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Inger B. Schipper, Roger K.J. Simmermacher, Tobias Hüttl, Röbi Frigg, Peter Messmer, Michael Schütz, Andreas Lenich, Chris van der Werken |
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Background: The Proximal Femoral Nail® (PFN) has an extra hip pin in the head-neck fragment, to prevent rotation of the fracture fragments. However, this hip pin brought along two unexpected complications: medial migration and cutout. In order to reduce the risk of migration and cutout, the hip pin should bear no or minimal load. For this reason, a modified PFN (mPFN) prototype was developed, with an oval instead of a round hole in the nail through which the hip pin passes. Under load-bearing conditions the hip pin could angulate, thereby reducing its load, but maintaining its antirotational function.
Material and Methods: A multicenter observational study was initiated, to investigate the handling of the mPFN, the stability and strength of the construct, the incidence and type of implant-related complications, and whether the angulating hip pin concept functioned in clinical practice.
Results: In six European teaching hospitals 250 patients with unstable trochanteric fractures were included and treated with the mPFN prototype. Handling was found to be equal to the use of the regular PFN. No breakage of the nail at the side of the oval hole was documented. The cutout risk was practically, but not completely, eliminated, if reduction of the fracture and position of fixation were adequate. Medial migration was no longer documented.
Conclusion: The angulation concept with the oval hole in the intramedullary nail of the mPFN worked in clinical practice, and helped further reducing the risk of specific implant-related complications.
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