Limb Lengthening : Distraction Phase
The process of limb lengthening, popularized by Gavriil Ilizarov’s principles, follows a three-phase sequence: the Latency Phase, the Distraction Phase, and the Consolidation Phase. This page will delve into the technicalities of the Distraction Phase, also known as the lengthening phase.
After a well-performed osteotomy (a surgical procedure where the bone is cut) and an adequate latency period (a period of rest allowing the initiation of a healing response), the Distraction Phase begins. This phase involves the gradual and controlled lengthening of the bone.
Lengthening is achieved through the use of an external fixator or an internal device. Both systems are designed to apply tension that results in distraction at the osteotomy site. The rate and rhythm of distraction are essential considerations during this phase.
-
Distraction Rate:
The distraction rate is typically set at approximately 1mm per day. This rate, as per the Ilizarov principles, ensures that new bone, called “regenerate,” is formed in the gap created by the distraction. This slow, progressive lengthening is critical in allowing the body to adjust to the changes, minimizing potential complications such as joint contractures and nerve damage. However, the optimal rate may vary depending on the patient’s age, the bone involved, and the individual’s response to the lengthening process.
-
Distraction Rhythm:
In addition to the distraction rate, the rhythm or frequency of distraction is also crucial. Typically, the lengthening is divided into small increments performed multiple times a day. This method is preferred over a single daily lengthening, as it has been shown to enhance the formation and quality of the regenerate bone.
During the distraction phase, the bone ends are gradually pulled apart, but new bone starts to form from the center and ends of the osteotomy site due to the bone’s natural healing process and the phenomenon of distraction osteogenesis. The process of bone formation during this phase is relatively soft and somewhat vulnerable, hence it’s sometimes referred to as the “soft callus” stage.
Constant monitoring is paramount during this phase to assess the formation of the new bone and to identify potential complications early. Regular radiographic examinations are used to visualize and assess the development of the regenerate bone.
The length of the distraction phase will depend on the amount of lengthening desired. Once the desired length has been achieved, the process will be stopped, leading into the next phase, the consolidation phase, during which the newly formed bone hardens and matures.
In conclusion, the distraction phase in limb lengthening is a meticulous process that requires a fine balance of precision and patience. It is a testament to the body’s remarkable capacity for adaptation and regeneration, guided by the expert hands of the orthopedic surgeon and the sophisticated design of modern lengthening devices.