Rapid Prototyping forIn VitroKnee Rig Investigations of Prosthetized Knee Biomechanics: Comparison with Cobalt-Chromium Alloy Implant Material

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.

Non-Sagittal Knee Joint Kinematics and Kinetics during Gait on Level and Sloped Grounds with Unicompartmental and Total Knee Arthroplasty Patients

“…Although not calculated, the authors presume that increased coefficients of friction, which usually occur between a cobalt-chromium alloy and an ultra-high-molecular-weight polyethylene (UHMWPE) [42,43], might contribute to the impaired internal knee rotation of both KA groups in comparison with the non-OP knee and CG. Moreover, due to increased friction higher stress might occur on the interface between the tibial tray and bony structures.…”

Rapid prototyping of replica knee implants for in vitro testing

“…In accordance with the surface roughness tests the ABS implants, which underwent post-treatment with acetone vapor, performed best during the kinematic experiments. PJM implants showed the worst results, which has been used in previous studies of van Haver et al [4] and Schröder et al [5]. Schröder et al stated that friction with PJM implants decreases under high loads down to original implant level during an active movement and can therefore be neglected.…”

“…Optical trackers were mounted on the femur, tibia and patella and characteristic landmarks were palpated to reconstruct bony coordinate systems according to Grood and Suntay [5].…”

“…Problematic is the expensive and time consuming manufacturing process of these new implants, when multiple designs have to be evaluated [3]. Since there are different requirements for in vitro tests than for in vivo implantation, especially in terms of durability and biocompatibility, rapid prototyping technologies might have the potential to offer an easy and fast access to various implant designs [4] and [5] investigated the use of rapid prototyping for in vitro knee experiments and concluded that replica prostheses manufactured by PolyJetModelling can reproduce the original implant kinematics, although higher friction levels under low axial loads have been determined. Despite their promising results, these studies only regarded the femoral component and one material and manufacturing technology.…”

Simplified Theoretical Model for Temperature Evaluation in Tissue–Implant–Bone Systems during Ultrasound Diathermy

“…Advancements and developments in both the qualities and quantities for implant materials have promoted the salutary treatments very promising in recent years. In addition to metals [14,15], a variety of polymers has been used as surgical implants or artificial joint prostheses [16,17]. Recently, newer biocompatible materials such as zirconia, roxolid, surface-modified titanium, and hydrogels have also shown potential as implants [18][19][20].…”