A new anchor augmentation technique with a cancellous screw in osteoporotic rotator cuff repair: an in vitro biomechanical study on sheep humerus specimens.

PURPOSE The aim of this study was to test a simple technique to augment the pullout resistance of an anchor in an over-drilled sheep humerus model. METHODS Sixty-four paired sheep humeri were harvested from 32 male sheep aged 18 months. Specimens were divided into an augmented group and non-augmented group. FASTIN RC 5-mm titanium screw anchors (DePuy Mitek, Raynham, MA) double loaded with suture material (braided polyester, nonabsorbable USP No. 2) were used in both groups. Osteoporosis was simulated by over-drilling with a 4.5-mm drill. Augmentation was performed by fixing 1 of the sutures 1.5 cm inferior to the anchor insertion site with a washer screw. This was followed by a pull-to-failure test at 50 mm/min. The ultimate load (the highest value of strength before anchor pullout) was recorded. A paired t test was used to compare the biomechanical properties of the augmented and non-augmented groups. RESULTS In all specimens the failure mode was pullout of the anchor. The ultimate failure loads were statistically significantly higher in the augmented group (P < .0001). The mean pullout strength was 121.1 ± 10.17 N in the non-augmented group and 176.1 ± 10.34 N in the augmented group. CONCLUSIONS The described augmentation technique, which is achieved by inferior-lateral fixation of 1 of the sutures of the double-loaded anchor to a fully threaded 6.5-mm cancellous screw with a washer, significantly increases the ultimate failure loads in the over-drilled sheep humerus model. CLINICAL RELEVANCE Our technique is simple, safe, and inexpensive. It can be easily used in all osteoporotic patients and will contribute to the reduction of anchor failure. This technique might be difficult to apply arthroscopically. Cannulated smaller screws would probably be more practical for arthroscopic use. Further clinical studies are needed.