The Relationship between Glenoid Bone Density and the Pullout Strength of Suture Anchors

Background: The use of suture anchors in glenoid labral reattachment is now routine in many shoulder procedures. However, debate still surrounds the biomechanical characteristics of suture anchors and the interplay with bone quality. Methods: Eight embalmed cadaveric glenoids were investigated using a microCT and a tensile testing machine to study the correlation between the bone mineral density of four different regions on the glenoid rim and the pullout strength of the suture anchor. Six constructs failed by suture breakage whilst the remaining 25 positions suffered suture pullout. This study differed from previous investigations by using Orthocord, a much stronger suture material permitting better evaluation of bone properties. Results: The mean failure load at pullout and suture compromise was 125 ± 40 N and 189 ± 25 N, respectively. The largest value of bone mineral density (BMD) was found at the posterior suture site, whilst the lowest occurred at the inferior edge of the anterior margin. For those constructs that failed by anchor pullout a significant correlation was observed between failure load and local bone mineral density (r_Pearson = 0.56, p = 0.004). Conclusion: This relationship between local bone quality and pullout strength maybe a clinical indicator of the relative risk of failure following the suture repairs and warrants further exploration.