Biomechanical comparison of fixation strategies for rotator cuff repair in simulated osteoporotic bone using pullout testing and finite element analysis

Background Poor bone quality can compromise suture anchor fixation during rotator cuff repair. This study compared five fixation strategies in a standardized model of osteoporotic bone and explored their mechanical behavior using finite element analysis. Methods Six groups of eight polyurethane foam constructs were tested: five osteoporotic configurations comprising non-reinforced single anchors, cement-augmented anchors, buddy anchors, conventional transosseous sutures, and transosseous suture tape, plus a higher-density non-reinforced anchor reference group. Anchor constructs were loaded through steel wire, whereas transosseous constructs used suture or tape. Axial loading was applied at 1 mm/s. Failure loads were summarized as means and standard deviations and compared using one-way analysis of variance with post hoc comparisons. Five CT-based finite element models were used to explore displacement and stress distributions. Results The mean ultimate failure load was 122.17 ± 10.08 N in the osteoporotic non-reinforced anchor group and 279.97 ± 18.38 N in the higher-density reference group (P < 0.001). Under osteoporotic conditions, cement augmentation had the highest mean failure load (338.55 ± 28.52 N), followed by transosseous suture tape fixation (201.05 ± 22.55 N), buddy anchor fixation (192.96 ± 12.78 N), and conventional transosseous suture fixation (116.00 ± 9.79 N). No statistically significant differences were detected between conventional transosseous and non-reinforced anchor fixation (P = 0.9882), or between buddy anchor and transosseous suture tape fixation (P = 0.9612). The simulations suggested different patterns of load transfer at the anchor interface and lateral bone tunnel outlet. Conclusions Cement augmentation produced the highest initial fixation strength under the tested conditions. Buddy anchor and transosseous suture tape fixation provided intermediate failure loads. These findings concern initial fixation in a simplified model and do not establish clinical superiority or resistance to repeated loading.