RESUMO
Skeletal muscles have been successfully linked to power mechanical support devices acutely. However, the required load bearing muscle to prosthetic interfaces have not been consistently durable. Tissue simply may not tolerate the repetitive pressure generated, ranging to 40,000 mm Hg, when necessary forces meet the crosssectional areas accessible by suture or clamp fixation. Dramatically increasing the force transfer surface by dispersing ultrafine polymer fibers in the distal muscle substance is the principle of a coupling device termed the MyoCoupler. Earlier, effective force transfer was computationally projected and confirmed in a pilot 30 day rabbit trial, with pull-out strength several times need. This investigation tested bonding strength after longer periods and examined the postulated fiber tissue integration. Devices and controls (buttressed suture fixation alone) were implanted contralaterally in the posterior tibial muscles of 28 rabbits for up to 90 days. Of the 28 rabbits, 21 were used for bond strength testing, and 3 were used for histology. Infection or procedural error disqualified 4 of the rabbits. Pull-out strength levels at 10-30 days (n = 7), 31-60 days (n = 10), 61-90 days (n=4), and all (n=21) were, respectively, 107.1 +/- 58.1, 111.4 +/- 42.7, 97.0 +/- 21.3, and 107.2 +/- 43.9 for MyoCouplers and 58.4 +/- 19.4, 52.3 +/- 34.7, 40.5 +/- 13.0, and 52.1 +/- 26.9 for the control animals. Differences were statistically significant (one-tailed t-test for paired data) and at progressively higher standards of probability for each successive period (p < 0.05 at 10-30 days, p < 0.01 at 31-60 days, p < 0.001 at 90 days, and p < 0.00001 for all). Histology showed fibrous tissue insinuation. Of 360 random fiber surface sites, 88% were closer to fibrous tissue structures than to other fibers. These findings support the aggressive pursuit of muscle powered mechanisms for artificial hearts, assist devices, and heart wall actuators.
