Total knee replacement: surgical technique and instrumentation.

The surgical technique and instrumentation of four systems of total knee replacement, two with intramedullary and two with extramedullary alignment systems, are discussed. The differences between the instrumentations, their advantages and disadvantages, and the basic 'philosophy' of each technique are compared in four 'crucial' operative stages, determinant for the final result: the anteroposterior and distal femoral osteotomies, the tibial osteotomy, and the mechanical axis. In expert hands the two systems are equally reliable. In our experience, the extramedullary system with the tensor is more versatile. The stages are more dependent on the surgeon than on the instruments, and the tensor enables the surgeon to control and balance the level of osteotomy and the soft-tissue release every time. The intramedullary femoral alignment system seems simpler: each step is a direct consequence of the previous one, except the first step, which is, of course, entrusted to the experience of the surgeon. The fact that each stage is predetermined may reduce the chances of error in less skilled hands.