Intramedullary Limb Lengthening by Stuart A. Green & Mark T. Dahl

Author:Stuart A. Green & Mark T. Dahl
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

Follow-up research, performed years later, showed that many patients subjected to this procedure developed knee joint problems in later life [3].

Valgus Prophylaxis with Intramedullary Lengthening Nails

Of necessity, an intramedullary lengthening nail elongates a femur along the axis of the implant—the centerline of the marrow canal. Thus, as with the Wagner external fixator, the knee and distal femur is pushed medially during lengthening.

To overcome this problem, Baumgart, the developer of the Fitbone® self-lengthening nail, devised a distally based (“retrograde”) nail insertion strategy to correct for the anticipated valgus angulation at the time of nail insertion. He calls this method “reverse planning,” because Baumgart originally used paper cutouts of the femur and tibia to trace the path of the angular correction needed to restore the knee to its proper relationship with the biomechanical axis of the limb [4].

His method works with any intramedullary lengthening nail system and should be considered in any femoral lengthening over 3 cm (Fig. 6.5).

Fig. 6.5The Baumgart reverse planning method for preventing valgization of the knee during intramedullary femoral lengthening. With paper cutouts or a computer program, transect the femur image at the planned level (a). Place the center of the femoral head along the upward extension of the biomechanical axis at the planned final length (b). Next, slide the shaft fragment down the biomechanical axis back to the osteotomy level, indicating the offset needed to correctly lengthen the bone (c-arrow). The completed elongation will have a zigzag in the shaft, but the alignment will be perfect (d). Copyright 2016 NuVasive

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