Distraction osteogenesis

Distraction osteogenesis is a surgicalprocess for the reconstruction of skeletaldeformitiesand for the lengthening of bones. A bone fractureis surgically created and the two ends of the bone are moved apart, slow enough so that new bone can grow in the gap. The uniqueness and value of distraction osteogenesis lie in its ability to simultaneously expand both the bone volume and the surrounding soft tissues.

Lengthening of up to a maximum of seven centimetres(cm) per bone has been recommended, meaning that a patient can gain up to 14 cm in total limb length. Although 12 cm per bone has been achieved, this is not normally recommended as it puts considerable strain on the body. Bone growth rates are affected by factors such as age, discipline, and lifestyle. The bones of a smoker, for example, grow more slowly than that of a non-smoker.

Although distraction technology has been used mainly in the field of orthopedics, early results indicate that the process can be equally effective in facialskeletal reconstruction.

Ilizarov surgery

Image:Ilizarov external fixator.jpg Ilizarov surgery, developed by Gavriel Ilizarov, a Russianorthopedic surgeon, in 1951, is the oldest and most common method of distraction osteogenesis. The process involves the following:

• Shattered bones and devascularisedones are removed from the patient, leaving a gap;
• The healthy part of the upper bone is broken into two segments with an external saw;
• The leg is then fitted with the Ilizarov frame that pierces through the skin, muscles, and bone;
• Screwsattached to the middle bone are turned 1 millimetre(mm) per day, so that new bone tissuesthat are formed in the growth zone are gradually pulled apart to decrease the gap (One millimetre has been found to be the optimalbone distraction rate. Lengthening too fast overstretches the soft tissues, resulting not only in pain, but also in the inability of the bone to fill up the gap; too slow, and the bone hardens before the full lengthening process is complete.);
• After the gap is closed, the patient continues to wear the frame until the new bone solidifies; the waiting period is usually 120 days before the leg can be used.

Ilizarov surgery is extremely painful, uncomfortable, infection-prone, and often causes unsightly scars. Frames used to be made of stainless steelrings weighing up to 7 kilogram(kg), but newer models are made of carbon, which though lighter, are equally cumbersome.

For decades, the Ilazarov procedure was the best chance for shattered bones to be restored, and crooked ones straightened. Breakthroughs in distraction osteogenesis in the 1990s, however, have resulted in hassle-free and less painful (albeit more expensive) alternatives.

Image:Ilizarov surgery.jpg

Intramedullary skeletal kinetic distractor

In 2001, the "IntramedullarySkeletal KineticDistractor" (ISKD) was introduced, allowing lengthening to take place internally, thereby drastically reducing the risk of infections and scarring.

With ISKD, a pin that can be gradually extended by kneeor anklerotations is implanted into the bone. Lengthening is monitored by a hand-held external magneticsensorthat tracks the rotation of an internal magneton a daily basis.

ISKD requires a physical leg movement to "crick" the device into lengthening, and can be quite painful, especially right after a surgery. In this method, there is also a risk of accidentally over-stretching the bones, causing improper bone formation.

Fitbone surgery

A new form of surgery, involving a fully implantable, electronically-motorisedlimb-lengthening device, called "Fitbone™", improves on several weaknesses of the ISKD method, and is the most technologicallyadvanced option thus far.

Developed in Germanyby Augustin Betzand Rainer Baumgart, the first successful operations were performed in 1996and the technique was patentedin 1997. Thus far, most of the surgeries using this method have been performed in Munich, Germanyby Baumgart and Peter Thaller. Since 2001, however, the surgery has also been performed in Tan Tock Seng Hospital, Singapore, and in Bumrungrad Hospital, Bangkok.In December 2005 Fitbone surgery was done in Malaysia at the [Mahkota Orthopaedic Reconstruction and Limb lengthening center], Melaka by Thirukumaran Subramaniam and Jeyaratnam T Satkunasingam.

Fitbone comprises a telescopic nail implantthat can extend, powered by an electric motor and controlled by a receiver with an antennathat is buried under the skin; the receiver in turn is controlled by a hand-held radio-frequencytransmitter. The procedure for lengthening the lower leg is as follows:

• A two-centimetre incision is made at the patient's knee, and a rimmer is used to create enough space in the bone for a stainless steel nail.
• The bone is broken about 14 cm below the knee from the inside with an internal saw.
• The stainless steel nail is held in place by two screws. The top of the nail is attached to a tiny, plastic-encased receiverthat is placed under the skin.
• The patient controls the lengthening process. By pushing a button on the transmitter when it is placed against the antenna, the built-in motor extends the nail one millimetre per day. When the leg has grown to the desired length, lengthening stops, and the bone is allowed to solidify.
• The device can be removed about two years after the initial surgery.

This convenient scar-free procedure, however, comes at a price. While the Ilizarov external fixatorcosts USD$4,000, and the ISKD implant about USD$8,500, the Fitbone device carries a price tag of USD$12,000 (all prices exclusive of surgery costs).

Image:Fitbone surgery.jpg

Post-surgical care

Following the initial surgery, patients must undergo a demanding physiotherapyregime comprising stretching exercisesand at times, they may be required to be hooked up to a "continuous passive motion" device. The purpose is to avoid stiffness and to stimulate the muscles, nervesand blood vesselsto grow alongside the bone. Patients are often prescribed painkillersand are unable to work while undergoing rehabilitation.

Possible uses of distraction osteogenesis

Although distraction osteogenesis is most often used in the treatment of post-traumaticinjuries, it is increasingly used to correct limb discrepancies caused by congenital conditionsand old injuries. A list of the possible uses of distraction osteogenesis are as follows:

• Congenital deformities (birth defects):
  • Congenital short femur;
  • Fibular hemimelia(absence of the fibula, which is one of the two bones between the knee and the ankle);
  • Hemiatrophy(atrophyof half of the body); and
  • Olliers disease.

• Developmental deformities
  • Neurofibromatosis(a rare condition which causes overgrowth in one leg); and
  • Bow legs, resulting from ricketsor secondary arthritis.

• Post-traumatic injuries
  • Growth platesfractures;
  • Malunion or non-union (when bones do not completely join, or join in a faulty position after a fracture);
  • Shortening and deformity; and
  • Bone defects.

• Infections and diseases
  • Osteomyelitis(a bone infection, usually caused by bacteria);
  • Septic arthritis(infections or bacterial arthritis); and
  • Poliomyelitis(a viraldisease which may result in the atrophy of muscles, causing permanent deformity).

• After tumors

• Short stature
  • Achondroplasia(a form of dwarfismwhere arms and legs are very short, but torsois more normal in size); and
  • Constitutional short stature.

Cosmetic lengthening of limbs

Generally, doctors tend to discourage cosmeticlengthening for people who wants to add a couple of inches to their frames because such people are:

• breaking perfectly functional limbs;
• consigning themselves unnecessarily to crutchesor a wheelchairfor over a year;
• voluntarily subjecting themselves to pain and discomfort;
• exposing themselves to unnecessary risk of infections, of damaged nerves and blood vessels, and fat embolismthat can result in death; and
• incurring unnecessary expenses as the procedure is not cheap.

People insistent on doing the procedure, however, are required to undergo a thorough body imageassessmentby a psychologistto help determine how far the person's quality of life has been affected by his perceived lack of height, and if doing the surgery will make a marked difference. The entire evaluation, which includes in-depth doctor-patient discussions, usually takes months during which time, the doctors hope that their patients will change their minds.

Given the advent of fully internal limb-lengthening devices like Fitbone, and the emphasis that modern society places on looking good, doctors are aware that the demand for cosmetic lengthening can only go up.

References

• New Sunday Times, Malaysia. 9 October 2005.

External links

• Distraction Osteogenesis informationfrom Seattle Children's Hospital Craniofacial Center
• Introduction to Distraction Osteogenesis by Dr. Martin Chin, D.D.S.
• Previous history of Prof. Betz?s Fitbone™-Surgeryms:Osteogenesis peregangan

This article is licensed under the GNU Free Documentation License.
It uses material from the http://en.wikipedia.org/wiki/Distraction+osteogenesis Wikipedia article Distraction osteogenesis.