic adenoma should be considered first
  • US: multiple anechoic internal areas
  • MRI: low T1, high T2 signal intensity
  • Salivary scintigraphy: Accumulation of Tc-99m pertechnetate due to high mitochondrium

Hatch RL, Shah S. Warthin tumor: a common, benign tumor presenting as a highly suspicious mass. J Am Board Fam Med 2005;18: 320-322.

November 1, 2012

Focal Fat Sparing

Figure 1: US image of the liver shows focal masslike area of hypoechogenicity of the left lobe posterior to the left portal vein branch. Note high echogenicity of the background liver, suggesting fatty change.

Figure 2 & 3: In-phase and out-of-phase MR images show liver signal intensity drop in the chemical shift imaging confirming diffuse fatty liver. The abnormality in the left lobe liver does not change between the two phases, suggesting a focal area of fat sparing.

Facts: Fatty Liver
  • Most common abnormality of the liver seen on cross-sectional imaging
  • Common patterns: diffuse fat accumulation, diffuse fat accumulation with focal sparing, and focal fat accumulation in an otherwise normal liver
  • Unusual patterns may mimick neoplasm, inflammation or vascular conditions
  • Pathology: triglyceride acculation within cytoplasm of hepatocytes
  • Term "fatty liver" is preferred over "fatty infiltration of the liver" because triglyceride accumulation occurs within hepatocytes but rarely other cell types. Infiltration of fat into parenchymal does not occur
Imaging Findings and Sensitivity/Specificity
  • US: 1) Liver echo greater than renal cortex and spleen with attenuation of sound wave, 2) loss of definition of diaphragm, 3) poor delineation of intrahepatic architecture (to avoid false-positive diagnosis, all three findings should be fulfilled).  Sensitivity 60-100%. Specificity 77-95%.
  • CT: Liver attenuation 10 HU less than that of spleen, or less than 40 HU. Sensitivity 43-95%. Specificity 90%.
  • MRI: Signal intensity loss on opposed-phase images in comparison with in-phase images. Sensitivity 81%. Specificity 100%.
  1. Diffuse deposition: most common
  2. Focal deposition and focal sparing: characteristically in specific areas (adjacent to falciform ligament or ligamentum venosum, porta hepatis, in GB fossa). Suggestive findings of fatty pseudolesions rather than true masses are:
    1. Fat content
    2. Characteristic location
    3. Absence of mass effect on vessels and other liver structures
    4. Geographic configuration (not round or oval)
    5. Poorly delineated margin
    6. Contrast enhancement similar to or less than that or normal liver parenchyma
  3. Multifocal deposition
  4. Perivascular deposition
  5. Subcapsular deposition


Hamer OW, Aguirre DA, Casola G, et al. Fatty liver: imaging patterns and pitfalls. Radiographics 2006;26: 1637-1653.