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Is Model-based Radiostereometric Analysis Suitable for Clinical Trials of a Cementless Tapered Wedge Femoral Stem?

Abstract：

BACKGROUND:In clinical trials of THA, model-based radiostereometric analysis (RSA) techniques may be less precise than conventional marker-based RSA for measurement of femoral stem rotation. We verified the accuracy and clinical precision of RSA based on computer-aided design models of a cementless tapered wedge femoral stem. QUESTIONS:We asked: (1) Is the accuracy of model-based RSA comparable to that of marker-based RSA? (2) What is the clinical precision of model-based RSA? METHODS:Model-based RSA was performed using combined three-dimensional computer-aided design models of the stem and head provided by the implant manufacturer. The accuracy of model-based RSA was compared with that of marker-based RSA in a phantom model using micromanipulators for controlled translation in three axes (x, y, z) and rotation around the y axis. The clinical precision of model-based RSA was evaluated by double examinations of patients who had arthroplasties (n = 24) in an ongoing trial. The clinical precision was defined as being at an acceptable level if the number of patients needed for a randomized trial would not differ from a trial done with conventional marker-based RSA (15-25 patients per group). RESULTS:The accuracy of model-based RSA was 0.03 mm for subsidence (translation along the y axis) (95% CI for the difference between RSA measurements and actual displacement measured with micrometers, -0.03-0.00) and 0.39° for rotation around the y axis (95% CI, -0.41 to -0.06). The accuracy of marker-based RSA was 0.06 mm for subsidence (95% CI, -0.04-0.01; p = 0.728 compared with model-based RSA) and 0.18° for the y axis rotation (95% CI, -0.23 to -0.07; p = 0.358). The clinical precision of model-based RSA was 0.14 mm for subsidence (95% CI for the difference between double examinations, -0.02-0.04) and 0.79° for the y axis rotation (95% CI, -0.16-0.18). CONCLUSIONS:The accuracy of model-based RSA for measurement of the y axis rotation was not quite as high as that of marker-based RSA, but its clinical precision is at an acceptable level. CLINICAL RELEVANCE:Model-based RSA may be suitable for clinical trials of cementless tapered wedge femoral stem designs.

journal_name

Clin Orthop Relat Res

journal_title

Clinical orthopaedics and related research

authors

Nazari-Farsani S,Finnilä S,Moritz N,Mattila K,Alm JJ,Aro HT

doi

10.1007/s11999-016-4930-0

subject

Has Abstract

pub_date

2016-10-01 00:00:00

pages

2246-53

issue

eissn

0009-921X

issn

1528-1132

pii

10.1007/s11999-016-4930-0

journal_volume

474

pub_type

临床试验,杂志文章

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Is Model-based Radiostereometric Analysis Suitable for Clinical Trials of a Cementless Tapered Wedge Femoral Stem?