Anatomy of the Bones of the Hand, Wrist, and Forearm
There are five bones of the hand, one for each finger and one for the thumb.  These are called the metacarpal bones.  Each of the fingers has three bones, called phalanges, and the thumb has only two.
The metacarpals of the hand are connected to the phalanges of the fingers at the metacarpophalangeal joints, commonly known as MP joints.
The metacarpals are also connected to the two bones of the forearm, the radius and ulna, through the wrist joint, which is comprised of eight separate bones.  These eight bones, called the carpal bones, are connected to each other through the ligaments of the wrist and have a specific relationship to one another.
The joint between the forearm and wrist is called the radiocarpal joint, and the joint between the carpus or wrist and the hand bones is called the carpometacarpal joint.

Types of Injury
If any of these bones is broken across, this is called a fracture.  Fractures of any of the bones of the hand—i.e., the metacarpals or the phalanges—are extremely common.  Fractures of the wrist joint most frequently involve the scaphoid bone of the wrist.  The other bones of the wrist may fracture, but less often.
Instead of the bone breaking, a joint may be disrupted.  The ligaments hold the joints together, and, if these are torn, one bone of the joint may lose contact with the other, thereby producing a dislocation.
An open fracture (also termed a compound fracture) occurs when the broken bone has pierced the skin.  If there is a communication between the outside and a fracture, there is a greater risk of infection.
If, following a fracture, the bone does not heal, this is called nonunion. Nonunion occurs if the bone is not immobilized in the appropriate position to allow healing, or if soft tissue such as muscle or tendon is interposed in the fracture site so that the bone cannot heal across the broken area.  If the bone heals in an abnormal position, this is termed a malunion.
An intraarticular fracture is one in which a fracture occurs into a joint and the healing of the joint is irregular.  With such a fracture, arthritis or abnormal wearing of the joint will occur over time.

Symptoms
Following a fracture, the area is generally painful and swollen, and often red or bruised.  This indicates that blood has accumulated under the skin from the ends of the broken bone.
It is usually very difficult and painful to move a bone that has been fractured.  Sometimes, however, fractures are not particularly painful and in such cases the diagnosis is not immediately evident.  Weeks or months later, it is chronic pain and poor function that may evidence that a fracture has occurred.

Diagnosis
The diagnosis of a fracture may be made initially by clinical evaluation, as indicated by pain, inability to function, tenderness at the fracture site, swelling, and instability.  The definitive diagnosis, however, is made upon X-ray.  Even so, occasionally X-rays do not initially show a fracture, and a subsequent MRI or CT scan will be required.

Treatment
A fracture must be treated by positioning the two fragments of bone in their preinjury, or anatomic, position.  This is called reduction of the fracture.  This reduction is then maintained, either with a cast which holds the bone in position, an external fixator consisting of metal pins which hold the bones in position, or by an open operation, in which case pins, plates, or screws are used to maintain the anatomic position of the bone.
This position needs to be held until the bone heals, for approximately three to four weeks in the case of the bones of the hand or fingers.  Healing may take considerably longer in the case of a fracture of the wrist bones.
Often a fractured bone can be realigned or reduced without opening the skin (closed reduction), and a cast is sufficient to hold the fracture in position while the bone heals.
Sometimes a closed reduction can be combined with the placement of percutaneous pins through the skin and across the fracture fragments.  These pins assist in holding the fracture fragments in perfect position.
In situations where a fracture cannot be reduced with closed methods, an open operation is needed to position the fracture and place the pins, screws, or plates to hold the fracture in anatomic position. There are a great many options of fixation techniques and devices.  Much research over the past several years has been directed at providing devices which are an exact fit for the fractured bones, making the fixation procedure extremely exact.
If the bones are so badly damaged at the fracture site that they cannot be brought back together, then a bone graft may be required.  This involves taking some bone from another part of the body, usually the iliac crest at the hip, or a bone graft from the end of the radius in the forearm, to fill in the gap.  This bone graft provides a scaffold for the healing bone cells to bridge across the fracture site.

Healing after the Initial Treatment
As part of the body's natural healing process, bone cells are deposited across a fracture.  Initially immature cells are deposited on a scaffold of tissue across the fracture, forming a fracture callus which ultimately matures into solid bone, resulting in healing of the fracture.
As soon as the fracture is stable, specifically designed exercises become an essential part of the rehabilitation process.  If this therapy is initiated only after solid healing has been accomplished, then the joints around the fracture site will be extremely stiff and the functional outcome will be poor.  For this reason, therapy is begun at the earliest possible time to maintain flexibility of the joints in the hand.  This treatment is essential to provide an excellent functional outcome and is well recognized by hand surgeons.  Early movement is more essential following hand injuries than it is in fractures of many other bones of the body.
Fractures that occur in combination with other soft-tissue injuries, such as tendon, nerve, and vessel injuries, have an even greater propensity to become stiff.  Expert management and appropriate timing of therapy are therefore very important.
After a bone has initially healed, then more resistive activities can slowly be included in the rehabilitation process.  The bone, however, is not fully healed for many months, and sports, especially contact activities, may need to be delayed.  In most cases, resumption of sports, musical, or other activities can be begun early on, as long as such activity is controlled and the directions of the physician and hand therapist are followed.
Children tend to remodel bone more than adults. Both children and adults, however, will correct minor deformities if the deformity is in the plane of movement of the finger or fractured part.  If there is an abnormality of rotation or angulation that is not in the direction of movement, this abnormality will not improve with time.

Characteristics of Specific Fractures

The phalanges of the fingers are the bones most commonly fractured in the body.  These fractures almost always heal solidly.  However, there are  three problems  relating to these fractures.
The most common problem is stiffness of the joints of the finger (discussed above), which may be avoided by early motion and therapy.
The second problem is malunion, or healing of the fracture in an incorrect position.  The most serious malunion is that of abnormal rotation, which means that the finger is abnormally rotated.  The finger bends underneath the adjacent finger when a fist is made and the fingers are brought to the palm.  Depending on which direction the malrotation presents, the finger will rotate toward either the thumb side or the small-finger side of the hand.
The third problem is that of arthritis in joints that either are fractured or where a fracture accompanies a dislocation, indicating that the joint is out of position.  This results in stiffness, swelling, and pain.

Fractures of the metacarpals are also extremely common.  Rotation is once again the most important problem, and angulation of the bone and shortening can also occur, resulting in poor function.  As with phalangeal fractures, stiffness of the adjacent joints is a common complication and must be specifically avoided.  This is especially true if the fracture is very close to the joints or actually goes into the joint.

The most frequently fractured wrist bone is the scaphoid bone.  Healing of this bone is always problematic because of the poor blood supply to it and the fact that the vessels enter into the bone from the distal (farthest) point, traveling longitudinally along the length of the bone.  If the bone is fractured, a portion of the bone's blood supply is therefore disrupted, often delaying healing.  Scaphoid fractures are best treated with screw fixation to provide secure positioning, which aides in healing.  If healing does not occur within three to six months, then an external bone-stimulation device using either electromagnetic fields or ultrasound may be helpful.  Otherwise, bone grafting might be necessary.

Until approximately ten years ago, distal radius fractures were treated in a rather cavalier fashion.  Over the past ten years, however, hand surgeons have come to recognize that these fractures can often result in significant long-term problems of pain, deformity, and decreased range of motion and that for this reason vigorous early treatment is essential.  A fracture of the end of the radius bone may result in shortening of this bone, or incorrect positioning.
If there is a malunion of a distal radius fracture, then inability to rotate the forearm is very frequently also a problem.  If the initial reduction is not ideal, then open surgery is indicated in order to provide the appropriate positioning.
If after surgery this is not accomplished and the fracture proceeds to a malunion with inadequate positioning of the fracture, then further surgery three to six months later may be indicated.  Often a bone graft is needed at the time of this second procedure, and other procedures to restore rotation of the forearm may also be necessary.