Is a helical shaped implant a superior alternative to the Dynamic Hip Screw for unstable femoral neck fractures? A biomechanical investigation

Internal fixation of fragility fracturesof the femoral neck

“…Another solution is to let a distally fastened strap override a trochanteric device before attaching it to the jig at the superior aspect. In this way, both the abductors and the iliotibial tract are simulated (Krischak et al 2007, Windolf et al 2009, Roderer et al 2010. The posteriorly directed torque is considered important in enhancing micromotions potentially leading to loosening of the implant, particularly concerning femoral stems.…”

“…Using human cadaver femurs are still regarded the gold standard by most researchers when conducting laboratory experiments on hip fracture fixation (Linden et al 2006, Windolf et al 2009, von der Roderer et al 2010. Cadaver femurs reflect the great variation in strength and anthropometry found in vivo.…”

“…A screw's holding power is determined by its inner and outer diameter, the pitch (distance between threads), depth and length of the screw threads , Ramaswamy et al 2010. The helical blade theoretically reduces the removal of bone during implant-insertion and increases the load-bearing surface with respect to conventional screw threads (Windolf et al 2009). Rigid angular-stable locking of screws within a plate results in no movement between the different components of the implant.…”

Does PFNA II Avoid Lateral Cortex Impingement for Unstable Peritrochanteric Fractures?

“…Positioning of the intramedullary device close to the weightbearing axis of the femur reduces forces on the implant. The primary innovation of the proximal femoral nail antirotation (PFNA, AO/ASIF) design is the helical neck blade that reduces the risk of bone loss and offers improved purchase in the femoral head as a result of compaction of cancellous bone around the blade during insertion [35,36,41]. Rotation of the head-blade combination as a whole is prevented by an intrinsic locking mechanism [3,38].…”

Comment on Stern et al.: Prospective randomised study comparing screw versus helical blade in the treatment of low-energy trochanteric fractures

“…Improved rotational stability along with better anchorage in a cancellous environment is supposed to reduce the risk of screw cut-out, delayed union and varus malunion. The higher resistance of helical blade to heavy loads and reduced chance of screw cut-out has been made evident by various anatomical and biomechanical studies [2][3][4][5]. However the proposed benefits of helical blade have not been construed by any clinical studies to demand a change in the conventional practice.…”