Patients with known deficiencies in the greater tuberosity pose a challenge for surgeons performing arthroscopic rotator cuff repairs. Due to the poor quality of bone, adequate fixation of commonly used suture anchors may not be achieved, resulting in soft tissue and bony fixation failure before healing can take place.
In a biomechanical study conducted at the Foundation for Orthopaedic Research and Education in Tampa, Florida, Diaz et al  investigated an alternative method to augment poor-quality bone: an injectable calcium phosphate bone substitute material (AccuFill BSM, Zimmer Biomet; Warsaw, Indiana). Augmentation with this material is intended to improve suture anchor fixation.
Figure 1. Mechanical test set-up for the foam blocks model (left) and the cadaveric model (right).
The researchers set up 2 testing models: a polyurethane foam block model to mimic osteoporotic bone and a cadaveric humerus model. Half of the foam block models and half of the cadaveric humerus models were injected with the calcium phosphate bone substitute material and half were not. The researchers then used a standard threaded rotator cuff suture anchor (5.5 mm Quattro X anchor Zimmer Biomet; Warsaw, Indiana).
The foam block and cadaveric humerus models were put through an axial load model consisting of 40 cycles. Those with an intact anchor after the 40 cycles were subjected to further load cycles until they failed.
The researchers then compared the cyclical loading and ultimate pull-out strength of the threaded suture anchor in models with and without the calcium phosphate bone substitute augmentation. They found that the augmented models had higher load-to-failure resistance than the non-augmented models.
What does this mean for clinical practice? Surgeons who are concerned about anchor pull-out may have a viable option to improve suture anchor fixation in patients with rotator cuff tears and poor-quality bone.
- Diaz MA, Branch EA, Paredes LA, Oakley E, Baker CE. Calcium phosphate bone void filler increases threaded suture anchor pullout strength: a biomechanical study. Arthroscopy. 2020 Jan 8. pii: S0749-8063(19)31195-8. doi: 10.1016/j.arthro.2019.12.003. [Epub ahead of print]