title: Imaging the implant-soft tissue interactions in total knee arthroplasty.
abstract: BACKGROUND
  In Total Knee Arthroplasty (TKA), residual pain may be secondary to soft tissue impingements, which are difficult to visualize around chromium-cobalt implants using medical imaging, so their interactions remain poorly understood. The goal of this work was to establish a protocol for in-vitro imaging of the soft tissues around TKA, usable during throughout the range of motion (ROM).
  
  
  METHODS
  The full size range of a commercially available TKA prosthesis was manufactured by 3D-printing in non-magnetic and non-radiopaque polymer and implanted in 12 cadaveric knees. The relations between these implants and the soft tissues (Popliteus tendon, Medial and Lateral Collateral Ligament, Patellar and Quadriceps tendons) were analyzed, using MRI (5 embalmed specimens) and CT scans after injection of the tissues with barium-sulfate (3 embalmed and 4 fresh-frozen specimens).
  
  
  RESULTS
  Both MRI and CT scans enabled good identification of the soft tissues before TKA implantation. MRI produced minimal loss in signal and contrast, and neither the low temperature nor the embalming fluids compromised image quality. CT scans were more precise after TKA implantation, particularly the borders of the implant and the differentiation of soft tissues. Full ROM investigation, manual segmentation and three-dimensional reconstructions were possible only with the CT scan.
  
  
  CONCLUSIONS
  The experimental approach described in this study was successful in visualizing the interactions between the soft tissue and the implants before and after TKA and during the full ROM. The coordinate system allows to localize precisely the different anatomic structures and to quantify any change due to prosthetic implantation.
authors.affiliation: Centre Orthopédique Santy, 24 Av Paul Santy, Lyon, France. bonnin.michel@gmail.com.|Hopital Privé Jean Mermoz, 55 Av Jean Mermoz, 69008, Lyon, France. bonnin.michel@gmail.com.
authors.forename: Michel P
authors.identifier: http://orcid.org/0000-0001-9957-751X
authors.initials: MP
authors.lastname: Bonnin
authors.affiliation: UZ Gent, De Pintelaan, 185, Gent, Belgium.
authors.forename: Tom
authors.initials: T
authors.lastname: Van Hoof
authors.affiliation: UZ Gent, De Pintelaan, 185, Gent, Belgium.
authors.forename: Arnoud
authors.initials: A
authors.lastname: De Kok
authors.affiliation: UZ Gent, De Pintelaan, 185, Gent, Belgium.
authors.forename: Matthias
authors.initials: M
authors.lastname: Verstraete
authors.affiliation: UZ Gent, De Pintelaan, 185, Gent, Belgium.
authors.forename: Catherine
authors.initials: C
authors.lastname: Van der Straeten
authors.affiliation: Accelerate Innovation Management, Rue de Hollande 4-6, 1204, Geneva, Switzerland.
authors.forename: Moreno
authors.initials: M
authors.lastname: Saffarini
authors.affiliation: UZ Gent, De Pintelaan, 185, Gent, Belgium.
authors.forename: Jan
authors.initials: J
authors.lastname: Victor
keywords: 3D printing; Painful TKA; Popliteus tendon; Soft tissue impingement