4
IM NAILING
Michael Blauth, Christopher Finkemeier
TFN-ADVANCED PROXIMAL FEMORAL NAILING SYSTEM (TFNA) Although PFNA and TFN nailing systems have been successfully used in the past, several clinical issues for improvement have been identified by surgeons and engineers. Many of these issues have now been addressed and solved by implant and instrument design changes incorporated into the new TFNA nailing system. The complications of penetration or anterior cortical impingement while using long intramedullary nails for pertrochanteric femur fractures are due to a mismatch of the femoral antecurvation with the radius of curvature (ROC) of currently available cephalomedullary nails. Bazylewicz et al [1] reported that most of the intramedullary nails with a ROC of 1800 mm ended up in the anterior half of the space available for the nail with 16% within 3 mm of the anterior cortex. Patients that are shorter and/or have an increased femoral bow as measured on a lateral x-ray are more likely to have an anterior nail tip position or cortical impingement [2]. To thoroughly investigate this issue, a comprehensive 3D computer graphical anatomy study of the femur was conducted to serve as a basis for a new nail design [3]. Analyzing 27 Caucasian and 13 Japanese subjects, the ROC resulted in 962±157 mm (Caucasian subjects) and 790±151 mm (Japanese subjects). These results indicate significant differences between ethnicities and that the ROC should be closer to these values instead of 1500 mm, which is a frequently chosen radius in current nail systems on the market. The new TFNA has a radius of curvature of 1000 mm to improve the anatomical fit and to help avoid impingement of the anterior cortex (Fig 1).
Fig 1 The TFNA nail, illustrated in green, has a 1000 mm ROC and perfectly follows the antecurvation of most femurs. The blue nail demonstrates a less favorable fit of a simulated nail with 1500 mm ROC.
AOTK SYSTEM INNOVATIONS 2015