Implant Materials in Joint Replacement: Metal, Ceramic and Gold

KL is just the WHO classification of osteoarthritis — it's not very good. Diagnosis is a clinical one: patients complaining of typical pain — pain while walking, pain while taking stairs, pain while sitting cross-legged — with definitive tenderness on the joint line, is almost confirmatory. That's the real gold standard, not the X-ray. X-ray is the baseline test, but it's not the criterion for deciding which patient should undergo surgery — a grade four KL arthritis patient with minimal pain treated well with physical therapy may not be a candidate for joint replacement, while a grade three patient who has tried all conservative measures without relief could be. It's a paradox, so X-ray grading alone isn't the gold standard. On location: for osteophytes, the location of weight-bearing matters more, but for me it's typically joint space reduction that matters most, because it indirectly shows the articular cartilage is gone — and that's irreversible.

Medical therapy is the first line of treatment — it should be tried first, and once pain is not relieved with medical therapy and physical therapy, and the patient is having difficulty in activities of daily living, then the patient becomes a candidate for surgery.

The survivorship of newer implants, taking an average value, is more than 20 to 25 years, though there's a range. To measure success there's a prerequisite: we presume the patient has taken care of the joint, followed the precautions, physical therapies and exercises they've been told — the value I've mentioned is the average assuming that's been taken care of.

It's a permanent, non-removable procedure — it doesn't need to be removed. The follow-ups: the first milestone is at two weeks, to remove the stitches, then six weeks post-surgery, then three months, six months, and then annually.

In athletes the demand of activity is much more than the normal population — jumping, contact sports — and there's wear and tear involved in the artificial joint over time. We generally tell patients not to jump or run, for the sake of the longevity of the implant — the more activity, the more wear, and the more chance of needing revision surgery. First we tell them to change their activity level if possible; if that's not possible, there are certain implant variations available, like hip resurfacing or metal-on-metal implants, which can be offered if it's mandatory for the athlete to continue their sport — though ceramic implants are not good for them because of a higher chance of breakage.

A cobalt, chromium and nickel alloy is the most commonly used material. Titanium is considered the most superior option currently available, and oxinium, a black coloured material, is also used in some cases.

Patients allergic to cobalt or chromium, sometimes identified from reactions to artificial jewellery containing similar metals, can be given gold-coated implants instead of standard alloy implants.

It is distinct from the implant itself and refers to where the actual movement occurs. Bearing surfaces can be plastic, ceramic or metal, combined as metal-on-metal, ceramic-on-ceramic or ceramic-on-plastic.

Cemented, uncemented, hybrid or reverse hybrid techniques, each suited to different bone quality and patient profiles.