LAUSR

In ‘Case series of shrinking hydroxyapatite orbital implants’, Han et al draws attention to a particularly interesting postoperative complication. The authors report the potential shrinking of mammalian bonederived hydroxyapatite orbital implants by osteoclastic activity, which may lead to orbital volume loss. This volume loss might affect the cosmesis and the prosthesis motility leading to a significantly reduced quality of life. However, this study did not analyse the exact clinical issues of the patients, especially not the exact fitting issues, the cosmesis and the motility of the prostheses. Therefore, further studies are necessary to investigate in more detail these clinical issues and their significance. In addition, since the shrinking of mammalian bonederived hydroxyapatite orbital implants might result in a potential orbital volume loss, the use of nonmammalian bonederived, synthetic orbital implants, such as MEDPOR porous polyethylene implants, might reduce this risk. Although most surgeons prefer porous implants because of their theoretical advantages, such as higher stability, lower extrusion rate due to ingrowth of fibrovascular structures and better muscle fixation, nonporous implants should be mentioned here for completeness. Nonporous implants are usually made of synthetic material including silicone, acrylic or polymethylmethacrylate and have good tolerability and complication rates similar to porous implants. However, the number of studies on these implants is significantly lower. Since current studies consider synthetic porous and nonporous implants to be equivalent, the choice of the appropriate implant and material ultimately depends on the clinical situation, the preference and experience of the surgeon. However, if mammalian bonederived hydroxyapatite orbital implants are to be used, patients should be informed about the potential risk of shrinking postoperatively.