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Orbital implants: material matters
  1. Ludwig M Heindl1,2,
  2. Alexander Christopher Rokohl1,2
  1. 1 Department of Ophthalmology, University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
  2. 2 Center for Integrated Oncology (CIO) Aachen-Bonn-Cologne-Dusseldorf, Cologne, Germany
  1. Correspondence to Professor Ludwig M Heindl, Department of Ophthalmology, University Hospital of Cologne, 50937 Cologne, Germany; Ludwig.heindl.BJO{at}

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In ‘Case series of shrinking hydroxyapatite orbital implants’, Han et al 1 draws attention to a particularly interesting postoperative complication. The authors report the potential shrinking of mammalian bone-derived 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.2–5 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 bone-derived hydroxyapatite orbital implants might result in a potential orbital volume loss, the use of non-mammalian bone-derived, 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, non-porous implants should be mentioned here for completeness.5–8 Non-porous implants are usually made of synthetic material including silicone, acrylic or polymethylmethacrylate and have good tolerability and complication rates similar to porous implants.5–8 However, the number of studies on these implants is significantly lower. Since current studies consider synthetic porous and non-porous 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.5–8 However, if mammalian bone-derived hydroxyapatite orbital implants are to be used, patients should be informed about the potential risk of shrinking postoperatively.

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  • Contributors Both authors conceived of the presented work and approved the final version of the manuscript. ACR drafted and LMH critically revised the manuscript.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; internally peer reviewed.

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