Abstract
Bi-cruciate-retaining (BCR) total knee arthroplasty (TKA), which retains both the anterior (ACL) and posterior cruciate (PCL) ligaments, serves as an alternative to the traditional TKA procedure. Despite the difficulty of ensuring the structural integrity of the prosthesis, the BCR TKA can yield improved patient outcomes such as range of motion, kinematics, and even the survivorship of the implant. When possible, BCR TKA can and should be considered as a viable option to treat end-stage arthritis of the knee. Reconsidering the frequency of the BCR TKA is necessary for several reasons. Patient outcomes following BCR TKA are similar to outcomes for mobile-bearing UKA. Patients with an intact ACL do better with preservation (UKA or BCR TKA) of the ACL. The corollary is also true that removing an intact ACL at the time of arthroplasty has worse outcomes than traditional TKA in patients with an absent ACL. Reported outcomes of BCR TKA include more normal knee function, excellent prosthetic survivorship, and greater patient satisfaction. The BCR TKA may provide a missing link in the continuum of constraint for primary knee arthroplasty.
Many early BCR designs fell out of favor because of high rates of prosthetic loosening, and because the procedure was more technically demanding than that of highly successful ACL-sacrificing TKA devices. Recently there has been a reemergence of the BCR arthroplasty concept with improvements in design. By retaining both the ACL and PCL, BCR TKA patients show more normal knee function and flexibility due to anterior stability and replication of the physiological tension in the ACL. Modern BCR TKA models have improved upon early designs but are limited in use mainly due to the lack of an optimal prosthesis design and the relative difficulty of the surgical procedure.
Bi-cruciate-retaining TKA is a viable procedure if an appropriate femorotibial gap can be created to mimic physiological tension of the ACL and PCL. In terms of the surgical technique, the procedure begins with femoral preparation to facilitate tibial preparation. Distal femoral resection is performed first taking care to avoid damage to the ACL. Femoral preparation is then completed with a four-in-one guide that incorporates a protector to ensure the ACL is not resected. Good exposure is essential to tibial preparation, which is the critical part of the procedure and involves several steps of setting the depth of resection, and making accurate cuts to protect the tibial eminence island of bone and set tibial component rotation. The medial and lateral tibial cuts must be absolutely parallel. Precise cement technique is required for the tibial baseplate, and care must be taken when trialing the dual bearings.
Normal kinematics are preserved when both the ACL and PCL remain intact. Bi-cruciate-retaining TKA knees have been shown to restore more normal kinematics and have better “feel” than traditional ACL-sacrificing TKA knees. Bilateral TKA patients with designs of both types prefer their BCR TKA to their ACL-sacrificing TKA more often than not. An intact ACL has been shown to be present in 60–80% of arthritic knees, further justifying the consideration to retain both cruciate ligaments during TKA. New materials and refined instrumentation and techniques have helped improve the viability of BCR TKA, which may represent an additional option in the continuum of constraint for knee arthroplasty.
