[Experimental study on improving stability of anchor by adding anchor]

To explore whether anchor placement could improve holding force of anchors under the condition of osteoporosis, in order to solve the problem of clinical treatment for rotator cuff injury associated with osteoporosis.

Twenty one bone modules, which included 13 males and 8 females aged from 60 to 95 years old with an average of (77.6±10.3) years old, and were divided into three experimental groups named as group A, B and C, and 7 in each group. A single anchor was inserted in group A, two parallel anchors were screwed in group B, and a single anchor was screwed in group C, then after the anchor was pulled out, anchor was screwed back and another anchor was screwed in close to the anchor. X-ray examination was performed in all three groups to observe situation of anchor in osteoporosis module; the maximum axial pull-out force (Fmax) of the three groups was measured.

Fmax of group A, B and C was (170.35±31.21) N, (314.47±23.47) N, and(292.74±25.36) N, respectively. Compared with group A, there were statistical difference of Fmax in group B and C(P<0.05), while no difference of Fmax between group B and C(P>0.05).

In the case of loose anchors in the osteoporosis module, holding force of anchors could be improved by adding anchor, which provide a remedy for single anchor failure in clinical operation.