Central Head Perforation, or "Cut Through," Caused by the Helical Blade of the Proximal Femoral Nail Antirotation

Objective: This study was designed to investigate the specific type and incidence of implant failure in patients with a proximal femur fracture treated with a proximal femoral nail antirotation. This device has a helical-shaped blade as a neck-head holding device, instead of the lag screw used in other intramedullary nails. The advantage of the blade is believed to originate from bone impaction and a larger bone-implant interface in comparison with the lag screw design, with consequential greater mechanical resistance to torsion in the cancellous bone. Patients and Methods: This is a retrospective cohort study conducted at the state hospital of Winterthur, Switzerland. From December 2006 until November 2008, 210 consecutive patients were treated with a pertrochanteric femur fracture (OTA type 31-A1, 31-A2, and 31-A3) using a proximal femoral nail antirotation. One hundred and twelve patients were followed up clinically for a minimum of 12 months after discharge. Clinical and radiologic assessment of fracture healing and/or implant failure was investigated. Results: We report 7 cases of implant failure with a "Cut Through," defined as a postoperative central perforation of the spiral blade into the hip joint, without any displacement of the neck-head fragment. Conclusions: Cut through needs to be distinguished from the well-known anterocranial perforation combined with a varus displacement of the neck-head fragment, known as "Cut Out," seen with intramedullary nails utilizing lag screws.