Distraction osteogenesis

Distraction osteogenesis, also called callus distraction, callotasis and osteodistraction is a surgical process used to reconstruct skeletal deformities and lengthen the long bones of the body. A corticotomy is used to fracture the bone into two segments, and the two bone ends of the bone are gradually moved apart during the distraction phase, allowing new bone to form in the gap. When the desired or possible length is reached, a consolidation phase follows in which the bone is allowed to keep healing. Distraction osteogenesis has the benefit of simultaneously increasing bone length and the volume of surrounding soft tissues.

Although distraction technology has been used mainly in the field of orthopedics, early results in rats and humans indicate that the process can be applied to correct deformities of the jaw. These techniques are now utilised extensively by Maxillofacial surgeons for the correction of micrognathia, midface, and fronto-orbital hypoplasia in patients with craniofacial deformities.

History
In 1905, Alessandro Codivilla introduced surgical practices for lengthening of the lower limbs. Early techniques had a high number of complications, particularly during healing, and often resulted in a failure to achieve the goal of the surgery.

The breakthrough came with a technique introduced by Russian orthopedic surgeon Gavril Ilizarov. Ilizarov developed a procedure based on the biology of the bone and on the ability of the surrounding soft-tissues to regenerate under tension; the technique involved an external fixator, the Ilizarov apparatus, structured as a modular ring. Although the types of complications remained the same (infection, the most common complication ocurring particularly along the pin tracks, pain, nerve and soft tissue irritation ) the Ilizarov technique reduced the frequency and severity of the complications. The Ilizarov technique made the surgery safer, and allowed the goal of lengthening the limb to be achieved.

Difficulties raising during distraction osteogenesis
Difficulties that may raise during distraction osteogenesis, are commonly classified in medical scientific literature, according to the standard introduced by professor Dror Paley in a 1990 article. Paley distinguished among problems (defined as "a difficulty that arises during the distraction or fixation period that is fully resolved by the end of the treatment period by non operative means"), obstacles, and complications.

Using exclusively an external fixator
The most common is the Ilizarov surgery with the Ilizarov external fixator. Other external fixators are Wagner, Orthofix and Judet. Dr. Helong Bai (8th Hospital in Chongqing, China) developed the technique "Micro-wound" with a different apparatus.

Ilizarov surgery
Ilizarov surgery, developed by Gavriel Ilizarov, a Russian orthopedic surgeon, in 1951, is the oldest and most common method of distraction osteogenesis. It often brings complications, while some new methods have a much lower rate of complications.

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 less painful (albeit more expensive) alternatives.

Combining external fixator and intramedullary nail
Drs. Paley and Herzenberg pioneered in 1990 "Lengthening Over Nails" (LON). 

Using exclusively an intramedullary nail
The techniques that use an intramedullary nail without an external fixator are: Albizzia, Bliskunov, Fitbone and ISKD. 

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 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, 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 than nine degrees of rotation of the two bone segments in relation to one another.

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 have 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. Dr. Bruce Foster of Adelaide, Austarlia, chairman of the "Bone Growth Foundation" - a charity established with the aim of helping children with crippling bone growth problems - is currently the only surgeon that uses the FITBONE device in the southern hemisphere.

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 cut 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 approximately USD$4,000, and the ISKD implant about USD$8,000, the Fitbone device carries a price tag of roughly USD$12,000 (all prices exclusive of surgery costs).

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.

Solid bone regeneration
The most important aspects for the success of bone distraction are an intact medullary blood supply, preservation of soft-tissue envelope, primarily the periosteum (which helps preserve the blood supply) and secondarly bone marrow and the stability of the fixator.

Distraction rate
The distraction rate must be gradual, as a rapid rate of distraction will result in a fibrous union in which the bone pieces are joined by fibrous, rather than osseous tissue.

Too slow of a distraction rate would result in early bone consolidation. A common distraction rate for lower limbs is 1 millimeter per day.

Complications
In a 2004 study lenghening with an exclusively intramedullary nail (Albizzia) had a "significant lower rate" of complications respect to exclusively external methods (Judet, Orthofix, Ilizarov and Wagner fixators).

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
 * Ollier's disease.
 * Developmental deformities
 * Neurofibromatosis (a rare condition which causes overgrowth in one leg); and
 * Bow legs, resulting from rickets or secondary arthritis.
 * 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.
 * Infections and diseases
 * Osteomyelitis (a bone infection, usually caused by bacteria);
 * Septic arthritis (infections or bacterial arthritis); and
 * Poliomyelitis (a viral disease which may result in the atrophy of muscles, causing permanent deformity).
 * After tumors
 * Short stature
 * Achondroplasia (a form of dwarfism where arms and legs are very short, but torso is more normal in size); and
 * Constitutional short stature.

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 relatively expensive.

People insistent on doing the procedure, however, are required by some doctors 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.