SET T0005 -
Emergency Department

Observations: increased area of density over the left side of the heart; medial aspect of the left dome of the diaphragm is no longer seen (the Sillhouette Sign). This - the loss of the silhouette - indicates that the pneumonia (ie the density) is situated in the left lower lobe.

Left lower lobe pneumonia.

Two fractures:

• Through the metaphysis of the proximal phalanx of the thumb.
• Through the metaphysis of the metacarpal of the index finger.

The other bones and joints appear normal; specifically the bases of the 4th and 5th metacarpals are anatomical.

Normal. No adverse finding.

The bases of the 4th and 5th metacarpals appear anatomical - no dislocation.

Observations:

1. On the PA view the " light of day " is not evident at the base of either the 4th or 5th metacarpals.    Conclusion: these two carpo-metacarpal joints are dislocated. 
2. Note the fracture of the dorsal aspect of the hamate . . .  part of this injury complex which has resulted from the punch during the brawl.

" Light of day appearance / rule " ???  This is a descriptive device (devised by us!) and it refers to the appearance of the joint at the base of the 4th and also of the 5th MC on the PA view of the hand - ie when the joint is normal.

Some doctors find it difficult to evaluate the normal appearance of these joints on the PA and oblique views. This is why we refer to the PA view in particular and ask : can you see the " light of day " at the bases of the 4th and 5th metacarpals? If you or your colleagues find assessment of these two joints difficult . . . the medical artist, Philip Wilson, has created clever explanatory drawings which will help you to understand the normal and abnormal anatomy.

See : Accident & Emergency Radiology : A Survival Guide (3rd edition) : Pages 157-158 and 167-168

The 3rd edition will be published in July 2014.