Novel UHMWPE sleeve for stabilizing loose suture anchors in rotator cuff repair

Suture anchors are frequently used for repairing torn rotator cuffs. However, post-operative anchor loosening is a common complication often caused by low bone density. The purpose of this study was to evaluate if a novel UHMWPE cortex locking sleeve could improve the anchor pullout strength after revision in synthetic bone. The initial failed anchor fixation was simulated by inserting a 4.5 mm anchor and pulling it out of the bone, which created an enlarged insertion hole for the revision anchor. After revision, two loosening conditions were simulated; (i) intra-operative anchor loosening where the revision anchor was directly pulled out from the block after insertion, and (ii) post-operative anchor loosening where the revision anchor was first subjected to cyclic loading and then pulled out. For both loosening conditions, the pullout strength and energy absorbed was recorded for the following configurations: (i) Group A, same-diameter anchor (SDA; 4.5 mm × 10 mm); (ii) Group B, larger-diameter anchor (LDA; 5.5 mm × 10 mm; ); and (iii) Group C, same-diameter anchor combined with the novel sleeve (SDA + NS). For intra-operative anchor loosening, the highest pullout strength was recorded in the SDA + NS group, with a mean value of 370.077 ± 32.699 N, which was significantly greater than both SDA and LDA groups (p < 0.05). Similarly with post-operative anchor loosening, the SDAP + NS group had a significantly higher pullout strength (311.114 ± 28.239 N) than the other groups. Using the UHMWPE sleeve with same diameter anchor as the initial insertion produced a significantly greater pullout strength than the revision with a larger diameter anchor but no sleeve.