RESEARCH ARTICLE


BMP-2 Dependent Increase of Soft Tissue Density in Arthrofibrotic TKA



Tilman Pfitzner*, 1, Eric Röhner1, Veit Krenn2, Carsten Perka1, Georg Matziolis1
1 Orthopaedic Department, Center for Musculoskeletal Surgery, Charité – Universitätsmedizin Berlin, Chariteplatz 1, D-10117 Berlin, Germany
2 MVZ for Histologie, Zytologie and Molekulare Diagnostik, Trier, Germany


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Creative Commons License
© Pfitzner et al.; Licensee Bentham Open.

open-access license: This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.

* Address correspondence to this author at the Orthopaedic Department, Center for Musculoskeletal Surgery, Charité – Universitätsmedizin Berlin, Chariteplatz 1, D-10117 Berlin, Germany; E-mail: tilman.pfitzner@charite.de


Abstract

Arthrofibrosis after total knee arthroplasty (TKA) is difficult to treat, as its aetiology remains unclear. In a previous study, we established a connection between the BMP-2 concentration in the synovial fluid and arthrofibrosis after TKA. The hypothesis of the present study was, therefore, that the limited range of motion in arthrofibrosis is caused by BMP-2 induced heterotopic ossifications, the quantity of which is dependent on the BMP-2 concentration in the synovial fluid.

Eight patients with arthrofibrosis after TKA were included. The concentration of BMP-2 in the synovial fluid from each patient was determined by ELISA. Radiologically, digital radiographs were evaluated and the grey scale values were determined as a measure of the tissue density of defined areas. Apart from air, cutis, subcutis and muscle, the soft-tissue density in the area of the capsule of the suprapatellar pouch was determined. The connection between the BMP-2 concentration and the soft-tissue density was then investigated.

The average BMP-2 concentration in the synovial fluid was 24.3 ± 6.9 pg/ml. The density of the anterior knee capsule was on average 136 ± 35 grey scale values. A linear correlation was shown between the BMP-2 concentration in the synovial fluid and the radiological density of the anterior joint capsule (R=0.84, p = 0.009).

We were able to show that there is a connection between BMP-2 concentration and soft-tissue density in arthrofibrosis after TKA. This opens up the possibility of conducting a prophylaxis against arthrofibrosis in risk patients by influencing the BMP-2 pathway.

Keywords: Arthrofibrosis, BMP-2, heterotopic ossifications, inflammation, stiff knee, total knee arthroplasty.