Minimum invasive, minimum scar, correct curvature legs simultaneously and established surgical method to minimize x-shaped leg occur. LON is a method first introduced in the mid-1990s by Dr. Paley. During 1st stage surgery, an intramedullary nail is inserted at the same time as the external fixator, so during the lengthening period intramedullary nail prevent angular deformity. And when lengthening is complete, the external fixator can be removed with the completion of the internal fixation(screw insertion). This method was a groundbreaking development compared to the original method that only involved the use of an external fixator (Ilizarov). Even today, many limb lengthening surgeons around the world use this method.
Rehabilitation period shorten over 6 weeks compared to LON, possible to return back to everyday life quickly, abundant bone regeneration formation. In the case of LATN, during 1st stage surgery, only an external fixator is installed, and after full lengthening, during 2nd stage surgery, the external fixator is removed and an intramedullary nail is inserted. During 1st stage surgery, future space needed for the internal rod needs to be considered when determining the positions for the external fixator pins. Also, the correction process before 2nd stage surgery requires much knowledge and care from the doctor. Rather than simply using the Ilizarov, computer assisted fixator systems like the Hexapod or ORTHO SUV must be used for accurate correction. Also, since the intramedullary nail is inserted during 2nd state surgery, the fixation is much stronger, and the rate of callus production accelerates after 2nd stage. A large advantage of LATN is that bone formation is fast and because of strong internal fixation, compared to LON, patients can return to normal activity 2 or more months faster. Also, since it undergoes a correction process, precise bone alignment can be met. One drawback is that the amount of time wearing the external fixator may be 2 or 3 weeks longer than LON, because of the correction process.
Traditional limb lengthening methods involving external fixators like the Ilizarov often result in complications regarding pin insertion. The most frequently occurring complication is pin-site infection, 2-80% being minor and up to 23% being major. Long-term developments in such methods have reduced various complications, but the inconvenience of wearing an external fixator for a long period of time and pin-related complications (pain, infection, stress, joint contrature) still remain a problem.
LON (Lengthening Over Nail) and LATN (Lengthening And Then Nail) are hybrid techniques that includes the advantages of both external and internal fixation. However, even with this method, an external fixator must be worn during the lengthening period, so complications caused by external fixation cannot be avoided. In LON, since the external fixator and the intramedullary nail are installed at the same time, there is a risk of minor pin-site infections leading to Intramedullary infections(the risk can be reduced to nearly 0% with careful management). Intramedullary lengthening methods not involving external fixators can reduce this risk of infection, reduce pain and ugly scars and also reduce the mental stress experienced by patients. Hence, since 1959, the hopeful development of such methods was attempted, but clinical practices were minimal. Currently, clinically well known Intramedullary lengthening devices are Albizzia® (France), Fitbone® (Germany), ISKD® (Intramedullary Skeletal Kinetic Diatractor; Orthofix, USA), and PRECICE nail® (Ellipse, USA).
In 1987, Dr Guichet from France developed a mechanical device (Albizzia®) that activates by torsional motion, and each rachet was designed to lengthen 0.07 mm. Later, clinical applications were successful, but much more rotational motion was necessary for at least 20 degrees of racheting movement required for lengthening. Pain resulted from this motion, and this became a drawback of the device. Later, Dr. Baumgart and Betz from Germany developed a motorized electronic nail (Fitbone®) which did not require rotational motion of the leg for lengthening, so pain was reduced to a large scale. Theoretically, Fitbone® has the advantage that the electronic activation method can precisely control lengthening rate and rhythm, but this is not been thoroughly proven. ISKD® was developed by Dr. Cole of the USA in 1995. Theoretical advantages are that small amounts of rotation (3-9 degrees) can activate racheting, which means that daily movement can activate lengthening and pain caused by the large motions needed for Albizzia is reduced. Also, lengthening rates can be seen on a monitor and controlled by patients. But clinical results of ISKD report that one significant drawback is the difficulty of controlling lengthening rate. Especially for femur lengthening, insufficient bone regeneration caused by unexpectedly high rates of lengthening (run away) has been reported, up to 25%. Rozbruch reported that femur lengthening with ISKD demonstrated an average lengthening rate of 1.9 mm/day, and that callus formation was not good compared to LON. Also, it has been reported that slow lengthening rates have led to premature consolidation and that unexpected additional surgeries have been required due to hardware malfunction. Currently, PRECICE® (Ellipse, USA), a device activated by a magnetic field, is being used under the approval of the FDA. This device does not require any racheting motion, precise rate control is possible, and shortening is also possible. However, clinical results of have not been proven yet. Future development in this area is foreseen to a great extent.