Wear Behaviours and Oxidation Effects on Different UHMWPE Acetabular Cups Using a Hip Joint Simulator.

Given the long-term problem of polyethylene wear, medical interest in the new improved cross-linked polyethylene (XLPE), with or without the adding of vitamin E, has risen. The main aim of this study is to gain further insights into the mutual effects of radiation cross-linking and addition of vitamin E on the wear performance of ultra-high-molecular-weight polyethylene (UHMWPE). We tested four different batches of polyethylene (namely, a standard one, a vitamin E-stabilized, and two cross-linked) in a hip joint simulator for five million cycles where bovine calf serum was used as lubricant.

A new protocol for wear testing of total knee prostheses from real joint kinematic data: Towards a scenario of realistic simulations of daily living activities.

A new tendency in the field of wear testing of total knee replacements is represented by realistic simulations of various motor tasks of daily living (chair sitting and rising, squat, stair ascent, etc.). Various studies have shown in fact the limits of the ISO 14243 standards, in particular the concern about the ability of the level walking simulations to recreate the main wear mechanisms which occur on the knee implant during its in vivo lifespan.

Wear simulation of total knee prostheses using load and kinematics waveforms from stair climbing.

Knee wear simulators are meant to perform load cycles on knee implants under physiological conditions, matching exactly, if possible, those experienced at the replaced joint during daily living activities. Unfortunately, only conditions of low demanding level walking, specified in ISO-14243, are used conventionally during such tests. A recent study has provided a consistent knee kinematic and load data-set measured during stair climbing in patients implanted with a specific modern total knee prosthesis design.

On the roughness measurement on knee prostheses.

The majority of total knee replacements currently implanted present an articulation composed of two metal parts, femoral and tibial components, between which there is a polyethylene insert serving as a bearing surface. The finishing surface of the metal components is a very important factor in minimizing the polyethylene wear rate and, later, the gradual production of metal and plastic debris. Considering the role of surface roughness on volumetric wear rates, the purpose of this study is to develop a protocol for the roughness characterization of total knee prosthesis (TKP) metal components, taking into consideration a limited number of points on each surface.

In vitro effects on mobile polyethylene insert under highly demanding daily activities: stair climbing.

Purpose: Wear and survival of total joint replacements do not depend on the duration of the implant in situ, but rather on the amount of its use, i.e. the patient's activity level.

A new protocol from real joint motion data for wear simulation in total knee arthroplasty: stair climbing.

In its normal lifespan, a knee prosthesis must bear highly demanding loading conditions, going beyond the sole activity of level walking required by ISO standard 14243. We have developed a protocol for in vitro wear simulation of stair climbing on a displacement controlled knee simulator. The flexion/extension angle, intra/extra rotation angle, and antero/posterior translation were obtained in patients by three-dimensional video-fluoroscopy.