Distraction osteogenesis

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Distraction osteogenesis is a surgical process for the reconstruction of skeletal deformities and for the lengthening of bones. A bone fracture is 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.

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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 facial skeletal reconstruction.

[edit] Ilizarov surgery

See main article at Ilizarov apparatus

Ilizarov surgery, developed by Gavriel Ilizarov, a Russian orthopedic surgeon, in 1951, is the oldest and most common method of distraction osteogenesis. The process involves the following:

  • Shattered bones and devascularised ones 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;
  • Screws attached to the middle bone are turned 1 millimetre (mm) per day, so that new bone tissues that are formed in the growth zone are gradually pulled apart to decrease the gap (One millimetre has been found to be the optimal bone 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 steel rings weighing up to 7 kilogram (kg), but newer models are made of carbon, which though lighter, are equally cumbersome.

For decades, the Ilizarov 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.

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[edit] Intramedullary skeletal kinetic distractor

In 2001, the "Intramedullary Skeletal Kinetic Distractor" (ISKD) was introduced, allowing lengthening to take place internally, thereby drastically reducing the risk of infections and scarring. The ISKD device was designed by Dr. J. Dean Cole, MD of Orlando, FL.

With ISKD, a telescopic rod that can be gradually extended by knee or ankle rotations is implanted into the bone. Lengthening is monitored by a hand-held external magnetic sensor that tracks the rotation of an internal magnet on a daily basis.

ISKD requires a physical leg movement to "click" 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. This risk is easily overcome with proper patient education and patient compliance with regards to utilizing the magnetic monitor.

While there is some pain associated with the immediate post-op lengthening, it is important to realize that the initial lengthening procedure is not to begin until one week after surgery. Furthermore, there is no noticeable "click" to the patient as there is less that nine degrees of rotation of the two bone segements in relation to one another. Patients who follow the post-op protocol typically experience less discomfort than those utilizing the Ilizarov technique because the daily length is achieved with many tiny adjustments as opposed to just four. This also allows for a greater length to be obtained on a daily basis.

[edit] Fitbone surgery

A new form of surgery, involving a fully implantable, electronically-motorised limb-lengthening device, called "Fitbone™", improves on several weaknesses of the ISKD method, and is the most technologically advanced option thus far. Nevertheless, this technology has not been submitted for FDA approval in the USA.

Developed in Germany by Augustin Betz and Rainer Baumgart, the first successful operations were performed in 1996 and the technique was patented in 1997. Thus far, most of the surgeries using this method have been performed in Munich, Germany by Baumgart and Peter Thaller. The first successful surgeries in Asia has been performed since 2001 by Dr Sarbjit Singh in Tan Tock Seng Hospital, Singapore, and Dr Sittiporn, 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 implant that can extend, powered by an electric motor and controlled by a receiver with an antenna that is buried under the skin; the receiver in turn is controlled by a hand-held radio-frequency transmitter. 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 receiver that 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 procedure, however, comes at a price. While the Ilizarov external fixator costs USD$4,000, and the ISKD implant about USD$8,000, the Fitbone device carries a price tag of USD$12,000 (all prices exclusive of surgery costs).

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[edit] Post-surgical care

Following the initial surgery, patients must undergo a demanding physiotherapy regime comprising stretching exercises and 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, nerves and blood vessels to grow alongside the bone. Patients are often prescribed painkillers and are unable to work while undergoing rehabilitation.

[edit] Possible uses of distraction osteogenesis

Although distraction osteogenesis is most often used in the treatment of post-traumatic injuries, it is increasingly used to correct limb discrepancies caused by congenital conditions and 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 (atrophy of half of the body); and
    • Olliers disease.
  • Post-traumatic injuries
    • Growth plates fractures;
    • 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.

[edit] Cosmetic lengthening of limbs

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

  • breaking perfectly functional limbs;
  • consigning themselves unnecessarily to crutches or a wheelchair for 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 embolism that 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 image assessment by a psychologist to 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 ISKD, and the emphasis that modern society places on looking good, doctors are aware that the demand for cosmetic lengthening can only go up.

[edit] References

  • New Sunday Times, Malaysia. 9 October 2005.

[edit] External links

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