Like many innovative concepts, orthopedic robot and navigation technology are still in transition, looking for the best match between the new technologies and clinical needs. From that field, two technologies — semi-active (collaborative) orthopedic robot and patient-specific templating — are currently attracting most of the attention. Coupled with less-invasive surgical techniques and innovative implant design, they offer new opportunities for surgeons to develop more reliable, efficient and accurate practices.
Although the idea of patient-specific templating was introduced by Radermacher in the early 90s, it has not been widely recognized in the joint reconstruction community until recently. This concept combines three-dimensional surgical planning with rapid design and manufacturing of custom templates. These templates uniquely mate with the bone and incorporate drilling or cutting guides consistent with the surgical plan. Because all the planning and preparation is performed before surgery, this approach shortens the preparation time in the operating room and significantly reduces instrumentation.
The idea for patient-specific templating was originally introduced in spine surgery for pedicle screw placement, using CT-based planning, and did not appear to be practical for joint replacement. Since the mating surfaces have to be clearly visible in the CT scan, any areas with cartilage would not be suitable as mating surfaces and the template would have to mate with the extra-articular cortical bone. Wider surgical access — to reach extra-articular bone — and larger incisions were required and that was not clinically acceptable.
Recently introduced systems circumvent this requirement and allow the templates to be directly applied to the joint surface, permitting less-invasive techniques. A number of systems have been introduced that incorporate similar basic principles of templating.. During surgery, the surgeon must remove any remaining cartilage until the articular bone is exposed in order to create a correct mating surface. This approach is coupled with a patient-specific custom resurfacing implant that can be uni- or bicompartmental or for total knee arthroplasty.
There is an approach that relies on MRI imaging to capture the patient-specific knee anatomy, including the cartilage. Based on the surgical plan, custom-fitted positioning guides are designed and manufactured using rapid prototyping technology. These templates are used to guide the insertion of pins which in turn guide standard cutting guides.
In other approaches, the cutting guides are already incorporated into templates. All these templating systems require that the CT or MRI images are acquired in advance of surgery, sent to the manufacturer for image processing and pre-planning. After the surgeon’s finalization and approval of the surgical plan, the manufacturer produces the templates and ships them in sterile packaging to be used in surgery.
Another significant recent development is a new class of “semi-active” robots. These systems combine the awareness and flexibility strengths of the surgeon and the advantages of accuracy, precision and rapid reaction through robotic technology. Compared to conventional robots, they offer a much more user-friendly platform, acting more like intelligent tools. Combined with the novel bone-sparing implants, particularly those for knee resurfacing, they could simplify difficult and heavily instrumented procedures while making them less invasive and more accurate.
All of these new technologies are also beginning to inspire and enable a new generation of implants – patient-specific and bone-sparing, permitting the development of a new generation of minimally invasive techniques for both large and small joint reconstruction surgery.