Accurate placement of glenoid components in reverse and total shoulder arthroplasty has been shown to reduce the risk of implant failure (1, 2, 6). Surgical techniques and literature describe methods to determine favorable positions for implant placement (3, 4, 5) but achieving that position surgically remains a challenge. Placement of glenoid components is faced with the challenge of variable glenoid morphology on which conventional instrumentation does not always provide a reliable reference (6, 7, 8). Limited surgical exposure is another challenge since many anatomic landmarks are not visible to the surgeon to use as spacial reference. Anatomic landmarks and angles can be more reliabily selected on CT scans with 3-dimentional reconstruction (9,10) yet few methods allow for the reproducible translation of these plans to surgery. Navigation has produced better accuracy and lower variability than conventional instrumentation (11), yet its regular usage remains limited, especially in the shoulder. A patient specific planning and guiding system has been developed for glenoid implant placement of total and reverse shoulder arthoplasty procedures. This method allows for preoperative planning on a patient specific virtual 3D model of the scapula derived from CT images (Figure 1), and guided placement of a pin which which serves as the central axis for determining proper implant position. An initial implant position was presented on the virtual model based on the methods described by the surgical technique of the corresponding procedure. These plans were either approved or adapted to a desired position within the planning software by the surgeons. Using this planned position as input, patient specific surgical guides were created which fit onto the exposed anatomy and guide the drilling of the pin (Figure 1). This method was tested on 14 cadavers, with attention directed to translation of the starting point from the original plan, the ability to reproduce the intended degree of inferior tilt, and the ability to reproduce the glenoid version angle.Background and Motivation
Methods
Humeral implant design in shoulder arthroplasty has evolved over the years. The third generation shoulder prostheses have an anatomic humeral stem that replicates the 3-dimensional parameters of the proximal humerus. The overall complication rate has decreased as a result of these changes in implant design. In contrast, the rate of periprosthetic humeral fractures has increased. To avoid stem-related complications while retaining the advantages of the third generation of shoulder implants, the stemless total evolutive shoulder system has been developed. The indications, the surgical technique, and the complications of this humeral implant in shoulder arthroplasty will be described.
