Biomechanical Evaluation of Interlocking Lag Screw Design in Intramedullary Nailing of Unstable Pertrochanteric Fractures

Abstract

The interlocking lag screw design reduced movement of the femoral head and relative movement between fracture fragments. Beyond that the trapezoidal nail design of the Intertan reduced toggling within the trochanteric area and prolonged survival. Although this study showed a decrease in the retention of stability over time, failure did not occur until the equivalent of 2-3 months of reduced physical activity in which healing may have occurred under normal clinical conditions.

Locked minimally invasive plating versus fourth generation nailing in the treatment of AO/OTA 31A2.2 fractures: A biomechanical comparison of PCCP® and Intertan nail®

“…2). Decreasing stiffness during cyclic testing following fixation with the IT has been reported before [7,24].…”

“…Fractures of the lateral wall however, have not been reported even in case of failure, thus demonstrating the preservation of the lateral wall by this implant [15,19]. Whereas in an unstable femoral neck fracture model, the IT showed a similar failure mode with a fracture of the femoral neck extending into the trochanteric region [36], Hoffmann et al experienced loss of fixation and shaft stability which led to nail medialisation proximally [24]. This tendency was also noted in the current study before the fracture of the femoral neck lead to fracture collapse or cut-out occurred (Fig.…”

“…Using a similar fracture model, Hoffmann et al reported failure loads of 1600 N for the IT and 1400 N for the Gamma3 nail. However, the number of cycles was much higher in their study [24]. Failure loads for the PCCP in unstable trochanteric fracture models range between 800 N and 3700 N [17,18].…”

“…An oscillating saw was used to create a 3-part fracture with posteromedial comminution (AO/OTA type 31A2.2, Evans type IV) (Fig. 1) [24,28]. Symmetry in fracture patterns was assured visually and radiographically using a fine digital goniometer (Pollin electronic GmbH, Pfö rring, Germany, accuracy 0.38) [25].…”

“…This Intertan nail 1 (IT, Smith & Nephew, Memphis, TN, USA) uses an interlocking lag screw mechanism which allows linear intraoperative compression and rotational stability of the headneck fragment. Despite lacking clinical advantages compared with the SHS [22], recent biomechanical studies showed an increased strength, stiffness and resistance torque, compared with the PFNA and the Gamma3 nail [23,24]. However, a comparison of the biomechanical behaviour of the PCCP and the IT using an AO/OTA type 31A2.2 fracture model has not yet been performed.…”