Suture Anchor Science: Microarchitecture & Footprint Mechanics

Matching anchor fixation mechanisms to regional cortical thickness and trabecular density across the rotator cuff and glenoid footprints.

Footprint Density Mapping (Kholinne et al., 2018): Trabecular bone mineral density and volume fraction (BV/TV) are concentrated proximally along the subchondral margin and centrally within the main supraspinatus footprint (G2-P: 29.8%, G2-I: 27.5%). Conversely, trabecular density drops substantially along the distal margin and lateral sulcus (G1-D to G3-D: 13.8%–16.9%). Medial row anchors leverage denser subchondral and proximal trabeculae, whereas lateral row fixation relies primarily on lateral cortical wall interference rather than cancellous shear.
Fixation Resilience in Low-Quality Bone: Cortical Thickness vs. Trabecular Purchase: Cadaveric testing (Tingart et al.) demonstrates that anatomical placement significantly impacts failure load (273 N proximally vs. 184 N distally). Crucially, conventional threaded anchors rely substantially on cancellous thread purchase, whereas subcortical all-suture anchors deploy beneath the cortical shell. Biomechanical studies show that adjacent cortical thickness (with ~0.4 mm needed to withstand 200 N in human humerus models) rather than local trabecular BMD alone governs all-suture anchor pullout resistance—though absolute failure loads vary widely by construct design, insertion angle, and testing setup.

Translating Biomechanical Literature into Clinical & Value Decisions

Empirical Biomechanical Finding Mechanistic Interpretation Clinical & Economic Implication
Regional Bone Quality Varies Markedly
(Tingart et al.; Kholinne et al.)		 Proximal/central GT exhibits higher trabecular density than distal/lateral zones. Anchor selection cannot be one-size-fits-all; medial and lateral rows face distinct osseous environments.
Subcortical Cortical Engagement
(Human Humerus Cortical Thickness Studies)		 All-suture anchors toggle beneath the cortex; adjacent cortical thickness (~0.4 mm threshold for 200 N) drives pullout resistance rather than local trabecular BMD alone. Preserving the cortical shell (avoiding aggressive decortication) is vital when deploying subcortical soft anchors.
Smaller Failure Defects
(Cadaveric Pullout Cavity Analysis, 2020)		 Upon catastrophic pullout, all-suture anchors leave smaller cortical holes and cavitating bone defects than rigid threaded screws. Protects native bone stock, simplifying revision surgery and reducing the need for structural bone grafting.
High Construct & Model Variability
(Multi-Study Biomechanical Reviews)		 Published ASA failure loads span ~133 N to >600 N depending on testing axis, cortical thickness, and suture eyelet design. Avoid claiming a universal pullout force advantage; evaluate systems within matched anatomical footprints.

Central-Proximal Zone (G2-P / G1-P): Prime Medial Row

• Osseous Microarchitecture: Highest trabecular volume fraction (BV/TV up to 29.8%) and intact subchondral bone plate.
• Anchor Selection: Accommodates subcortical all-suture anchors (preserving footprint biology) or fully threaded 4.5–5.5 mm screws.
• Failure Mode: Typically suture cut-through through degenerated tendon rather than anchor pullout when bone stock is intact.

Intermediate Zone (G1-I to G3-I): Central Compression Bed

• Osseous Microarchitecture: Transitional cancellous architecture (18.4%–27.5% BV/TV), with central G2-I maintaining solid support.
• Anchor Selection: Broad-pitch cancellous screws or expandable soft anchors; avoid over-tapping in osteopenic bone.
• Failure Mode: Cancellous stripping if pilot holes are oversized relative to local trabecular density.

Distal Zone (G1-D to G3-D): Lateral Cortical Wall

• Osseous Microarchitecture: Lowest trabecular volume fraction (13.8%–16.9% BV/TV), bordered by the dense lateral humeral cortex.
• Anchor Selection: Rigid knotless interference anchors (3.5 mm to 5.5 mm) designed to wedge suture tape against the cortical collar.
• Failure Mode: Cortical wall fracture or pullout if placed too close to the articular edge or in thin lateral walls.

Glenoid Rim Microarchitecture (Bankart / Instability Fixation)

The glenoid rim presents tight spatial constraints (narrow anterior-posterior vault width, particularly in Asian cohorts). As documented by Lee & Shin (OJSM 2025):

Literature Citations & Microarchitecture Methodology

Synthesized from peer-reviewed micro-CT footprint evaluations and cadaveric biomechanical testing:

Footprint Bone Density & Micro-CT:
  • Kholinne E, Lee HJ, Kim SJ, Park SH, Jeon IH. (2018). The relationship between age, rotator cuff integrity, and osseous microarchitecture of greater tuberosity: Where should we put anchor? Acta Orthop Traumatol Turc.
  • Tingart MJ, Apreleva M, Zurakowski D, Warner JJ. (2003). Pullout strength of suture anchors used in rotator cuff repair. J Bone Joint Surg Am / AJSM.
Footprint Bone Density & Micro-CT:
  • Kholinne E, Lee HJ, Kim SJ, Park SH, Jeon IH. (2018). The relationship between age, rotator cuff integrity, and osseous microarchitecture of greater tuberosity: Where should we put anchor? Acta Orthop Traumatol Turc.
  • Tingart MJ, Apreleva M, Zurakowski D, Warner JJ. (2003). Pullout strength of suture anchors used in rotator cuff repair. J Bone Joint Surg Am / AJSM.
Cortical Thickness, Defect Size & Deployment:
  • Ntalos D, et al. (2020). Biomechanical evaluation of all-suture anchors vs. conventional anchors in human cadaveric humeri: Role of cortical thickness and failure defect size. Arthroscopy / JSES.
  • Barber FA, Herbert MA. (2013). Cyclic loading biomechanical analysis of the pullout strengths of rotator cuff and glenoid anchors. Arthroscopy.
  • Lee JH, Shin SJ. (2025). All-suture anchor deployment configurations in arthroscopic Bankart repair. Orthop J Sports Med.