TKA Becomes More Precise With Computers, Robots
TKA Becomes More Precise With Computers, Robots
If the various approaches to knee replacement were arranged according to level of performance, freehand surgeries would be the base of a pyramid, CAS the middle, and robotic surgery the top, Drs. Raklewicz and Jinnah agree. Each heightened level of sophistication provides advantages for the patient and increased precision for the surgeon, they say.
CAS and robotic surgery eliminate the intramedullary alignment guide that must be pushed into the end of the femur when replacing knees freehand. These rods, which are associated with risks for microembolism and bleeding, are needed in order to measure alignment of the bones and prosthesis. Markers attached to the tibia and femur by pins and monitored by infrared cameras are used in their place when doing computer- and robot-assisted surgery. The cameras record the positions of the bones, which a computer then uses to precisely calculate bone alignment.
While substantially less imposing than the intramedullary guides that they replace, the pins have raised concerns about infection and weakened bone, potentially leading to fractures if the patient falls soon after surgery. Published research supports the improved alignment that results from use of these pins and discounts concerns about them.
Early experience at the Center for Computer Assisted and Reconstructive Surgery at New England Baptist Hospital by Dr. Stephen B. Murphy, associate professor of orthopedic surgery at Tufts University School of Medicine, Boston, Massachusetts, showed femoral component alignment of 0.4 degree of varus, tibial component alignment of 0.8 degree of valgus, and overall alignment of 0.4 degree of valgus. In this experience with 137 consecutive total knee replacements, reported at the 2004 meeting of the International Conference on Computer-Assisted Orthopaedic Surgery, 1 of the 548 pins became infected and another broke on insertion. Neither complication was serious.
The argument in favor of CAS would strengthen considerably if there were long-term data to support its use. Attempts to show midterm advantages on the basis of 5-7 years of experience have produced mixed results.
Research performed in Germany at the University of Aachen found no significant differences between freehand surgeries and CAS with regard to midterm clinical outcomes in 100 patients.In contrast, A collaborative study between Royal Perth Hospital in Australia and Brighton and Sussex University Hospitals in the United Kingdom demonstrated that total knee replacements performed under computer-assisted navigation decrease contact stresses and reduce abnormal wear patterns. The researchers speculated that this will reduce wear rates and increase structural longevity of the implant, although no clinical data were provided as support.
The case for using CAS, therefore, hinges on whether the surgeon believes that the increased precision possible with this technology translates into clinical advantages. Detracting from the argument is the failure of CAS to account for the soft tissues around the joint. These tissues are important in determining the long-term success of joint replacement, according to Dr. Jinnah, who notes that robotic surgery has no such shortcomings.
Surgical Hierarchy
If the various approaches to knee replacement were arranged according to level of performance, freehand surgeries would be the base of a pyramid, CAS the middle, and robotic surgery the top, Drs. Raklewicz and Jinnah agree. Each heightened level of sophistication provides advantages for the patient and increased precision for the surgeon, they say.
CAS and robotic surgery eliminate the intramedullary alignment guide that must be pushed into the end of the femur when replacing knees freehand. These rods, which are associated with risks for microembolism and bleeding, are needed in order to measure alignment of the bones and prosthesis. Markers attached to the tibia and femur by pins and monitored by infrared cameras are used in their place when doing computer- and robot-assisted surgery. The cameras record the positions of the bones, which a computer then uses to precisely calculate bone alignment.
While substantially less imposing than the intramedullary guides that they replace, the pins have raised concerns about infection and weakened bone, potentially leading to fractures if the patient falls soon after surgery. Published research supports the improved alignment that results from use of these pins and discounts concerns about them.
Early Experience
Early experience at the Center for Computer Assisted and Reconstructive Surgery at New England Baptist Hospital by Dr. Stephen B. Murphy, associate professor of orthopedic surgery at Tufts University School of Medicine, Boston, Massachusetts, showed femoral component alignment of 0.4 degree of varus, tibial component alignment of 0.8 degree of valgus, and overall alignment of 0.4 degree of valgus. In this experience with 137 consecutive total knee replacements, reported at the 2004 meeting of the International Conference on Computer-Assisted Orthopaedic Surgery, 1 of the 548 pins became infected and another broke on insertion. Neither complication was serious.
The argument in favor of CAS would strengthen considerably if there were long-term data to support its use. Attempts to show midterm advantages on the basis of 5-7 years of experience have produced mixed results.
Research performed in Germany at the University of Aachen found no significant differences between freehand surgeries and CAS with regard to midterm clinical outcomes in 100 patients.In contrast, A collaborative study between Royal Perth Hospital in Australia and Brighton and Sussex University Hospitals in the United Kingdom demonstrated that total knee replacements performed under computer-assisted navigation decrease contact stresses and reduce abnormal wear patterns. The researchers speculated that this will reduce wear rates and increase structural longevity of the implant, although no clinical data were provided as support.
The case for using CAS, therefore, hinges on whether the surgeon believes that the increased precision possible with this technology translates into clinical advantages. Detracting from the argument is the failure of CAS to account for the soft tissues around the joint. These tissues are important in determining the long-term success of joint replacement, according to Dr. Jinnah, who notes that robotic surgery has no such shortcomings.
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