An interface device and method for interfacing instruments to a vascular access simulation system serve to interface peripherals in the form of mock or actual medical instruments to the simulation system to enable simulation of medical procedures. The interface device includes a catheter unit assembly for receiving a catheter needle assembly, and a skin traction mechanism to simulate placing skin in traction or manipulating other anatomical sites for performing a medical procedure. The catheter needle assembly and skin traction mechanism are manipulated by a user during a medical procedure. The catheter unit assembly includes a base, a housing, a bearing assembly and a shaft that receives the catheter needle assembly. The bearing assembly enables translation of the catheter needle assembly, and includes bearings that enable the shaft to translate in accordance with manipulation of the catheter needle assembly. The shaft typically includes an encoder to measure translational motion of a needle of the catheter needle assembly, while the interface device further includes encoders to measure manipulation of the catheter needle assembly in various degrees of freedom (e.g., translation, pitch and yaw) and the skin traction mechanism. Alternatively, the shaft may include an additional encoder to measure translational motion of an instrument inserted through the catheter needle assembly. The simulation system receives measurements from the interface device encoders and updates the simulation and display, while providing control signals to the force feedback device to enable application of force feedback to the catheter needle assembly.