The meniscus in the knee works by “Hoop Stresses” – by being attached at the front and back of knee, and with its triangular cross section, it spreads the load through that compartment of the knee, protecting the knee from arthritis. A particular problem for the medial meniscus is a popping sensation, where the posterior horn becomes detached. It usually isn’t major trauma, but squatting, or walking up stairs can do it in middle age and above. The “pop” has a very high specificity (99% in a Korean study) but not sensitivity (35%). The natural history is poor – most patients go on to develop osteoarthritis. If there is bone marrow oedema, or a subchondral fracture, the arthritis may be rapid in evolution.

Fortunately, meniscal roots can be repaired if the tear is within 10mm of the root with a surprisingly high success rate.

But, typically we require six weeks of non weight bearing after the surgery, use of knee braces to restrict motion, minimal arthritis, and our patient needs to be on board with the plan. Being heavy isn’t too much of a problem, but if significantly bow legged, a realignment osteotomy is also required. When this surgery was initially advocated, an age limit of 65 was proposed, but in the Australian Knee Society group, plenty of orthopaedic surgeons are operating on folk older than that – if they can tolerate the recovery requirements.

Mr David Mitchell
Orthopaedic Surgeon
MBBS (Melb), FRACS (Orth), FAOrthA, GAICD

Since 2000, every joint replacement done in Australia goes into a central registry, and if further surgery undertaken, it is recorded against the implant. The surgeon is also able to access his own results to compare with other surgeons of Australia. This has had substantial impact not only in Australia, but internationally.

Twenty year results indicate re-operation on 7% of joint replacements where the patients are still alive (the average age for joint replacement is 68). Implants that are no longer available are not included in this. It doesn’t matter if hip, knee or shoulder. Various improvements over the years probably improve these results – highly cross linked polyethylene was not available 20 years ago – and basically doesn’t show wear at 15 years. Vitamin E has been in my hip replacements also reducing oxidation and delamination since 2009.

The old days of annual reviews don’t make sense. There will be special patients that do – but given the average age for joint replacement is 68 in Australia, the likelihood of requiring further surgery is small. Given standard referrals run out at 12 months – following up for six months is probably easiest for all parties, but if there is a reason to follow up long term – so be it !

Mr. David Mitchell
Orthopedic Surgeon

For twenty years we’ve been doing Birmingham Hip Resurfacing – and in perfectly selected patients they have done extremely well! Going forward though – the company is probably ceasing supply in 2027.

Hip resurfacing was a great idea of Derrick McMinn in the 1990’s – at that time – hip replacements used to wear out, or not really allow normal function. Birmingham’s basically solved that problem, so by 2010, represented about 10% of all joint replacements done in Australia. Ordinary hip replacements though have improved – the plastic is better, longer lasting, anterior hip replacement has reduced the dislocation rate, and maybe the shorter stems of modern hip replacements have removed thigh pain as a complication.

The number of Birminghams done in Australia in 2022 was down to 93. Ceramic on ceramic resurfacing has become more popular, at 231 in 2022. Again though, a hundred less than the previous year. I’ll be attending the AOA Annual Scientific Meeting in October, and working out my plan going forward.

Mr. David Mitchell
Orthopedic Surgeon

It is claimed 16% of knee replacements patients aren’t that impressed with their outcome – I’d be devastated if that’s what we saw at Ballarat Orthopaedics & Sports Medicine. Metal allergy probably contributes to this percentage.

Maybe 5% of people can’t tolerate nickel – be it in cheap earrings, or stainless steel watches. Nickel turns out to be a common impurity in chrome-cobalt alloys used for the femoral component of knee replacements. To its credit – that alloy is hard to scratch, easy to coat the surface rubbing against the femur with titanium which helps bone ongrowth.

Titanium is a rare allergy – used in the tibial component of most knee replacements, but is too soft to use as a bearing surface for the femoral component, it scratches too easily. Most low allergy knee replacements – for example the Persona Titanium/Niobium coated implant (Zimmer-Biomet), or the Oxiniuim coated Journey knee (Smith & Nephew) both have titanium tibial baseplates. Whilst all polyethylene tibial components exist – most surgeons are avoiding them in younger patients.

B.Braun Columbus offers a multiply coated implant – both femur and tibia components. Admittedly there is still the question of cement allergy. At the end of the day – we have a case by case solution. Routine testing for allergies has not been demonstrated to improve outcomes, but where someone seems to be at risk, we’re keen to have a solution.