Affiliations: [a] Division of Orthopedics, Sendai City Hospital, Sendai, Japan | [b] Division of Orthopedics, Saiseikai Matsuyama Hospital, Ehime, Japan | [c] Department of Orthopaedic Surgery, Tohoku University School of Medicine, Sendai, Japan | [d] Department of Nano Mechanics, Graduate School of Engineering, Tohoku University, Sendai, Japan
Abstract: BACKGROUND: Failure of inserted anchors has been recognized as one of the major pathomechanisms of re-tearing after rotator cuff repair. OBJECTIVE: To predict the inserted anchor failure using CT-based 3-dimensional finite element method (CT/3D-FEM). METHODS: Among twenty patients who underwent rotator cuff repair, 5 had anchor failure (failed anchor group) and 15 had no anchor failure (stable anchor group). A 3D model of proximal humerus was developed for each patient based on the CT data. A virtual pullout testing of TWINFIX™ anchors inserted into bone at 6 different sites was performed using FEM. Then, mean failure load of 6 anchors for each patient was compared between two groups. Moreover, an optimal cut-off value of the mean failure load was determined for predicting anchor failure. RESULTS: The mean failure load in the failed anchor group (70.3 N) was significantly lower than that in the stable anchor group (119.0 N; p<0.0001). In our method, the optimum cut-off value of the mean failure load was 75.4 N. CONCLUSIONS: Failure of the inserted TWINFIX™ anchor could be predicted using CT/3D-FEM. In this method, there seemed to be a high risk of anchor failure in shoulders with a mean failure load of <75.4 N.
