Sir John Charnley introduced the first successful hip replacement in the 1960’s for the treatment of osteoarthritis. The damaged femoral head was removed and the hip replaced with a polythene socket and a stainless steel ball, both of which were attached to the skeleton with acrylic bone cement.
There is no doubt that Charnley's operation has transformed millions of lives by relieving pain of hips with arthritis and avascular necrosis, whilst also restoring mobility and correcting deformity. Total hip replacement (THR) is one of the most successful and cost-effective operations in the whole of medicine.
As experience has grown, THR has been performed on increasingly younger patients with greater physical demands for work, family life and recreation.
Patients are increasingly dissatisfied with long-term analgesic use and advice that they are too young for a hip replacement. However it is well documented that these patients' increased physical demands cause their implants to wear out more quickly and therefore need revision surgery earlier. In addition, their longer life expectancy increases the time the implant is exposed to these active conditions. Whilst the National Institute for Clinical Excellence (NICE) recommends implants which fail at a rate of 1 per cent per year, this failure rate is clearly less than ideal for patients in their 30’s and 40’s who will almost certainly face at least one revision in their lifetime. Charnley recognised that his metal on plastic bearing could wear out and so would not perform the operation on patients under 70 years old.The problem with the wear process is that it is directly responsible for the loosening of implants, with subsequent renewed pain, loss of bone, and possible catastrophic failure of the whole joint. During normal activities millions of tiny polyethylene wear particles are liberated from the socket into the joint. The body's defence cells take up these particles and the cells become activated to erode bone as they cannot tell the difference between wear particles and bacteria. Over time, this can gradually destroy the foundations to which the implants are fixed, causing loosening. It therefore follows that if polyethylene wear debris and can be excluded from hip replacements and the implants are effectively fixed to the host skeleton, then in theory one has a hip replacement that doesn't wear out or loosen.
Fortunately, materials used in hip replacements have developed since Charnley’s first implants and modern hip replacements can now meet the needs of younger active patients. Ceramic on ceramic (CoC) bearing surfaces wear out at a tiny fraction of the rate of metal on plastic hip replacements and therefore they may not wear out in the patient’s lifetime.
Ceramic hip replacements also have bigger heads without increasing socket size, thereby improving range of motion and stability in the hip. Ceramic bearings are attached to the skeleton without using bone cement since the bearings themselves are attached to titanium implants. These have a special coating into which bone grows directly, thereby fusing the implant directly with the bone. These advances mean we no longer need to consider hip replacement as a last resort but as a safe predictable one-off procedure, which returns people to a normal pain-free life. Modern hip replacements also allow patients to return to most recreational sporting activities including cycling, golf, skiing, tennis and swimming.
As well as improvements in the implants, there have also been great advances in the operation itself. Modern instruments have allowed hip replacements to be performed through smaller incisions with lower blood loss and shorter hospital stay. Spinal anaesthesia www.en.wikipedia.org/wiki/Spinal_anaesthesia allows patients to wake up from their operation pain free so they may start eating and drinking straight after surgery. Spinal anaesthesia also reduces bleeding during surgery and the risk of clots (deep vein thrombosis – DVT). Postoperative pain is managed with tablets (oxycodone, paracetamol and ibuprofen) and surgical drains are not used. This allows patients to mobilise straight after surgery unencumbered by drips and tubes.