Bone Defects

Ahmed Thabet, M.D.

 

Introduction/ description:

Long bone defects are devastating injuries and can be difficult to manage. Bone defects may be the result of acute injury (e.g. open fractures where the skin is open with bone loss) or occur after debridement for nonunion (a bone which is not healing), infection, or bone tumors. The options for surgical treatment include shortening the bone, bone transport distraction osteogenesis (a technique where a metal external frame is used to help create new bone), and bone grafting (bone or a bone substitute is placed within the defect to help promote the body to create new bone).

 

Causes:

Bone defects can be caused by after surgical treatment to remove bone infection, bone tumors, or non-union (which is when a bone does not heal). They can also occur with severe open fractures, where the skin is open and the bone is exposed to the environment.

 

Symptoms:

Pain, impaired weight bearing, and limitation of the limb function are the main symptoms. The past surgical history usually reveals the original problem. There may be a history of multiple previous surgeries to get the bone to heal.

 

Doctors exams:

Your surgeon will assess the quality of the muscle and skin, the level of function of the nerves and blood vessels, and the motion of the joints of the limb. This is important to understand how well the limb can eventually function, and to plan surgical treatment.

 

Treatment options:

The choice of the treatment options is generally complex and involves a detailed discussion between the treating orthopedic surgeon and the patient.  Many variables affect the decision-making. These include the presence or absence of infection, the size of the bone defect, the patient’s goals, and the condition of the soft tissues.

The treatment can be done using internal fixation (all implants inside the body) or external fixation (external metal supports connected to the bone by wires and pins).

Smaller defects, usually under 2 cm, can be treated with bone graft, which is obtained from different resources. Bone graft can be taken from the patient’s own body (autologous or autogenous bone grafting) with or without the feeding artery of grafted bone. The most common sources for non-vascularized bone graft (bone graft without the feeding artery) is from the pelvis or from the canal of the thighbone. A free vascularized fibular graft (FVFG) can harvested from the leg and moved to the site of injury using special microscope. This can lead to some problems at the donor site but provides high quality bone that is necessary in some circumstances.

Medium sized defects, generally between 2 cm and 6 cm, can be treated with distraction osteogenesis. This is a technique where the bone is cut in a healthy site and then distracted using an external fixator frame or an internal lengthening nail. New bone forms in the gap to restore the overall length of the bone. The site of the bony defect can either be shortened at the same time when the distraction osteogenesis surgery is done, or it can be gradually closed as the new bone is being made (referred to as bone transport). This type of treatment allows for correction of severe bone loss but does involve a large amount of effort. Although complications and setbacks are relatively common, in most cases the end goal of achieving length and filling the defect can be achieved.

Bone defects after infection may be treated in a two-step process. First, the surgeon removes any infected bone. Bone cement mixed with a high concentration of antibiotics is placed in the defect.  This acts as a space holder. The antibiotics in the cement help fight the infection and stimulates a tube of tissue (called an induced membrane) which has the ability to growth new bone. In a second surgery the cement spacer is removed, the tube of tissue is kept in place, and bone graft is added to help encourage the regeneration of bone.

In some cases the bone defect and the associated damage to the muscles, skin nerves and blood vessels is severe enough that amputation is recommended. This can be a difficult decision in many circumstances and oftentimes an evaluation by a limb deformity specialist is very helpful.