A NOVEL TISSUE ATTACHMENT SCHEME FOR BIOMECHANICAL PROSTHESES

Abstract

Hamessing in situ muscle power for circulatory support requires a reliable means to anchor a biomechanical actuator to both muscle and bone. The objective of this study was to determine the long-term stability of a tissue attachment scheme designed to secure a piston-based hydraulic actuator to the latissimus dorsi (LD) and underlying ribcage. Woven stainless-steel mesh was used as a porous backing plate for fixing the device to the chest wall (using heavy suture tied through the mesh and around the ribs). LD attachment was made by wrapping the humeral tendon in Dacron fabric and pressing it between toothed clamping plates machined into the piston head. A prototype device was implanted beneath the LD of a mongrel dog and the muscle stimulated for 8 weeks (33 Hz, 9 pulses/burst, >2.6x106 contractions) following a 7-day recovery period. Piston position was fixed to maximize forces across tissue/device attachment points. Stimulation produced palpable contractions throughout the implant period. At explant, the device was fully encapsulated in its original location with LD tendon firmly attached. LD adhesions to the device were minimal, but were significant around and above the piston head. Thick fibrous ingrowth through the wire mesh formed a secure bond to the chest wall. A thinner, non-adherent fibrous layer encased the main housing and piston head. Biopsies from LD and surrounding tissues appeared normal under histologic examination. This study suggests that the use of a porous backing plate and Dacron-reinforced tendon clamp mechanism may provide an effective means to anchor motor prostheses for muscular actuation.