Comparison of 45° and 90° Medial Row Anchor Insertion Angles in Double-Row Suture Bridge Rotator Cuff Repair: A Biomechanical and Finite Element Analysis
APPLIED SCIENCES-BASEL, vol.16, no.6, 2026 (SCI-Expanded, Scopus)
- Publication Type: Article / Article
- Volume: 16 Issue: 6
- Publication Date: 2026
- Doi Number: 10.3390/app16063084
- Journal Name: APPLIED SCIENCES-BASEL
- Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Compendex, INSPEC, Directory of Open Access Journals
- Keywords: rotator cuff repair, suture anchor, anchor insertion angle, biomechanics, finite element analysis
- Dokuz Eylül University Affiliated: Yes
Abstract
Rotator cuff suture anchors have traditionally been inserted at the 45 degrees "deadman" angle, but this recommendation was largely derived from single-row constructs and may not reflect the biomechanics of contemporary double-row suture bridge repairs. This study compared the biomechanical performance and stress distribution of medial row anchors inserted at 45 degrees versus 90 degrees in a double-row suture bridge construct. Sixteen ovine humeri with intact infraspinatus tendons were randomized to 45 degrees or 90 degrees medial anchor insertion (n = 8 each), and double-row suture bridge repair was performed using 3.5 mm metallic and PEEK anchors. Specimens underwent uniaxial tensile testing (10-N preload, 5 mm/min) to failure, measuring yield load, failure load, displacement, stiffness, and energy absorption; additionally, a CT-based finite element model of the human humerus assessed von Mises stress, strain, and deformation under 200 N loading. Mean failure load was 161.96 +/- 50.99 N for 45 degrees and 185.61 +/- 60.97 N for 90 degrees (p = 0.447), and stiffness was 31.63 +/- 8.18 N/mm versus 36.79 +/- 9.26 N/mm (p = 0.291). Displacement at failure was greater with 90 degrees insertion (8.11 +/- 0.51 mm vs. 6.65 +/- 0.83 mm; p = 0.002), while energy absorption was higher but not significantly different (p = 0.255). Finite element analysis demonstrated lower bone von Mises stress with 90 degrees insertion (14.03 MPa) compared with 45 degrees (24.77 MPa), with similar deformation. In double-row suture bridge repair, 90 degrees medial anchor insertion provides comparable fixation strength to that at 45 degrees while reducing bone stress, suggesting a biomechanical advantage.