Avulsion Fracture of Base of 5th Metatarsal & Os Peroneum

Figure: Oblique radiograph of the foot shows a transverse avulsion fracture (arrow) of the 5th metatarsal bone with displacement and extension into the cuboid-metatarsal joint. Note a nearby 'os peroneum' (arrowhead).

Avulsion Fracture of Base of 5th Metatarsal

• Most common fracture at this location
• Usually extra-articular
• Due to sudden contraction of peroneus brevis muscle or lateral band of plantar fascia during inversion
  
• Treated conservatively, unless there is displacement or large fragment involving cuboid-metatarsal joint
  
• Other two types of fractures (at proximal 5th metatarsal) are Jones (AKA fracture at metadiaphyseal junction within 1.5 cm distal to tuberosity of 5th metatarsal), and stress fracture.

Key Things to Include in Report

1. Location (tip, tuberosity, metadiaphyseal junction, diaphysis)(to distinguish between different types of proximal 5th metatarsal fractures)
   
2. Joint involvement (cuboid-metatarsal, 4th-5th intermetatarsal)
3. Displacement

Os Peroneum = ossicle in peroneus longus, seen at the tip of 5th metatarsal base, common

Reference:
Nunley JA. Fractures of the base of the fifth metatarsal. Orthopedic Clinics of North America (January 2001)

A child with scalp mass

Sagittal T1W image demonstrates a parieto-occipital scalp mass with a band of soft tissue anterosuperior to the mass running through a small skull defect which appears to connect to the intracranial compartment.

Sagittal T2W image demonstrates a persistent embryonic falcine sinus/vertically oriented straight sinus and prominence of the superior cerebellar cistern.

The mass shows a thin peripheral enhancement as well as enhancement of the soft tissue band.

Diagnosis:

Atretic (en)cephalocele

Facts:

- A midline mass typically parietal in location, occasionally seen in occipital region.

- Contain meninges and neural rests. A fibrous stalk connects the lesion to the dura.

- A vertically positioned straight sinus/persistent embryonic falcine sinus commonly
associated with these malformations. Anomalies of the tentorial incisura and superior sagittal
sinus have also been reported.
- Associated intracranial anomalies are variable, and some children may have normal clinical outcomes with no associated intracranial anomalies

References:

AJNR Am J Neuroradiol 19:791–795, April 1998
RadioGraphics 2004; 24:1655–1674

Nipple Shadows?

Fig.1: Chest radiograph shows a suspicious nodule in the right lower lung. Fig.2: Repeat exam with nipple markers (arrowheads) confirmed the nodule to be a nipple shadow. Note that the left nipple shadow is visualized on this exam but not on the previous one performed on the same date.

Classic Nipple Shadows

• Bilateral symmetric
• Fuzzy margins with radiolucent halo, or sharp lateral but poorly defined medial margins
• Characteristic location (fifth or sixth anterior ribs or near bottom of breast shadow)
• Not present on a very recent film
• Could be identified on lateral film

Problems

• Nipple shadows can be seen in up to 10% of chest radiographs
• Although most of these can be resolved as 'classic nipple shadows' and no further imaging is needed, about 1.4% need repeat examination
• Repeat examinations are related to increased cost, time and burdensome to patients

Nipple Markers

• A 1.5 mm lead shot that, given its size, should not obscure a true pulmonary nodule
• Very helpful to determine whether the suspicious nodule is actually a nipple shadow, or not.
• Chance of having a true pulmonary nodule lying beneath the nipple shadow is very slim

Reference:
Miller WT, et al. The troublesome nipple shadow. AJR 1985 (September)

Gastric Cancer on CT

Figure: Axial CT shows thickening (arrows) and mucosal enhancement of the lesser curvature of the stomach in a patient with known gastric carcinoma. The fat plane is preserved. No lymphadenopathy is seen.

Gastric Carcinoma

• Etiology: atrophic gastritis, adenomatous polyp, Lynch syndromes, gastric stump cancer, Menetrier's disease
• Usually present in advanced stage
• Major determination of staging of gastric carcinoma = extent of tumor beyond gastric wall and lymph node involvement
• CT usually used to determine presence and extent of perigastric spread
  

Gastric Carcinoma on CT

• Wall thickening, soft tissue mass (polypoid or ulcerated mass), perigastric fat stranding, lymphadenopathy
• Differentiation from lymphoma: lymphoma usually has a very thick wall, no perigastric stranding, and bulky lymph nodes
• CT accuracy for staging is better with multiplanar reformations (coronal and sagittal), better for T staging than N staging

T Staging by CT

• T1 lesion = focal thickening of the inner layer of the wall
• T2 lesion = transmural thickening of the wall without or with minimal perigastric stranding
• T3 lesion = blurring of at least 1/3 of tumor extent or wide reticular stranding around tumor border
• T4 lesion = invasion of adjancent organ or fat plane obliteration between tumor and adjacent organ
• Accuracy based on this description was 77% in one study, when axial + MPR images were used
  

Reference:
Hur J, et al. Diagnostic accuracy of multidetector row computed tomography in T- and N staging of gastric adenocarcinoma with histopathologic correlation. J Comput Assist Tomogr 2006 (May/June)

Calcium Pyrophosphate Dihydrate (CPPD) Crystal Deposition Disease of the Wrist

Fig. Frontal radiograph of the wrist shows calcifications of the lunotriquetral ligament (arrowhead) and triangular fibrocartilage (red arrow). Joint space narrowing with sclerosis of the trapezioscaphoid and carpometacarpal joints (yellow arrows) are noted. Note absence of osteophytes.

This patient presents with classic radiographic features of CPPD, which include:

1. Chondrocalcinosis
2. Degenerative change without apparent osteophytosis

Facts:

• At the wrist, the most common location of calcification in the area of triangular fibrocartilage is at the lunotriquetral ligament > triangular fibrocartilage > lunotriquetral cartilage.
• Degenerative change in CPPD differs from osteoarthritis in that there is less osteophyte formation.

Reference:
1. Yang B, et al. Distribution of calcification in the triangular fibrocartilage region in 181 patients with calcium pyrophosphate dihydrate crystal deposition disease. Radiology 1995; 196:547.
2. Saffar P. Chondrocalcinosis of the wrist. J Hand Surg [Br] 2004; 29:486.