Tissue-engineered augmentation of a rotator cuff tendon using a reconstituted collagen scaffold: a histological evaluation in sheep.

To determine if an absorbable collagen scaffold of high porosity would allow rapid tissue in-growth and permit the functional maturation and alignment of tendon-like tissue, scaffolds were sutured to the superficial surface of the infraspinatus tendons of adult sheep. Histology demonstrated complete ingrowth with fibrovascular tissue by 6 weeks and by 12 weeks the scaffold had induced the formation of a layer of dense, regularly-oriented collagenous tissue which significantly increased the thickness of the native tendon. This new tissue was well-integrated into the host tissues at both the bone interface and along the length of the tendon. At 26 weeks the scaffold was completely absorbed leaving a stable layer of mature tendon-like tissue over the surface of the host tendon which was still present at 52 weeks. The use of a reconstituted collagen scaffold consistently increased the thickness of a rotator cuff tendon by inducing the formation of a well-integrated and mature tendon-like tissue.