Posterior cruciate ligament-retaining, posterior stabilized, and varus/valgus posterior stabilized constrained articulations in total knee arthroplasty.

The degree of constraint required to achieve immediate and long-term stability in total knee arthroplasty (TKA) is frequently debated, with most authors favoring the least degree of constraint possible. There are generally three surgical biases in TKA involving the posterior cruciate ligament (PCL): surgeons who always retain the PCL, those who always sacrifice it, and those who decide to retain or sacrifice the PCL based on pathology. Surgeons who retain the PCL argue that it is one of the strongest ligaments about the knee and affords inherent stability to the TKA, whereas the proponents of PCL sacrifice argue that the PCL is compromised as a result of the degenerative process. With the pathologic approach, the diseased state of the knee at the time of arthroplasty dictates whether the PCL is retained or sacrificed. In patients without significant varus or valgus malalignment and without significant flexion, contracture may be addressed by retaining the PCL, whereas the PCL should be removed in patients with these deformities. Certain disease processes are more amendable to PCL sacrifice, such as end-stage degenerative joint disease secondary to rheumatoid arthritis, previous patellectomy, previous high tibial osteotomy or distal femoral osteotomy, and posttraumatic arthritis with disruption of the PCL. The degree of constraint of the articulation in TKA should be dictated by the degree of disease and associated deformity. A pathologic approach is rational and has clinically based evidence of success. Surgeons should have the option of modifying the degree of constraint at the time of surgical intervention. Currently, many TKA implant systems offer such flexibility.