Mr Ian McDermott, Consultant Orthopaedic Surgeon at London Sports Orthopaedics, looks at the future of knee replacement surgery.
Despite what some may say, knee replacement is actually a very good operation. 95 per cent of prostheses can be expected to ‘survive’ after five years, with 80 per cent survivorship after 20 years. Patient satisfaction rates of 80 to 85 per cent have been reported with standard off-the-shelf prostheses (which is not improved by the use of million-dollar robots). However, satisfaction rates of 95 per cent can be expected with the use of custom-made knee prostheses.
One of the main issues that we are facing, however, is that we are seeing younger and younger patients presenting with premature degenerative changes, or even with end-stage arthritis, and age is a definite issue when it comes to knee replacement surgery. The younger a patient is when they have a knee replacement, the more active they are and the higher their functional demands are likely to be. This means an increased rate of wear and tear on a knee prosthesis, which means that it may wear out faster, and hence fail sooner. Combined with this is the fact that younger patients tend to live longer, and hence this is a double-whammy, and there is a significantly higher risk of revision in patients who undergo knee replacement at younger ages. If a patient has a knee replacement in their 70s, then there’s only a 10 per cent risk of revision within their lifetime. However, if a patient has a knee replacement in their 50s, then they have a 50 per cent lifetime risk of revision. Does this matter? Yes: revision knee replacement is twice as technically complex as primary surgery, it has double the complication rates, it is associated with poorer outcomes and higher (re-)revision rates.
So, if a revision can possibly be avoided, then it should be; and one of the best ways to avoid revision surgery is not to have your first knee replacement too young. (The other best way to prolong the
life of a knee prosthesis is to respect the prosthesis, and not to
abuse it by pounding it with heavy impact exercise, such as tennis or skiing.)
So, what do we do with this ever-increasing cohort of patients who present with premature knee arthritis?
If the patient has generalised primary osteoarthritis, with widespread damage within the joint, then there are few options available, apart from conservative management (painkillers, anti-inflammatories, physiotherapy, walking aids etc), intra-articular injections of corticosteroid (which is the only thing worth injecting into an arthritic joint), or arthroscopy, which in selected cases can reduce symptoms, help keep people keep their knee going for longer, buy them extra time and delay the eventual need for knee replacement surgery. In this cohort of patients, ‘biological reconstruction’ is not normally a viable option.
The patients that we are, however, sometimes able to help significantly, are those people with premature degenerative changes, predominantly in one compartment of their knee subsequent to previous injuries and previous operations, where they are developing premature post-traumatic secondary arthritis, and with the increase in popularity of high-impact type sports, we are seeing ever increasing numbers of these patients.
Meniscal tears
The meniscal cartilages are two crescent-shaped wedges of elastic fibrocartilage that sit in the knee between the femur and the tibia, acting as load sharers within the knee. The medial meniscus sits in the medial compartment and takes about 50 per cent of the load in that compartment; the lateral meniscus sits in the lateral side, and it takes about 70 per cent of the load passing through the lateral compartment. The posterior horn of the medial meniscus is also a secondary stabiliser against anterior tibial drawer, that is of particular importance in the ACL-deficient knee.
Meniscal tears are very common, with an approximate incidence of 65 per 100,000 population per year. It’s hard to give accurate numbers, b