ACL substitution may improve kinematics of PCL-retaining total knee arthroplasty
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One of the key factors responsible for altered kinematics and joint stability following contemporary total knee arthroplasty (TKA) is resection of the anterior cruciate ligament (ACL). However, ACL retention can present several technical challenges, and in some cases may not be viable due to an absent or nonfunctional ACL. Therefore, the goal of this research was to investigate whether substitution of the ACL through an anterior post mechanism could improve kinematic deficits of contemporary posterior cruciate ligament (PCL) retaining implants.
Kinematic analysis of different implant types was done using KneeSIM, a previously established dynamic simulation tool. Walking, stair-ascent, chair-sit, and deep knee bend were simulated for an ACL-substituting (PCL-retaining) design, a bi-cruciate-retaining and ACL-sacrificing (PCL-retaining) implant, as well as the native knee. The motion of the femoral condyles relative to the tibia was recorded for kinematic comparisons.
The ACL-substituting and ACL-retaining implants provided similar kinematic improvements over the ACL-sacrificing implant, by reducing posterior femoral shift in extension and preventing paradoxical anterior sliding. During all simulated activities, the ACL-sacrificing implant showed between 7 and 8 mm of posterior shift in extension in contrast to the ACL-retaining implant and the ACL-substituting design, which showed overall kinematic trends similar to the native knee.
The absence of ACL function has been linked to abnormal kinematics and joint stability in patients with contemporary TKA. ACL-substituting implants could be a valuable treatment option capable of overcoming the limitations of contemporary TKA, particularly when retaining the native ACL is not feasible or is challenging.
KeywordsTotal knee arthroplasty ACL substitution Kinematics Dynamic simulation
The work reported herein was supported by departmental grants at Massachusetts general Hospital. The authors would also like to thank Rajan Patel for technical assistance with various aspects of the analysis.
All authors contributed to the implant concept described herein, and the study design. Authors TZ, MPD, and KMV conducted the implant design and simulation work. Authors HER and HM gave clinical inputs and assisted with cadaver surgeries. Author OKM gave advice regarding material strength and testing of the implant design. Authors TZ and KMV wrote the manuscript, and all authors read and provided feedback on various aspects of the manuscript.
Compliance with ethical standards
Conflict of interest
One or more co-authors are listed inventors on a patent application related to the technology analysed as part of this research.
This study was funded in part by departmental research grant.
Although this study did not involve human participants, it made use of data collected from past studies involving human subjects. All such past studies were in accordance with the ethical standards of the institutional and/or national research committee, and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
Although this study did not involve human participants, it made use of data collected from past studies involving human subjects. Informed consent was obtained from all individual participants included in these prior studies.
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