The History of Limb Lengthening Implants

The Limbplastx Institute • Las Vegas, Nevada

Implantable limb lengthening using noninvasively adjusted telescopic nails dates back to 1983. The latest, most advanced limb lengthening implant is the PRECICE 2.2 Nail from Nuvasive® that is used by LimbplastX. A retrospective study of the first version of the 65 PRECICE nails was carried out for the treatment of limb length discrepancies (unilateral) and for short stature (bilateral). Successful lengthening was achieved in all patients. Numerous lengthening and hardware complications in early versions of implantable nails have been resolved with continued development.

Surgical limb lengthening dates back to the turn of the 20th century. Over the first half of the 20th century, the lengthening devices ranged from the traction Thomas splint device of Codivilla, to various bed mounted and semiportable external fixation devices. The early limb lengtheners employed distraction osteogenesis, the natural re-generation of bone to fill gaps in bones, to fill the distraction gap produced by external fixators. It was not, however, until the 1950s and 1960s that the biology of distraction osteogenesis became understood. This was largely due to Ilizarov and his group in Kurgan, USSR. Despite their ability to predictably achieve desired length, external fixators were and remain plagued by high complication rates including pin-tract infections, risks of deep infections, neurovascular injuries, prolonged treatment time until removal, muscular and soft-tissue transfixation that leads to contractures and stiffness, pain and discomfort, re-fracture of bones after removal of the fixators, physical awkwardness as well as the psychosocial burden and requirement to perform daily pin cleaning.

Due to the numerous, significant problems with external fixators, several means for lengthening limbs with internal devices were conceived. Implantable limb lengthening using distraction osteogenesis also takes it origins in the Soviet Union. Alexander Bliskunov from Sinferopel, Ukraine first published his method in 1983. This was before most of the western world had heard of Ilizarov. Bliskunov developed a telescopic lengthening nail that used a crankshaft connected to the pelvis to drive his mechanism and lengthen the femur. Rotational motion of the femur produced lengthening of the nail. The rotation was through the hip joint and not through the surgical break in the bone. His technology was not available outside of the Soviet Union. Even today it is only used by a few medical practitioners in Ukraine.

Fitbone Nail
Other implantable lengthening nails have been developed over the last 30 years. Baumgart and Betz from Germany developed a motorized nail in 1991 (now called Fitbone). The Fitbone is a fully implantable lengthening nail whose mechanism is driven by an internal motor that requires an external transmitter. An antenna comes out of one end of the nail and is implanted beneath the skin. It is powered and controlled by a radio remote control and the lengthening is performed at night when the patient is in bed to mimic natural growth. Data for this device is limited, as there are only 3 studies in English literature that have reviewed a total of 37 implants, although they report good overall results. One study reported that 2 patients required bone grafting after their procedure. They also had 2 implants that needed to be removed and exchanged for large diameter implants because the gears in the original nails were not strong enough to achieve adequate lengthening. Another study reported that 2/12 nails had faulty motors that required reoperation and only 1 patient required a later bone graft procedure.

The Gradual Lengthening Nail: Albizzia / Guichet Nail
Guichet and Grammont from France, developed a telescopic nail in 1994 using a ratchet mechanism which rotates the 2 sections of the nail through the break in the separated bone. The Gradual Lengthening Nail also known as Albizzia was later modified and released as the Betzbone and the Guichet nail. It takes 20 degrees of rotation to move the ratchet one notch. Each notch is 1/15 of a millimeter. Many reports exist of patients suffering from severe pain and discomfort, which limit their ability to independently perform the lengthenings. In some cases, these patients required re-admission to a hospital with general anesthesia and closed manipulation. In other reports, 12% of the lengthenings remained incomplete because the patients were simply unable to tolerate the pain of the manipulation.

The Intramedullary Skeletal Kinetic Distractor (ISKD) - REMOVED FROM MARKET
Using the same concept of lengthening by rotation through the surgical break in the bone, Cole developed a double-clutch mechanism to cause lengthening. Only 3 to 9 degrees of rotation was required to cause the nail to lengthen. The Intramedullary Skeletal Kinetic Distractor (ISKD) was FDA approved in 2001. It was recently removed from the market and is no longer available. As the lengthening was so easy to activate, and as there was no “governor” to the lengthening mechanism, the nail was free to lengthen at any rate. Too rapid distraction was a frequent complication. Due to uncontrolled lengthening rates the ISKD had a very high complication rate. The nail would often lengthen at a rate that exceeded the ability for bone to regenerate and soft tissues to grow and expand leading to many complications. Restriction of activities and bracing were required to try and prevent and control overly rapid lengthening. Failure of bone formation required separate bone grafting procedures.

The Phenix Nail System
Arnaud Soubieran from France developed the Phenix nail. The Phenix has a mechanism activated by a large external, hand-held magnet. By rotating the magnet around the leg an internal crankshaft mechanism in the nail was rotated. This lead to traction on a wire pulley, which caused lengthening of the nail. The mechanism for the Phenix was first used in a spinal distractor, and, in a lengthening prosthesis manufactured by the same company. Rotating the magnet one direction leads to lengthening, whereas rotating it the other way leads to shortening. This device was self marketed by Soubieran until 2012 at the time of his accidental death. The Phenix produced excellent results in the small number of cases in which it was used. There was anecdotal reporting that the nail was not able to lengthen against too much force. A version of this mechanism is contracted to Smith and Nephew and awaits FDA clearance and release.

The PRECICE Nail System
Nuvasive developed the PRECICE nail with a team of surgeons headed by Dr. Stuart Green. Nuvasive used the same mechanism that they had developed for their spinal growing rod called “the MAGEC System.” There is a magnetic metal spindle that is connected to a series of gears. The gears are connected to a coupling, which is connected to a threaded drive shaft. The mechanism is activated by an external remote control (ERC). The ERC employs 2 motor-driven rotating magnets to magnetically couple to and rotate the magnetic metal pins. The ERC performs 30 revolutions per minute. It takes 7 minutes and 210 revolutions to achieve 1mm of lengthening. Facing the ERC 1 direction causes the nail to lengthen, whereas facing it the other direction would go in the reverse (shortening) direction. The PRECICE is the second FDA cleared implantable lengthening nail device (July 2011) and the first one to have bidirectional control (lengthening and shortening). The initial experience with this device in the United States and several countries around the world has been excellent.