2.1. Xin1 System
The Xin1 technology is a generic, X-ray-based tracking and navigation concept, designed to assist implant positioning in various orthopedic applications. The underlying principle is based on feature extraction from projections of cylindrical holes in X-ray images for determining the spatial alignment of the implant and anatomy. It was first described by Windolf et al. [For proximal humeral plating, a stainless-steel marker comprising three cylindrical holes arranged in a defined pattern and two polymer clamps is clipped on a drill sleeve which is attached to a conventional anatomic locking plate (PHILOS ref: 441.901, DePuy Synthes Inc., Raynham, MA, USA) (