Knee Joint Replacements

Conclusion

Due to the absence of a unique center of rotation, the knee requires more complex geometry in its prosthetic replacement. The relative motions of the components are a combination of rolling and sliding, so causing a much more complex wear, whose debris remain trapped between articulating surfaces, producing three-body wear. Contact areas smaller than in total hip prosthesis can lead to more pronounced creep and greater possibility of local fatigue cracks developing. Where there is severe loss of articular cartilage but the normal bony structure is preserved, procedures that involve lowest resection of bone from both the femur and the tibia must be utilized, because the implant designs that require a great deal of excavation, so producing large cavities in the femur and in the tibia, leave relatively insufficient bone stock for revision or arthrodesis. Long stems require a large amount of intramedullary cement for fixation that may create difficulties in case of infection. If a prosthetic component becomes loose, the cement attached to it may abrade and destroy the surrounding bone and create an even larger cavity, which makes revision impossible or arthrodesis difficult to achieve. Finally, it is essential to restore the normal tibiofemoral valgus angle, because an eccentrically loaded tibial component on either the medial or lateral aspect can produce uneven wear and early loosening. So, jigs and guides which make it as easy as possible to resect the bone surfaces with precision have to be available. At present, there is a multitude of implants on the market. The selection of a prosthesis depends on many factors, including the surgeon’s preference and his familiarity with the device.