Contribution of Suture Elasticity and Insertion Angle to Suture Anchor Displacement and Failure in Osteoporotic Bone Models
Year: 2025
Type: article
Abstract: Overview:This biomechanical study investigates the individual and combined contributions of suture elasticity, insertion angle, and anchor type (internal vs. external) to total anchor displacement and failure modes in rotator cuff repair constructs. Using a standardized osteoporotic bone mimic, the study isolates mechanical components—suture, anchor, and bone—under cyclic tensile loading to better understand how each contributes to displacement and eventual failure in rotator cuff repairs.Key Findings:Suture Elasticity as a Major Contributor to Displacement: Tensile testing of isolated sutures demonstrated a mean elongation of 0.7987 ± 0.396 mm, equating to approximately 1.6% elongation of a 0.5 cm loop under 10–60 N cyclic loading. This suture elongation accounted for a significant portion of overall displacement observed in complete anchor systems, particularly in the 60-degree internal anchor configuration, where total displacement could be attributed entirely to suture elasticity. The variability in elongation highlights the critical role of knot integrity and placement in minimizing mechanical failure.Impact of Anchor Insertion Angle: Six anchor configurations were tested at insertion angles of 30°, 45°, and 60°, with both internal and external anchors. Internal anchors exhibited decreased displacement with increasing insertion angle, supporting their use at more obtuse angles relative to the angle of pull. In contrast, external anchors demonstrated the opposite trend, with unpredictable displacement likely due to inconsistent suture positioning and bone-anchor interface instability. This suggests that external anchors are less reliable in osteoporotic conditions, especially at acute angles.Failure at Deadman’s Angle (90° to Pull): Contrary to historical orthopedic dogma that a 90° effective angle (Deadman’s angle) maximizes pullout strength, both anchor types failed under this condition in osteoporotic bone. External anchors experienced catastrophic bone failure due to the suture sawing through the bone block, resulting in displacements exceeding 17 mm. Internal anchors failed through plastic deformation and fracture of the biodegradable anchor body after prolonged cyclic loading. These failures occurred in four distinct stages: preload, cyclic tension, material yield, and bone damage due to sawing.Clinical Implications: The findings challenge long-standing surgical practices regarding optimal anchor insertion angles, especially in osteoporotic bone. In such cases, the Deadman’s angle appears detrimental, increasing the risk of bone damage and construct failure. The study recommends favoring insertion angles more obtuse than 90° (e.g., 30°, 45°, 60° to the bone surface) to reduce displacement and avoid anchor or bone failure, particularly with internal anchors in compromised bone.Conclusion:This study underscores the importance of considering suture mechanics, bone quality, and anchor design during surgical planning for rotator cuff repair. Suture elasticity alone can account for significant displacement, and conventional insertion angles such as Deadman’s angle may not be appropriate in osteoporotic bone. The results advocate for a paradigm shift in anchor insertion techniques, with attention to optimizing anchor angle and accounting for biomechanical properties of the repair system to reduce failure risk.
Source: Figshare
Authors: Miller, Cameron, Astle, Zachary, Johnson, Ezra, Dikwa-Nkrumah, Britney, Kane, Steven, Roper, D. Keith
Language: English
Subfield: Surgery
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W6902317504
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