Long-term results of posterior cruciate-substituting total knee arthroplasty.

Posterior cruciate ligament-substituting total knee prostheses have been used extensively since the original posterior-stabilized condylar prosthesis was introduced more than 2 decades ago. The key design principle of this prosthesis was the incorporation of a cam and post mechanism on the femoral and tibial components. This mechanism was intended to function as a mechanical substitute for the posterior cruciate ligament, to optimize prosthesis roll back in flexion, and to avoid flexion instability by preventing posterior subluxation. Central to the use of these devices was the surgical technique, which required resection of both cruciate ligaments and creation of symmetric flexion and extension gaps with equal medial and lateral soft tissue tension. Modifications to the original design have been introduced gradually; these include changes to the patellofemoral geometry, and the addition of monoblock and modular metal-backed tibial components. Despite these changes, the key concepts of the prosthesis design and surgical technique have remained constant. The clinical results obtained with the use of these designs have been reported extensively. Long-term results at greater than 10 years continue to duplicate the outstanding early results with prosthesis survivorship exceeding 95% and high levels of patient function.