Total hip replacement (THR) is a commonly performed procedure to relieve pain and improve function from arthritis or traumatic injury. However, implant failure can occur from fretting corrosion at the head-stem modular junction. Modular implants are almost always used due to added surgical flexibility and ease of future revision. Studies show that damage at the head-stem modular junction starts mechanically, and mechanical damage leads to eventual chemical corrosion or combined chemical/mechanical modes of fretting corrosion. Implant design and material factors are likely contributors to the progression of mechanical to chemical damage. The mechanical damage occurs because of small relative motions between the contacting surfaces of the modular junction, termed micromotion. The head must be properly seated onto the stem during surgery to avoid micromotion. Despite the significant risk of damage with improper assembly, the literature and educational material for the orthopedic community fails to include any consensus as to how the surgeon should perform head-stem assembly that will minimize the risk of damage. The long-term goal of this work is to maximize the longevity of the modular THR by introducing an assembly protocol and provide recommendations to implant manufacturers to improve patient outcomes and inform future taper designs. The study's objective is to determine the effect that surgeon experience and surface topography, an implant design factor, influence the risk for micromotion between the modular junction surfaces. The central hypothesis is that insufficient dynamic loading applied to the femoral head during assembly leads to less favorable taper contact mechanics, which change depending on surface topography. A multidisciplinary approach will be used to test this hypothesis, including benchtop THR assembly and finite element analysis (FEA). The goal of Aim 1 is to characterize the differences in dynamic load magnitude and direction applied during THR assembly by surgeons of varying experience. Aim 2 will develop a 3D FEA model of the modular junction to determine how applied load magnitude, direction, and surface topography influence modular junction stability. Collectively, the aims will yield new insight into how to properly assemble THRs to lower the risk of failure.