Mobile bearing shows larger rollback motion than fixed bearing in total knee arthroplasty using a medial stabilising technique with a navigation system

Abstract

AbstractPurposeThis study aimed to investigate the intraoperative knee kinematics of cruciate‐retaining total knee arthroplasty with a medial stabilising technique (MST‐TKA) and compare the kinematics between mobile‐ and fixed‐bearing MST‐TKAs. We hypothesised that mobile‐bearing MST‐TKA would result in greater physiological kinematic motion than fixed‐bearing MST‐TKA.MethodsTwenty‐one and 20 knees underwent mobile‐ and fixed‐bearing MST‐TKAs using a navigation system (Orthopilot® ver. 6.0; B. Braun Aesculap), respectively. In the preoperative and postoperative kinematic analysis, the knee was moved manually from 0° to 120°, and femoral anteroposterior translations of the medial femoral condyle (MFC) and lateral femoral condyle (LFC) were recorded every 0.1 s from 0° to 120°. Data were subsequently extracted from the software every 10° of flexion and compared between the two groups, and the correlation coefficients between preoperative and postoperative kinematics were calculated.ResultsIn the postoperative analysis, the MFC in the mobile‐bearing group showed significant posterior translation at 100°, 110° and 120° compared to the fixed‐bearing group (p < 0.01). Similarly, the LFC in the mobile‐bearing group showed significant posterior translation at 100°, 110° and 120° compared to the fixed‐bearing group (p < 0.05, p < 0.01 and p < 0.05, respectively). In the mobile‐bearing group, the preoperative and postoperative anteroposterior translations of the MFC and LFC were correlated (p < 0.01), while in the fixed‐bearing group, there was no correlation.ConclusionThe femoral rollback motion in the mobile‐bearing MST‐TKA correlated with the preoperative kinematics and was larger than that in the fixed‐bearing group.Level of EvidenceLevel II, therapeutic prospective cohort study.