Preoperative Planning and Patient-specific Instrumentation for Total Shoulder Replacement
It is my belief that every surgery should be approached to meet the needs of the individual patient. Each patient has unique anatomy. In the case of shoulder replacements, the size, shape, and orientation of the glenoid or socket can vary. A successful outcome depends on matching the anatomic needs of each patient. Preoperative planning and Patient-specific instrumentation (PSI) facilitate this process and I believe provide a critical part of obtaining a long-lasting good outcome. In addition to improving component position, this process facilitates a more efficient and less-invasive procedure. Below is an overview of my process for preoperative planning and PSI.
Problems with Implant Positioning
Over the past several decades there have been significant advances in the implants used in shoulder arthroplasty. Despite this, improper positioning of a shoulder implants, particular of the glenoid (the socket component) can occur. This is because compared to the hip or the knee, visualization of the shoulder is more limited. Improper positioning of the glenoid component can result in problems such as:
- Incomplete contact of the component with the bone
- Early loosening
- Scapular notching
- Perforation of the glenoid
- Cement extravasation
Studies evaluating preoperative planning have demonstrated the understanding of anatomy or bony deformity is improved with advanced imaging. Plain x-rays provide a good overview, but understanding is improved with further imaging such as MRI or CT scans. In particular 3D CT scans provide important information prior to shoulder replacement. In a sense, the plain x-ray provides the “30,000 foot view” and the CT provides the fine detail.
Once a CT scan is obtained the images are uploaded in a special software program. In most cases I use a system called VIP (Virtual Implant Positioning). which allows me to better understand a particular patient’s anatomy, and then “virtually implant” the desired component in the desired position. In a sense, the procedure is performed virtually before it takes place. Studies have shown this step improves component position, particularly if there is significant bony deformity.
In addition to planning, in some cases patient-specific instrumentation (PSI) is used to place the component. PSI has been shown to improve component position when there is significant deformity of the glenoid or socket. Once the CT is uploaded and the implant is virtually placed, a plan is produced and a targeting device can be used to place the components. The device allows me to accurately place shoulder implant in terms of position and orientation.