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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 distraction 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 were anecdotal reports that the nail was not able to lengthen against too much force. A version of his mechanism is contracted to Smith and Nephew and awaits FDA clearance and release.

Ellipse Technologies (Ellipse Technologies, Irvine, CA) developed the Precice nail with a team of surgeons headed by Dr Stuart Green. Ellipse used the same mechanism that they had developed for their spinal growing rod called “the MAGEC System.”31 There is a magnetic metal spindle that is connected to a series of gears (Fig. 2). 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) device (Fig. 3). 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 FDAcleared implantable lengthening nail device (July 2011) and the first one to have bidirectional control (lengthening and shortening). I had the privilege of implanting the first Precice nail in the United States on December 1, 2011. The initial experience with this device in the United States and several countries around the world has been excellent. Nevertheless, there have been many lessons from the learning curve of this device. The purpose of the rest of this paper is to review the surgical technique and lessons from the first 65 nails implanted in a consecutive series of 48 patients at a single center.

PRECICE NAIL

The Precice 1 nail used in this study is made up of 2 parts that are connected together by the surgeon; the modular locking segment and the rest of the nail, which contains the mechanism and the telescopic parts. The mechanism housing is welded to the rest of the larger diameter tube of the nail. There are a total of 3 welds in the larger diameter tube of the nail and 1 set screw connection point to add various type and length insertion segments. The fully constructed nail is available in lengths of 230, 255, 280, 305, 330, and 355 mm. To change the length, different locking segments are used. The maximum distraction (stroke) for each of these nails is 6.5 cm.

Preoperative planning is important before surgery to determine the ideal nail length, insertion point (eg, trochanteric vs. piriformis), osteotomy level, and direction of the nail (antegrade vs. retrograde). The nail length and osteotomy level are very interrelated. To avoid too much friction the osteotomy level is planned to leave 1 to 3 cm of the wider tube of the nail engaged in the opposite segment of the bone (this is explained in detail below). When there is a larger femoral bow we prefer to make the osteotomy at the level of the apex of the bow. Working backwards this can help calculate the ideal length of the nail to use. In most cases a relatively short nail is used compared with nailing for fixation of fractures. The femur can be reamed with flexible or straight rigid reamers. The latter are less available and less forgiving. However, they conform to the shape of the nail better and are preferred if available. Piriformis start is preferred in most adult femurs unless there is a coxa breva or valga. In children with open proximal femoral physes, a trochanteric start point is preferred to minimize the risk of avascular necrosis. Retrograde nailing is used in the femur in conjunction with angular deformity correction of the distal femur or if there is a quadriceps lag that needs to be tightened (1 case in the series below had retrograde nailing for the quadriceps lag). Retrograde tibial nailing is used in patients with pantalar arthrodesis.