Degradation-structure-mechanical relationships of PLGA suture anchors and PCL coating-mediated mechanical preservation via degradation-induced crystallization

PLGA suture anchors are widely used for orthopedic soft-tissue fixation, yet their degradation-structure-mechanical evolution and the potential for coating-mediated mechanical regulation remain incompletely characterized. Here, we investigated the in vitro degradation of uncoated PLGA anchors over 24 weeks, structure-mechanical correlations through molecular weight-compression force coupling, and whether PCL coatings (5%, 10%, 20%) preserve mechanical performance through degradation-induced crystallization, complemented by a preliminary rat fascia-defect in vivo assessment. Uncoated anchors showed staged degradation: mass loss was modest through 8 weeks (<5.4%) but accelerated after 16 weeks (>35%), while Mn declined from ∼185,000 to ∼105,000 Da by 12 weeks and further thereafter. Compression Fmax remained at or above its initial value through 16 weeks despite ongoing chain scission, indicating structural-mechanical decoupling in which molecular degradation preceded macroscopic mechanical change. DSC confirmed that the material remained amorphous, with Tg remaining approximately 65 °C during degradation, and SEM revealed progressive surface pore formation. Among coated groups, PCL10% preserved mechanical performance best, with an initial ΔHm of about 46 J/g (Xc ≈ 33%) that increased further after 4 weeks, indicating a crystalline physical crosslink network; PCL5% degraded too rapidly and PCL20% showed no corresponding advantage. At Day 8 in vivo , blood and biochemical parameters showed individual deviations (n = 2 per group), and the implant caused notable local tissue reactions. Histology showed HE inflammatory cell density lower in sham (∼340–375 cells/mm 2 ) than suture (∼743–813) and anchor (∼775–882), and CD206-positive densities remained below 10 cells/mm 2 in all groups, with no inferential statistics. These findings define the structure-mechanical relationship governing PLGA anchor degradation and show that PCL10% coating preserves compression performance, providing a design rationale for absorbable anchor coatings, with boundaries set by the small in vivo sample, descriptive histology, batch differences, and single-point GPC data.