Clinical Orthopaedics and Related Research®

, Volume 472, Issue 2, pp 767–768 | Cite as

Reply to the Letter to the Editor: Adverse Reactions of Artificial Bone Graft Substitutes: Lessons Learned From Using Tricalcium Phosphate geneX®

  • Joerg Friesenbichler
  • Werner Maurer-Ertl
  • Patrick SadoghiEmail author
  • Ulrike Pirker-Fruehauf
  • Koppany Bodo
  • Andreas Leithner
Reply to the Letter to the Editor


Calcium Sulfate Cystic Formation Bone Graft Substitute Bone Window Tricalcium Phosphate 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

To the editor,

We appreciate the authors’ serious concern for the safety of their product, and confirm the mentioned constructive site visit. However, in order to elucidate our perspective, we once again report a 16% complication rate following curettage plus filling the bone void with geneX®, which is not acceptable for a new medical device.

The previously reported complications for allografts include nonunion, delayed bone healing, infection, and plate breakage. The complication rate of nearly 30% [1, 3] is different from the rate currently reported with the use of geneX® in our series.

It is correct that in the current series, one patient used Vitoss™ (Stryker Orthopaedics, Mahwah, NJ, USA) combined with geneX® and allograft struts to refill the bony void after the curettage of a relapsed juvenile bone cyst of the humerus (patient 30). It is also correct, that the instructions for use advise against this approach. Nevertheless, we do not believe that the combination of these bone graft substitutes caused the cystic formation due to the relation of the substitutes with a relatively large mass (45 cc) of geneX® combined with only 5 cc of Vitoss™. Additionally, researchers identified a second case of a cystic formation in the soft tissue without using other bone graft materials. Resorption of the sulfate component of geneX® may induce a chemical reaction leading to the development of gas, but this fact needs further investigation. In 46 cases, we have yet to encounter cystic formations or severe inflammation when using Vitoss™, according to an unpublished prospective controlled trial.

We placed the allograft inside the bony defect before filling the resting space with geneX®. Overfilling and pressurizing is rarely possible in such large bone defects with a long cortical bone window. Additionally, “sealing” or closure of the bone window is not possible in most of the tumor cases.

We further want to clarify that we have read the comments made regarding the paper by Saadoun et al. [4] as well as the published response [2] and the clarification statement published by the authors [5]. We do not believe these comments are relevant for the current manuscript and that the information does not change the outcome of our reported series. The comments of Saadoun et al. concerning complication rates of geneX® were used as templates [5], and have been marked as citation.

In conclusion, we encountered severe complications after using geneX®, which we have not reported in the literature before. We suppose that these side effects could be caused by the calcium sulfate component of the product, a decrease of the local pH value, the product becoming fluid-like some days after its initial hardening, or the invasion of inflammatory cells.


  1. 1.
    Bullens PHJ, Minderhoud NM, de Waal Malefijt MC, Veth RPH, Buma P, Schreuder HWB. Survival of massive allografts in segmental oncological bone defect reconstructions. Int Orthop. 2009;33:757–760.PubMedCentralPubMedCrossRefGoogle Scholar
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    Fitzer S, Cooper JJ. Biocomposites Ltd response. J Neurol Neurosurg Psychiatry. 2011;82:e3.CrossRefGoogle Scholar
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    Saadoun S, Macdonald C, Bell BA, Papadopoulos MC. Dangers of bone graft substitutes: lessons from using GeneX®. J Neurol Neurosurg Psychiatry. 2011;82:e3.PubMedCrossRefGoogle Scholar
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    Saadoun S, Macdonald C, Bell BA, Papadopoulos MC. Dangers of bone graft substitutes: lessons from using GeneX®. Clarification. J Neurol Neurosurg Psychiatry. 2011;82:e3.PubMedCrossRefGoogle Scholar

Copyright information

© The Association of Bone and Joint Surgeons® 2013

Authors and Affiliations

  • Joerg Friesenbichler
    • 1
  • Werner Maurer-Ertl
    • 1
  • Patrick Sadoghi
    • 1
    Email author
  • Ulrike Pirker-Fruehauf
    • 1
  • Koppany Bodo
    • 2
  • Andreas Leithner
    • 1
  1. 1.Department of Orthopaedic SurgeryMedical University of GrazGrazAustria
  2. 2.Institute of PathologyMedical University of GrazGrazAustria

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