Three-dimensional planning and use of patient-specific instrumentation (PSI) in total shoulder arthroplasty

Three-dimensional (3D) templating of the glenoid in total shoulder arthroplasty allows for more accurate planning and better positioning of the glenoid component through an improved understanding of the pathologic glenoid morphology, version, and inclination in reference to an idealized calculated glenoid position. Loosening of the glenoid component remains the most common mode of late failure after anatomic total shoulder arthroplasty. Reasons for malposition of the glenoid component might be inaccurate assessment of the pathologic anatomy of the glenoid, incorrect choice and/or position of the implant to correct the pathologic condition, and inaccurate surgical execution of the preoperative plan. Because of the limitations of standard radiographs, many surgeons use two-dimensional (2D) CT scans to evaluate glenoid morphology and version. However, multiple studies have shown that 3D CT scans are more accurate and reliable than 2D scans, particularly in the face of advanced osseous defects. With the use of 3D CT templating, the surgeon can select the implant and define the optimal placement of that implant to correct the pathologic condition. We describe the available commercial systems used for advanced 3D CT templating, the principles of planning and the procedure.