Effect of Cog Threads under Rat Skin

Abstract

Background The aging face loses the tensile strength of structural integrity. Cog threads have been used recently to tighten lax skin and soft tissue. Objective A comparative study of the effects of cog, monofilament, and multifilament threads under rat skin. Methods Each cog, monofilament, and multifilament thread was inserted under the facial skin of a cadaver and the panniculus carnosus of rat dorsal skin. The maximum holding strength (MHS) of the thread and the tearing strength of the skin around the thread were measured with a tensiometer. The thickness of the capsule around the thread and the myofibroblasts was observed histologically. Results In the cadaver, the MHS of the cog thread was 190.7 ± 65.6 g. It was greater than that of the monofilament (22.4 ± 7.7 g) or multifilament (40.4 ± 19.7 g) thread. In the rat, the MHS of the cog thread was 95.1 ± 18.8 g. It was greater than that of the monofilament (4.3 ± 1.3 g) or multifilament (10.9 ± 2.1 g) thread in the second week. The thickness of the capsule around the cog thread was 93.0 ± 3.2 μm. It was thicker than the monofilament thread's capsule, 39.2 ± 12.1 μm, in the fourth week. The number of myofibroblasts presented significantly more in the cog (96.0 ± 72.4) than in the monofilament thread (4.3 ± 4.4). The rumpled in-between skin suspended by each of the three different threads returned to its original state in 2 weeks. Conclusion The cog thread placed under the rat skin immediately pulled the skin and subcutaneous tissue. The myofibroblasts around the thread played a role in fibrous tissue contracture 4 weeks postinsertion of the thread. These findings could be the basis for clinical application.