Poor accuracy of plain radiographic measurements of prosthetic migration and alignment in total ankle replacement.

Matthias Braito,Rainer Biedermann,Martin Pfurner,Martin Krismer,Dietmar Dammerer,Michael Liebensteiner

doi:10.1186/s13018-015-0220-x

Matthias Braito, Rainer Biedermann + Show 4 more

Open Access

https://doi.org/10.1186/s13018-015-0220-x

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Abstract

BackgroundThe rotational position of the leg substantially influences measurements in ankle radiographs after total ankle replacement (TAR). The aim of our study was to further specify the influence of different projections on radiographic parameters used to assess component position after TAR.MethodsThe effect of varying degrees of internal rotation, flexion, and ab-/adduction on reference lines in anteroposterior and lateral ankle radiographs was investigated in a cadaveric TAR model. Observed variations were then compared with those found in 34 consecutive patients that received a HINTEGRA total ankle prosthesis in our department.ResultsA change of rotation of 20° resulted in a variation of measured reference lines of more than 1.3 cm in anteroposterior radiographs and more than 1 cm in lateral radiographs in our experimental setting. Even higher intraindividual changes of up to 1.4 cm were observed in our in vivo series.ConclusionsThe findings suggest that rotational position of the leg highly influences measurements in ankle radiographs after TAR. It further raises the question, if previously described radiographic parameters do provide accurate information for the outcome after TAR in clinical routine as suggested in literature.

Highlights

The rotational position of the leg substantially influences measurements in ankle radiographs after total ankle replacement (TAR)
Experimental series Results of measured reference lines measurements in anteroposterior and lateral radiographs are shown in Tables 1 and 2
A change of rotation from 0° to 20° of internal rotation resulted in a maximum change of 13.02 mm in anteroposterior radiographs and in a maximum change of 6.56 mm in lateral radiographs

Summary

Introduction

The rotational position of the leg substantially influences measurements in ankle radiographs after total ankle replacement (TAR). Hindfoot and total ankle component alignment with regard to biomechanical contact stresses and clinical outcome have been studied extensively [6,7,8,9,10,11,12,13] Those radiographic parameters used to investigate component malalignment [6, 12,13,14], subsidence [15, 16], ankle alignment [3, 11, 17, 18], and range of motion [9, 10, 19] are substantially influenced by the rotational position of the leg while taking the radiographs.

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