Limits...
Rapid prototyping for in vitro knee rig investigations of prosthetized knee biomechanics: comparison with cobalt-chromium alloy implant material.

Schröder C, Steinbrück A, Müller T, Woiczinski M, Chevalier Y, Weber P, Müller PE, Jansson V - Biomed Res Int (2015)

Bottom Line: Friction coefficients between these materials and polytetrafluoroethylene (PTFE) were additionally tested as this latter material is commonly used to protect pressure sensors in experiments.No statistical differences were found between friction coefficients of both materials to PTFE.UHMWPE shows higher friction coefficient at low axial loads for RPM, a difference that disappears at higher load.

View Article: PubMed Central - PubMed

Affiliation: Department of Orthopaedic Surgery, Physical Medicine and Rehabilitation, University Hospital of Munich (LMU), Campus Grosshadern, Marchioninistraße 15, 81377 Munich, Germany.

ABSTRACT
Retropatellar complications after total knee arthroplasty (TKA) such as anterior knee pain and subluxations might be related to altered patellofemoral biomechanics, in particular to trochlear design and femorotibial joint positioning. A method was developed to test femorotibial and patellofemoral joint modifications separately with 3D-rapid prototyped components for in vitro tests, but material differences may further influence results. This pilot study aims at validating the use of prostheses made of photopolymerized rapid prototype material (RPM) by measuring the sliding friction with a ring-on-disc setup as well as knee kinematics and retropatellar pressure on a knee rig. Cobalt-chromium alloy (standard prosthesis material, SPM) prostheses served as validation standard. Friction coefficients between these materials and polytetrafluoroethylene (PTFE) were additionally tested as this latter material is commonly used to protect pressure sensors in experiments. No statistical differences were found between friction coefficients of both materials to PTFE. UHMWPE shows higher friction coefficient at low axial loads for RPM, a difference that disappears at higher load. No measurable statistical differences were found in knee kinematics and retropatellar pressure distribution. This suggests that using polymer prototypes may be a valid alternative to original components for in vitro TKA studies and future investigations on knee biomechanics.

Show MeSH

Related in: MedlinePlus

The Columbus CR prosthesis (Aesculap AG, Tuttlingen, Germany; top) and the test pieces (bottom) for the friction test made of the standard material (CoCr29Mo6) on the left and the rapid prototype material (RGD840) on the right side.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4388012&req=5

fig1: The Columbus CR prosthesis (Aesculap AG, Tuttlingen, Germany; top) and the test pieces (bottom) for the friction test made of the standard material (CoCr29Mo6) on the left and the rapid prototype material (RGD840) on the right side.

Mentions: Femoral components of a fixed bearing knee prosthesis (Columbus CR, Aesculap, Tuttlingen, Germany) manufactured from casted CoCr27Mo6 (standard prostheses material; SPM) and rapid prototype material (RPM; RGD 840 vero blue, Stratasys GmbH, Frankfurt) were obtained from the manufacturer (Figure 1). The material specifications of the RPM are shown in Table 1. Original CAD data were used to produce rapid prototypes for the femoral components in sizes 2 until 5 for each side (left/right knee) with a professional 3D-printer (Object Eden 350, Rehovot, Israel). These specimens were printed in thin layers (down to approximately 50 μm) of a liquid photopolymer resin (Table 1), which immediately polymerized under UV-light. Afterwards the rapid prototyped prostheses were polished submerged with fine grained sandpaper (up to grain size 1000). Finally, a roughness of Ra = 0.44 μm was reached for the surrogates, while the prostheses made of SPM reached Ra < 0.05 μm.


Rapid prototyping for in vitro knee rig investigations of prosthetized knee biomechanics: comparison with cobalt-chromium alloy implant material.

Schröder C, Steinbrück A, Müller T, Woiczinski M, Chevalier Y, Weber P, Müller PE, Jansson V - Biomed Res Int (2015)

The Columbus CR prosthesis (Aesculap AG, Tuttlingen, Germany; top) and the test pieces (bottom) for the friction test made of the standard material (CoCr29Mo6) on the left and the rapid prototype material (RGD840) on the right side.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4388012&req=5

fig1: The Columbus CR prosthesis (Aesculap AG, Tuttlingen, Germany; top) and the test pieces (bottom) for the friction test made of the standard material (CoCr29Mo6) on the left and the rapid prototype material (RGD840) on the right side.
Mentions: Femoral components of a fixed bearing knee prosthesis (Columbus CR, Aesculap, Tuttlingen, Germany) manufactured from casted CoCr27Mo6 (standard prostheses material; SPM) and rapid prototype material (RPM; RGD 840 vero blue, Stratasys GmbH, Frankfurt) were obtained from the manufacturer (Figure 1). The material specifications of the RPM are shown in Table 1. Original CAD data were used to produce rapid prototypes for the femoral components in sizes 2 until 5 for each side (left/right knee) with a professional 3D-printer (Object Eden 350, Rehovot, Israel). These specimens were printed in thin layers (down to approximately 50 μm) of a liquid photopolymer resin (Table 1), which immediately polymerized under UV-light. Afterwards the rapid prototyped prostheses were polished submerged with fine grained sandpaper (up to grain size 1000). Finally, a roughness of Ra = 0.44 μm was reached for the surrogates, while the prostheses made of SPM reached Ra < 0.05 μm.

Bottom Line: Friction coefficients between these materials and polytetrafluoroethylene (PTFE) were additionally tested as this latter material is commonly used to protect pressure sensors in experiments.No statistical differences were found between friction coefficients of both materials to PTFE.UHMWPE shows higher friction coefficient at low axial loads for RPM, a difference that disappears at higher load.

View Article: PubMed Central - PubMed

Affiliation: Department of Orthopaedic Surgery, Physical Medicine and Rehabilitation, University Hospital of Munich (LMU), Campus Grosshadern, Marchioninistraße 15, 81377 Munich, Germany.

ABSTRACT
Retropatellar complications after total knee arthroplasty (TKA) such as anterior knee pain and subluxations might be related to altered patellofemoral biomechanics, in particular to trochlear design and femorotibial joint positioning. A method was developed to test femorotibial and patellofemoral joint modifications separately with 3D-rapid prototyped components for in vitro tests, but material differences may further influence results. This pilot study aims at validating the use of prostheses made of photopolymerized rapid prototype material (RPM) by measuring the sliding friction with a ring-on-disc setup as well as knee kinematics and retropatellar pressure on a knee rig. Cobalt-chromium alloy (standard prosthesis material, SPM) prostheses served as validation standard. Friction coefficients between these materials and polytetrafluoroethylene (PTFE) were additionally tested as this latter material is commonly used to protect pressure sensors in experiments. No statistical differences were found between friction coefficients of both materials to PTFE. UHMWPE shows higher friction coefficient at low axial loads for RPM, a difference that disappears at higher load. No measurable statistical differences were found in knee kinematics and retropatellar pressure distribution. This suggests that using polymer prototypes may be a valid alternative to original components for in vitro TKA studies and future investigations on knee biomechanics.

Show MeSH
Related in: MedlinePlus