AUTHOR: Marc Mitnick DPM
REVIEWED BY: Podiatric Medical Review Board
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If you are reading this section it is probably due to the fact that your doctor has suggested the use of a bone stimulator for you and you would like more information. These devices are used for fractures that are not healing, occurring all over the body.
Approximately six million extremity fractures occur in the United States every year. It is estimated that five to ten percent of these fractures will not heal in the “normal" period of time. These types of fractures then become classified as delayed healing fracture which implies that the fracture still has the potential to heal over a longer time period than anticipated or non-union fractures which implies that the fracture site will not heal at all on its own.
WHY A FRACTURE DOES NOT HEAL
There can be many reasons why a fracture will not heal. These include the following:
- displacement of the fracture ends in such a manner that the blood supply is cut off to the fracture site. (Fractures heal by increased blood flow to the area)
- extensive soft tissue injury in the site of the fracture which will also diminish the blood flow to the fracture site.
- separation of fractured ends. There is too much space between the broken bone ends and the body is unable to “bridge" the gap.
- over debridement (removal) of bone in compound fractures by the attending surgeon, thus once again resulting in too much space between the broken bone ends.
- inadequate reduction. In poorly aligned fractures the surgeon must realign the bones and sometimes the bones are poorly aligned.
- infection at the fracture site.
- inadequate immobilization of the fracture.
- people on steroids. Steroids reduce the inflammation which is needed to initiate healing, plus people on long term steroids suffer from bone atrophy and thus increase their risk of pathological fractures.
- anti-inflammatories, NSAIDs. They too reduce inflammation around the fracture site.
- smokers. Once again the blood supply to the area is inhibited.
- poor nutrition
- poor circulation
- excessive alcohol intake
- people on immunosuppressive drugs
- people on anticoagulant therapy. (coumadin, Plavix, etc.)
STAGES OF BONE HEALING
Fracture repair occurs in three stages. The inflammatory stage is the initial stage and generally lasts 3-4 days. In this stage there is an increased blood flow to the area; that is why the fracture site is usually swollen, red and painful. During this phase the body is removing all dead tissue and bone from the area.
The second stage is known as the reparative stage. This stage lasts for 3 to 4 weeks and during this phase “bridging" of the fracture site occurs as the body lays down cells that form a lattice network between the two broken ends of bone. This is known as bone callus.
The third stage is known as the remodeling stage where the soft bone callus becomes hard bone. This stage can last from a few months to a year. Even though this stage may be still going on a patient may be considered clinically healed if there is no longer any pain in the surgical site and the patient is able to do their daily activities without pain or use of splints, casts, etc.
The progress of a healing fracture can be followed by serial x-rays. Every couple of weeks your doctor will x-ray the fracture site and look for certain signs characteristic of that part of the healing process. In conjunction with observation of the actual site and patient interview, he or she will determine if your progress is on schedule.
TYPES OF NON-HEALING FRACTURES
If your fracture falls behind the normal time line of healing it is first characterized as a delayed union. If upon repeat x-rays there is no further evidence of healing it is then considered a non-union.
Years ago a fracture was considered a non-union if nine months had passed without healing. This was due primarily to insurance issues as most insurance companies would not pay for a bone stimulator unless an excessive amount of time had passed. It was an archaic rule; the problem being is that the patient would have wasted nine months before they finally got a bone stimulator which could then set them back another 12 months. In this day and age most insurance companies will pay for a bone stimulator in a much shorter period of time.
There are three types of non-unions. The first is known as hypertrophic non-union. In this case there has been adequate blood flow and bone repair activity to the fracture, but the fracture has failed to close. The most common cause of this type of fracture is due to excessive motion within the fracture site due mainly to poor immobilization.
The second type of non-union is known as an atrophic non-union. This is basically an opposite reaction. There has been no activity at the site of fracture. The primary cause of this non-union is poor vascularity. In the foot there are a couple of sites of inherently poorly vascularized bone.
The third type of non-union is a pseudoarthrosis otherwise known as a false joint. What has happened here is that the fracture space has filled in with scar tissue instead of hard bone. So even though the two bone ends are now connected there is still pain because there will be motion (and pain) within this area because of the scar tissue.
ONE OPTION FOR NON-UNION, A BONE STIMULATOR
One option available for most fractures is the use of a bone stimulator. It will not work on all fractures particularly fractures where there is too much space between the bones. It will also not work on pseudoarthosis.
Back in the 1950’s and 1960’s it was first recognized that the bending of bone creates a strain that results in electrical streaming potentials within the bone. It is thought that this electrical streaming potential signals the body to start bone remodeling.
A bone stimulator is an external device that creates electro-magnetic fields that mimic the same electrical streaming potentials that the body produces thereby initiating bone healing.
Bone stimulators fall into different subsets. Some bone stimulators may be implanted into the fracture site to promote healing, while others are completely external with electrodes placed on either side of the fracture in an effort to create an electro-magnetic field. When used they are painless, but patient compliance is mandatory; different devices have different time frames for which they have to be used. Failure to completely follow your doctor’s orders will doom you to failure. Patient compliance is such an issue that most of the newer bone stimulators have built in memory so that the doctor can check to see if the device has been used as instructed.
Bone stimulators can still take up to 12 weeks to completely heal a difficult fracture. There are hundreds of peer reviewed studies concerning bone stimulators and in general there is a reported success rate of anywhere between 50 to 85 percent. Success is predicated on how many adverse factors are present as listed earlier in this article.
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