Total Hip Replacements and High Performance Bearings

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) suggests that implants which fail at >5% at 10 years may be acceptable, this failure rate is clearly less than ideal for patients in their 30s and 40s 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 themselves, 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.

Information on Marcus hip replacement practice and the hospitals he works in from the National Joint Registry can be found here. Of interest is that the average age of THR patients he operates on is 46yo, compared with 68yo as the national average. Patient reported outcomes (PROMS) are also excellent with the average Oxford Hip Score prior to surgery being 24/48 improving to 45/48 1 year after surgery.


 

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.


 

Frequently asked questions

I am very young to have a hip replacement. How long will it last?

As patients have become more active, they are less willing to accept a life of compromise and painkillers. Modern ceramic bearings wear out at a fraction of the rate of traditional metal on plastic hip replacements making it increasingly likely that hip replacement is a once in a lifetime procedure at whatever age it is performed. Whilst hip replacement is not entirely without risk, deterioration in function and increasing pain from an arthritic hip are inevitable.

Hip disease in young patients is not as uncommon as is often believed. Whilst the average age of hip replacement surgery nationally is 68 years old, it is 46 years old in Marcus’ practice. Ceramic on ceramic hip replacements in their current form have been around nearly twenty years and show no sign of wearing out at this stage, so a conservative estimate of another ten years after that is not unreasonable as it seems unlikely that they will suddenly fail having functioned well without much wear for two decades.

How long will it take to recover after a hip replacement?

Patients are in hospital two to four nights and are on crutches three to six weeks. It is normal for the whole leg to swell after a hip replacement, reaching its maximum at seven days. It is also normal for bruising to appear at the back of the knee due to the effects of gravity on the bruise round the hip. Swelling with pain and redness in the calf may indicate a blood clot.

Traditionally patients are advised to take 6 weeks off work, but clearly this varies between individuals, particularly as working from home in some capacity is possible for many. However, patients may underestimate how much the surgery affects their stamina and there is no doubt that the longer patients take off work, the easier they find it on return. Patients should not do any work at all during the week of surgery and the week after so there are no distractions to recovery. Some gentle work email is reasonable in weeks three and four, with a potential return to the office for the odd half-day from the end of week four onwards, provided the patient is driven to and from work.

Return to full work is usually possible after six weeks but be aware it will initially be tiring being back at work. In addition, physiotherapy will be continuing and setting time aside for exercise is still required. Patients with long or challenging commutes to work should adjust their hours to avoid peak-times to ensure they get a seat. By three months, the hip should function almost normally in day-to-day life and patients should have resumed golf and their usual gym activities, albeit at lower intensity. Hip replacements continue to improve further for up to a year after surgery, and sometimes even longer for very young patients.

What tablets will I need after surgery?

Patients can usually tell the day after surgery that the pain from the arthritic hip has gone and is replaced with a severe stiffness in the buttock from the operation itself. The absence of hip joint pain so soon after surgery gives patients a great psychological boost, as they can already tell that the operation has worked.

Clearly painkillers are required for the surgical pain and initially patients are given slow-release oxycodone, a synthetic morphine type drug (Targinact, Oxycontin), ibuprofen (Nurofen, the non-steroidal anti-inflammatory drug), and paracetamol. The day is “bookended” with the slow release oxycodone morning and evening with the day covered by dovetailing four doses of paracetamol with three doses of ibuprofen. The initial dose of oxycodone is reduced in hospital and it can even be discontinued prior to discharge in some patients. Patients have usually stopped taking oxycodone in the first two weeks after leaving hospital, following which they should reduce and then stop the ibuprofen. By four weeks patients are usually just taking the odd paracetamol tablet although discomfort at night can continue for a number of weeks. As well as slow-release oxycodone, patients are also sent home with a three-week supply of the blood-thinning capsule, Dabigatran or injections of Fragmin. Patients should also have a supply of the over the counter painkillers Nurofen and paracetamol at home.


 

What kind of anaesthetic will I have? Will I be asleep during my operation?

Our preference is spinal anaesthesia with sedation. This means that you will be asleep during your operation but that there will also be an injection of local anaesthetic with a very fine needle into the bottom of the spine. This blocks sensation from the waist down for 4 to 6 hours so that sensation returns gradually well after the operation is completed. A urinary catheter is also placed as the spinal anaesthetic can also stop the bladder emptying properly; the catheter is only in overnight and is removed the morning following surgery. 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.

Epidural anaesthesia is similar to spinal anaesthesia but is seldom needed for hip replacement surgery, although it is often mentioned as the only alternative to general anaesthesia in patient guides. It involves actually placing a tiny tube into the spine and allows local anaesthetic to be continually added during and after surgery (“topped up”).

Will I need a blood transfusion for my total hip replacement?

Blood transfusion is now a rare event after a total hip replacement and is necessary in less than 5%. This is due to a number of factors. Surgery is performed more efficiently through smaller incisions and spinal anaesthesia with sedation reduces bleeding during the operation further. Blood loss is fairly predictable in primary hip surgery so the higher the level of haemoglobin in the blood prior to surgery, the higher the level will be afterwards.

The haemoglobin level should ideally be at least 135 g/l to remove the risk of a transfusion completely. Female patients, in particular, may benefit from iron tablets in the few weeks before surgery. If unpredictable blood loss is encountered the cell-saver machine recycles blood lost during the procedure and returns it to the patient thereby reducing the possibility of transfusion even further.

How long should I wear the white compression stockings?

6 weeks. Whilst they may be inconvenient and uncomfortable, they are an extremely important part of blood clot prevention, along with blood thinning medication and regular activity

Must I always sleep on my back after my hip replacement?

No. Modern hip replacements are very stable and do not dislocate turning over in bed. After surgery, it is perfectly safe to sleep on either side with a pillow between the legs, although patients usually prefer to lie on the non-operated side

When can I drive after my hip replacement?

If patients are confident walking without crutches and able to enter a car unaided then a return to driving is reasonable, provided at least four weeks have elapsed. Advice from the insurance company is recommended if driving before six weeks.

How much physiotherapy will I need after surgery?

Patients are advised to take two walks per day, gradually increasing distance as confidence and strength return. Patients are encouraged to bear full weight on their operated leg. Most patients have discarded their crutches by the six-week follow-up visit. Weekly land-based physiotherapy is essential for successful rehabilitation after surgery. As well as providing appropriate guidance for the hip itself, a visit to the physiotherapist provides an important focus for the week and allows the patient to see real progress at each visit. Use of an exercise bike is strongly encouraged from two weeks after surgery, initially starting with low resistance for a few minutes. Hydrotherapy can also be helpful in the first six weeks if it is available, but it is not crucial.

Will I need to take precautions to avoid dislocation?

No. Modern hip replacements are much less prone to dislocate and there is less reliance on traditional “dislocation precautions” in the majority of cases. Patients can sleep on either the operated or non-operated side straight after surgery provided there is a pillow between their knees and flexion beyond 90º is encouraged after two or three weeks to stop the hip getting too stiff and to allow patients to get down to their shoes and socks. Return to swimming varies between individuals and the facilities at the swimming pool. Clearly patients can get back in the pool sooner is there is step rather than ladder access. Crawl kick or a leg float should be used initially but, as familiarity and fitness return over the first two or three months, breast-stroke kick can be resumed. It has been shown that traditional “dislocation precautions” not only do not reduce the risk of dislocation but may also be harmful by delaying return to normal activities (Do lifestyle restrictions and precautions prevent dislocation after total hip arthroplasty? A systematic review and meta-analysis of the literature Clinical Rehabilitation 2015)

Are there any stitches to remove?

No. The stitches are under the skin and dissolvable.

When can I fly after my hip replacement?

The additional risk of blood clots after a hip replacement has almost gone after six weeks. It is for this reason that patients are advised not to fly long haul within this time. Shorter flights to Europe pose little, if any, additional clot risk.

Will my hip replacement set off airport metal detectors?

Definitely yes when both hips have been replaced, and usually yes when one has been replaced. Airport security is extremely familiar with travellers who have metal implants, not just hip replacements but also replacements of knees and shoulders, plates and screws from broken bone surgery, and heart pacemakers. When the detector goes off, patients should calmly step to the side, explain they have a metal implant, and make themselves available to be frisked. It is unnecessary for the patient to go into great detail about what type of surgery they have had, unless of course they particularly feel the need to share this information with the airport staff. A medical letter confirming the presence of an implant is available to patients on request but in practice is seldom helpful.

What can go wrong with a hip replacement?

Complications are rare with modern surgical and anaesthetic techniques. Blood clot risk (deep vein thrombosis or DVT) is kept to a minimum with use of a combination of measures. The blood-thinning tablet Dabigatran (or the injection Fragmin or Clexane) is given for four weeks after surgery and the patient is advised to wear compression (TED) stockings for six weeks after surgery. In addition, whilst in hospital, foot pumps are used to enhance blood flow in the legs whilst the patient is in hospital.

Infection in a hip replacement is a devastating complication but fortunately occurs in less than 0.3% of cases. Risk factors include age, obesity, coexisting skin conditions such as psoriasis, and previous open hip surgery. Whilst the infection can usually be eradicated, it does involve lengthy treatment with antibiotics and surgery.

An unexpected inequality in leg length is also unusual with contemporary implants and templating software (picture of templated x-ray). This is why it is important that a current x-ray with a calibration marker is available before the operation.

Dislocation occurs in approximately 1% of hip replacements and is seldom recurrent. Recurrent dislocation usually indicates malposition of implants.

Major nerve injury to either the femoral or sciatic nerves is extremely rare in routine cases; the risk is slightly greater in cases involving deliberate lengthening of the leg or if there has been previous hip surgery.

Clicking from slight separation of the hard ceramic surfaces is not uncommon in the first two or three weeks after surgery and quickly resolves as the muscle strength and tone recover. More serious mechanical problems such as grating or audible squeaking are very much less common and are usually associated with very particular movements such as deep squatting. The problems of squeaking are grossly over represented in the scientific literature because many of the studies focus on a particular design of ceramic on ceramic hip replacement which is associated with particularly high rates of squeaking.

Recurrent groin pain from psoas tendon irritation occurs after 1-2% of hip replacements and seems to particularly affect young men. The tendon runs over the front of the hip joint and is occasionally irritated by the hip replacement surgery. The patients recognise that the pain is more superficial than their original arthritis hip pain. If an injection of local anaesthetic and steroid is not effective at treating it, the problem is easily solved with a small day-case operation to release the tendon in the groin.

Thigh pain from the stem of the hip replacement is another unusual complication, which usually develops as the patient is stepping up their activity level a few months after surgery, although it can sometimes occur many years after the original operation. It is poorly understood but seems to be related to remodelling of the bone in response to a change in the loading pattern. The fact that the implant may be stiffer than the bone is also thought to be relevant. Fortunately, thigh pain is almost always temporary and subsides after a few weeks.

Reoperation on a hip replacement for failure is always a possibility as it would be for any mechanical device, although these risks are greatly reduced with modern un-cemented ceramic on ceramic total hip replacements.