FRACTURE HEALING

Those concerned with sports must fully realize the potential seriousness of a bone fracture.  Time is required for proper bone union to take place.

1. The osteoblast is the cellular component of bone and forms its matrix

2. the osteocyte forms  bone, and

3. osteoclasts destroy and resorb bone.

The constant ongoing remodeling of bone is caused by osteocytes; osteoclasts are related mainly to pathological responses

Acute Fractures of the Bone

Acute fracture healing follows similar phases as soft tissue but is more complex. In general there are five stages

1. Hematoma formation

2. Cellular proliferation

3. Callus formation

4. Ossification

5. Remodeling

Hematoma Formation

1. Acute inflammation usually lasts approximately 4 days.

2. When a bone fractures, there is trauma to the periosteum and surrounding soft tissue.

3. With hemorrhaging, a hematoma accumulates in the medullary canal and surrounding soft tissue in the first 48 to 72 hours.

Cellular Formation

As with a soft-tissue injury, the hematoma begins its organization in granulation tissue and gradually builds a fibrous junction between the fractured ends.

1. First a fibrous callus is produced

2. then cartilage

3. and finally a woven bone.

Bone will develop at the fracture site when oxygen tension and compression are in the proper amounts.

Callus Formation

The soft callus, in general, is an unorganized network of woven bone formed at the ends of the broken bone that is later absorbed and replaced by bone.

1. At the soft callus stage, both internal and external calluses are produced that bring an influx of osteoblasts that begin to immobilize the fracture site.

2. The internal and external calluses are formed by bone fragments that grow to bridge the fracture gap.

3. The internal callus grows rapidly to create a rigid immobilization. Beginning in 3 to 4 weeks, and lasting 3 or 4 months, the hard callus forms.

Ossification

1. With adequate immobilization and compression, the bone ends become crossed with a new Haversian system that will eventually lead to the laying down of primary bone.

2. The ossification stage is the completion of laying down bone.

3. The fracture has been bridged and firmly united. Excess callus has been resorbed by osteoclasts.

Remodeling

1. Remodeling occurs after the callus has been resorbed and trabecular bone is laid down along the lines of stress.

2. Complete remodeling may take many years.

3. Remodeling is considered complete when a fractured bone has been restored to its former shape or has developed a shape that can withstand imposed stresses.

Management of Acute Fractures

In the treatment of acute fractures the bones commonly must be immobilized completely until x-ray studies reveal that the hard callus has been formed. 

During healing, fractures can keep an athlete out of participation in his or her particular sport for several weeks or months, depending on the nature, extent, and site of the fracture.

During healing certain conditions can seriously interfere with the healing process:

1. A poor blood supply to the fractured area

• if one of the parts of the broken bone is not properly supplied by the blood, that part will die and union or healing of the fracture will not take place.

• This condition is known as aseptic necrosis and often occurs in the head of the femur, the navicular bone in the wrist, the talus in the ankle, and isolated bone fragments.

• The condition is relatively rare among vital, healthy, young athletes except in the navicular bone of the wrist.

2. Poor immobilization of the fracture site

• resulting from poor casting  permits motion between the bone parts

• may not only prevent proper union but may also, in the event that union does transpire, cause deformity to develop.

3. Infection

• can materially interfere with the normal healing process, particularly in the case of a compound fracture, which offers an ideal situation for development of a severe streptococcal or staphylococcal infection. 
• If the fracture site should become and remain infected, the infection could interfere with the proper union of the bone.

Healing of Stress Fractures

Stress fractures may be created by forces that adversely load a bone at a susceptible site.  

• If osteoclastic activity is greater than osteoblastic activity the bone becomes increasingly susceptible to stress fractures.

1. Healing of stress fractures involves restoring a balance of osteoclastic and osteoblastic activity

• achieving this balance requires recognition of the situation as early as possible.

2. Stress fractures that go unhealed will eventually develop into complete fractures that may, over a period of time, become displaced.

3. A decrease in activity and elimination of other factors in training that cause stress will allow bone remodeling and the ability to withstand stress.