Bennett's fracture
Encyclopedia
Bennett's fracture is a fracture
of the base of the first metacarpal bone
which extends into the carpometacarpal
(CMC) joint. This intra-articular
fracture is the most common type of fracture of the thumb
, and is nearly always accompanied by some degree of subluxation
or frank dislocation of the carpometacarpal joint.
, Professor of Surgery (1873–1906) at Trinity College of the University of Dublin
, who described it in 1882. Bennett said his fracture "passed obliquely across the base of the bone, detaching the greater part of the articular surface, and "the separated fragment was very large and the deformity that resulted there-from seemed more a dorsal subluxation of the first metacarpal".
metacarpal. This type of compression along the metacarpal bone is often sustained when a person punches a hard object, such as the skull
or tibia
of an opponent, or a wall. It can also occur as a result of a fall onto the thumb. This is a common injury sustained from bike falls, as the thumb is generally extended while around the handle bars.
With this in mind, failure to properly recognize and treat the Bennett's fracture will not only result in an unstable, painful, arthritic CMC joint with diminished range of motion: it will also result in a hand with greatly diminished overall function.
In the case of the Bennett's fracture, the proximal metacarpal fragment remains attached to the anterior oblique ligament
, which in turn is attached to the tubercle of the trapezium
bone of the CMC joint. This ligamentous attachment ensures that the proximal fragment remains in its correct anatomical position.
The distal fragment of the first metacarpal bone possesses the majority of the articular surface of the first CMC joint. Unlike the proximal fracture fragment, strong ligaments and muscle tendon
s of the hand tend to pull this fragment out of its correct anatomical position.
Specifically:
Tension from the APL and ADP muscles frequently leads to displacement of the fracture fragments, even in cases where the fracture fragments are initially in their proper anatomic position. Because of the aforementioned biomechanical
features, Bennett's fractures nearly always require some form of intervention to ensure healing in the correct anatomical position and restoration of proper function of the thumb CMC joint.
s of Bennett's fracture are instability of the CMC joint of the thumb, accompanied by pain and weakness of the pinch grasp. Characteristic signs
include pain, swelling, and ecchymosis
around the base of the thumb and thenar eminence
, and especially over the CMC joint of the thumb. Physical examination demonstrates instability of the CMC joint of the thumb. The patient will often manifest a weakened ability to grasp objects or perform such tasks as tying shoes and tearing a piece of paper. Other complaints include intense pain experienced upon catching the thumb on an object, such as when reaching into a pants pocket.
, they can result in severe long-term dysfunction of the hand if left untreated. In his original description of this type of fracture in 1882, Bennett stressed the need for early diagnosis and treatment in order to prevent loss of function of the thumb CMC joint, which is critical to the overall function of the hand.
Regardless of which approach is employed (nonsurgical, CRPP, or ORIF), immobilization in a cast or thumb spica splint is required for four to six weeks.
fractures) are allowed to heal in a displaced position, significant post-traumatic osteoarthritis
of the base of the thumb is virtually assured. Some form of surgical treatment (typically either a CRPP or a ORIF) is nearly always recommended to ensure a satisfactory outcome for these fractures, if there is signicant displacement.
The long-term outcome after surgical treatment appears to be similar, whether the CRPP or the ORIF approach is used. Specifically, the overall strength of the affected hand is typically diminished, and post-traumatic osteoarthritis tends to develop in almost all cases. The degree of weakness and the severity of osteoarthritis does however appear to correlate with the quality of reduction of the fracture. Therefore, the goal of treatment of Bennett's fracture should be to achieve the most precise reduction possible, whether by the CRPP or the ORIF approach.
Fracture
A fracture is the separation of an object or material into two, or more, pieces under the action of stress.The word fracture is often applied to bones of living creatures , or to crystals or crystalline materials, such as gemstones or metal...
of the base of the first metacarpal bone
First metacarpal bone
The first metacarpal bone or the metacarpal bone of the thumb is the first bone of the thumb. It is connected to the trapezium of the carpus at the first carpometacarpal joint and to the proximal thumb phalanx at the first metacarpophalangeal joint....
which extends into the carpometacarpal
Carpometacarpal joint
The carpometacarpal joints are five joints in the wrist that articulates the distal row of carpal bones and the proximal bases of the five metacarpal bones....
(CMC) joint. This intra-articular
Joint
A joint is the location at which two or more bones make contact. They are constructed to allow movement and provide mechanical support, and are classified structurally and functionally.-Classification:...
fracture is the most common type of fracture of the thumb
Thumb
The thumb is the first digit of the hand. When a person is standing in the medical anatomical position , the thumb is the lateral-most digit...
, and is nearly always accompanied by some degree of subluxation
Subluxation
A subluxation may have different meanings, depending on the medical specialty involved. It implies the presence of an incomplete or partial dislocation of a joint or organ. The World Health Organization defines both the medical subluxation and the chiropractic subluxation...
or frank dislocation of the carpometacarpal joint.
Nomenclature
The Bennett's fracture is named after Edward Hallaran BennettEdward Hallaran Bennett
Edward Hallaran Bennett was an Irish surgeon remembered for describing Bennett's fracture. He studied at Trinity College, Dublin of the University of Dublin, graduating M.Ch. in 1859 and M.D. in 1864. He was professor of anatomy and surgery at Trinity College from 1873-1906...
, Professor of Surgery (1873–1906) at Trinity College of the University of Dublin
University of Dublin
The University of Dublin , corporately designated the Chancellor, Doctors and Masters of the University of Dublin , located in Dublin, Ireland, was effectively founded when in 1592 Queen Elizabeth I issued a charter for Trinity College, Dublin, as "the mother of a university" – this date making it...
, who described it in 1882. Bennett said his fracture "passed obliquely across the base of the bone, detaching the greater part of the articular surface, and "the separated fragment was very large and the deformity that resulted there-from seemed more a dorsal subluxation of the first metacarpal".
Mechanism of injury
The Bennett's fracture is an oblique intraarticular metacarpal fracture dislocation, caused by an axial force directed against the partially flexedFlexion
In anatomy, flexion is a position that is made possible by the joint angle decreasing. The skeletal and muscular systems work together to move the joint into a "flexed" position. For example the elbow is flexed when the hand is brought closer to the shoulder...
metacarpal. This type of compression along the metacarpal bone is often sustained when a person punches a hard object, such as the skull
Human skull
The human skull is a bony structure, skeleton, that is in the human head and which supports the structures of the face and forms a cavity for the brain.In humans, the adult skull is normally made up of 22 bones...
or tibia
Tibia
The tibia , shinbone, or shankbone is the larger and stronger of the two bones in the leg below the knee in vertebrates , and connects the knee with the ankle bones....
of an opponent, or a wall. It can also occur as a result of a fall onto the thumb. This is a common injury sustained from bike falls, as the thumb is generally extended while around the handle bars.
Significance and complicating factors
Many important activities of daily life are dependent on the ability to grasp, pinch, and oppose the thumb. In fact, thumb function constitutes about 50% of overall hand function. These abilities are in turn dependent on an intact and functional thumb CMC joint. The CMC joint of the thumb allows a wide range of motion while maintaining stability for grasp and pinch.With this in mind, failure to properly recognize and treat the Bennett's fracture will not only result in an unstable, painful, arthritic CMC joint with diminished range of motion: it will also result in a hand with greatly diminished overall function.
In the case of the Bennett's fracture, the proximal metacarpal fragment remains attached to the anterior oblique ligament
Ligament
In anatomy, the term ligament is used to denote any of three types of structures. Most commonly, it refers to fibrous tissue that connects bones to other bones and is also known as articular ligament, articular larua, fibrous ligament, or true ligament.Ligament can also refer to:* Peritoneal...
, which in turn is attached to the tubercle of the trapezium
Trapezium (bone)
The trapezium bone is a carpal bone in the wrist.The trapezium is distinguished by a deep groove on its palmar surface. It is situated at the radial side of the carpus, between the scaphoid and the first metacarpal bone...
bone of the CMC joint. This ligamentous attachment ensures that the proximal fragment remains in its correct anatomical position.
The distal fragment of the first metacarpal bone possesses the majority of the articular surface of the first CMC joint. Unlike the proximal fracture fragment, strong ligaments and muscle tendon
Tendon
A tendon is a tough band of fibrous connective tissue that usually connects muscle to bone and is capable of withstanding tension. Tendons are similar to ligaments and fasciae as they are all made of collagen except that ligaments join one bone to another bone, and fasciae connect muscles to other...
s of the hand tend to pull this fragment out of its correct anatomical position.
Specifically:
- tension from the abductor pollicis longus muscleAbductor pollicis longus muscleThe abductor pollicis longus muscle is one of the extrinsic muscles of the hand. It lies immediately below the supinator muscle and is sometimes united with it.-Origin and insertion:...
(APL) subluxates the fragment in a dorsal, radial, and proximal direction - tension from the APL rotates the fragment into supinationSupinationSupination is a position of either the forearm or foot; in the forearm when the palm faces anteriorly, or faces up . Supination in the foot occurs when a person appears "bow-legged" with their weight supported primarily on the anterior of their feet.The hand is supine in the anatomical position...
- tension from the adductor pollicis muscle (ADP) displaces the metacarpal head into the palmHandA hand is a prehensile, multi-fingered extremity located at the end of an arm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs...
Tension from the APL and ADP muscles frequently leads to displacement of the fracture fragments, even in cases where the fracture fragments are initially in their proper anatomic position. Because of the aforementioned biomechanical
Biomechanics
Biomechanics is the application of mechanical principles to biological systems, such as humans, animals, plants, organs, and cells. Perhaps one of the best definitions was provided by Herbert Hatze in 1974: "Biomechanics is the study of the structure and function of biological systems by means of...
features, Bennett's fractures nearly always require some form of intervention to ensure healing in the correct anatomical position and restoration of proper function of the thumb CMC joint.
Controversy
Some authors have recently made the assertion that the widely held belief that the APL tendon is a deforming force on the Bennett fracture is incorrect.Symptoms and signs
SymptomSymptom
A symptom is a departure from normal function or feeling which is noticed by a patient, indicating the presence of disease or abnormality...
s of Bennett's fracture are instability of the CMC joint of the thumb, accompanied by pain and weakness of the pinch grasp. Characteristic signs
Medical sign
A medical sign is an objective indication of some medical fact or characteristic that may be detected by a physician during a physical examination of a patient....
include pain, swelling, and ecchymosis
Ecchymosis
An ecchymosis is the medical term for a subcutaneous purpura larger than 1 centimeter or a hematoma, commonly called a bruise. It can be located in the skin or in a mucous membrane.-Presentation:...
around the base of the thumb and thenar eminence
Thenar eminence
The thenar eminence refers to the group of muscles on the palm of the human hand at the base of the thumb...
, and especially over the CMC joint of the thumb. Physical examination demonstrates instability of the CMC joint of the thumb. The patient will often manifest a weakened ability to grasp objects or perform such tasks as tying shoes and tearing a piece of paper. Other complaints include intense pain experienced upon catching the thumb on an object, such as when reaching into a pants pocket.
Treatment
Though these fractures commonly appear quite subtle or even inconsequential on radiographsRadiography
Radiography is the use of X-rays to view a non-uniformly composed material such as the human body. By using the physical properties of the ray an image can be developed which displays areas of different density and composition....
, they can result in severe long-term dysfunction of the hand if left untreated. In his original description of this type of fracture in 1882, Bennett stressed the need for early diagnosis and treatment in order to prevent loss of function of the thumb CMC joint, which is critical to the overall function of the hand.
- In the most minor cases of Bennett's fracture, there may be only small avulsion fractures, relatively little joint instability, and minimal subluxation of the CMC joint (less than 1 mm). In such cases, closed reduction followed by immobilization in a thumb spica cast and serial radiography may be all that is required for effective treatment.
- For Bennett's fractures where there is between 1 mm and 3 mm of displacement at the trapeziometacarpal joint, closed reduction and percutaneous pin fixation (CRPP) with Kirschner wireKirschner wireKirschner wires or K-wires or pins are sterilized, sharpened, smooth stainless steel pins. Introduced in 1909 by Martin Kirschner, the wires are now widely used in orthopaedics and other types of medical and veterinary surgery. They come in different sizes and are used to hold bone fragments...
s is often sufficient to ensure a satisfactory functional outcome. The wires are not employed to connect the two fracture fragments together, but rather to secure the first or second metacarpal to the trapezium.
- For Bennett's fractures where there is more than 3 mm of displacement at the trapeziometacarpal joint, open reduction and internal fixation (ORIF) is typically recommended.
Regardless of which approach is employed (nonsurgical, CRPP, or ORIF), immobilization in a cast or thumb spica splint is required for four to six weeks.
Prognosis
If intraarticular trapeziometacarpal fractures (such as the Bennett's or RolandoRolando fracture
The Rolando fracture is a comminuted intra-articular fracture through the base of the first metacarpal bone . It was first described in 1910 by Silvio Rolando. This is a fracture consisting of 3 distinct fragments; it is typically T- or Y-shaped.-Treatment:There are several proposed methods of...
fractures) are allowed to heal in a displaced position, significant post-traumatic osteoarthritis
Osteoarthritis
Osteoarthritis also known as degenerative arthritis or degenerative joint disease, is a group of mechanical abnormalities involving degradation of joints, including articular cartilage and subchondral bone. Symptoms may include joint pain, tenderness, stiffness, locking, and sometimes an effusion...
of the base of the thumb is virtually assured. Some form of surgical treatment (typically either a CRPP or a ORIF) is nearly always recommended to ensure a satisfactory outcome for these fractures, if there is signicant displacement.
The long-term outcome after surgical treatment appears to be similar, whether the CRPP or the ORIF approach is used. Specifically, the overall strength of the affected hand is typically diminished, and post-traumatic osteoarthritis tends to develop in almost all cases. The degree of weakness and the severity of osteoarthritis does however appear to correlate with the quality of reduction of the fracture. Therefore, the goal of treatment of Bennett's fracture should be to achieve the most precise reduction possible, whether by the CRPP or the ORIF approach.
External links
- http://www.med.wayne.edu/diagRadiology/TF/MS/MS18.html
- http://www.wheelessonline.com/ortho/bennetts_fracture_dislocation