Effect of one- and two-pin reference anchoring systems on marker stability during total knee arthroplasty computer navigation

Objective: This study investigated different infrared marker reference base attachments in cadaveric bone and their effects on alignment outcome when different loads were applied. Material and Methods: Five cadaveric specimens were used to test four reference base attachments: a locking one-pin (4.0 mm and 5.0 mm pins) and a two-pin clamp (Hoffman fixator, 3.0 mm and 5.0 mm pins, Stryker Inc., NJ). Each was tested with metaphyseal and diaphyseal attachments. A navigation system (Stryker Navigation, MI) was used for testing with applied incremental loads and torques (65 N and 1.0 Nm) to the different reference base configurations. Results: With 65 N the maximum change in distance to a verification point was 4.3 + 1.6 mm with the 4.0 mm locking pin in metaphyseal bone. No difference in verification point distances was found with any two-pin configuration. Alignment changes greater than 4° resulted with the 65 N loads and a 4.0 mm pin. Conclusion: The results may prove beneficial in comparing the resulting error of different manufacturers and allow surgeons to realize the variability that may occur through incidental contact in the operating room.