Abstract
Introduction
Total knee arthroplasty (TKA) is the definitive treatment for osteoarthritis of the knee. The primary goal of the operation is to minimize or eliminate pain associated with osteoarthritis and secondarily to regain functional mobility and stability around the knee joint in order improve overall quality of life. The vast majority of techniques utilized for this procedure involves removal of the anterior cruciate ligament (ACL). In a native knee the ACL is a primary stabilizing ligament and essential for providing proprioceptive feedback. In the absence of the ACL, the kinematics of the knee are compromised. In an effort to more accurately replicate normal knee stability, new implant designs have emerged which maintain an intact ACL. Described herein is a cadaveric study looking at ACL competency after implantation of a TKA in which the cruciate ligaments are preserved.
Methods
Twenty fresh, frozen cadaveric knees were utilized in which the ACL was intact. Specimens were excluded if there was concern for ACL stability as determined by physical examination, direct visualization during the arthrotomy and a KT-1000 measurement of anterior tibial translation in millimeters at 67N and 89N of anterior force. Each KT-1000 measurement was repeated three times using three individual examiners at both force values for a total of six data points. Bicruciate retaining components were implanted into each knee using a medial parapatellar approach. After adequate sagittal and coronal balancing was obtained, the knee was reexamined using the KT-1000 protocol described above to assess for any changes in ACL competency. The ACL was then transected and the knee was examined for a third time with the same KT-1000 protocol. For statistical analysis, a 2-way repeated-measures ANOVA was utilized. Pairwise differences were assessed utilizing Fisher's least significant difference method.
Results
The KT-1000 measurement in millimeters of anterior tibial translation in relation to the femur provided the primary data points. The anterior translation of the tibia of the cadaveric knees before insertion of the components averaged 2.2mm at 67N of force and 3.6mm at 89N of force. After insertion of the components, the anterior tibial translation averaged 3.6mm at 67N of force and 5.0mm at 89N of force. After the ACL was transected, the averaged KT-1000 measurements were 6.8mm at 67N and 9.2mm at 89N of force.
Discussion and Conclusion
Significant debate remains regarding which knee implant provides the optimum outcome in patients undergoing total knee arthroplasty. As the indications for TKA continue to expand and younger more active patients, with higher post-operative performance expectations pursue surgical intervention for degenerative knee osteoarthritis, bicruciate-retaining designs have re-emerged as potential alternative to traditional implants. While this study does demonstrate an increase in anterior translation after implantation of the components, the amount of increased laxity is unlikely to be of clinical significance. Overall ACL integrity is maintained and joint stability preserved.
