White Rat Experiment 1 (Bidirectional Cog PDO vs. Multiple Bidirectional Cog PDO)
In the previous animal study on white Yucatan pigs, we examined the histological outcomes of PDO monofilament threads. In this study involving white rats, we examined the physical behavior of cogged PDO thread, which was developed after introduction of the PDO monofilament type. PDO monofilament threads had the advantage of convenience, however, the treatment outcome could vary widely depending on the skill level of the doctor. Increasing the number of threads can enhance the efficacy, however, this causes bruising and edema that can last for a long period of time.
For these reasons, the bidirectional cog PDO thread was developed to increase efficacy, reduce downtime and narrow the gap between doctors. The bidirectional cog PDO thread can be pulled toward the appropriate vector after insertion to strengthen the lift. As this procedure can be done using a cannula, it causes less bruising and edema, drastically reducing the downtime. However, various other problems emerged after treatment, the most common of which were migration and protrusion of the suture material, facial asymmetry, and short duration of the lift.
The part of the bidirectional cog PDO thread that maintains the pull is the first cog of the opposing cogs. If this pull is loosened due to muscle movements and gravity, the lift is lost and the tissues return to its original sagging state before treatment. The problem here is the weak pull from the cogs. Pulling the thread forcefully to increase the lift during the procedure shortens the cogs near the entry point of the thread and may risk destroying the balance of tension between the top and bottom cogs. This may weaken the tension in the top and result in a quick loss of the lift or lateral or inferior migration of the thread.
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On average, PDO is hydrolyzed in 6 months and renally excreted. Shorter threads may be absorbed more quickly. Creating cogs on the thread can thin the thread further, increasing the risk of breakage. Once the thread breaks, the distal end of the broken thread can migrate within tissues. However, the multiple bidirectional cog PDO thread has at least 6 small bidirectional cogs. There are at least 6 bidirectional cogs that face each other and are expected to provide a 6 times stronger pull compared to the previous bidirectional cog PDO thread.
Even if the segments between cogs are broken with time, bidirectional cogs still remain, which are likely to prevent migration. For these reasons, we conducted an animal study on white rats to examine how each subcutaneously placed strand of the bidirectional cog PDO thread and multiple bidirectional cog PDO thread hold onto the tissues, whether the strands can withstand a weight of 260g, the body weight of a white rat, and how they behave when forcibly removed from the tissues.
-To be continued
