Biomechanical Study of Acetabular Tridimensional Memoryalloy Fixation System

We developed the acetabular tridimensional memoryalloy fixation system (ATMFS), which is made of NiTi shape memory alloy, according to the specific mechanical properties of biological memory material, NiTi shape memory alloy and measured distribution of contact area and pressure between the acetabulum and the femoral head of cadaveric pelvis. Seven formalin-preserved cadaveric pelves were used for this investigation. Pressure-sensitive film was used to measure contact area and pressure within the anterior, superior, and posterior regions of the acetabulum. The pelves were loaded under the following four conditions: (1) intact; (2) following a creation posterior wall fracture defect; (3) following reduction and standard internal fixation with reconstruction plate; and (4) following reduction and internal fixation with a new shape memory alloy device named ATMFS. A posterior wall fracture was created along an arc of 40° to 90° about the acetabulur rim. Creation of a posterior wall defect resulted in increased load in the superior acetabulum (1485 N) as compared to the intact condition (748 N, P = 0.009). Following reduction and internal fixation, the load distributed to the superior acetabulum (1545 N) was not statistically different from the defect condition. Following the fixation with ATMFS, the load seen at the superior region of the actabulum (964 N) was familiar with fixation with reconstruction plate and was not different from intact state (P = 0.45). These data indicate that the use of ATMFS as a fracture internal fixation device resulted a partial restoration of joint loading parameters toward the intact state. ATMFS fixation may result in a clinical benefit.