Bennett's fracture

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Bennett fracture is the first metacarpal bone fracture that extends into the carpometacarpal joint (CMC). This intra-articular fracture is the most common type of fracture of the thumb, and is almost always accompanied by some degree of subluxation or frank dislocation of the carpometacarpal joint.

Video Bennett's fracture

Symptoms and signs

Symptoms of Bennett's fracture are instability of the CMC thumb joint, accompanied by the pain and weakness of the pinch grip. The characteristic signs include pain, swelling, and ecchymosis around the base of the thumb and eminence protruding, and especially above the thoracic CMC joint. Physical examination shows CMC thumb joint instability. Patients will often show weak ability to hold objects or perform tasks such as tying shoes and tearing a piece of paper. Other complaints include severe pain experienced when capturing the thumb on an object, such as when reaching into a trouser pocket.

Complications

Many important activities in everyday life depend on the ability to understand, pinch, and defy the thumb. In fact, the thumb function is about 50% of the total hand function. This capability in turn depends on the CMC thumb together intact and functional. The CMC joint of the thumb allows various motions while maintaining stability for grasp and pinching.

With this in mind, the failure to accurately recognize and treat Bennett's fracture will not only result in an unstable, painful, and arthritic joint of CMC with reduced range of motion: it will also produce a hand with a greatly reduced overall function.

In the case of Bennett's fracture, the proximal metacarpal fragments remain attached to the anterior oblique ligaments, which in turn are attached to the trapezium tubercle of the CMC joint. The attachment of this ligament ensures that the proximal fragment remains in the correct anatomical position.

The distal fragments of the first metacarpal bone have most of the articular surfaces of the first CMC joint. Unlike proximal fracture fragments, strong ligaments and tendons of the hand muscles tend to pull these fragments out of their correct anatomical positions.

In particular:

• the tension of the abductor pollicis longus muscle (APL) reflects the fragments in the dorsal, radial, and proximal directions
• The voltage from the APL rotates the fragment to supination
• the strain of adductor pollicis (ADP) muscle moves the metacarpal head into the palm of the hand

The tension of the APL and ADP muscles often leads to fracture fragment displacement, even in cases where fracture fragments are initially in an appropriate anatomical position. Due to the above mentioned biomechanical features, Bennett fractures almost always require some form of intervention to ensure healing in the correct anatomical position and proper function recovery of the CMC thumb joint.

Maps Bennett's fracture

Injury Mechanism

Bennett fracture is a dislocation of an oblique intraarticular metacarpal fracture, caused by axial forces directed against partially flexed metacarpals. This type of compression along these metacarpal bones often survives when a person hits a hard object, such as an opponent's skull or tibia, or a wall. It can also happen as a result of falling to the thumb. This is a common injury he suffered from falling bikes, because the thumb is generally extended around the handlebars. It is also a common injury in a car crash, especially a fixed object, from the driver holding the wheel during a collision. The hand moves forward, while the steering wheel blocks the thumb.

Some writers have recently made a statement against popular belief that the APL tendon is not a deformation style on Bennett's fracture.

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Treatment

Although these fractures usually appear quite subtle or even unimportant on radiography, they can lead to severe long-term dysfunction in the hands if left untreated. In its original description of this type of fracture in 1882, Bennett emphasized the need for early diagnosis and treatment to prevent the loss of CMC thumb joint function, which is essential for the overall functioning of the hands.

• In a few cases of Bennett fractures, there may be only minor fracture fractures, relatively few joint instability, and minimal subluxation of CMC joints (less than 1 mm). In such cases, closed reduction followed by immobilization of the thoracic spica and serial radiography may be all that is required for effective treatment.
• For Bennett fractures where there is between 1 mm and 3 mm displacement in the trapeziometacarpal joint, closed reduction and percutaneous pin fixation (CRPP) with Kirschner wire are often sufficient to ensure satisfactory functional outcomes. The cable is not used to connect two common fracture fragments, but to secure the first or second metacarpal to the trapezium.
• For Bennett fracture where there is more than 3 mm of displacement in the trapeziometacarpal joint, open reduction and internal fixation (ORIF) are usually recommended.

Regardless of the approach used (non-surgical, CRPP, or ORIF), immobilization on cast or spica splint is required for four to six weeks.

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Prognosis

If an intraarticular trapeziometacarpal fracture (such as a Bennett or Rolando fracture) is allowed to heal in a neglected position, significant post-traumatic osteoarthritis from the base of the thumb is almost certain. Some forms of surgical treatment (usually CRPP or ORIF) are almost always recommended to ensure satisfactory results for this fracture, if there is significant displacement.

Long-term results after surgical treatment appear to be the same, whether CRPP or ORIF approach is used. In particular, the overall strength of affected hands is usually reduced, and post-traumatic osteoarthritis tends to develop in almost all cases. The degree of weakness and severity of osteoarthritis seem to correlate with the quality of fracture reduction. Therefore, Bennett's fracture treatment goals should be to achieve the most appropriate reduction, either by CRPP or the ORIF approach.

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Nomenclature

Bennett's fracture was named after Edward Hallaran Bennett, Professor of Surgery (1837-1907) at Trinity College of the University of Dublin, who described it in 1882. Bennett said the fracture "passes skewed across the base of the bone, releasing a larger portion of the articular surface, and "very large separated fragments and deformities generated there-from appearing to be more of the first dorsal metacarpal subluxation".

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See also

• Rolando Fracture
• Boxer Fracture
• Gamekeeper thumb

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References

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External links

• Bennett fracture on Who Named It?
• http://www.med.wayne.edu/diagRadiology/TF/MS/MS18.html
• http://www.wheelessonline.com/ortho/bennetts_fracture_dislocation

Source of the article : Wikipedia