Conventional instruments in total knee replacement: what should we do with them?

The accuracy of implantation of knee replacement components depends on several factors; the design and accuracy of the instrumentation, the decisions taken on how the jigs are applied to the bone, the accuracy of the saw cuts, how well the components are seated on the bone and the accuracy and reliability of the imaging system used to assess the results. In most studies, computer-assisted replacement appears to outperform conventional instrumentation [l,2–4]. That is not to say that perfect placement is achieved in every case, but outliers are eliminated. In practical terms uptake of computer-assisted surgery is likely to be patchy and performed by technically adroit surgeons with an interest in the technique. Most surgeons are likely to continue to use conventional instrumentation either as suggested by the manufacturers or according to their own preferred modification. The resultant implantation will not be formally assessed save for the usual inadequate postoperative X-rays. Rather than abandoning conventional instrumentation in favour of navigation, instruments should be developed and used in novel ways to improve accuracy. From an engineering standpoint, current instrumentation is very accurate. The real issue is how it is employed. Manufacturers’ surgical manuals offer conflicting advice on how to perform a knee replacement as evidenced by a study of those which form the basis of this review. (Table 1) Similarly confusing is the current literature on the best way to employ the instrumentation.