Pertrochanteric Fracture Fixation In Elderly Adults Using Proximal Femoral Nail Anti-rotation (HERACLES) With a T-shaped Parallel Blade: A New Design

Overview

This is a prospective case series of elderly adult patients sustaining pertrochanteric fractures who will be treated by a proximal femoral nail with a non-helical (straight) blade. This study seeks to observe and evaluate the outcomes, advantages and complication rates in using the HERACLES PFN with a non-helical (T-shaped parallel) blade.

The trochanteric area is defined by AO as the area bordered by the tip of the greater trochanter, extracapsular portion of the femoral neck extending to a line parallel to the inferior most border of the lesser trochanter. Pertrochanteric fracture is a fracture is of the trochanteric area which is usually reducible. Unstable pertrochanteric fracture is defined as AO-31A2 or AO-31A3. Instability arises from the degree of comminution, the presence, and comminution of the posteromedial fragment and lastly, lateral wall involvement The ideal implant for fixation of this kind of fractures is still under debate, but intramedullary implants are preferred than extramedullary implants in these unstable fractures. On the other hand, unique fracture configurations predispose to instability such as reverse obliquity fractures and fractures extending to the subtrochanteric area. Proximal femoral locking plate as used in unstable pertrochanteric fracture has a high complication rate. In one study in 2014, there is up to 41.4% failure rate due to the proud plate, screw malposition, too rigid construct when used as a bridge plate. Intramedullary implants specifically cephalomedullary nails has been the mainstay of treatment in unstable pertrochanteric fractures primarily because of the short moment arm and load-sharing properties. It employs relative stability and can be applied in a minimally invasive manner. In 1997, the AO/ASIF group developed the proximal femoral nail. The proximal femoral nail has two proximal screws that traverse the neck to the femoral head. The inferior screw is the load-bearing screw, and the superior screw is the anti-rotation screw. Good to excellent results were observed using this implant compared to previous implant designs, but complications still exist. These complications are related to the position of the two screws. There is difficulty attaining the ideal placement of proximal locking screws. As a result, the early medial cutout of one screw and lateral migration of the second screw occurs which is the so-called Z-effect. To address these disadvantages, the AO/ASIF group in 2004 developed a new implant design wherein the two proximal locking screws are replaced by a single helical blade. This improvement in design maximizes bone purchase and bone contact in cancellous bone hereby improving cutout rates. Even with the new PFNA implant is not exempted from complications. Zhou and Chang in 2012 identified 12 cases of helical blade protrusion in 6 papers. Biomechanically, the helical blade migrates axially through the porotic bone in the geriatric population. The new design of the blade includes a T-shaped anchor for stable fixation in osteoporotic bone. The nail also features a flat lateral design with a smooth radius transition from proximal to distal portion of the nail compared to the bulky profile of conventional nail resulting in easier insertion. Locking mechanism inherent to the nail and blade limits gliding and rotation of the blade. One of the advantages of the system is the use of a radiolucent arm with targeting options for an anti-rotation pin and determination of the superior most aspect of the femoral head for reference. This case-series introduces a modification in implant design of the PFNA and aims to observe outcomes, advantages, and complications related to its use.