Biodegradable shoulder anchors have unique modes of failure

Biodegradable suture anchors have facilitated and revolutionized arthroscopic tissue-to-bone repair, especially in the shoulder. However, the anchor is but a part of the repair construct, which also includes a suture, tied in a knot, that attaches the tissue (tendon or labrum) to bone. Bioabsorbable anchors may result in loose bodies. Two cases are reported as sentinel events highlighting this potential risk. In the first case, combining a nonabsorbable suture (forming the anchor eyelet) with an anchor body made from rapidly degrading copolymer resulted in the suture becoming a loose body as the anchor body reabsorbed. In the second case, a portion of the eyelet and upper screw thread, itself composed of a biodegradable copolymer, became a loose body as the anchor absorbed, perhaps because the eyelet became proud with regard to the host bone during cyclic loading. Biodegradable anchors offer many advantages over metal anchors but do not eliminate the risk of a glenohumeral loose body. Unexpected postoperative symptoms such as painful catching, popping, or "squeaking" may indicate a glenohumeral loose body and warrant an arthroscopic evaluation. In the future, improved shoulder suture anchor design may lower the risk of this complication.