Mechanisms of Suture Integration in Living Tissue: Biomechanical and Histological In Vivo Analysis in Sheep.

The potential of nonabsorbable suture material to augment tissue strength in the long-term is by far not exploited by most of the currently used sutures. The authors hypothesized that different sutures yield specific histological tissue reactions associated with specific mechanical shear resistance of the suture against the tissue. Four different suture types (Orthocord, Ethibond, FiberTape, and FiberWire) were implanted in 36 sheep shoulders (supraspinatus/greater tuberosity). One thread at each time point (6, 16, and 22 weeks) was used for histology, and 11 threads at each time point (0, 6, 16, and 22 weeks) were used for biomechanical longitudinal pullout testing. Histology included tissue maturity, activity of tissue reaction, and invasion of cells and tissue into the suture material. Fiber-Tape had the highest mean pullout strength at 6, 16, and 22 weeks of 4.4 N/cm (SD, 2.1 N/cm), 10.1 N/cm (SD, 5.1 N/cm), and 12.8 N/cm (SD, 6.0 N/cm), respectively. However, general pullout strength at 22 weeks was surprisingly low, particularly for Ethibond, Orthocord and FiberWire. The overall maturity of the surrounding tissue correlated (r=0.84, P=.001) with mechanical performance. Interestingly, in all 4 suture types, an intimate in- and on-growth of fibrous tissue to the filaments and into the space between suture fibers could be shown. However, for Ethibond, Orthocord, and FiberWire, the authors found an unexpected circumferential space around the sutures, often forming an inner and outer capsule, separating the sutures from the surrounding tissue with a shifting layer. [Orthopedics. 2019; 42(3):168-175.].