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Xiaflex for the Treatment of Capsular Fibrosis after Silicone Implants
Sebastian Fischer, MD1, Maximilian Kueckelhaus, MD1, Muayyad Alhefzi, MD1, Mario A. Aycart, MD1, Alex Dermietzel, MD1, Ulrich Kneser, MD2, Ericka M. Bueno, PhD1, Bohdan Pomahac, MD1.
1Brigham and Womens Hospital, Boston, MA, USA, 2BG Trauma Center Ludwigshafen, Ludwigshafen, Germany.

Purpose
The collagenase Xiaflex is approved for the treatment of Dupuytrens contracture, owing to its ability to selectively dissolve collagen subtypes. Collagen is the main constituent of capsular fibroses. Aim of this study was to demonstrate applicability and effectiveness of Xiaflex injection in the treatment of capsular fibrosis.
Methods
Silicone implants were inserted subcutaneously in the dorsum of 80 rats and allowed to develop capsular fibroses for 100 days. For optimal dosage finding capsules of 20 rats were incubated in-vitro with different concentrations of Xiaflex. Subsequently, the optimum dose of Xiaflex was injected in-vivo (n=30). Saline solution was injected in the control group (n=30). Outcome measures involved high-resolution ultrasound, 7-tesla MRI as well as histology, immunohistochemistry and PCR analysis at 2,10 and 60 days after injection.
Results
In-vitro studies suggested an optimum dosage of 0.3mg/ml Xiaflex. In-vivo, significant reduction of capsular thickness with respect to control groups was observed on days 2, 10 and 60 after injection of Xiaflex. Immunohistochemistry and PCR analyses revealed decreased concentration of collagen subtypes 1, 2 and 3 as well as underexpression of pro-fibrotic markers in the treatment group. Of note, digestion of the skin was seen in 15% of animals who received Xiaflex injection, and euthanasia was mandated.
Conclusion
This study demonstrates the effectiveness of Xiaflex at dissolving capsular fibrosis. Damage of adjacent structures, however, remains a challenge and requires further studies regarding dosage adjustment to individual capsule thickness and density.


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