An Injectable Calcium Phosphate Bone Graft Substitute Improves the Pullout Strength of Various Suture Anchor Designs in an Osteoporotic Bone Model

Abstract

To compare various suture anchor designs with and without calcium phosphate (CaP) augmentation in an osteoporotic foam block model and decorticated proximal humerus cadaveric model. This was a controlled biomechanical study, consisting of 2 parts: (1) an osteoporotic foam block model (0.12 g/cc; n= 42) and (2) a matched pair cadaveric humeral model (n= 24). Suture anchors selected were an all-suture anchor, PEEK (polyether ether ketone)-threaded anchor, and a biocomposite-threaded anchor. For each study arm, one half the samples were first filled with injectable CaP and the other half were not augmented with CaP. For the cadaveric portion, the PEEK- and biocomposite-threaded anchors were assessed. Biomechanical testing consisted of a stepwise, increasing load protocol for a total of 40 cycles, followed by ramp to failure. For the foam block model, the average load to failure for anchors with CaP was significantly greater when compared with anchor fixation augmented without CaP; the all-suture anchor was 135.2 ± 20.2 N versus 83.3 ± 10.3 N (P= .0006); PEEK was 131 ± 34.3 N versus 58.5 ± 16.8 N (P= .001); and biocomposite was 182.2 ± 64.2 N versus 80.8 ± 17.4 N (P= .004). For the cadaveric model, the average load to failure for anchors augmented with CaP was again greater than anchor fixation without CaP; PEEK anchors went from 41.1 ± 21.1 N to 193.6 ± 63.9 N (P= .0034) and biocomposite anchors went from 70.9 ± 26.6 N to 143.2 ± 28.9 N (P= .004). Augmenting various suture anchors with CaP has shown to significantly increase pull-out strength and stiffness in an osteoporotic foam block and time zero cadaveric bone model. Rotator cuff tears are common in the elderly patients, in whom poor bone quality jeopardizes treatment success. Exploring methods that increase the strength of fixation in osteoporotic bone to improve outcomes in this patient population is important.