Since April 2010, Austin Orthopedic Institute’s Dr. Tyler Goldberg has utilized patient specific instrumentation (PSI) technology in nearly all of his total knee replacements. In fact, Dr. Goldberg was fortunate enough to be a part of the design team for PSI technology. He went on to teach the technology to surgeons all over the world. This article will give in-depth insight on PSI technology – know your result, before the operation!
There are essentially three techniques utilized to implant a total knee. The first is the conventional or standard technique. In this technique, alignment rods guide the surgeon to make the bony resections desired for the implant.
The second technique originated in the mid-1990s – Computer-Assisted Orthopedic Surgery (CAOS). With CAOS, anatomical landmarks of the patient are registered into a computer navigation system intra-operatively, which aids the surgeon in performing the total knee replacement. In addition, robotics may be added to the technology for increased precision.
Patient specific instrumentation is the newest of the three techniques, and was introduced in the late 2000s.
PSI utilizes a pre-operative X-ray, MRI, or CT scan of the lower extremity to create a three-dimensional model of the patient’s anatomy. This model is then used to preoperatively plan the patient’s surgery, implantation, and outcome. Once planned, unique patient-specific resection blocks are constructed utilizing 3-D printing and robotic technology.
The PSI technology that Dr. Goldberg helped develop is called MyKnee® by Medacta. He prefers to utilize a CT scan in order to recreate the patient’s anatomy. Once the CT is performed, it is uploaded into the proprietary software, at which point Medacta engineers and Dr. Goldberg collaborate to perform surgical planning.
Once the plan is validated, the cutting guides are printed and shipped to the hospital for use during the procedure. Medacta is based in Switzerland, so the process of planning the surgery, creating the guides, and shipping them overseas typically takes a few weeks.
Once the guides arrive, they are sterilized and used to make the bony resections required during surgery.
MyKnee® cutting guides are made of polyamide PA 2200, a medical-grade nylon manufactured using laser sintering technology, typical of rapid prototyping applications. Dr. Goldberg has published his results with this technology and given many lectures discussing its benefits. For example, in 2019, he published an article where he modeled the economic, logistical, and safety effects for PSI.