Metal Ions and Wear Rates in the Birmingham Hip Resurfacing - Hena Ziaee 2006
In this lecture from 2006, Biomedical Scientist Hena Ziaee discusses metal ions and the wear rates of the Birmingham Hip Resurfacing (BHR), a bone-conserving hip arthroplasty implant. Wear from the implant is described as the removal of material from one or both of the hard surfaces from a rolling, sliding or impact motion.
There are several modes of wear which vary from primary surface wear to secondary and third party debris wear. The Birmingham Hip Resurfacing is a polar bearing, which when looked at in detail, allows a small amount of fluid to adhere to each of the surfaces. When in motion the fluid velocity forces the fluid into the joint space and creates a film between the two surfaces, in correctly positioned acetabular and femoral components this can mean the bearing surfaces do are not touching creating very little wear.
‘Big Ben’ is Derek McMinn’s swinging 500kg weight which is solely supported by a Birmingham Hip Resurfacing – the video shows how the lubricant fluid which is drawn into the joint creates little friction and the huge weight is easily moved with a finger, or a single sheet of paper. This low friction hip replacement joint is ideal for patients who want high impact activity – videos of former Derek McMinn patients show veteran Judo and Badminton champions.
The Birmingham Hip Resurfacing has the same metallurgy as the first generation of metal on metal hip replacement implants from the 1960s – the design may be different but the microstructure is very similar giving the BHR strength and durability. The BHR is mostly made up of Cobalt and Chromium with smaller percentages of Molybdenum, Carbon and other metals. Metal ions are soluble and can pass into the blood stream freely – in large quantities this could be toxic and have adverse affects on the body. However the metal ions released by the Birmingham Hip Resurfacing are all essential elements that are needed and found in the body.
Hena Ziaee looks at different techniques for analysing blood, serum and urine samples from patients and comments on which produce the most reliable results. Results from Birmingham Hip Resurfacing patients are compared with other groups of patients, including patients with Ring first generation metal on metal hips.