Will the hold of solid biodegradable implants be influenced by swelling during the degradation process? An in-vitro study with Meniscus Arrows.

Water uptake after implantation of biodegradable devices induces swelling, as mentioned in literature. The hold in bone of solid devices will increase if the swelling is substantial enough. The results of weighing six Meniscus Arrows (MAs) before and after immersion in a sterile phosphate buffered saline solution during different time intervals were compared with the outcome of measurements under a field emission scanning electron microscope of six other MAs, stored under comparable conditions. The data were statistically evaluated with the Wilcoxon's signed rank test. The weight increase of 2.1 mg or 9.16% was statistically significant in the first 2 h following immersion, remaining stable afterwards with an average weight gain of 1.7 mg or 7.18%. The core diameter of the MAs increased to 0.01 mm or 1.01% with time. Although this is statistically significant, it is not expected to have any consequences for the hold. However, a remarkable and statistically significant decrease in the outer inter-barb diameter of 0.15 mm or 8.6% was noted with time. Mechanical testing should reveal the clinical relevance of the results of this study.