Further morphologic studies on collagen injected into canine vocal folds

We compared the morphologic fate of three types of soluble bovine collagen injected into vocal folds of dogs: 1) Zyderm collagen implant containing 35 mg/mL of collagen (ZCI I), 2) Zyderm collagen implant containing 65 mg/mL of collagen (ZCI II), and 3) GAX collagen containing 35 mg/mL of collagen minimally cross-linked with 0.0075% glutaraldehyde. Light and electron microscopy showed good host tolerance and a long-term persistence of the three types of collagen at the site of injection. The collagen implants were progressively colonized by fibroblasts and capillaries accompanied by host collagen deposition. No inflammatory process or foreign body reaction occurred, in contrast to the typical host reaction to injected Teflon. The colonization of GAX collagen was slower than for ZCI I and ZCI II. No other significant difference was evident among the three types of injectable collagen. All three appear to be very suitable materials for laryngeal implants; moreover, they seem to best meet accepted requirements for a good implant: they are easy to inject, they are well tolerated, and they persist for a long time. We prefer GAX collagen for clinical use because of its lower reactivity and higher stability, and because overinjection is not necessary (GAX shrinks less than ZCI I and ZCI II).