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Notes on the use and interpretation of radiostereometric analysis.

Derbyshire B, Prescott RJ, Porter ML - Acta Orthop (2009)

Bottom Line: With increasing numbers of research groups carrying out radiostereometric analysis (RSA), it is important to reach a consensus on how the main aspects of the technique should be carried out and how the results should be presented in an appropriate and consistent way.In this collection of guidelines, we identify a number of methodological and reporting issues including: measurement error and precision, migration and migration direction data, and the use of RSA as a screening technique.Alternatives are proposed, and a statistical analysis is presented, from which a sample size of 50 is recommended for screening of newly introduced prostheses.

View Article: PubMed Central - PubMed

Affiliation: Centre for Hip Surgery, Wrightington Hospital, Appley Bridge, UK. Brian.Derbyshire@wwl.nhs.uk

ABSTRACT
With increasing numbers of research groups carrying out radiostereometric analysis (RSA), it is important to reach a consensus on how the main aspects of the technique should be carried out and how the results should be presented in an appropriate and consistent way. In this collection of guidelines, we identify a number of methodological and reporting issues including: measurement error and precision, migration and migration direction data, and the use of RSA as a screening technique. Alternatives are proposed, and a statistical analysis is presented, from which a sample size of 50 is recommended for screening of newly introduced prostheses.

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Four displacement vectors are shown in the x–y plane. Each is symmetrically distributed about the x-axis and the y-axis. The mean of the vector components in the x- or y-directions would be reported as zero even though each individual vector is much greater than zero.
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Figure 0001: Four displacement vectors are shown in the x–y plane. Each is symmetrically distributed about the x-axis and the y-axis. The mean of the vector components in the x- or y-directions would be reported as zero even though each individual vector is much greater than zero.

Mentions: For statistical purposes, it is valid to gather all of the x-components of translation (say) into a collection of positive and negative scalar quantities and to calculate a mean. The summary statistic may be misleading, however. For the 4 vectors shown in Figure 1, the sum—and therefore the mean—of the scalar components in the x-direction is zero. However, none of the vectors or their components is even close to zero. The results might therefore be reported something like this: “overall, there was no migration in the mediolateral direction”. The zero mean therefore tells us nothing about the mean magnitude of the displacement vectors (or their components) acting on all of the prostheses. The standard deviation would give an indication of the dispersion of the scalars, but this is not as informative as a mean magnitude of the vectors.


Notes on the use and interpretation of radiostereometric analysis.

Derbyshire B, Prescott RJ, Porter ML - Acta Orthop (2009)

Four displacement vectors are shown in the x–y plane. Each is symmetrically distributed about the x-axis and the y-axis. The mean of the vector components in the x- or y-directions would be reported as zero even though each individual vector is much greater than zero.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2823227&req=5

Figure 0001: Four displacement vectors are shown in the x–y plane. Each is symmetrically distributed about the x-axis and the y-axis. The mean of the vector components in the x- or y-directions would be reported as zero even though each individual vector is much greater than zero.
Mentions: For statistical purposes, it is valid to gather all of the x-components of translation (say) into a collection of positive and negative scalar quantities and to calculate a mean. The summary statistic may be misleading, however. For the 4 vectors shown in Figure 1, the sum—and therefore the mean—of the scalar components in the x-direction is zero. However, none of the vectors or their components is even close to zero. The results might therefore be reported something like this: “overall, there was no migration in the mediolateral direction”. The zero mean therefore tells us nothing about the mean magnitude of the displacement vectors (or their components) acting on all of the prostheses. The standard deviation would give an indication of the dispersion of the scalars, but this is not as informative as a mean magnitude of the vectors.

Bottom Line: With increasing numbers of research groups carrying out radiostereometric analysis (RSA), it is important to reach a consensus on how the main aspects of the technique should be carried out and how the results should be presented in an appropriate and consistent way.In this collection of guidelines, we identify a number of methodological and reporting issues including: measurement error and precision, migration and migration direction data, and the use of RSA as a screening technique.Alternatives are proposed, and a statistical analysis is presented, from which a sample size of 50 is recommended for screening of newly introduced prostheses.

View Article: PubMed Central - PubMed

Affiliation: Centre for Hip Surgery, Wrightington Hospital, Appley Bridge, UK. Brian.Derbyshire@wwl.nhs.uk

ABSTRACT
With increasing numbers of research groups carrying out radiostereometric analysis (RSA), it is important to reach a consensus on how the main aspects of the technique should be carried out and how the results should be presented in an appropriate and consistent way. In this collection of guidelines, we identify a number of methodological and reporting issues including: measurement error and precision, migration and migration direction data, and the use of RSA as a screening technique. Alternatives are proposed, and a statistical analysis is presented, from which a sample size of 50 is recommended for screening of newly introduced prostheses.

Show MeSH