The use of ultrasound in the diagnosis of adverse reaction to metallic debris following metal on metal hip replacement.

BACKGROUND AND PURPOSE: The role of imaging in the diagnosis of adverse reaction to metallic debris (ARMD) with metal on metal (MoM) hip replacements is still unclear. A comparative study was undertaken to evaluate the efficacy of ultrasound in diagnosis of ARMD. PATIENTS AND METHODS: The study group included 35 patients with a clinical and histological diagnosis of ARMD. The control group included 16 asymptomatic patients of MoM hip replacements with low blood metal ions levels. Various sonographic features around hip in patients diagnosed with ARMD were recorded. RESULTS AND INTERPRETATION: Fluid collection around iliopsoas and gluteal tendons following a MoM hip replacement is highly suggestive of ARMD and should not be thought of as an uncomplicated tendonitis. This study shows ultrasound as a reliable investigation in the diagnosis of ARMD following MoM hip replacements.

Determining material loss from the femoral stem trunnion in hip arthroplasty using a coordinate measuring machine.

In contrast to the articulating and taper surfaces of failed total hip replacements, volumetric wear analysis of trunnions is not routinely performed. Metal wear particles from the trunnion may contribute not only to the failures of metal-on-metal total hip replacements but also to all hip replacements utilising metal trunnions. A validation study was performed with the material removed in stages from the trunnions of an Exeter V40 stem, a Corail stem and an Accolade stem to simulate different magnitudes of wear. The material loss from the trunnions was measured both volumetrically with a coordinate measuring machine and gravimetrically with a high-precision balance. A cohort of 28 ex vivo trunnions was also measured using the coordinate measuring machine. The maximum error between the two methods was found to be 0.13 mm(3). This result was comparable with the coordinate measuring machine method for the taper surface (0.2 mm(3)). The ex vivo trunnions had a median wear volume of 0.14mm(3) (range: 0.04-0.28 mm(3)). This is the first study to determine the accuracy of volumetric wear measurements of trunnions by comparing against gravimetric measurements. Volumetric wear analysis of trunnions may provide additional insights into failures of modular total hip prostheses and will be performed routinely at our centre.