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Orthopaedic Proceedings
Vol. 101-B, Issue SUPP_5 | Pages 137 - 137
1 Apr 2019
Oladokun A Vangolu Y Aslam Z Harrington J Brown A Hall R Neville A Bryant M
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Introduction

Titanium and its alloys are attractive biomaterials attributable to their desirable corrosion, mechanical, biocompatibility and osseointegration properties. In particular, β – titanium alloys like the TMZF possess other advantages such as its lower modulus compared to Ti6Al4V alloy. This reduces stress shielding effect in Total Hip Arthroplasty (THA) and the replacement of V in the Ti6Al4V alloy, eliminates in-vivo V-induced toxicity. Unfortunately, implants made of TMZF were later recalled by the FDA due to higher than acceptable revision rates. The purpose of this study was to compare the fretting corrosion characteristics of Ti6Al4V and TMZF titanium alloys. It is hoped the findings will inform better design of β – titanium alloys for future applications in THA.

Method

A ball-on-flat configuration was utilised in this study to achieve a Hertzian point contact for CoCrMo – Ti6Al4V and CoCrMo – TMZF material combinations. These were assessed at a fretting displacement of ±50 µm at an initial contact pressure of 1 GPa. Each fretting test lasted 6000 cycles at a frequency of 1 Hz. A two-electrode cell set-up was used to monitor in-situ open circuit potential (OCP). The simulated physiological solution consisted of Foetal Bovine Serum (FBS) diluted to 25% with Phosphate Buffered Saline (PBS) and 0.03% Sodium Azide (SA) balance. The temperature was kept at ∼37°C. Corrosion products on the worn surfaces and subsurface transformations in both alloys were characterised using the Scanning and Transmission Electron Microscopy (SEM/TEM) to obtain high resolution micrographs. The samples were prepared using a FIB-SEM. Bright-field, dark-field and selected area electron diffraction (SAED) patterns were all captured using a scanning TEM (STEM) and Energy Dispersed X-Ray spectroscopy (EDX) mapping was carried out.


Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_II | Pages 87 - 87
1 Feb 2012
Patel R Stygall J Harrington J Newman S Haddad F
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We aimed to measure cerebral microemboli load during total hip [THA] and knee arthroplasty (TKA) using transcranial Doppler ultrasound (TCD) and to investigate whether cerebral embolic load influences neuropsychiatric outcome. The timing of the microemboli was also related to certain surgical activities to determine if a specific relationship exists and the presence of a patent foramen ovale was investigated.

Patients undergoing primary THA and TKA underwent a battery of ten neuropsychiatric tests pre-operatively and at 6 weeks and 6 months post-operatively. Microembolic load was recorded using TCD onto VHS tape for subsequent analysis. Patent foramen ovale detection was performed using bolus intravenous injection of agitated saline followed by valsalva manoeuvre. The timing of specific surgical steps was recorded for each operation and embolic load calculated for that period. All patients were assessed for quality of life and orthopaedic outcome measures.

Results

45 THA patients and 50 TKA patients were studied. Cerebral microembolisation occurred in 35% of all patients (10 THA patients and 19 TKA patients). Mean microembolic load was 2.8 per patient for THA and 3.76 per patient for TKA patients. PFO was detected in 29 patients overall. Insertion of the femoral component and deflation of the tourniquet were associated with a larger microembolic loads. Neuropsychiatric outcome was not affected by the low embolic loads. Quality of life and Orthopaedic outcome at 6 months was good.

Conclusion

Cerebral microembolisation occurs in a significant proportion of patients during total hip and knee arthroplasty. The presence of a patent foramen ovale does not appear to influence the incidence of microembolisation or load. Specific surgical activities are associated with generating greater embolic loads and methods of avoiding these emboli such as venting the femur may minimise complications and optimise outcomes. Neuropsychiatric outcomes do not seem to be affected by microembolisation of the brain during total joint arthroplasty.