Predicting failures of suture anchors used for rotator cuff repair: a CT-based 3-dimensional finite element analysis.

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.