The Great Orion Nebula in the Constellation of Orion, (NASA, Hubble Space Telescope)

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1 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.

2 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.

3 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.

4 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).

5 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

6 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.

7 MRI MRI is also useful for imaging the carpal bones in cases where plain radiography in inconclusive yet clinical suspicion remains high. Management Occult horizontal fracture of the trapezium, detected on MRI scan 1. Give analgesia as clinically indicated. 2. All fractures of the trapezium should be referred to the orthopedic unit. 3. Reduction ORIF may be required for complex fractures. Closed reduction of dislocations of the trapezium may be attempted however ORIF will usually be required. 4. Immobilization: Immobilization in plaster will be required for 4-6 weeks.

8 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. 3 rd ed 1996, p Wheeless Orthopaedic Website: Dr J. Hayes Reviewed January 2010