Download Trapezium Fracture

TRAPEZIUM FRACTURE
The Great Orion Nebula in the Constellation of Orion, (NASA, Hubble Space Telescope)
One thousand, five hundred light years away, in the constellation of Orion lies the Great
Nebula of Orion, (or Messier 42). This awesome cosmic structure is a cloud of gas and
dust a staggering 25 light years in extent. In technical terms this nebula is an “emission”
nebula. The ultraviolet radiation of nearby stars heat the nebula making it fluoresce like
the glowing gases within a neon light bulb. This is why we can see it.
Apart from its obvious beauty, its significance in cosmic terms is that it is a region of
stellar birth, a “cradle of creation”. As sections of this cloud condense under the
influence of its own gravity immense swirling proto stars and planets are evolving into
new solar systems.
When we look at this structure whose light has taken 1,500 years to reach us, we are
glimpsing a vision of our own Sun and solar system’s creation 4.5 billion years ago.
Current theory holds that our own Solar system was created out of a similar massive
nebula. Within M42 are thousands of protostars and young stars, less than one million
years old. Will one of these stars in a far distant time provide the conditions that allow
the evolution of life on one of its planets, long after our own Earth has ceased to exist?
Will the product of this evolution become sentient? Will future beings there one day look
back across the immense gulf of space to the last remnants of our own solar system and
begin to understand the ultimate of their own world? Perhaps these beings will not have
evolved on the Orion home worlds at all, but travelled to them from another distant
place, and when they peer curiously at our own long dead region of space, it will not be
in order to understand their ultimate fate, but rather…where they came from!
Stellar nursery that the Orion nebula is, our descendents, just 100,000 years from now,
who look to this region of the sky with technology probably unimaginable to us today,
will not see a nebula at all! It will be gone. Close inspection of the nebula reveals a small
trapezoidal grouping of stars within the very heart of its structure. Known to astronomers
as “the trapezium” because of their relative spatial arrangement, they are very young
supermassive giants, each with over 100,000 times the radiant luminosity of our own Sun.
They radiate ultraviolet radiation so fiercely that they are producing a “stellar wind”,
which is destroying all space around them, dispersing the great nebula that gave rise to
their formation. Thousands of proto-solar systems evolving within the nebula will be
destroyed by the trapezium, within 100,000 years before they have a chance to coalesce
into fully formed systems. Only a relative few of the more distant systems will survive the
brilliant but short lived super giants at the heart of the nebula. The great nebula giving
birth to whole star systems has paradoxically produced four rogue offspring which will
eventually destroy it.
Among the “constellation” of bones of the carpus, lies a little recognized one that goes
by the name of the “trapezium”. Very rarely is this bone fractured, yet when it is, it is
important to recognize the fact. As the trapezium of Orion acts to bring about the
destruction of its fellow star systems around it, so too will an unrecognized fractured
carpal trapezium act to bring about the destruction of it neighbours, not by the process of
stellar wind of course but rather by the process of secondary osteoarthritic degeneration.
TRAPEZIUM FRACTURE
Introduction
The trapezium bone is one of the small bones that make up the carpus.
Trapezium fractures in isolation are uncommon.
They are usually associated with other carpal bone fractures/ dislocations, as well as
fractures of the first metacarpal and the radius.
Fractures of this bone are easily overlooked.
Anatomy
The Trapezium, (the lesser multangular refers to the trapezoid, navicular refers to the
scaphoid) (Gray’s Anatomy 1918)
The trapezium has 4 articulating surfaces.
●
The distal saddle-shaped surface articulates with the first metacarpal.
●
The more ulnar (medial) distal surface articulates with the base of the second
metacarpal.
●
Medially, the trapezium articulates with the trapezoid
●
Proximally it articulates with the distal scaphoid.
The volar surface is narrow and rough. At the upper part is a deep groove, running from
above obliquely downward and medially, it transmits the tendon of the Flexor carpi
radialis.
Blood supply:
The trapezium receives nutrient arteries through two non articular surfaces, as well as
extensive intraosseous anastomoses which explain the rare occurrence of avascular
necrosis in injuries to this bone.
Mechanism
Most commonly due to a fall on the outstretched hand.
Complications
Complications may include:
●
Secondary degenerative osteoarthritic changes are very likely; these can be
chronic and very debilitating.
●
Osteomyelitis in cases of compound injury
●
Avascular necrosis is rare with injuries to this bone
Classification
There are five types of trapezium fracture.
These include:
●
Vertical transarticular (most commonly), due to axial force loading along the line
of the thumb and first metacarpal bone.
●
Horizontal, due to direct shearing forces.
●
Dorsal radial tuberosity, due to vertical shearing forces.
●
Anteromedial ridge, due to antero-posterior crush injury.
●
Comminuted.
Trapezium dislocations in isolation are very rare. If they occur they may also be
displaced in dorsal or palmar directions.
Clinical features
Clinical features may include:
●
Localized tenderness
Immediately distal to the tuberosity of the scaphoid.
The maximal tenderness of the body fracture of the trapezium is most easily
elicited at the tip of the anatomical snuffbox, (making it difficult to distinguish
from the far more commonly injured scaphoid bone at the base of the anatomical
snuffbox).
Tenderness will also be elicited by axial compression of the tip of the thumb,
however this sign is non-specific as tenderness may also be elicited in this way
from fractures radially aligned, ie of the metacarpal, the scaphoid or the radial
styloid.
●
Localized swelling.
●
The range of motion at the wrist may be relatively pain free.
●
Pinch strength specifically is weakened due to the pain which will be elicited.
●
Fractures of the trapezial ridge may be associated with symptoms of carpal tunnel
syndrome secondary to median nerve compression.
Investigations
Plain radiography
Above, normal A-P radiograph of the left carpus. The trapezium is seen in the distal row
of the carpus at the far right as it articulates with the first metacarpal.
Views should include:
●
A-P
●
Lateral
●
Ulna deviation.
●
Trapezium, trapezoid, pisiform, and hamate fractures may also benefit from
additional carpal tunnel views.
Horizontal fracture through the trapezium 2
In some cases, plain radiography may simply not show a trapezium fracture, and the
persistence of clinical symptoms should prompt further investigation with CT scan or
MRI scan.
CT scan
The trapezium, trapezoid, pisiform, and hamate bones will frequently require an
additional CT scan when the plain radiography is unclear and/ or the extent of injury
needs to be more fully assessed, particularly in more complex injuries.
MRI
MRI is also useful for imaging the carpal bones in cases where plain radiography in
inconclusive yet clinical suspicion remains high.
Occult horizontal fracture of the trapezium, detected on MRI scan
Management
1.
Give analgesia as clinically indicated.
2.
All fractures of the trapezium should be referred to the orthopedic unit.
3.
Reduction
4.
●
ORIF may be required for complex fractures.
●
Closed reduction of dislocations of the trapezium may be attempted
however ORIF will usually be required.
Immobilization:
●
Immobilization in plaster will be required for 4-6 weeks.
Magnified view of the region of the “trapezium”, showing the four supermassive stars
destroying the Great Nebula of Orion.
References
1.
Trapezium dislocation in, Practical Fracture treatment, McRae R. 3rd ed 1996, p.
190.
2.
Wheeless Orthopaedic Website: www.wheelessonline.com
Dr J. Hayes
Reviewed January 2010