Objective To compare and analyze the biomechanical differences of different anchor methods in the repair of rotator cuff injury complicated with osteoporosis using the finite element method.

Methods An elderly patient with rotator cuff injury was selected, and five groups of three-dimensional models with different anchor methods were established according to the thin-slice CT and anchor data of shoulder joint, followed by the traditional suture bridge model (A model), internal 90° naddling model (B model), four-anchor single-interlocking model (C model), four-anchor double-interlocking model (D model), and three-anchor single-interlocking model (E model). 50 N load was applied to the five groups of models, and the stress distribution changes and ultimate load of the five groups of models were compared.

Results The maximum stress of humerus and anchor in the anchor implantation of 90° model and interlocking anchor model were lower than those in the traditional suture bridge model, and the ultimate load of three models was significantly higher than that in traditional suture bridge model. The maximum humeral stress of three-anchor model was similar to that of the suture bridge model, but the maximum stress of anchor was significantly higher than that of suture bridge model, and the ultimate load of three-anchor model was lower than that of traditional suture bridge model.

Conclusions For elderly patients with rotator cuff injury complicated with osteoporosis, implantation of the anchor at 90° can effectively reduce the stress on the humerus and anchor compared with the traditional implantation of the anchor at 45° when using threaded anchor for rotator cuff repair, and increase the uplift resistance of anchor. The interlocking method of inner and outer row of anchor can further enhance the uplift resistance of the anchor on this basis, and improve the stability of rotator cuff structure. Among them, the method of double interlocking with anchor has the greatest improvement.