Dataset Information

Revision of broken knee megaprostheses: new solution to old problems.

ABSTRACT:

Background

Low-cost indigenous megaprostheses used in the developing world are prone to mechanical failure but the frequency and causes are not well established.

Questions/purposes

We retrospectively analyzed the causes of failure, particularly design, and suggest changes to reduce the breakage. We also report our experience with revision surgery.

Methods

We identified 28 breakages in 266 megaprosthetic knee arthroplasties performed between January 2000 and December 2006. Twenty-six breakages were revised to another prosthesis. The complications were studied and the function was evaluated. Prostheses were studied for failure by the computer-aided design program SolidWorks(®) and Hyperworks(®) for finite element analysis (FEA). Design improvements were performed based on these results.

Results

In 21 cases, the failure occurred at the stem-collar junction, the point of maximum stress predicted by FEA. Stainless steel implants were prone to failure. There was one early and one late infection. Three patients died of metastatic disease. The most difficult surgical step involved the removal of the well-cemented broken stem from the intramedullary canal. Musculoskeletal Tumor Society scores varied from 27 to 29 after revision. FEA revealed stress could be reduced by filleting the stem-collar junction and by two-piece stems.

Conclusions

Revisions of broken total knee megaprostheses, though technically difficult, have allowed patients reasonable function. We recommend design analysis for custom prostheses to point to areas of weakness. Breakages can be reduced by using titanium stems and filleting the junction or by having two-piece inserted stems. Incorporating these changes has reduced the failures in our experience.

SUBMITTER: Agarwal M

PROVIDER: S-EPMC2947678 | biostudies-literature | 2010 Nov

REPOSITORIES: biostudies-literature

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Publications

Revision of broken knee megaprostheses: new solution to old problems.

Agarwal Manish M Gulia Ashish A Ravi B B Ghyar Rupesh R Puri Ajay A

Clinical orthopaedics and related research 20101101 11

<h4>Background</h4>Low-cost indigenous megaprostheses used in the developing world are prone to mechanical failure but the frequency and causes are not well established.<h4>Questions/purposes</h4>We retrospectively analyzed the causes of failure, particularly design, and suggest changes to reduce the breakage. We also report our experience with revision surgery.<h4>Methods</h4>We identified 28 breakages in 266 megaprosthetic knee arthroplasties performed between January 2000 and December 2006. T ...[more]

PMID: 20544320

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Project description:BACKGROUND: The transcriptomes of several cyanobacterial strains have been shown to exhibit diurnal oscillation patterns, reflecting the diurnal phototrophic lifestyle of the organisms. The analysis of such genome-wide transcriptional oscillations is often facilitated by the use of clustering algorithms in conjunction with a number of pre-processing steps. Biological interpretation is usually focussed on the time and phase of expression of the resulting groups of genes. However, the use of microarray technology in such studies requires the normalization of pre-processing data, with unclear impact on the qualitative and quantitative features of the derived information on the number of oscillating transcripts and their respective phases. RESULTS: A microarray based evaluation of diurnal expression in the cyanobacterium Synechocystis sp. PCC 6803 is presented. As expected, the temporal expression patterns reveal strong oscillations in transcript abundance. We compare the Fourier transformation-based expression phase before and after the application of quantile normalization, median polishing, cyclical LOESS, and least oscillating set (LOS) normalization. Whereas LOS normalization mostly preserves the phases of the raw data, the remaining methods introduce systematic biases. In particular, quantile-normalization is found to introduce a phase-shift of 180°, effectively changing night-expressed genes into day-expressed ones. Comparison of a large number of clustering results of differently normalized data shows that the normalization method determines the result. Subsequent steps, such as the choice of data transformation, similarity measure, and clustering algorithm, only play minor roles. We find that the standardization and the DTF transformation are favorable for the clustering of time series in contrast to the 12 m transformation. We use the cluster-wise functional enrichment of a clustering derived by LOS normalization, clustering using flowClust, and DFT transformation to derive the diurnal biological program of Synechocystis sp.. CONCLUSION: Application of quantile normalization, median polishing, and also cyclic LOESS normalization of the presented cyanobacterial dataset lead to increased numbers of oscillating genes and the systematic shift of the expression phase. The LOS normalization minimizes the observed detrimental effects. As previous analyses employed a variety of different normalization methods, a direct comparison of results must be treated with caution.

Dataset Information

Revision of broken knee megaprostheses: new solution to old problems.

Background

Questions/purposes

Methods

Results

Conclusions

Publications

Revision of broken knee megaprostheses: new solution to old problems.

Similar Datasets

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