Factors Affecting The Rate Of Healing Of A Fracture

1 TYPE OF BONE

Cancellous bone (spongy bone) Healing in cancellous bone is generally well advanced 6 weeks from (he time of the injury, and protection of the fracture can almost invariably be abandoned by that time. This applies to fractures of bones which are composed principally of cancellous (issue, and also to fractures involving the cancellous bone to be found at the ends of long bones. This rule is illustrated in the following examples:

1. Weight bearing after a fracture of the calcaneus may be permitted after about 6 weeks.

2. A patient with a traumatic wedge fracture of a vertebral body may commence full mobilisation after 6 weeks.

3. Plaster fixation may be discarded after 5-6 weeks following a Colles fracture.

4. Weight may be allowed through the leg 6 weeks alter a fracture of the tibial table.

5. Bed rest for 6 weeks is usually advised for any fracture of the pelvis involving those parts through which weight transmission is mediated.

Cortical bone (compact bone) Endosteal callus may take many months to become reasonably well established, and many uncomplicated long bone fractures may take 9-18 weeks to unite. In some eases, however, abundant external bridging callus may allow an earlier return of function. For example:

1. The average lime to union of a fracture of the tibial shaft treated conservatively is 16 weeks

2. Fractures of the humeral shaft can often be left unsupported after 10 weeks.

3. On the other hand, fractures of the metatarsals, metacarpals and phalanges, where external bridging callus is usually substantial, are usually quite firm in 4-5 weeks.

2 PATIENT AGE

In children, union of fractures is rapid. The speed of union decreases as age increases until skeletal maturity is reached. There is then not a great deal of difference in the rale between young adults and the elderly. For example, in a child, union may be expected in a fractured femur a little after the number of weeks equivalent to its numerical age have passed, i.e. a fractured femur in a child of 3 years is usually united after 4 weeks; a fractured femur in a child of 8 years is usually sound al ter 9 weeks. In contrast, a fracture of the femoral shaft in an adult may take 3-6 months to unite.

Apart from great rapidity of union it should be noted that children have remarkable powers of remodelling fractures. These powers are excellent as far as displacement is concerned, and are often good for slight to moderate angulation. Remodelling is poor in the case of axial rotation in both adults and children. The power to remodel decreases rapidly once adolescence is reached and epiphyseal fusion is imminent.

Fracture Medical Treatment
1. Supracondylar fracture of humerus with soft iissue between bone ends.
Fracture Remodeling Images

2. Chronic bone infection and failure of union of tibia following plating (plate removed).

2. Chronic bone infection and failure of union of tibia following plating (plate removed).

3 MOBILITY AT FRACTURE SITE

Excessive mobility persisting at ihe fracture site (due. for example, to poor fixation) may interfere with vascuiarisation of the fracture haematoma: ii may lead to disruption of early bridging callus and may prevent endosteal new bone growth. One of the main aims of all forms of internal and external splintage is to reduce mobility at the fracture site, and hence encourage union. If splintage is inadequate, union may be delayed or prevented.

4 SEPARATION OF BONE ENDS

Union will be delayed or prevented if the bone ends are separated, for this interferes with the normal mechanisms of healing. (The converse is also true, namely that compression of the fracture facilitates union.) Separation may occur under several circumstances:

1. Soft tissue interposition. For example, in fractures of the femoral shall, one of the bone ends may become isolated from the other by herniating through some of the surrounding muscle mass, thereby delaying or preventing union. Fractures of the medial malleolus may fail to unite due to infolding of a layer of periosteum between the fragments.

2. Excessive traction. Excessive traction employed in the maintenance of a reduction may lead to separation of the bone ends and non-union. This may occur, for example, in femoral shaft fractures, particularly those treated by skeletal traction.

3. Following internal fixation. In some situations where internal fixation is used to hold a fracture, resorption of bone may occur at the fracture site; the fixation device may continue to hold the bone fragments in such a way that they are prevented from coming together, and mechanical failure may ensue. A bulky internal fixation device may in itself interfere with the local blood supply and the fracture haematoma. Where possible, steps should be taken to avoid this (e.g. by employing a wave plate or a LISS plate).

5 INFECTION

Infection in the region of a fracture may delay or prevent union. This is especially the case if. in addition, movement is allowed to occur at the fracture. Infection of the fracture site is extremely rare in conservatively treated closed fractures; infection, if it occurs, follows either an open injury or one treated by internal fixation. Where infection becomes well established in the presence of an internal fixation device, it is often difficult to achieve healing without remov al of the device, which acts as a foreign body and a nidus for persisting infection. This is especially the case if there is breakdown of the overlying skin and the establishment of a sinus. Not infrequently the situation arises where cast fixation alone is unable to provide the degree of fixation necessary for union if the device is removed, and where infection is likely to remain if i( is not. In such circumstances it is usually wiser to retain the fixation device until union is reasonably well advanced, or to consider using an external fixator. In some cases, where sound healing can be obtained and maintained after removal of an internal fixation device, it may be possible to repeal the internal fixation in ihe sterile environment that has been obtained.

6 DISTURBANCE OF BLOOD SUPPLY

li is obvious that lor the normal multiplication of bone cells and their precursors an adequate blood supply is required. Where the blood supply to an area is reduced, or where there is interference with the blood supply to both major fragments - e.g. in radionecrosis of bone - healing may be interfered with. On the other hand, reduction of the blood supply to one fragment, especially if cancellous bone is involved, may not interfere with union; indeed, in some situations it may apparently stimulate it. The most striking examples of this arc fractures of the femoral neck and scaphoid, where the phenomenon of avascular necrosis is most frequently discovered in soundly united fractures. Interference with the blood supply to one fragment at the time of injury leads to immediate bone death; this is frequently followed by sound union of the fracture. Collapse of necrotic bone beyond the level of union is observed at a later date.

Again, a bulky internal fixation device may in itself interfere with the local blood supply and the fracture haemaloma. delaying union. Where possible this should be avoided by choosing the most appropriate device.

7 PROPERTIES OF THE BONE INVOLVED

Fracture healing is also affected by a number of imperfectly understood factors which lead to variations in the speed of union. The clavicle is a spectacular example; non-union is extremely rare, the time to clinical union is unexcelled by any other part of the skeleton, yet movement at the fracture site cannot be controlled with any efficiency. Union of the tibia is often slow to a degree that is difficult to explain even when the influence of its nutrient artery and fracture mobility are taken into account.

8 OTHER FACTORS

• Effects of smoking. Smoking has a deleterious effect on fracture union, often being a significant factor in the rate and quality of union.

• Joint involvement. When a fracture involves a joint, union is occasionally delayed. This may be due to dilution of the fracture haemaloma by synovial fluid.

• Bone pathology. Many of the commonest causes of pathological fracture do not seem to delay union in a material way. (Union may progress quite normally in, for example, osteoporosis, osteomalacia. Paget's disease and most simple bone tumours.) Some primary and secondary malignant bone tumours may delay or prevent union (see pp. 105-108).

COMPLICATIONS OF FRACTURES _____

Complications which may occur in a patient who has suffered a fracture or dislocation may be grouped in the following way:

+3 -3

Responses

  • Reija
    Why synovial fluid prevent fracture haematoma?
    1 year ago
  • RICKEY
    What factors accomplish healing of a fracture?
    11 months ago
  • GIOELE
    What are the factors which influence the rate of bone healing?
    8 months ago
  • Ottavia
    What are factors that hinder bone healing?
    6 months ago
  • Lewis
    What is excessive traction in healing of a bone?
    3 months ago
  • zuzanna wood
    What are the factors that delay healing of fractures?
    3 months ago
  • Lelia Fanucci
    Why synovial fluid affect fracture healing?
    28 days ago

Post a comment