FitboneTM Trochanteric

The FitboneTM Trochanteric is a fully implantable intramedullary lengthening nail designed to lengthen the femur in adult and pediatric patients (ages 12–21 years). The nail is implanted into the femur's medullary canal and connected to an external receiver placed under the skin; an external transmitter wirelessly activates an internal motor to gradually lengthen the nail through distraction. The device is available in two diameter sizes (9mm and 11mm) with varying lengths and lengthening capabilities.

The subject device is made of implant-grade stainless steel (1.4441 AISI 316LVM) and silicone (Nusilmed), with nail lengths ranging from 217–357mm (compared to predicate 225–365mm). The key design change is a modification from 3 screw holes to 2 screw holes in the distal tail of the nail. Maximum distraction capability ranges from 40mm to 80mm depending on nail length, identical to the predicate. The electromagnetic distraction mechanism and gas plasma sterilization method are identical to the predicate.

ASTM F138-13 (wrought stainless steel bar and wire for surgical implants UNS S31673), ASTM F899-20 (wrought stainless steels for surgical instruments), and silicone material specifications (NuSil MED-4870, MED-1511, MED 4750, MED1-161, MED2-4502). Static cantilever bending testing was performed on subject nails compared to the original predicate design and reference device PRECICE.

The subject device has identical intended use, anatomical site (femur), materials, sterilization method, and distraction mechanism as the predicate K233867. The sole design modification (2 holes versus 3 holes in the distal tail) does not affect the validity of prior testing results. Static cantilever bending tests demonstrated that this geometric change maintains substantial equivalency with the predicate and reference devices, and the worst-case maximum distraction (80mm) is identical to the predicate.