Assessment of wear and periacetabular osteolysis using dual energy computed tomography on a pig cadaver to identify the lowest acceptable radiation dose

Abstract

Objectives: Computed tomography (CT) plays an important role in evaluating wear and periacetabular osteolysis (PAO) in total hip replacements. One concern with CT is the high radiation exposure since standard pelvic CT provides approximately 3.5 millisieverts (mSv) of radiation exposure, whereas a planar radiographic examination with three projections totals approximately 0.5 mSv. The objective of this study was to evaluate the lowest acceptable radiation dose for dual-energy CT (DECT) images when measuring wear and periacetabular osteolysis in uncemented metal components.

Materials and methods: A porcine pelvis with bilateral uncemented hip prostheses and with known linear wear and acetabular bone defects was examined in a third-generation multidetector DECT scanner. The examinations were performed with four different radiation levels both with and without iterative reconstruction techniques. From the high and low peak kilo voltage acquisitions, polychrmoatic images were created together with virtual monochromatic images of energies 100 kiloelectron volts (keV) and 150 keV.

Results: We could assess wear and PAO while substantially lowering the effective radiation dose to 0.7 mSv for a total pelvic view with an accuracy of around 0.5 mm for linear wear and 2 mm to 3 mm for PAO.

Conclusion: CT for detection of prosthetic wear and PAO could be used with clinically acceptable accuracy at a radiation exposure level equal to plain radiographic exposures.Cite this article: B. Sandgren, M. Skorpil, P. Nowik, H. Olivecrona, J. Crafoord, L. Weidenhielm, A. Persson. Assessment of wear and periacetabular osteolysis using dual energy computed tomography on a pig cadaver to identify the lowest acceptable radiation dose. Bone Joint Res 2016;5:307-313. DOI: 10.1302/2046-3758.57.2000566.

Keywords: Accuracy; Low-dose dual-energy computed tomography; Osteolysis; Wear.

Conflict of interest statement

ICMJE conflict of interest:None declared.

© 2016 Sandgren et al.

Figures

Measurement of periacetabular osteolysis (PAO) and wear. On the left side (image) the ‘osteolysis’ was connected to the acetabular central grove which made it difficult to define where the osteolysis began; a) PAO, left side depth; b) PAO, right side width.; c) wear on left side. The shortest distance between inner border of the component and head was measured.

Fig. 2

Actual drilled depth and width measured from a plastic mould using a micrometer for the man-made periacetabular osteolysis. Drilled wear measured with a micrometer.

Fig. 3

Box plots show the difference between the micrometer measurement and the observed measurment for each observer, for each trial designated as B1, B2 and M1 and M2. Caliper measurements of plastic casts (1, 2) : upper left: left osteolysis; 19 mm depth, upper right: right osteolysis, 24 mm width; lower left: left linear wear, 3.4 mm; lower right: right linear wear, 2.9 mm. Osteolysis on the left side was connected to the acetabular central groove which can explain the difference between measurements from BS and MS.

Images showing a) osteolysis accuracy: the difference in measurements for both observers compared with actual measured distances. There were too many missing values at 10% radiation levels for both observers, hence these results are not shown; b) wear accuracy: accuracy is between 0.5 mm and 1.0 mm for all measurements.