Managing Glenoid Deformity in Shoulder Arthroplasty: Role of New Technology (Computer-Assisted Navigation and Patient-Specific Instrumentation).

The glenoid is considered a weak link in total shoulder arthroplasty because failure on the glenoid side is one of the most common reasons for revision of total shoulder arthroplasty. Glenoid wear is commonly seen in glenohumeral arthritis and compromises glenoid bone stock and also alters the native version and inclination of the glenoid. It is critical to recognize glenoid wear and correct it intraoperatively to avoid component malposition, which can negatively affect the survivorship of the glenoid implant. The end point of correction for the glenoid wear in shoulder arthroplasty is controversial, but anatomic glenoid component positioning is likely to improve long-term survivorship of the total shoulder arthroplasty. Preoperative three-dimensional (3-D) computer planning software, based on CT, is commercially available. It allows the surgeon to plan implant type (anatomic versus reverse), size, and position on the glenoid, and also allows for templating deformity correction using bone graft and/or augments. Guidance technology in the form of computer-assisted surgery (CAS) and patient-specific instrumentation (PSI) allows the surgeon to execute the preoperative plan during surgery with a greater degree of accuracy and precision and has shown superiority to standard instrumentation. However, the proposed benefits of this technology including improved glenoid survivorship, reduced revision arthroplasty rate and cost-effectiveness have not yet been demonstrated clinically. In this review, we present the current evidence regarding PSI and CAS in managing glenoid deformity in total shoulder arthroplasty.