TechniquesThe “Norris PSI”: 3D Planning and Patient-specific Instruments for Reconstruction of Large Glenoid Defects and Reverse Shoulder ArthroplastyEid, Karim MD*; Haefeli, Mathias MD*; Norris, Tom R. MD†Author Information *Center for Orthopaedic Surgery, State Hospitals Aarau and Baden, Baden, Switzerland †San Francisco Shoulder, Elbow and Hand Clinic, San Francisco, CA The authors declare no conflict of interest. Reprints: Karim Eid, MD, Center for Orthopaedic Surgery, State Hospitals Aarau and Baden, Im Ergel, 5404 Baden, Switzerland (e-mail: [email protected]). Techniques in Shoulder & Elbow Surgery: June 2018 - Volume 19 - Issue 2 - p 62-66 doi: 10.1097/BTE.0000000000000128 Buy Metrics Abstract Large glenoid defects after revision surgery for total arthroplasty of the shoulder impose a surgical challenge. The use of a tricortical bone graft from the iliac crest has been advocated to restore osseous integrity between the scapular bone and the glenoid baseplate. However, in the absence of osseous landmarks correct base plate implantation regarding inclination and version is extremely difficult. A new technique for a staged exchange of a chronically infected shoulder prosthesis is described. After removal of all implants, 3-dimensional (3D) computed tomographies of the scapula and of the ipsilateral pelvis were obtained. A 3D model of the glenoid defect was generated and “transposed” to the 3D model of the iliac crest. Implantation of the baseplate into the pelvic bone and resection of the pelvic bone block were both guided by patient-specific instruments (PSI). The glenoid base plate and the pelvic bone block were transferred to the native glenoid. Press fit was immediately achieved and fixation screws were placed with the PSI-drill guides. Postoperative radiologic assessment showed accurate implantation of the glenoid baseplate within 5 degrees of the preoperatively planned position for inclination and version. Combined preoperative 3D planning and the use of PSI allow precise bony reconstruction and implantation of glenoid baseplate even in difficult revision cases. Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved.