Objective: The purpose of this study was to examine a procedure designed to judge the tibial posterior slope angle corresponding to the posterior condylar offset (PCO) during posterior cruciate-retaining total knee arthroplasty (CR TKA). The details and short-term clinical results with this surgical technique are reported herein.

Methods: The subjects were patients with osteoarthritis of the knee (47 knees) and the mean age at the time of surgery was 74.9 years old. The measured resection technique was used. Osteotomy of the tibia was applied vertically to the tibial shaft axis. A femoral trial was placed and the extension and flexion gaps were measured. The difference between these gaps was defined as Δgap. Using 70% of the anteroposterior diameter of the tibial trial as the base and Δgap as the height, the slope angle was calculated using an inverse trigonometric function. Based on the calculated slope angle, additional osteotomy of the tibia was performed using the navigation system. The clinical results by this surgical technique were investigated.

Results: The extension gap was 8.1 mm, the flexion gap was 5.4 mm, Δgap was 2.8 mm, and the mean slope angle was 5.6°. No partial posterior cruciate ligament release was performed in any patient and postoperative clinical results were favorable.

Conclusion: The results of this study show that the tibial posterior slope angle determined based on the PCO in this new surgical technique, may serve as a rough guide to the optimum posterior slope angle of the tibia in CR TKA.