Critical steps in total knee arthroplasty. A method of analyzing operative procedures.

We have analyzed the operation of knee arthroplasty using the Whiteside Mark II prosthesis, and found that it could be broken down into 42 steps, some of which are more important than others and can be considered as critical. We have identified 4 criteria to evaluate a critical step: 1) it must be necessary to complete the procedure, 2) it must take a significantly longer time to perform than other steps, 3) it must be revised significantly more frequently than other steps and 4) it must take significantly longer to revise than other steps. Two steps have been found to which all 4 criteria applied, namely placement of the femoral cutting jig and the first femoral saw cuts.