When deadman theory meets footprint decortication: a suture anchor biomechanical study

Abstract

Background The optimal insertion angle for suture anchor insertion has long been of great interest. Although greater tuberosity decortication is commonly performed during rotator cuff repair, the effect of decortication on the suture anchor insertion angle remains unclear. The purpose of this study was to compare the pullout strength of threaded suture anchors inserted at 45° and 90° in decorticated and non-decorticated synthetic bone models. Methods Two kinds of synthetic bones were used to simulate the decorticated and non-decorticated conditions, for which 40 metallic suture anchors were used. Anchors were inserted at 45° and 90° in both decorticated and non-decorticated models and tested under cyclic loading followed by load-to-failure testing. The number of completed cycles, ultimate failure load, and failure modes was recorded. Results In the decorticated model, the ultimate failure load of anchors inserted at 45° (67.5 ± 5.3 N) was significantly lower than that of anchors inserted at 90° (114.1 ± 9.8 N) ( p < 0.001). In the non-decorticated model, the ultimate failure load of anchors inserted at 45° (591.8 ± 58 N) was also significantly lower than that of anchors inserted at 90° (724.9 ± 94 N) ( p = 0.003). Due to the diverse failure modes in the non-decorticated model, specimens with a failure mode of suture anchor pullout were analyzed in greater detail, with results showing a significantly larger pullout strength for anchors inserted at 90° (781.6 ± 53 N) than anchors inserted at 45° (648.0 ± 43 N) ( p = 0.025). Conclusion Regardless of decortication, the pullout strength of anchors inserted at 90° was greater than those inserted at 45°. The clinical relevance is that inserting suture anchors at 90° is recommended due to the significantly larger ultimate failure load in both decorticated and non-decorticated bones.

All-suture anchor pullout results in decreased bone damage and depends on cortical thickness

“…In 1995, Burkhart first proposed the so‐called “deadman’s” angle to be the best choice based on trigonometric calculations [7]. Since then, the optimal insertion angle has been widely discussed in several biomechanical models and with different anchor types [8, 14, 17, 22, 23, 29]. In contrast to Burkhart, other authors have demonstrated superior biomechanical properties at an angle of 90° or more [8, 13, 22, 29].…”

Comparison of Biomechanical Failure Loads Between Tape-Type and Conventional Sutures in Internal Knotless Anchor–Based Constructs

“…The bone blocks comprised solid, rigid polyurethane foam blocks (density, 0.16 g/cm 3 ) with a 2-mm layer of short fiber-filled epoxy (density, 1.63 g/cm 3 ) on top, simulating human cancellous and cortical bone, respectively. 14 Similar bone blocks have been used in previous biomechanical studies to simulate the human greater tuberosity, the density of which ranged from 0.10 ± 0.03 to 0.18 ± 0.04 g/cm 3 . 37 Overall, 3 types of knotless suture anchors with diameters of 4.5 mm were examined in the present study, for which the fixation mechanism was internal.…”