Retrieval analysis and principal variable analysis of 127 M2a-38 Mm™ metal on metal hip replacements

Abstract

Background
The objective of this study was to investigate the factors which affected the material loss from 127 M2a-38 mm™ hip replacements.

Methods
The alignment and patient data was obtained for 127 patients. The explants bearings and tapers were measured to determine the level of material loss and their geometry.

Results
87 joints were edge wearing (EW), 28 normally wearing (NW) and 12 had edge interaction (EI). The NW joints were wearing at a mean bearing combined rate of 0.34 mm3/yr. For the NW joints, bearing clearance was linked to the bearing combined volumetric loss rate (r = 0.446). The rates of loss from the head's taper was 0.21 mm3/yr. Lower wearing and lower clearance joints had higher values of loss from the tapers. The taper loss from joints with a positive clearance were significantly higher (p = .026) than those with a negative clearance.

Conclusions
The results demonstrate that bearing loss rates for NW joints was as expected. The high number of joints showing signs of edge wearing resulted from low clearances and a low cup articular arc angle. The taper loss was lower than other similar joint designs with positive clearances resulting in greater loss.

More information

Identifiers

ORCID for Richard Cook: orcid.org/0000-0002-2468-5820

ORCID for David Culliford: orcid.org/0000-0003-1663-0253

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