Augmentation of suture anchors with magnesium phosphate cement - Simple technique with striking effect

Suture anchors have a large field of application in orthopedic trauma surgery like the refixation of patellar, quadriceps and Achilles tendon or the treatment of rotator cuff tears. The fixation of suture anchors in osteoporotic bone is difficult, a problem that becomes increasingly relevant in the elderly.

Two types of suture anchors: 1.) Titanium CorkScrew Fast Track II with a knotted eyelet and 2.) polyether ether ketone (PEEK) SwiveLock C with a knotless eyelet were chosen for evaluation in open cell bone blocks with densities of 5-20 pcf supplied by Sawbones AB. A pilot hole of 7 mm diameter and 20 mm depth was drilled in the bone blocks and filled with an experimental drillable magnesium phosphate cement (powder: 92.5 wt% Mg₃(PO₄)₂, 7.5 wt% MgO, liquid: 25 wt% phytic acid (C₆H₁₈O₂₄P₆)). Anchors were then inserted into the cement and allowed to cure for 24 h (37 °C, 100% humidity) before pullout testing was conducted with a material testing machine. Suture anchors inserted in the blocks after predrilling and tapping served as control.

Through augmentation with magnesium phosphate cement pullout strength and stiffness of the suture anchors could be significantly increased in all bone blocks up to 22-fold. CorkScrew anchors failed by rupture of the eyelet with higher pullout strengths, whereas no failure of SwiveLock C anchors could be observed when reinforced with additional FibreWire at the tip.

We present a simple technique, whereby pullout strength of suture anchors can be significantly increased in bone with compromised density. The experimental resorbable and drillable magnesium phosphate cement proved to be effective in resisting tensile load, dispersing in the adjacent bone, and thus increasing the bone-anchor contact surface. Therefore, the experimental magnesium phosphate cement is a promising candidate for clinical application in the numerous scenarios mentioned.