Limb lengthening is distraction ostegenesis, also called callus distraction, a surgical process used for reconstruction of skeletal deformities, and for lengthening bones. Limb lengthening is a procedure in which a bone segment is surgically cut and a distraction device is used to slowly pull the two ends apart. After the desired limb extension has been achieved the bone consolidates until the lengthened gap has completely calcified.
The limb lengthening procedure works by gradually growing new bone and soft tissues (skin, muscle, nerves, blood vessels, etc). This new growth is called tissue regeneration. In this limb lengthening operation, bone and soft tissue regenerate when they are distracted (pulled apart) at a very slow rate of approximately 1 mm per day. If the rate of distraction is faster than this, bone may fail to form between the two ends of the bone that are being pulled apart and soft tissues, such as muscle, may experience contracture (get too tight) or nerves may become paralyzed. If the rate of distraction is too slow, premature consolidation may occur (the bone may consolidate too soon), preventing the lengthening device from further pulling it apart. There are many different lengthening devices used. The most common are external fixators, which are devices that attach to the bone by means of thin wires or thicker pins that have a screw threading at their attachment to the bone. There are also lengthening devices that are fully implanted inside the bone. These devices do not require external pins. The different devices are described separately.
There are two phases of lengthening until the bone is fully healed: the distraction phase and the consolidation phase.
A variety of orthopedic devices are used to distract the bone and soft tissues. The decision regarding which device to use is individualized for each case, so that the best method to achieve the desired correction can be chosen. There are two general types of devices: external fixators and internal fixators. The external devices attach to the bone from outside the body by means of wires and threaded pins. The internal devices are implanted inside the body and lie on the bone or inside the marrow cavity of the bone. The best known and most versatile techniques are with monolateral (one-sided or straight bar) external fixators (e.g., Orthofix, EBI) and circular external fixators (e.g., Ilizarov, TSF). External fixators are applicable to almost all cases. To shorten the time in the external fixator, doctors often combine the external fixator method with an internal nail to perform the lengthening over nail (LON) technique. This method is not applicable to all cases.
The most popular and widely used device is the Ilizarov apparatus which was designed by Ilizarov. Circular frames are connected by thin wires at multiple panels.
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