LIMB LENGTHENING METHODS – LON, RING APPARATUSES, AND MONOLATERAL APPARATUSES

Extension over an intramedullary nail (LON) – procedure description

Lengthening over a nail (LON) is a procedure designed to lengthen bones that are shorter than normal due to trauma, growth disorders, or congenital defects. The goal of treating bone defects is to achieve equal limb length. This is important not only for aesthetic reasons but also for functional ones.

The method of lengthening over an intramedullary nail was developed to reduce the duration of external fixation. It involves placing a small-diameter metal nail in the middle of the bone, in addition to the external fixator mounted around the limb. The wires and tips of the external fixator are strategically positioned in the bone so that they do not come into contact with the intramedullary nail.

Once the desired bone length has been achieved, the intramedullary nail is locked in place with screws to prevent shortening of the limb; the external fixator can then be removed. The nail remaining in the medullary canal stabilizes the bone during the remodeling of the bone callus into mature, hard bone tissue.

The technique of lengthening over an intramedullary nail represented a major step forward. However, with the advent of modern, magnetically driven telescopic lengthening nails (Precice), it has become significantly less common. Today, it is used mainly in countries where the Precice system is not available.

Limb lengthening using ring plates

External fixators are metal devices that are attached to the bones of the arm, leg, or foot using threaded wires or pins. The wires or pins are inserted through the skin and muscles into the bone. Most of the device is located outside the body, which is why it is called an external fixator.

External fixators are used to gradually lengthen bones, correct bone deformities, or reduce stress on a joint during distraction. During the procedure, the surgeon makes small incisions and then inserts wires or pins into the bone. A frame is then attached to these wires or pins using clamps and rods.

After the procedure, a waiting period of 5 to 7 days is observed to allow repair processes to begin between the bone segments. The distraction phase then begins. The bone segments are gradually separated at a rate of about 1 mm per day, and the gap is filled with newly formed bone tissue—bone regenerate.

Types of external stabilizers – annular and monolateral

External ring fixators consist of two or more rings or half-rings that encircle the affected arm, leg, or foot. The rings are connected by rods, wires, or pins. One example of a ring fixator is the Ilizarov fixator.

External monolateral (clamp-type) stabilizers consist of a single straight splint placed on one side of the affected arm, leg, or foot. The splint is secured to the bone using screws, which are often coated with hydroxyapatite to improve osseointegration.