Biomedical subjects

C Kaddick

Publications and source records attributed to C Kaddick.

11 recordsLinked to original sources

PubMed2005

Fluid composition impacts standardized testing protocols in ultrahigh molecular weight polyethylene knee wear testing.

Wear of total knee replacements is determined gravimetrically in simulator studies. A mix of bovine serum, distilled water, and additives is intended to replicate the lubrication conditions in vivo. Weight gain due to fluid absorption during testing is corrected using a load soak station. In this study, three sets of ultrahigh molecular weight polyethylene tibial plateau were tested against highly polished titanium condyles. Test 1 was performed in two different institutions on the same simulator according to the standard ISO 14243-1, using two testing lubricants. Test 2 and test 3 repeated both previous test sections. The wear and load soak rates changed significantly with the lubricant. The wear rate decreased from 16.9 to 7.9 mg weight loss per million cycles when switching from fluid A to fluid B. The weight gain of the load soak specimen submersed in fluid A was 6.1 mg after 5 x 10(6) cycles, compared with 31.6 mg for the implant in fluid B after the same time period. Both lubricants were mixed in accordance with ISO 14243 (Implants for surgery - wear of total knee-joint prostheses), suggesting that calf serum should be diluted to 25 +/- 2 per cent with deionized water and a protein mass concentration of not less than 17 g/l. The main differences were the type and amount of additives that chemically stabilize the lubricant throughout the test. The results suggest that wear rates can only be compared if exactly the same testing conditions are applied. An agreement on detailed lubricant specifications is desirable.

Body Fluids↗

PubMed2001

Hip simulator wear testing according to the newly introduced standard ISO 14242.

Ultra-high molecular weight polyethylene (UHMWPE) acetabular cups were tested against alumina-ceramic femoral heads using a new type of hip joint simulator according to ISO/FDIS 14242-1. Bovine serum as well as newborn calf serum were used as test fluids. Total polyethylene wear was determined by weight loss of the cups. In addition. wear depth and its distribution were recorded by means of a coordinate measurement system. Wear particle analysis and inspection of the worn polyethylene surfaces using light and scanning electron microscopy (SEM) were performed to analyse damage and identify the acting wear mechanisms. The total wear rate was determined to be 22.07 +/- 1.75 mg/10(6) cycles for the bovine serum group and 26.57 + 3.55 mg/10(6) cycles for the calf serum group. Unexpectedly, the formation of two wear vectors corresponding to recent clinical findings was detected. Retrieved polyethylene wear debris was comparable in size and shape with clinical findings. The test method described by ISO/FDIS 14242-1 produced reliable and reproducible wear data using UHMWPE acetabular cups articulating against alumina-ceramic heads. In the authors' opinion, the lubricant composition should be described in more detail, since the protein and additive content seem to have a high impact on the wear results. It needs to be emphasized that the findings of this study cannot be regarded as a general validation of hip wear tests according to ISO/FDIS 14242-1 but are limited to the material combinations investigated herein. Further testing of other clinically relevant materials and interlaboratory ring tests must follow.

Aluminum Oxide↗

PubMed1997

Mechanical simulation of composite hip stems.

Calculation of new orthopedic implants prior to manufacturing of prototypes can be economic in the case of complex production processes. The use of composite materials for highly loaded hip stems is one application of the Finite-Element Method. Due to the anisotropic behaviour of composite structures, special routines had to be programmed for element alignment and failure analysis. Stability of carbon fibre-reinforced epoxy hip stems could be confirmed by experimental results. The risk of neck fracture was found to be one of the critical features in the design process.

Anisotropy↗

PubMed1997

[Load bearing capacity of CFK hip prosthesis with ceramic femoral heads].

Wear of the articulating surfaces of mating components of total hip endoprostheses is the most important technical factor limiting the functional lifetime of the prosthesis. Biolox ceramic femoral heads have been used successfully throughout the world for more than 20 years. In vitro tests and clinical results show that the artificial modular hip joint system employing a Caproman stem and a ball made of Biolox or Biolox -forte is resistant to mechanical failure. The threshold values for burst load and cyclic load prescribed by the FDA are achieved or bettered. Clinical results support those of the in vitro tests. The femoral head made of Biolox or Biolox -forte used in combination with cups and stems made of Caproman thus complies with the required standards.

Biomechanical Phenomena↗

PubMed1997