A soft-tissue preserving method for evaluating the impact of posterior tibial slope on kinematics during cruciate-retaining total knee arthroplasty: A validation study.

BACKGROUND: The reconstructed posterior tibial slope (PTS) plays a significant role in restoring knee kinematics in cruciate-retaining total knee arthroplasty. However, conventional methods for the investigation of PTS can be limited by sample size or prone to errors due to damages to the bone and/or soft tissues. The purpose of this study was to validate a novel method for the evaluation of the effects of PTS on knee kinematics.

METHODS: Seven computer-assisted cruciate-retaining TKAs were performed by two surgeons on healthy cadaveric knees. The implanted tibial baseplates allowed precise and easy modification of the PTS in situ. Knee kinematics were evaluated during passive full range of motion test. The evaluation was performed three times at each of the five PTSs in the order of 10°, seven degrees, four degrees, one degree, and back to ten degrees. The variability of the repeated measurements, inter-surgeon variation of the data, and test reproducibility were investigated.

RESULTS: The test method was shown to be highly repeatable (low root-mean-squared errors) and has low sensitivity to surgeon variability (ANOVA). No statistical difference was found in the knee kinematics between the first and last measurements at 10° PTS (paired t-test).

CONCLUSION: The results suggested that the developed method can be used to investigate the impact of PTS on knee kinematics without disrupting the soft-tissue environment of the knee. The use of the novel tibial baseplate allowed for adjusting the PTS without re-cutting the tibia and removing the components. The method may be applied to improve the future investigation of PTS.