Implications of minimally invasive surgery and CAOS to TKR design

Abstract

Based on the long-term follow-up data of some of the earlier designs, and the gradual evolution in design since then, the evidence is that today's knee replacements can provide satisfactory function for one to two decades or even longer. This applies whether posterior cruciate retaining or substituting, whether fixed bearing or mobile bearing. However all of the long-term data was obtained for standard incisions giving full exposure, and mechanical instrumentation using intra-medullary or extra-medullary guides for overall alignment. The relatively small percentages of failures were due mainly to misalignment and instability and, in some circumstances, to polyethylene wear. With the recent introduction of MIS and CAOS, an important question is the impact that these new surgical modalities will have on total knee design, and on the short and long-term results. Early experience with smaller incisions with less invasion of muscle tissue has shown advantages in the recovery period, but disadvantages at the time of surgery due to the more limited exposure. In fact, the required space for placing the jigs and fixtures and accessing the saw blades, and the size of present total knee components, places a lower limit on the size of the incision. © 2007 Springer Medizin Verlag Heidelberg.