INFLUENCE OF BONE DENSITY ON THE PULLOUT STRENGTH IN DIFFERENT SUTURE ANCHORS FOR ROTATOR CUFF REPAIR

Abstract

Absorbable suture anchors have become more and more important in rotator cuff surgery due to their easy revisability. In osteoporotic bone however they are thought to be of minor primary stability. Purpose of the present study was to compare different absorbable and non-absorbable suture anchors in their pullout strength depending on bone density

The absorbable screw-anchor SPIRALOK5mm (DePuyMitek, Raynham, MA, USA), the titanium screw-anchor SUPER-REVO5mm and the tilting-anchor ULTRASORB (both ConmedLinvatec, Largo, FL, USA) were tested, each anchor representing a different material and design. On the basis of bone density measurement by CT-scans a healthy (mean-age. 42 years) and a osteopenic (mean-age: 74 years) group of cadaveric human humeri were formed. Each anchor was inserted in the greater tuberosity six times. They were inserted according to the manufacturers instructions with the supplied suture material. An incremental cyclic loading was performed, starting with 75N. Until failure the tensile load was increased by 25N after every 50 cycles. The ultimate failure loads, the anchor displacements and the modes of failure were recorded.

In the non-osteopenic bone group, the absorbable SPIRALOK achieved a significantly better pullout strength (mean: 274N) than the titanium screw-anchor SUPER-REVO (mean: 188N) and the tilting-anchor ULTRASORB (mean: 192N). In the osteopenic bone group no significant difference in the pullout strength was found. The failure mechanisms, such as anchor pullout, rupture at eyelet, suture breakage and breakage of eyelet, varied between the anchors. In the osteopenic group the number of anchor pullouts clearly increased.

The present study demonstrates that absorbable suture anchors do not have lower pullout strengths than metal anchors. Depending on their design they can even outmatch metal anchor systems. The results of our study suggest that the anchor design has a crucial influence on primary stability, whereas the anchor material is less important.